FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K for the year ended December 31, 2021, contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), which are subject to the “safe harbor” created by those sections, concerning our business, operations, and financial performance and condition as well as our plans, objectives, and expectations for business operations and financial performance and condition. Any statements contained herein that are not of historical facts may be deemed to be forward-looking statements. You can identify these statements by words such as “anticipate,” “assume,” “believe,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “should,” “will,” “would,” and other similar expressions that are predictions of or indicate future events and future trends. These forward-looking statements are based on current expectations, estimates, forecasts, and projections about our business and the industry in which we operate and management’s beliefs and assumptions and are not guarantees of future performance or development and involve known and unknown risks, uncertainties, and other factors that are in some cases beyond our control. As a result, any or all of our forward-looking statements in this Annual Report on Form 10-K may turn out to be inaccurate. Factors that could materially affect our business operations and financial performance and condition include, but are not limited to, those risks and uncertainties described herein under “Item 1A - Risk Factors.” You are urged to consider these factors carefully in evaluating the forward-looking statements and are cautioned not to place undue reliance on the forward-looking statements. The forward-looking statements are based on information available to us as of the filing date of this Annual Report on Form 10-K. Unless required by law, we do not intend to publicly update or revise any forward-looking statements to reflect new information or future events or otherwise. You should, however, review the factors and risks we describe in the reports we will file from time to time with the Securities and Exchange Commission (the “SEC”) after the date of this Annual Report on Form 10-K.

This Annual Report on Form 10-K also contains market data related to our business and industry. These market data include projections that are based on a number of assumptions. If these assumptions turn out to be incorrect, actual results may differ from the projections based on these assumptions. As a result, our markets may not grow at the rates projected by these data, or at all. The failure of these markets to grow at these projected rates may harm on our business, results of operations, financial condition and the market price of our common stock. See our Summary of Risk Factors on page 49.

PART I

Item 1.  Business

Overview

Vaxart Biosciences, Inc. was originally incorporated in California under the name West Coast Biologicals, Inc. in March 2004 and changed its name to Vaxart, Inc. (“Private Vaxart”) in July 2007, when it reincorporated in the state of Delaware.

On February 13, 2018, Private Vaxart completed a reverse merger (the “Merger”) with Aviragen Therapeutics, Inc. (“Aviragen”), pursuant to which Private Vaxart survived as a wholly owned subsidiary of Aviragen. Under the terms of the Merger, Aviragen changed its name to Vaxart, Inc. and Private Vaxart changed its name to Vaxart Biosciences, Inc. Unless otherwise indicated, all references to “Vaxart,” “we,” “us,” “our” or the “Company” in this Annual Report on Form 10-K mean Vaxart, Inc., the combined company.

We are a clinical-stage biotechnology company primarily focused on the development of oral recombinant vaccines based on our Vector-Adjuvant-Antigen Standardized Technology (“VAAST”) proprietary oral vaccine platform. Our oral vaccines are designed to generate broad and durable immune responses that may protect against a wide range of infectious diseases and may be useful for the treatment of chronic viral infections and cancer. Our investigational vaccines are administered using a room temperature-stable tablet, rather than by injection.

We are developing prophylactic vaccine candidates that target a range of infectious diseases, including SARS-CoV-2 (the virus that causes coronavirus disease 2019 (“COVID-19”)), norovirus (a widespread cause of acute gastro-intestinal enteritis), seasonal influenza and respiratory syncytial virus (“RSV”) (a common cause of respiratory tract infections). We have completed a Phase 1 clinical trial for our first SARS CoV-2 vaccine candidate, that commenced in October 2020; the study met its primary and secondary endpoints. A Phase 2 study with our second-generation SARS CoV-2 vaccine candidate commenced dosing in October 2021 and is currently ongoing. Three Phase 1 human studies for our norovirus vaccine candidate have been completed, including a study with a bivalent norovirus vaccine which, as we disclosed in September 2019, met its primary and secondary endpoints. Additional Phase 1 studies with our norovirus vaccine are currently ongoing. Our monovalent H1 influenza vaccine protected participants against H1 influenza infection in a Phase 2 challenge study, as published in 2020 (Lancet ID). In addition, we are in early development of our first therapeutic vaccine targeting cervical cancer and dysplasia caused by human papillomavirus (“HPV”).

Vaccines have been essential in eradicating or significantly reducing multiple devastating infectious diseases, including polio, smallpox, mumps, measles, diphtheria, hepatitis B, influenza, HPV and several others. According to a MarketsandMarkets research report titled “Vaccines Market - Global Forecast to 2023”, the global market for vaccines is expected to reach $50.42 billion by 2023 from $36.45 billion in 2018, at a compound annual growth rate of 6.7%.

We believe our oral tablet vaccine candidates offer several important advantages:

First, they are designed to generate broad and durable immune responses, including systemic, mucosal and T cell responses, which may enhance protection against certain infectious diseases, such as COVID-19, influenza, norovirus and RSV, and may have potential clinical benefit for certain cancers and chronic viral infections, such as those caused by HPV.

Second, our tablet vaccine candidates are designed to provide a more efficient and convenient method of administration, enhance patient acceptance and reduce distribution bottlenecks, which we believe will improve the effectiveness of vaccination campaigns. For example, according to the U.S. Centers for Disease Control and Prevention (the “CDC”), in the 2018/2019 seasonal influenza season, only approximately 49% of the U.S. population was vaccinated against influenza, with particularly low vaccination rates among adults between ages 18 and 49.

Business Update Regarding COVID-19

The COVID-19 outbreak has presented a substantial public health and economic challenge around the world and is affecting employers, employees, patients, communities and business operations, as well as the U.S. economy and financial markets. The full extent to which the COVID-19 outbreak will directly or indirectly impact our business, results of operations and financial condition will depend on future developments that are highly uncertain and cannot be accurately predicted, including new information that may emerge concerning COVID-19, the actions taken to contain it or treat its impact and the economic impact on local, regional, national and international markets.

To date, we have been able to continue our operations and do not anticipate any material interruptions in the foreseeable future. However, we are continuing to assess the potential impact of the COVID-19 pandemic and the development of other competing COVID-19 vaccines on our business and operations, including our expenses, supply chain and clinical trials. Our office-based employees have been mostly working from home since mid-March 2020 and will continue to do so until we believe it is safe to return to the workplace. Our partners have mostly continued to operate their facilities at or near normal levels. While we currently do not anticipate any interruptions in our operations, it is possible that the COVID-19 pandemic and response efforts may have an impact in the future on our operations and/or the operations of our third-party suppliers and partners. Any recovery from negative impacts to our business and related economic impact due to the COVID-19 outbreak may also be slowed or reversed by a number of factors, including the recent emergence of coronavirus strains with mutated S proteins.

Our Product Pipeline

Fig. 1.  The following table outlines the status of our oral vaccine development programs:

We are developing the following tablet vaccine candidates, which are all based on our proprietary platform:

According to the CDC, an outbreak of COVID-19, caused by the virus SARS-CoV-2, began in Wuhan, China, in late 2019 and rapidly spread worldwide. By February 23, 2022, more than 429 million COVID-19 cases had been identified globally, including in the United States, where the CDC had reported over 78 million infections and 936,000 deaths. While most COVID-19 restrictions, such as stay-at-home orders, have been lifted, COVID-19 continues to spread, particularly among the unvaccinated population, and remains a public health threat, not least due to the emergence of new variants. The COVID-19 risk remains even greater in developing regions where vaccination rates still remain low.

On September 14, 2020, we announced that the U.S. Food and Drug Administration (the “FDA”) had cleared our Investigational New Drug (“IND”) application to allow initiation of human clinical testing of our first oral COVID-19 (S and N proteins) vaccine candidate VXA-CoV2-1. On October 13, 2020, we announced that Phase 1 clinical testing had commenced and on February 3, 2021, we announced the preliminary results of the trial. The study achieved both its primary and secondary endpoints of safety and immunogenicity, respectively. We announced in February 2021 that we would evaluate vaccine candidates that contain just the Spike protein, and different variant-specific vaccines in research. After preclinical evaluations (including in non-human primate studies) showed that an improved antibody response could be achieved with a new vaccine candidate that expressed just the Spike protein, we decided to move this candidate forward for clinical evaluation. This new vaccine candidate, VXA-CoV2-1.1-S, was also able to elicit antibody responses against human coronavirus strain variants such as Beta (first identified in South Africa) and Delta (first identified in India) in animals. Further, this new vaccine candidate was tested in a vaccine breakthrough/transmission model led by Duke University and found to inhibit aerosol transmission to vaccine-naïve animals better than an injected S-protein-based vaccine candidate. These results were published in bioRxiv in October 2021.

A new IND was filed for this S-only vaccine candidate in June 2021 and was cleared by the FDA in July 2021. We initiated dosing with this candidate in a Phase 2a clinical study in October 2021, with approximately 896 participants planned for enrollment utilizing a two-part study design. The first part of the study is currently underway and will enroll 48 participants aged 18 to 55 and 48 participants aged 56 to 75, to further evaluate safety and immunogenicity and to assess optimal dosage. Further, half the subjects in the trial will be prior vaccinated (have received two doses of an mRNA vaccine) to test the ability of the Vaxart COVID-19 vaccine candidate to boost immune responses and enhance variant-specific cross-reactivity, and half the subjects will be naïve to prior vaccinations. We expect data from this portion of the trial to be available during the first half of 2022. Upon dose selection from Part 1, the second part of the study will enroll approximately 800 subjects aged 18 to 75 and will test preliminary vaccine efficacy to protect against SARS-CoV-2 infection.

Additionally, international Phase 1b and Phase 2 COVID-19 trials, including a placebo-controlled efficacy trial in India, are anticipated to begin this year, though there can be no assurance that these trials will occur.

The first-generation vaccines seem to have varying levels of efficacy to emerging strains of COVID-19. The current selective pressure of strain adaptation has been in an environment of very low levels of a vaccinated public and strain change may increase in speed as the vaccinated population grows.

There was significant vaccine hesitancy reported before the vaccines were offered to the public and in some countries more than 50% of the population stated they would not take a COVID-19 vaccine. This vaccine hesitancy appears to be waning slightly as more people are being vaccinated without serious adverse events and may end up being similar to rates of vaccine hesitancy for other vaccines such as the influenza vaccine.

We expect this to remain a public market vaccine opportunity for the foreseeable future. However, because of the impact to the freedom of movement for the public and the economic fallout, the overall market needs for doses may be many times higher than the global market for seasonal influenza vaccines because there may be higher demand by working adults then we see for seasonal influenza vaccine.

Norovirus is the leading cause of acute gastroenteritis symptoms, such as vomiting and diarrhea, among people of all ages in the United States. Each year, on average, norovirus causes 19 to 21 million cases of acute gastroenteritis and contributes to 56,000 to 71,000 hospitalizations and 570 to 800 deaths, mostly among young children and older adults. Typical symptoms include dehydration, vomiting, diarrhea with abdominal cramps, and nausea. In a study by the CDC and Johns Hopkins University, published in 2016, the global economic impact of norovirus disease was estimated at $60 billion, $34 billion of which occurred in high income countries including the United States, Europe and Japan. An update by the lead authors estimated the burden in the U.S. alone to be $10.5 billion in 2018. Virtually all norovirus disease is caused by norovirus GI and GII genotypes, and we are developing a bivalent vaccine designed to protect against both. We anticipate that, if approved, the vaccine will be an annual, one-time administration ahead of the winter season when norovirus incidence is at its peak, similar to the influenza season.

Clinical Trial Update. In 2019, we completed the active phase of a Phase 1b clinical trial with our bivalent oral tablet vaccines for the GI.1 and GII.4 norovirus strains. Both the oral norovirus GI.1 and GII.4 vaccines were well tolerated with no serious adverse events reported. Most solicited and unsolicited adverse events were mild in severity, and there were no significant differences observed between the vaccine and placebo treatment groups.

Importantly, Vaxart’s bivalent vaccine (GI.1 and GII.4 co-administered) demonstrated robust immunogenicity, with an IgA ASC response rate of 78% for the GI.1 strain and 93% for the GII.4 strain for the bivalent cohort of the study, when compared to 86% and 90%, respectively, for the two monovalent cohorts of the study. These results indicate that co-administration of the two vaccines, the intended approach for proceeding into phase 2 and 3 trials, shows no cross-interference, or reduction from the response observed with individual (monovalent) vaccine delivery.

As summarized above, we resumed clinical development of our norovirus vaccine candidate in late 2020 by planning the conduct of three clinical trials. In early 2021 we initiated dosing a subset of subjects (second dose after more than one year) in the Phase 1b bivalent study.   In results announced on July 29, 2021, we reported that we were able to successfully boost immune responses with the G1.1 norovirus tablets in prior vaccinated subjects. These responses include IgA antibody secreting cells, as well as IgG and IgA serum antibody responses. In mid-2021 we initiated conduct of a placebo-controlled, dose ranging study in elderly adult subjects aged 55 to 80 to evaluate the safety and immunogenicity of the vaccine in the older population.  This study has completed enrollment and study assessments through the active portion of the trial (4 weeks post last dose); sample analysis is currently underway with database lock and topline results expected in H1-2022.  Lastly, we also conducted an open-label trial to evaluate the optimal timing of boost administration in young adults in which 3 cohorts of subjects received their second dose (boost) at varying timepoints between 1 and 3 months post initial vaccination. This study was performed as data from trials with adenovirus vaccines indicate that boost administration at a later timepoint (e.g., 12 weeks) may offer a more robust immune response. This study has completed enrollment and study visits through the active phase; sample analysis is currently underway with database lock and topline results expected in Q1-2022. 

Within 2022, we plan to initiate Phase 2 clinical trials with our norovirus vaccines.  The first trial, which has recently been initiated, is a Phase 2 norovirus challenge study which will evaluate safety, immunogenicity and clinical efficacy of a norovirus GI.1 vaccine against placebo control post viral challenge. The second clinical trial to be initiated will be a Phase 2 multi-center, placebo-controlled dose confirmation trial evaluating the safety and immunogenicity of Vaxart’s bivalent norovirus vaccine in subjects aged 18 years and older. The data from these Phase 2 studies will form the basis (safety, immunogenicity and preliminary efficacy data) for an End of Phase 2 Meeting with the FDA to gain concurrence on the scope and design of the Phase 3 pivotal efficacy study in adults over 18 years of age.

Influenza is one of the most common global infectious diseases, causing mild to life-threatening illness and even death. An estimated 350 million cases of seasonal influenza occur annually worldwide, of which three to five million cases are considered severe, causing 290,000 to 650,000 deaths per year globally. During the flu season of 2018/2019 there were 34,200 flu related deaths in the U.S. alone, according to the CDC. Very young children and the elderly are at the greatest risk. In the United States, between 5% and 20% of the population contracts influenza, 226,000 people are hospitalized with complications of influenza, and between 3,000 and 49,000 people die from influenza and its complications each year, with up to 90% of the influenza-related deaths occurring in adults older than 65. The total economic burden of seasonal influenza has been estimated to be $87.1 billion, including medical costs which average $10.4 billion annually, while lost earnings due to illness and loss of life amount to $16.3 billion annually.

We believe our tablet vaccine candidate may potentially address many of the limitations presented by injectable egg-based influenza vaccines for the following reasons: (i) our tablet vaccine candidates are designed to create broad and durable immune responses, which may provide more effective immunity and protect against additional strain variants; (ii) our vaccine is delivered as a room temperature-stable tablet, which we believe would provide a more convenient method of administration, enhancing patient acceptance and simplifying the distribution and administration process; (iii) we believe our tablet vaccine may be manufactured more rapidly than vaccines manufactured using egg-based methods by using recombinant methods; and (iv) using our tablet vaccine in lieu of egg-based vaccines would eliminate the risk of experiencing allergic reactions to egg protein.

In September 2018, we completed a $15.7 million contract with the U.S. Government through the Department of Health and Human Services, Office of Biomedical Advanced Research and Development Authority (“HHS BARDA”) under which a Phase 2 challenge study of our H1N1 flu vaccine candidate was conducted. Previously, we had announced that, in healthy volunteers immunized and then experimentally infected with H1 influenza, our H1 influenza oral tablet vaccine reduced clinical disease by 39% relative to placebo. Fluzone, the market-leading injectable quadrivalent influenza vaccine, reduced clinical disease by only 27%. Our tablet vaccine also showed a favorable safety profile, indistinguishable from placebo.

On October 4, 2018, we presented data from the study demonstrating that our vaccine elicited a significant expansion of mucosal homing receptor plasmablasts to approximately 60% of all activated B cells. We believe these mucosal plasmablasts are a key indicator of a protective mucosal immune response and a unique feature of our vaccines. This data also indicates that our vaccines provide protection by inducing mucosal immunity (the first line of defense against mucosal infections such as flu, norovirus and RSV), marking what could be a key advantage over injectable vaccines.

In addition to our conventional seasonal flu vaccine, we entered into a research collaboration agreement with Janssen in July 2019 to evaluate our proprietary oral vaccine platform for the Janssen universal influenza vaccine program. Under the agreement, we produced a non-GMP oral vaccine candidate containing certain proprietary antigens from Janssen and tested the product in a preclinical challenge model. The preclinical study has been completed and we have submitted a report to Janssen.

Based on the positive results of our preclinical cotton rat study, we believe our proprietary oral vaccine platform has the potential to be the optimal vaccine delivery system for RSV, offering significant advantages over injectable vaccines.

Cervical cancer is the fourth most common cancer in women worldwide and in the United States with about 13,000 new cases diagnosed annually in the United States according to the National Cervical Cancer Coalition.

We have tested our HPV-16 vaccine candidate in two different HPV-16 solid tumor models in mice. The vaccine elicited T cell responses and promoted migration of the activated T cells into the tumors, leading to tumor cell killing. Mice that received our HPV-16 vaccine showed a significant reduction in volume of their established tumors.

In October 2018, we filed a pre-IND meeting request with the FDA for our first therapeutic vaccine targeting HPV-16 and HPV-18 and we subsequently submitted our pre-IND briefing package. We received feedback from the FDA in January 2019 to support submission of an IND application to support initiation of clinical testing. Vaxart plans to initiate its clinical program of an oral HPV tableted vaccine with a clinical trial in young adult women with HPV 16 or 18 associated Cervical Intraepithelial Neoplasia (CIN) Grade 2/3 or 3, pending regulatory and IRB/EC approvals. The trial will evaluate the safety, immunogenicity and preliminary clinical efficacy with repeat dose vaccine administration against a placebo control group.

Additional Objectives

Anti-Virals

Our Tablet Vaccine Platform

Vaccines based on our proprietary VAAST platform are designed to generate broad local and systemic immune responses, which may offer important advantages in addressing a wide range of infectious diseases.

Platform Components

Our platform technology employs a vector-based approach and consists of the following components:

Fig. 2.  Our VAAST Platform.

Caption. Vector-Adjuvant-Antigen Standardized Technology Platform

Our Platform. Combination of the vector-based delivery system, with antigen and adjuvant expressed by the vector.

Adenovirus 5 Vector

Ad5 is an extensively studied and well-characterized vector. Over 200 clinical trials conducted by others have used Ad5 for a wide range of applications, and we believe that using the same adenovirus in our tablet vaccine candidates will reduce regulatory risk, given that it is known to regulatory authorities.

Recombinant Antigen

Our vector contains cloning space where DNA encoding for any recombinant antigen can be inserted. In the vaccine programs pursued to date, we have chosen recombinant antigens that are known to be key targets of the immune system with the ability to generate protection against the corresponding pathogen. The Ad5 vector-adjuvant gene cassette allows for a modular approach.

Adjuvant

We use a short section of double-stranded RNA (“dsRNA”) as an adjuvant to enhance the immunogenicity of our tablet vaccine candidates. dsRNA is a TLR3 agonist and is recognized by the innate immune system as a signal that an undesired viral replication is ongoing, triggering it to mount an immune response in defense. dsRNA is one of the few signals available for use in the intestine as the natural large reservoir of bacteria (the “microbiome”) makes it difficult to use bacteria- related signals. We chose this adjuvant because of its ability to complement the non-replicating adenovirus when administered orally, and because very few pathways of immune system recognition signals occur in the small intestine. Importantly, our adjuvant is expressed within a cell, not provided as a separate component, resulting in a localized response.

Enteric-Coated Tablet

While tablets are typically used to deliver small molecules to the intestine, we have designed our tablets to deliver the much larger adenovirus particles. We hold intellectual property related to the composition and formulation of our tablet vaccine candidates. Our tablet manufacturing does not require sterile fill and finish processing, such as for injectables, but rather uses standard tableting equipment.

How Our Tablet Vaccine Candidates Work

Our tablets are designed to deliver vaccines to the small intestine. The tablets are covered with a protective coating that remains intact in the low pH environment of the stomach and protects the active ingredient contained in the tablet core from the acidic environment in the stomach. The coating is designed to dissolve in the neutral pH environment of the small intestine which we are targeting to generate an optimal immune response. Once the coating has dissolved, the tablets disintegrate, and the vaccine is released into the small intestine where it can reach and enter the mucosal cells lining the intestine. Once inside the mucosal cells, the antigen protein and adjuvant are expressed, or manufactured, by the cells. The adjuvant is molecular in nature and always produced within the exact same intestinal cells that also produce the antigen. Importantly, the production of antigens delivered using our approach is identical to that of the actual pathogen when it invades the mucosa. In addition, we believe that delivering the replication incompetent Ad5-vectored vaccine via tablet directly to the gut avoids neutralization by blood or muscle tissue-based immune cells.

Fig. 3. Our Oral Recombinant Vaccine Platform.

Caption. 1. Enteric-coated tablet is administered. The tablet coating protects the active ingredient from stomach acid degradation. 2. When the tablet reaches the small intestine, it releases the active ingredient, the viral vector, that can then transfect the epithelial cells in the mucosal epithelium and deliver the genes for the two payloads (antigen and adjuvant). 3. Expression of the antigen and adjuvant in the epithelial cells then leads to the TLR3 signaling cascade that can activate B and T cells.

Immune cells come in contact with proteins, and if the protein elicits an immune recognition signal, the immune cell becomes activated. This eventually leads to an immune response, producing either memory cells or large quantities of antibodies that bind to a key antigen. The expressed antigen and adjuvant of its platform, like other vaccines, cause induction of B and T cells specific for the antigen. Induction is believed to begin when an immature dendritic cell (specialized immune cell) absorbs an epithelial cell expressing both the antigen and adjuvant that were delivered by the Ad5 vector. Upon induction, dendritic cells migrate to the regional lymph nodes where they interact with recirculating naive B and T cells. The dendritic cell presents pieces of the antigen on its surface to stimulate T cells, and some of the antigen drains into the lymph node to stimulate B cells. Upon recognizing its specific antigen, small B or T cells stop migrating and enlarge. These then multiply in a clonal fashion and eventually recirculate to the tissues. B cells secrete antibodies that recognize the antigen and T cells find cells that have antigen presented on their surface and either kill the presenting cell or stimulate a local inflammatory response. A successful vaccination occurs if the B cells and T cells can form either memory cells (cells specialized to respond quickly to the protective antigen upon subsequent exposure) or enough antibody to a key antigen is made in large quantity to block infection.

The Significance of Mucosal Immunity and T Cell Responses

The immune system has developed defenses against pathogens by creating a special class of immune effectors, such as mucosal antibodies that are directed to wet surfaces and killer T cells that can kill pathogen infected cells. Most vaccines available today have been developed primarily to elicit blood circulating, or systemic B cell responses. However, there remain many infections, such as norovirus and RSV for which no vaccines exist. These and other pathogens may need greater immune responses outside of serum antibodies. Organisms that cause these infections largely evade the antibody immune response generated by serum antibodies in the blood because the pathogenic organism can pass through cells that line the open, mucosal membranes without coming into direct contact with blood. Alternatively, the serum antibodies are unable to penetrate the cells infected by the pathogen.

Injectable vaccines available today typically do not induce mucosal immune responses, and subunit vaccines do not typically induce strong killer T cell immune responses, which are required to produce an effective level of immunization against several difficult pathogens. Administering vaccines through non-mucosal routes often leads to poor protection against mucosal pathogens primarily because such vaccines do not generate memory lymphocytes that migrate to mucosal surfaces. Although mucosal vaccination induces mucosa homing memory lymphocytes, we believe no complete mucosal recombinant oral vaccines are commercially available. Live attenuated vaccines can pose safety risks, whereas killed pathogens or molecular antigens are usually weak immunogens when applied to intact mucosa. Moreover, the immune mechanisms of protection against many mucosal infections are poorly understood.

One of the key benefits of our technology is delivery to the gastrointestinal tract, enabling the vaccine to directly enter the mucosal surface of the intestine and activate the immune system of the gut. Mucosal vaccine delivery is believed to enhance protection against mucosal pathogens by generating immunity at the very surface where such pathogens invade. Our tablet vaccine candidates target the mucosal immune cells with a vector-based approach and are designed to create a more potent cytotoxic T cell response and mucosal antibody response, which may provide more effective immunity for certain diseases. Besides robust mucosal and systemic antibody responses, we observed potent and poly-functional T cell responses in our human clinical trials, demonstrating that our tablet vaccine candidates efficiently activate both B and T cells.

Oral Non-Replicating Ad5 Vector is Designed to Circumvent Anti-Vector Issues

Injected Ad5 vectored vaccines generate strong anti-Ad5 responses, with up to a 100-fold increase in the anti-Ad5 neutralizing antibody titers. In contrast, our oral Ad5 vectored vaccine is designed to circumvent the complications related to anti-Ad5 immunity, allowing the platform to be used for multiple vaccines and repeat annual and booster vaccinations.

Anti-vector responses have been studied in our H1 influenza Phase 1 and Phase 2 studies, as well as in the two norovirus Phase 1 studies. In the first H1 influenza oral tablet vaccine study in 12 subjects, there were no significant rises in the neutralizing antibody titers to Ad5 following immunization. A Phase 2 challenge study was performed using the same H1 flu oral tablet vaccine in more than 60 subjects. This study found a 2.2 geometric fold rise in neutralizing antibody titers to Ad5, compared to a rise of 1.1-fold in the placebo group. Finally, the rise in vaccine anti-vector immune responses were monitored in the two Phase 1 norovirus vaccine studies, study #101 and study #102. There were no significant increases in the neutralizing anti-Ad5 antibody titers following either one or two doses of vaccine, even at the high dose (see figure below).

Fig. 4. Anti-vector titers pre- and post-immunization.

Caption. In the single dose 101 study, anti-vector titers were measured 28 days after the only dose. In the two-dose 102 study, these were measured 28 days after the second dose. No significant increase in Ad5 titers were observed in any group in the two studies.

In addition, in all studies to date, immune responses to the antigen of choice appeared to be independent from the recipient’s pre-existing anti-Ad5 immune status. In studies with our Ad5 vectored H1 influenza oral tablet vaccine, the pre-existing antibody titers to Ad5 had no effect on the ability of the vaccine to induce a neutralizing antibody response (by hemagglutinin inhibition or microneutralization assay) to influenza. In the two completed Phase 1 studies with our Ad5 vectored norovirus GI.1 oral tablet vaccine, the ability of the vaccine to generate a rise in antibody titers to norovirus or specifically blocking titers to norovirus virus-like particles (“VLP”) (BT50 assay), was not reduced in subjects with pre-existing anti-Ad5 antibody titers. These results are shown below. In conclusion, performance of our Ad5 vectored vaccine delivered orally does not appear to be adversely affected by the pre-existing serum antibody status of the recipient.

Fig. 5. Anti-vector immunity had no effect on the ability of the norovirus vaccine to induce BT50 titers.

Caption. Subjects in the high dose groups were divided based on the preexisting anti-Ad5 titers on day 0. Those with titers ≥ 100 were considered Ad5 positive, those <100 were considered Ad5 negative. The fold increase in BT50 titers for each subject were plotted. Average increase in the BT50 titers for the Ad5 positive group were not lower than the BT50 Ad5 negative group.

Our COVID-19 Program

Market Overview

Vaccines for COVID-19 have been purchased at large scale by governments for mass distribution within countries. In addition, non-government organizations (“NGOs”) and the World Health Organization have set-up purchasing organizations such as COVAX to purchase on behalf of countries without domestic manufacturing and/or with limited resources to make pre-purchase agreements. This central government purchasing is most likely to continue for the next few years. Many of the more affluent countries such as the United States and Canada, have made pre-purchase agreements for doses equating to many times their population. The first wave of vaccines has been effective in Phase 3 trials against the first strain of COVID-19 however distribution and administration issues have been slower than anticipated because of the storage and handling requirements for these vaccines.

The first-generation vaccines seem to have varying levels of efficacy to emerging strains of COVID-19. The current selective pressure of strain adaptation has been in an environment of very low levels of a vaccinated public and strain change may increase in speed as the vaccinated population grows.

There was significant vaccine hesitancy reported before the vaccines were offered to the public; in some countries more than 50% of the population stated they would not take a COVID-19 vaccine. This vaccine hesitancy seems to be waning as more people are vaccinated without SAEs and may end up being similar to rates of vaccine hesitancy for other vaccines such as the influenza vaccine.

We expect this to remain a public market vaccine opportunity for the foreseeable future, however, because of the impact to the freedom of movement for the public and the economic fallout, the overall market for doses may be many times higher than the global market for seasonal influenza vaccines because there may be higher demand by working adults.

Variability of the circulating strains of SARS-CoV-2

SARS-CoV-2 is an RNA virus that naturally evolves genetic mutations over time producing numerous viral variants. Since December of 2019 coordinated global efforts have traced the emergence of SARS-CoV-2 variants, and identified frequent genetic mutations occurring in multiple countries. Viral variants rapidly emerging in many regions of the world, have several genomic changes leading to significant shifts in amino acid sequence and protein structure. During the second half of 2020, three divergent SARS-CoV-2 variants quickly spread - Alpha (B.1.1.7), which originated in the United Kingdom, Beta (B.1.351), which originated in South Africa and Gamma (P.1), which originated in Brazil. In 2021, two additional variants of concern (VOC) have appeared called Delta (B.1.617.2), which originated in India, and Omicron (B.1.1.529), which originated in Botswana. All variants have alterations in key regions of the outer S protein which is utilized by the virus to infect human cells through a receptor called ACE2. Structural changes in the receptor binding portion of the S protein in these variants have been shown to enhanced viral transmission, possibly leading to higher viral loads and worse disease outcomes. More recent data shows that variants have substantial ability to circumvent serum antibodies from the vaccines (https://www.nature.com/articles/s41586-021-04387-1_reference.pdf). Currently, most vaccine strategies under development or approved for emergency use by the FDA, employ the S protein as a vaccine antigen to elicit antibodies responses to block the SARS-CoV-2 virus from entering cells. All existing vaccine formulations comprise of the S protein are derived from the original strain, which may not elicit cross protective antibody responses that block new viral variants from binding to the receptor and entering cells. Data from Johnson & Johnson’ s Phase 3 trial showed that 28 days after vaccination 66% of participants in Latin America and 57% in South Africa were protected from the circulating strains. The recent omicron outbreak showed that three mRNA vaccinations could induce some protection against severe disease and hospitalization, but only 37% protection against infection (proof Canadian study https://www.medrxiv.org/content/10.1101/2021.12.30.21268565v1.full.pdf). These results indicate that, as novel S protein variants continue to emerge, current vaccination approaches will need to be updated or modified to provide sufficient protection against new SARS-CoV-2 mutants. Alternatively, new approaches are needed which create cross-reactive (pan-coronavirus) antibodies and T cells.

Our COVID-19 Vaccine Candidates

Our first vaccine candidate (rAd-S-N, known as Vaxart clinical candidate, VXA-CoV2-1) expresses two different genes from the SARS-CoV-2 virus, the spike protein and the nucleoprotein (“N”). The N protein is more conserved among the coronavirus family of viruses, and inclusion in our vaccine candidate was done in order to create a T cell target even if new and emerging strains of SARS-CoV-2 had substantial mutations in the S protein, thereby reducing the ability of the vaccine to create protective immune responses that recognize the S from these strains. Our candidate was chosen in spring of 2020 based on preclinical results in mice showing that the construct had the ability to elicit antibody and T cell responses in mice, as well as mucosal IgA against SARS-CoV-2 in lungs.

Our second vaccine candidate (rAd-S, known as Vaxart clinical candidate VXA-CoV2-1.1-S) expresses only the S protein from SARS-CoV-2 Wuhan strain. This candidate made improved antibody immune responses in a non-human primate (“NHP”) study compared to other vaccine candidates and was able to inhibit transmission in a hamster transmission experiment.

Preclinical Results

In order to evaluate efficacy of our COVID-19 vaccine, we conducted a hamster challenge study at Lovelace Biomedical (Albuquerque, NM). Hamsters are a good model of SARS-CoV-2 infection because they can be infected via the intranasal route, and can get clinical symptoms such as weight loss, labored breathing, and ruffled fur. They also get lung problems similar to humans. Microcomputed tomographic imaging of hamsters given SARS-CoV-2 revealed severe lung injury that shared characteristics with SARS-CoV-2−infected human lung, including severe multi-lobular ground glass opacity, and regions of lung consolidation. A study by Janssen reported results showing that their vaccine can prevent disease in the same animal model. 

Our topline results showed that two oral administrations of VXA-CoV2-1 (rAd-S-N) at 1e9 IU could substantially protect hamsters from weight loss associated with infection (Fig. N1A), protect against the lung weight gain associated with lung CoV-2 mediated damage (Fig. N1B), and substantially protect against high viral titers in the lungs five days post challenge (Fig. N1C). Oral vaccination with VXA-CoV2-1 reduced the viral titers in the lungs four to five logs (Fig. N1C). Histopathological comparisons between the lungs of untreated animals and VXA-CoV2-1 oral immunized animals showed substantial differences. All untreated animals had mostly moderate (six of eight animals) to marked (two of eight animals) mixed cell inflammation, minimal (one of eight animals) to moderate (two of eight animals) epithelial hypertrophy/hyperplasia in centriacinar areas, mostly minimal (five of eight animals) to mild (three of eight animals) alveolar hemorrhage, and mild (eight of eight animals) epithelial hypertrophy/hyperplasia in the bronchi. All animals that received two doses of the vaccine VXA-CoV2-1 had minimal mixed cell inflammation. There was no evidence of epithelial hypertrophy/hyperplasia in centriacinar areas, alveolar hemorrhage or epithelial hypertrophy/hyperplasia in the bronchi of these animals. Control vaccination by intranasal (i.n.) delivery of VXA-CoV2-1 also induced a similar level of protection as oral delivery. 

The vaccine induced antibody responses in the serum of animals, with both binding Immunoglobulin G (“IgG”) antibodies to S1, as well as neutralizing antibodies measured after oral or intranasal immunization (Fig. N2). Neutralizing antibody titers were measured using the surrogate neutralizing assay (Genscript). The IgG ELISA titers to S increased after boosting the animals in the fourth week of the study.

The second clinical candidate was explored in NHP and hamster studies conducted in 2021.  In a study funded by the Bill and Melinda Gates Foundation and managed by Duke University, hamsters were used to model aerosol transmission from vaccine breakthrough.  Given that even fully vaccinated people are getting infected with the latest variants of concern, and can infect other people, strategies that impact SARS-CoV-2 transmission may be beneficial.  Index hamsters were vaccinated with two doses of oral r-Ad-S (aka VXA-CoV2-1.1-S), using intranasal (IN) r-Ad-S as a control for mucosal stimulation, intramuscular spike protein (IM S) as a protein control, and oral PBS as a mock control. Index animals were then infected via IN delivery, with a high titer of SARS-CoV-2 to replicate a post-vaccination breakthrough infection. One-day post viral challenge, index hamsters were placed upstream of vaccine-naïve hamsters in a chamber that allowed aerosol movement but not direct contact or fomite transmission. Importantly, oral and IN r-Ad-S vaccination significantly decreased or delayed aerosol transmission of SARS-CoV-2 (Fig. N3A) and reduced disease indicators such as lung inflammation and weight loss in unvaccinated naïve animals (Fig. N3E-G), despite the presence of substantial viral RNA in nasal swabs of index immunized animals.  These data demonstrate that oral r-Ad-S immunization resulted in reduced disease and decreased SARS-CoV-2 transmission in the preclinical model, even to unvaccinated/unprotected animals. 

NHP studies were used to measure immunogenicity among different vaccine candidates.  NHPs were immunized with rAd5 by intranasal administration of 5x10¹⁰ I.U on days 1 and 30. Four cynomolgus monkeys per group received vaccine test articles:  ED88 (rAd5-S-N Wuhan), ED90 (rAd-S Wuhan), ED94 (rAd-S beta) and the naïve group received Saline.  A fourth group received an intramuscular injection of purified S protein (from the NIH) on day 1 followed by a boost administration of ED88 on day 30. Animals vaccinated with ED90 induced elevated serum IgG antibody responses against SARS-Cov-2 Wuhan, Beta, Delta S proteins compared to ED88 (Figure N4). Animals immunized with ED90 elicited serum specific IgG to both full length trimerized S and receptor binding domain (RBD).  IgA specific responses to Wuhan, Delta and Beta S proteins were measured. Animals that were immunized with ED90 had higher IgA responses against Wuhan, Delta, and Beta strains compared to ED88 vaccinated animals. ED90 had similar responses to ED94 against the beta variant S protein, but outperformed ED94 against the Wuhan and Delta variants. In summary, the ED90 vaccine candidate induced better serum and mucosal antibody responses against important SARS-CoV-2 variants in the NHPs compared other candidates, and was advanced into the clinic as clinical vaccine candidate VXA-CoV2-1.1-S.

Fig. N1

Figure N1.  Hamsters were immunized on weeks 0 and 4, and challenged intranasally with SARS-CoV-2 on week 8. rAd-S-N was given at 1e9 IU per hamster (either orally or by i.n.).  Untreated animals were given no vaccine, but challenged at the same time as the vaccine groups. N=8 per group.  A. Animals were monitored for weight for 5 days following challenge. Mean (+/- SEMs) are shown for each group.  B. Lung weights on day 5 were taken and normalized by the actual animal weight to calculate a percent of body weight.  Mean (+/- SEMs) are shown for each group.  *** p<0.001 by one way ANOVA with Dunnett's Multiple Comparison's Test. All groups compared to untreated.  C. Lung SARS-CoV-2 titers as measured by qRT-PCR on day 5 post challenge.  Samples with undetectable values were set to ½ the Limit of Quantitation.

Fig. N2

Figure N2.  Antibody responses in serum after 1 or 2 doses of vaccine given at weeks 0 and 4.  Post challenge at week 8.  A. IgG serum ELISA antibody titers to the S1 protein over time.  B. Neutralizing antibody responses (sVNT) at week 8.

Fig. N3

Figure N3.  Oral and intranasal SARS-CoV-2 vaccination decreased SARS-CoV-2 transmission and clinical indicators of disease.  (A) Nasal swabs were collected in naïve animals on days 1, 3 and (B) 5 after exposure to index, infected hamsters in aerosol chamber. Viral RNA loads in these samples were determined by quantitative reverse transcription PCR (qRT-PCR) of the N gene. (C) Lung tissue was collected at necropsy (day 5) and RNA was isolated for SARS-CoV-2 detection by qRT-PCR of the N gene and (D) infectious viral titers were determined by TCID₅₀. (A-D) The dotted line represents LOD, with data below the limit of detection plotted at ½ LOD. Data were analyzed by a one-way ANOVA and Dunnett’s multiple comparisons. (E) terminal body weights were determined by the percent of day 0 (relative to SARS-CoV-2 inoculation). (F) Terminal lung weights and (G) lung pathology scores were determined. Severity grade for red discoloration of the lung was based on a 0 to 4 scale indicating percent of whole lung affected: none (no grade), minimal (1), mild (2), moderate (3), marked (4) correlating to 0, 1-25, 26-50, 51-75, and 76-100% affected, respectively. (E-G) Data were analyzed by a one-way ANOVA and Tukey’s multiple comparisons. (A-G) Error bars represent the SEM. *P <0.05, ** P <0.01, *** P < 0.001, **** P<0.0001.

Fig. N4

Figure N4: Mucosal immunization with ED90 elicits strong cross-reactive IgG in the serum and nasal IgA. Animals were immunized on D1 and D30 with vehicle control (open circles), ED88 (green circles), ED90 (black circles), ED94 (red circles), or primed on D1 with IM delivery of spike protein followed with ED88 boost on D30 (blue circles). Serum IgG to full length trimerized spike (A) Wuhan (B) Beta variant (B.1.351) and (C) Delta variant lineage (B.1.617.2) was measured at D0, D15, D30, D45 and D60 post vaccination. MSD relative light units; SEM (n = 4). Specific nasal IgA against full length trimerized spike (D) Wuhan (E) Beta variant (B.1.351) and (F) Delta variant lineage (B.1.617.2) was quantified and normalized to total IgA in each sample timepoint. Nasal IgA expressed at fold change from baseline levels.

Clinical Trial

Phase 1 - VXA-COV2-101

The Phase 1 study utilized an open-label, dose-ranging design to evaluate the safety and immunogenicity of Vaxart’s tablet adenoviral-vector based vaccine (VXA-CoV2-1), which expresses a SARS-CoV-2 antigen and dsRNA adjuvant, when administered orally to Healthy Adult Volunteers. Under the Phase 1 protocol 35 participants were enrolled (October - November 2020) and received either a low dose (n=20) or mid dose (n=15) of the vaccine VXA-CoV2-1. Five subjects in the low dose group received a boost 4 weeks after their initial vaccination. Study subjects were followed for safety and immunogenicity for 4 weeks following their last vaccination, and then entered a safety follow-up period which will last for 1 year following their last vaccination.

Male or female volunteers who were between the ages of 18 to 54 years with body mass index (BMI) between 17 and 30 kg/m² at screening, inclusive who are at low risk of exposure to SARS-CoV-2, screened negative for SARS-CoV-2 infection at the time of screening and were in general good health, without significant medical illness, based on medical history, physical examination, vital signs, and clinical laboratories (complete blood count, chemistry, and urinalysis) as determined by the investigator in consultation with the medical monitor and sponsor were eligible to participate in this study. Post confirmation of eligibility, 5 sentinel subjects were enrolled into Cohort 1 and immunized with the low dose (1x10¹⁰ IU ± 0.5 log) VXA-CoV2-1 oral vaccine.

The primary objective was to determine the safety of a SARS-CoV-2 (VXA-CoV2-1) oral vaccine delivered by enteric tablet. Safety and tolerability were evaluated through the detection and documentation of solicited symptoms of reactogenicity (7 days post each vaccination), unsolicited AEs (through 28 days post last vaccination (Day 29); Day 57 for Cohort 1), SAEs, MAAEs, including evidence of COVID-19, and vaccine enhanced disease (through Day 360). Clinical laboratory (blood chemistry, hematology, and urinalysis) results, physical examination, and vital signs results were also assessed.

Safety Results

Solicited symptoms were reported by 40% of study participants (15 out of 35 subjects), with more subjects reporting symptoms in the mid dose (67%) versus the low dose (20%). The most commonly reported solicited symptoms were nausea (14%) and headache (14%), followed by diarrhea (11%) and malaise/fatigue (11%). Most reported solicited symptoms were mild in severity and resolved without the need for medical treatment; additionally, no subjects discontinued due to a solicited AE.

A total of nine unsolicited AEs were reported by six subjects during the study active period (through Day 57). All unsolicited AEs were mild in severity and resolved without the need for medical treatment. Subjects are currently within the safety follow-up period four to five months post initial vaccinations. No SAEs have been reported to date.

Immunogenicity Results

T cell Polarization and T cell Induction.  As part of the anti-viral immune response, T cells are important as they can act as specific ‘killers’ that can seek out and destroy viral infected cells to control infection and prevent severity of disease. Vaccination with a SARS-CoV-2 vaccine (such as with VXA-CoV2-1) should induce an increase in T cells that recognize SARS-CoV-2 infected cells. However, T cells can produce either a protective (Th1) or an allergic response (Th2) upon activation. A primary immunological endpoint in this clinical study was to measure the polarization of the SARS-CoV-2 specific T cells, whether it was towards a protective Th1 response or an allergic Th2 response. This was measured using a restimulation assay where peripheral blood mononuclear cells (“PBMCs”) taken both pre- and post-vaccination were cultured with SARS-CoV-2 peptides from either the spike protein (S) or Nucleoprotein (N) and the Th1/Th2 responses were measured. 26 pairs of PBMC samples from day one and day eight were able to be assessed from the study, pre and post a single dose; the remaining samples were not either not available or of poor quality to assess. No significant increase of Th2 responses, defined as IL5/IL4/IL13 released from CD4 T cells, was observed to either the Spike (S) or Nucleoprotein (N) in any of the subjects measured, with 0/26 having a twofold increase at day eight post vaccination and with the average percent increase on day eight in response to N was 0.09/0.02/0.04 percent and to S was 0.02/0.09/0.1 for IL5/IL4/IL13 respectively (Fig. N5c).

The majority of subjects had an increase in Th1 responses, defined as IFNg/TNFa/CD107a, particularly from CD8+ T cells in response to S peptides (Fig N5A-B). In response to S peptides, 13 of 26 (50%) subjects had a twofold or higher increase in Th1 cytokine release, or in the case of CD107a, expression from CD8 T cells and 17 of 26 (65%) had a 1.5-fold or higher increase. 19 of 26 (73%) subjects had any measurable CD8 T cell response above baseline. Average percent increase on d8 above pre-vaccinated baseline was 1.5/4.6/1.95 for IFNg/TNFa/CD107a respectively. Five of 26 (19%) of subjects had CD4 T cells that had a twofold or higher increase, with 14 of 26 (54%) having any measurable CD4 T cell response above baseline. The average percent increase of CD4 T cells was 0.6/1.0/0.9 for IFNg/TNFa/CD107a respectively. In response to N peptides nine of 26 (35%) had a twofold or higher increase of Th1 responses from CD8 T cells over pre-vaccinated baseline, with 11 of 26 (42%) having a measurable CD8 T cell response. Only one of 26 had a Th1 CD4 T cell response to N that was twofold or higher, with nine of 26 (35%) having some measurable CD4 T cell response to N. The average % increase in CD8 was 0.1/0.2/0.6 and in CD4 was 0.08/0.08/0.2 for IFNg/TNFa/CD107a respectively. The high magnitude Th1 CD8 T cell response to S without discernible Th2 response suggests that vaccinating subjects with VXA-CoV2-1 increased the protective anti-viral responses without the potential adverse events occurring from Th2 responses.

Fig. N5

Figure N5.  T cell polarization and characterization.  A. Increase in IFN-γ producing CD8 T cells post immunization on day 8 versus day 1. Paired T test was used to compare frequencies before and after vaccination.  B. IFNγ, TNFα, and CD107a percent of CD8 T cells increase over background post immunization.  C. Polarization toward Th1 responses versus Th2 responses in subjects immunized by VXA-CoV2-1.

B cell responses. The major goal of vaccination is to induce an immune response that mediates protection from infection or disease. B lymphocytes, also known as B cells, play an important role towards this goal by producing antibodies that can specifically recognize and inhibit infectious agents. B cells can produce antibodies in different forms, each type with distinct characteristics and roles. B cells with the isotype A (“IgA”) antibodies are the ones preferentially secreted at mucosal surfaces, such as the respiratory tract, where they prevent foreign substances from entering the body. The ability of our candidate vaccine to promote specific B cells capable of making high levels of antibodies (called ‘plasmablasts’) was tested using both flow cytometry-based measurements and an antibody-secreting cell (ASC) assay by ELISPOT. Flow cytometry allows measurement of proteins expressed by the cells, either on the surface or inside the cell. We explored immune cell populations in the peripheral blood. This analysis revealed a significant expansion in the overall plasmablast population 8 days after vaccination (p<0.0001, Wilcoxon test) with 69% of vaccinees in this study showing a twofold or higher increase in the frequencies of these antibody-secreting cells when compared to baseline levels (Figures N6A-B). Further investigation indicated upregulation of both IgA and the mucosal homing receptor b7 on the surface of circulating plasmablasts post vaccination, particularly in the higher dose cohort (p=0.0261, Mann-Whitney test), thus suggesting vaccine-induced migration of this IgA-producing B cell population to mucosal tissues (Figure N6c). Contextually, the ELISPOT assay also confirmed a strong production of IgA-secreting ASC on day 8 after vaccination (fourfold median increase over day 1 levels), additionally highlighting the ability for these cells to recognize and bind the S1 domain of the SARS-CoV-2 S protein (Figure N6d).

Fig. N6

Figure N6.  A. Frequency of CD27++ CD38++ plasmablasts in peripheral blood before (day one) and after (day eight) vaccination as measured by flow cytometry. Bars represent median values, while error bars correspond to 95% confidence intervals. Wilcoxon test was used to compare frequencies before and after vaccination;  B. Fold change (day eight compared to day one) in plasmablast frequencies. A total of 24 of 35 subjects (69%) showed a twofold or higher increase (with a 3.3 median fold change increase overall);  C. Fold change (day eight compared to day one) of IgA- and B7-expressing plasmablasts in low and high dose vaccine cohorts. Mann-Whitney test was used to compare frequencies between the two different dose groups;  D. Fold change (day eight compared to day one) in the number of IgA-positive antibody-secreting cells (ASC) reactive against the S1 domain of S.

Antibody Responses.  Serum samples were measured for neutralizing antibodies. No neutralizing antibodies were found in the serum at day 29 (and day 56 for the five subjects given two low doses). Increases in IgG responses were measured in the serum of only a few subjects. Local immune responses at the site of infection are of particular interest due to their ability to block viral entry, and IgA is considered to be the first line of defense at most mucosal tissues. To measure the immune response in the mucosa, nasal and saliva samples were taken. Sera samples were taken as well, as serum can also contain IgA. Levels of IgA antibodies were measured using a multiplex assay on the Meso Scale Discovery platform that measures antibodies to SARS-CoV-2 S protein, N protein and the Spike Receptor Binding Domain (“RBD”). This platform allows capture of antibodies specific for multiple antigens at once using a lower sample volume than a traditional ELISA format. In a preliminary analysis, a twofold or more increase above pre-vaccination samples in SARS-CoV-2 specific IgA found in the various compartments was detected in 18 of 35 subjects (52%) 29 days post vaccination. 11 of 35 (32%) had a twofold or above response to S protein, 13 of 35 (37%) had a twofold or above response to N protein, 16 of 35 (46%) had a twofold or above response to RBD, with 14 of 35 (40%) having a twofold or above response to two or more antigens. In Cohort 1, where subjects had two doses, four of five (80%) had SARS-CoV-2 IgA responses twofold or above and five of five (100%) had responses 1.5-fold or above in one or more compartments. These results include all subjects. Because samples that may lack any IgA in them are unlikely to show specific antibody responses, future work will normalize samples by the total amount of IgA and discard samples without any IgA from the analysis.

Fig. N7

Phase 2a Study VXA-COV2-201:  Part 1 - Dose Optimization in Adults

We initiated dosing in Part 1 of a Phase 2a study in the October 2021 utilizing an open-label, dose-ranging design (Part 1) to evaluate the safety and immunogenicity of Vaxart’s tablet adenoviral-vector based vaccine (VXA-CoV2-1.1-S), which expresses a SARS-CoV-2 antigen (S protein) and dsRNA adjuvant, when administered orally to healthy adult volunteers. Under Part 1 of this Phase 2a protocol 96 participants are being enrolled in two cohorts of 48 participants each, to receive either a low dose (n=24) or a high dose (n=24) of the vaccine VXA-CoV-2-1.1-S. Cohort 1 will enroll subjects that are naïve to any prior SARS-CoV-2 vaccination or prior SARS-CoV-2 infection, and Cohort 2 will enroll subjects who have received two prior mRNA SARS-CoV-2 vaccinations at least 6 months prior with no history of prior SARS-CoV-2 infection. Additionally, each cohort will enroll 24 subjects that are young adults aged 18 to 55 and 24 subjects aged 56 to 75.  As such the study will be enrolled in 8 cohorts of 12 subjects each, as shown in Table 1. All subjects will receive a boost four weeks after their initial vaccination. Study subjects will be followed for safety and immunogenicity for four weeks following their last vaccination, and then entered a safety follow-up period which will last for one year following their last vaccination. The study design is shown in the table below:

Table 1. VXA-COV2-201 Dose Proposal

After signing an informed consent, participants will undergo screening assessments to determine study eligibility over a 30-day screening period. On Day 1, eligible participants will be enrolled sequentially to receive their first oral vaccination according to their assigned cohort. During the active study period, participants will record daily symptoms of reactogenicity for one week post each vaccination, administered on Day 1 and Day 29 using a Solicited Symptom Diary. They will return to the site to have safety assessments and samples collected for evaluation of immunogenicity periodically during the study period.

At Day 29, participants will have pre-vaccination safety assessments to determine eligibility to continue with the second vaccination (negative pregnancy test, absence of acute illness or new medical condition, occurrence of any treatment related Grade 3 or 4 AE or SAE). All participants who receive both vaccine administrations (Day 1 and Day 29) will enter the follow-up period after Day 57, and will be monitored for SAEs, MAAEs and for exposure to and/or symptomatic COVID-19 through Month 13/End of Study (EOS) visit. In addition, these participants will be evaluated for immunogenicity.

The primary objective in this study will be to determine the safety and tolerability of a SARS-CoV-2 (VXA-CoV2-1.1-S) oral vaccine delivered by enteric tablet to allow dose selection for the larger Part 2 of the Phase 2a protocol. Safety and tolerability will be evaluated through the detection and documentation of solicited symptoms of reactogenicity (seven days post each vaccination), unsolicited AEs (through 28 days post last vaccination (Day 29); Day 57 for Cohort 1), SAEs, MAAEs, including evidence of COVID-19, and vaccine-activated enhanced disease. Clinical laboratory (blood chemistry, hematology, and urinalysis) results, physical examination, and vital signs results will also be assessed. Secondary endpoints will include assessment of long-term safety (through Day 390), and assessment of immunogenicity with a repeat-dose vaccination schedule in healthy adults at three dose levels. Topline data from Part 1 of the clinical study is expected to be available in the first half of 2022.

Additionally, international Phase 1b and Phase 2 COVID-19 trials, including a placebo-controlled efficacy trial in India, are anticipated to begin this year, though there can be no assurance that these trials will occur.

Our Norovirus Program

Market Overview

Norovirus is the leading cause of vomiting and diarrhea from acute gastroenteritis among people of all ages in the United States. Each year, on average, norovirus causes 19 to 21 million cases of acute gastroenteritis, and contributes to 56,000 to 71,000 hospitalizations and 570 to 800 deaths, mostly among young children and older adults. Typical symptoms include dehydration, which is the most common complication, vomiting, diarrhea with abdominal cramps, and nausea. A study conducted by the CDC and Pittsburg School of Medicine in 2012 estimated that the total economic burden of norovirus in the United States was $5.5 billion. In the U.S., we believe a norovirus vaccine would be beneficial for high-risk groups such as infants and children up to five years old, older adults and the elderly, as well as for workers in the food and travel industries, for healthcare, childcare and elder care workers, first responders, the military, and leisure and business travelers. In a study published by Johns Hopkins University and the CDC in 2016, the total global economic burden of norovirus was estimated at $60 billion, $34 billion of which occurred in high income countries including the United States, Europe and Japan. In a more recent health economic study published in the Journal of Infectious Diseases in July 2020 the economic impact to the U.S. was estimated to be $10.5 billion annually and in a January 2021 publication in the American Journal of Preventive Medicine the potential cost savings afforded by of a norovirus vaccine were estimated to be $500 per year in children under five and $75 per year in adults aged 65 and older. There are currently no approved vaccines or therapies to prevent or treat norovirus infection.

Our Norovirus Vaccine Candidate

We plan to develop a VP1-based bivalent oral tablet vaccine that protects against norovirus GI and norovirus GII, the two major norovirus genogroups affecting humans, by targeting the norovirus GI.1 Norwalk strain and the norovirus GII.4 Sydney strain. Because norovirus is an enteric pathogen that infects epithelial cells of the small intestine, we believe that a vaccine that produces antibodies in the intestine against norovirus locally in the intestine, such as our tablet vaccine candidate which is delivered directly to the gut, may provide optimal protection against infection.

Preclinical Results

We have conducted multiple preclinical studies of our norovirus vaccine candidate in mice and ferrets. Overall, as compared with injectable VP1 protein vaccine, our norovirus vaccine candidate generated comparable levels of serum antibody and superior levels of mucosal antibody to the VP1 injectable protein vaccine.

Clinical Trials

We have completed two Phase 1 studies with our monovalent tableted norovirus GI.1 oral tablet vaccine, and one Phase 1b study with our bivalent tableted vaccine (co-administration of GI.1 and GII.4 vaccines). In all three studies, the primary endpoint was safety and the secondary endpoint was immunogenicity. In the bivalent study we also evaluated potential interference with co-administration.

Study 101. Placebo Controlled Study

In the Phase 1 study designed to evaluate the norovirus vaccine (VXA-GI.1-NN), 66 healthy adults were randomized in three groups, with 23 subjects receiving a single low dose of 1 x 10¹⁰ IUs, 23 subjects receiving a single high dose of 1 x 10¹¹ IU, and 20 subjects receiving the matching placebo control.

Safety Results. 101 Study

Solicited Events. In the first seven days following study drug administration, 35 study subjects had at least one SAE reported with 25 of 46 (54%) subjects in the VXA-GI.1-NN vaccine groups and 10 of 20 (50%) of subjects in the placebo group (See table below). All the solicited AEs reported (n=46) were grade 1 or 2 in severity with the majority being mild events (44 grade 1 and two grade 2 events). The percentage of subjects with any solicited symptoms was similar among treatments (See table below). Diarrhea and headache were the most common solicited symptoms following VXA-GI.1-NN administration, both reported by 15 (33%) subjects in the treated groups. Headache and nausea were reported evenly across treatments, including placebo. The only solicited symptom demonstrating a statistically significant difference from placebo was diarrhea (p = 0.0275), reported by 11 subjects in the high dose group. Nine of the 11 subjects reported mild severity diarrhea, while two subjects reported moderate severity episodes following the high dose vaccine. Onset of diarrhea (verbatim term “loose stools”) ranged from day 1 to day 6 following vaccine administration, and most episodes resolved within one day. At no point did any of the loose stools impact normal activity such as work or school, and none required treatment with anti-diarrheal medications or rehydration therapy. In summary, the vaccine appeared well-tolerated without causing any dose limiting toxicities.

Table 2. Norovirus Study 101 Solicited Systems – Number and Percent of Subjects Reporting Treatment Emergent Adverse Events (“TEAEs”).

(1) Solicited symptoms were collected from subjects for seven days following immunization.

Unsolicited Events. A total of 83 unsolicited TEAEs, were reported by 33 of the 66 subjects within the first 28 days post dosing, with slightly more placebo subjects 12/20 (60%) reporting adverse events than low dose 11/23 (48%) or high dose vaccinated subjects 10/23 (44%). Headache was the most common adverse event reported in all treatment arms. Most TEAEs were mild or moderate in severity. The site investigator considered 28 TEAEs possibly related, 42 unlikely related, and 13 not related.

Study 102. Dose and Schedule Optimization

The open-label, dose optimization study was designed to evaluate the norovirus GI.1 monovalent vaccine (VXA-GI.1-NN) in 60 subjects given multiple doses with some differences in schedule for the lower dose groups. The first three groups enrolled (N=15 each) used low doses of 1 x 10¹⁰ infectious units (IU). Group A received two doses of VXA-GI.1-NN on days 0 and 7, group B received three doses on days 0, 2, and 4, and group C received two doses on days 0 and 28. The fourth group, group D (N=15), evaluated two high doses of 1 x 10¹¹ IU given on days 0 and 28. The primary endpoint of the study was to evaluate the safety and tolerability of all dosing regimens and the secondary endpoint was to compare immunogenicity between groups by BT₅₀ titers and antibody secreting cells (ASC) counts.

Safety Results. 102 Study

In the first seven days following study drug administration, there were 27 subjects reporting adverse events, distributed across the groups with the highest number of reporting adverse events in group C (11 of 15) and the lowest in group D (3 of 15). The most common adverse event reported was headache, reported in 21 subjects out of 60. Group C reported the highest number of headaches, and adverse events overall. This group was given two low dose vaccines 28 days apart. This was not observed in group D, a vaccine group given the exact same dosing schedule, but receiving two tenfold higher doses of vaccine.

Table 3. Norovirus Study 102 Solicited Symptoms – Number and Percent of Subjects Reporting TEAEs.

Group A:  Low Dose - Day 0, 7                    Group B:  Low Dose - Day 0, 2, 4 

Group C: Low Dose - Day 0, 28                   Group D: High Dose - Day 0, 28

Solicited symptoms were collected from subjects for seven days following immunization.

Study 103. Placebo Controlled Study

In this Phase 1 study (VXA-NVV-103) designed to evaluate the bivalent norovirus vaccine administration (VXA-GI.1-NN and VXA-GII.4-NS), 80 healthy adults were randomized into one of four treatment groups. Treatment Group 1 had an open-label sentinel group of five subjects who were enrolled prior to initiation of the subsequent treatment groups. The five sentinel subjects received the monovalent GII.4 vaccine and were monitored for safety and immunogenicity. Randomization was 1:1:2:1 for Treatment Groups 1 through 4, respectively. Patients received the complete investigational dose of 5 × 10¹⁰ IU within the monovalent vaccine treatment arms and 1x 10¹¹ IU in the bivalent treatment arm or placebo tablets.

Safety Results. 103 Study

Solicited Symptoms. In the first seven days following study drug administration, 37 study subjects had at least one solicited adverse event reported with 33/65 (51%) subjects in the VXA-NNV-103 vaccine groups and 4/15 (27%) of subjects in the placebo group (See Table 3). Most subjects reported solicited symptoms that were mild in intensity. Five subjects reported solicited symptoms of Grade 3 severity. The percentage of subjects with any solicited symptoms was similar among treatments (See table below). Diarrhea and malaise were the most common solicited symptoms following vaccine administration, reported by subjects in all three active treated groups (20%-27% subjects). The incidence of diarrhea was higher across the vaccine treated subjects compared to placebo. The incidence of nausea and headache was highest in Bivalent GII.4/GI.1 group compared to other groups. The incidence of malaise/fatigue was higher across the vaccine treated subjects compared to placebo. Myalgia and fever were reported only in the vaccine treated subjects. In summary, both vaccines were safe when given as a monovalent vaccine or in combination as a bivalent vaccine. The most common symptoms were mild diarrhea and mild malaise both reported in about 20% of vaccine recipients. There were no deaths, serious adverse events, adverse events of special interest, new onsets of chronic illness, or subject discontinuations due to TEAEs in this study.

Table 4. Norovirus Study 103 Solicited Systems – Number and Percent of Subjects Reporting TEAEs.

Solicited symptoms were collected from subjects for seven days following immunization

Unsolicited Events. A total of 14 subjects reported a TEAE. The incidence of TEAEs was highest in the placebo group (33.3%) compared with the monovalent GI.1 group (26.7%), monovalent GII.4 group (15.0%), and the bivalent GII.4/GI.1 group (6.7%). The incidence of study vaccine related TEAEs was highest in the monovalent GI.1 group (20%) compared with the placebo group (13.3%), monovalent GII.4 group (5.0%), and the bivalent GII.4/GI.1 group (3.3%). One subject in the monovalent GII.4 group reported an SAE of Hyperemesis Gravidarum which was deemed by the site investigator to be unrelated to study drug.

Safety Summary from the Three Studies.

186 subjects were treated with Vaxart norovirus vaccines in the three Phase 1 studies. The vaccine was well tolerated, with no severe adverse events that were attributable to the vaccine reported in any study. The most common solicited adverse event was headache (27.5%), but this was relatively similar to the 28.6% of subjects in the placebo group. In two of the studies there was a higher incidence of diarrhea (20.5%) reported in the vaccine treatment groups versus the placebo group (11.4%). However, in the high dose group in the 102 study, there was only one subject (6.7%) reporting diarrhea even after receiving two administrations of vaccine at the highest dose. These results in total suggest that there were no dose dependent effects that impacted safety.

Immunogenicity Results-Study 101

BT50 Titers. The primary immunological endpoint was to measure antibody titers by an assay that assessed the ability of antibodies to block interaction of a norovirus VLP to histogroup blood antigen (HGBA). This assay is known as the BT50 (for 50% inhibition of blocking titer) assay. BT50 titers were assessed using Le^b synthetic glycan as the coating antigen. Titers rose in the vaccine recipients, and at all timepoints (Figure 6). By the Le^b BT50 assay, 14/23 (61%) of the subjects in the low dose group, and 18/23 (78%) in the high dose group, had at least a two-fold rise. One subject in the placebo group had a greater than two-fold rise. On Day 28, the geometric mean titer (GMT) for the low dose vaccine group was 59.0, a 2.3-fold geometric mean fold rise (“GMFR”) over the initial GMT of 26.2 at baseline. The GMT for the high dose vaccine group was 98.5, a 3.8-fold GMFR over the initial GMT of 25.8 at baseline. The high dose group was significantly increased over placebo on day 28 (P=0.0003). Complete results are given in the table below.

GMT for Le^b BT50 assays

Table 5. Study 101, Least Squared Geometric Mean Titer (LSGMT) for Le^b BT50 assay.

*Significance by Mann-Whitney vs. placebo; overall significance by Kruskal-Wallis Test.

Antibody Secreting Cell (ASC). The ability of the vaccine to induce norovirus specific B cells in the peripheral blood was measured by ASC assay. This assay essentially counts the number of B cells that emerge after immunization and recognize norovirus in the peripheral blood. The number that circulate in the blood pre-immunization is very low, so the assay is a meaningful way to evaluate the vaccine specific effects. In the low dose group, 16 of 23 (70%) of subjects responded and in the high dose group, 19 of 23 (83%) of subjects responded on day seven for both IgA and IgG ASCs (Figure 7). Background ASCs were generally negligible on day 0. For the high dose vaccine treated group, an average of 561 IgA ASCs and 278 IgG ASCs each per 1 x 10⁶ peripheral blood mononuclear cells (“PBMC”), were found on day 7. For the low dose vaccine treated group, an average of 372 IgA ASCs and 107 IgG ASCs were found on day 7. The placebo group had no responders with an average of 3.3 spots for IgA ASCs and 2.2 spots for IgG ASCs per 1 x 10⁶ PBMC on day 7. The treated groups were significantly different than placebo in terms of the ability to elicit an IgG or an IgA ASC response at day 7 (P<0.0001, Mann-Whitney). There was no statistical difference in the number of spots for IgA and IgG ASCs between the high and low dose groups (P=0.21 for IgA, P=0.28 for IgG).

Enzyme-linked immunosorbent assay (ELISA) IgA and IgG. Serum antibody responses were measured by IgG and IgA ELISA, and the changes in titers at EC50 between days 0 and 28 were calculated for each subject. Most subjects had an increase in antibody titers post immunization. The average change in EC50 for the low dose group was 16 and 7.1-fold in IgA and IgG, respectively. Similarly, the average change in the EC50 for the high dose group were 9 and 5.4-fold for IgA and IgG, respectively. The changes in each subject’s EC50 are plotted, separated by group (Figure 8).

Memory Cells. Memory cells are long-lived cells that are important for the rapid induction of immunity following infection. A goal of most vaccines is to safely induce immunological memory to protect people from actual infection. Antigen specific memory B cells were investigated after culturing PMBCs with polyclonal stimulators. VP1 specific IgG memory B cells were higher than IgA memory B cells in the day 0 samples (Figure 9). Post immunization, the response at day 7 was higher for IgA memory B cells, with a GMFR of 15.3 for IgA versus 6.5 for IgG between day 0 and 7, before declining again at day 28. In the low dose group, the GMFR was 7.4 for IgA and 3.7 for IgG was observed between days 0 and 7. This decline from day 7 to day 28 may have resulted from homing of circulating B cells from the peripheral blood to the intestinal lymphoid tissues via expression of high levels of the mucosal homing receptor, α4β7. In the high dose group at day 7, 20/23 (87%) IgA and 19/23 (83%) for IgG showed ≥ 2-fold increase over day 0. In the low dose group at day 7, 18/23 (78%) for IgA and 13/23 (57%) for IgG showed ≥2-fold increase over day 0.

Fecal and Saliva IgA. Norovirus VP1 specific mucosal IgA was explored directly by looking at fecal and saliva samples. Because the quantity of IgA is highly variable within these samples, total IgA was also measured and the ratio between VP1- specific IgA/total IgA for each sample was examined. Samples with IgA levels below the detection limit were excluded from analysis. The increase in the ratio of specific IgA to total IgA was measured between baseline and day 28 (and baseline and day 180 for fecal IgA). In the high dose group, 9 of 19 (47%) fecal samples were responders with a four-fold rise or greater IgA response at day 28, and 9 of 21 (43%) at day 180 (Figure 10). The average fold increases in specific IgA/total IgA ratio were 17.2 and 9.7. These results are significantly higher than the placebo group where 2/18 (11%) and 0/16 (0%) were found to have fourfold or better increases on days 28 and 180 (P=0.029 and P=0.0049 respectively), with average increases of 1.8 and 1.0 (Figure 10). The low dose group had a similar response as the high dose, with 7 of 20 (35%) and 5 of 16 (31%) with fourfold or greater increases on days 28 and 180 respectively. The number of responders trended higher than placebo on day 28, but the difference was statistically significant on day 180 (P=0.13 and 0.043). The low dose group had a 36.2-fold increase on day 28, and a 5.6-fold increase on day 180 (Figure 10). Fewer subjects had detectable increases in the specific IgA to total IgA ratios in saliva samples of treated subjects at day 28 (Figure 11). The average increase in the specific IgA/total IgA ratio was 2.0 for the low dose, 2.9 for the high dose group, and 1.2 for the placebo group. The high dose and low dose groups had each had four subjects with a fourfold rise in the specific response, versus none for the placebo group. These results demonstrate that the vaccine can induce antibody responses that are measured in the mucosa, particularly in the intestinal mucosa, which is the site of norovirus infection.

Fig. 6. Geometric Mean Titers vs. Time.

Caption. Geomean Serum BT50 Titers over time for Le^b.

Fig. 7. ASC Titers on Day 7 post immunization.

Caption: ASC counts on day 7 for both IgG and IgA responses to norovirus VLP. This assay measures antigen specific B cells in the peripheral blood that occur post vaccination.

Fig. 8. ELISA antibody changes post immunization.

Caption. Change in IgA or IgG ELISA titers post immunization between days 0 and 28 for all subjects divided by treatment group. Each symbol represents an individual subject. The long horizontal line represents the mean, with the smaller lines the 95% confidence interval.

Fig. 9. Memory Cell Responses pre- and post-immunization.

Caption: Norovirus VP1 specific memory B cell counts were plotted for each time point. Each symbol represents an individual subject. The long horizontal line represents the geometric mean.

Fig. 10. Fold Induction in Norovirus Specific Fecal IgA Responses Post Immunization.

Caption. Fecal responses to the vaccine, with fold increase in specific IgA/total IgA for each subject (divided by group and each timepoint) plotted. Average increase is the black bar.

Fig. 11. Fold Rise in Norovirus Specific Responses in Saliva.

Caption. Saliva IgA responses were measured. The plot shows fold rise of specific IgA/ total IgA post immunization. Responses were compared between days 0 and 28.

Immunological Results - 102 Study

BT50 Titers. The objective of the study was to compare schedules and dosing for the ability to elicit immune responses, particularly by evaluating BT50 titers. BT50 titers were assessed at multiple times points, given that multiple doses were given. In the high dose group, 12 of 15 subjects had a 2-fold or greater increase in BT50 titers after the first dose and 14 of 15 subjects (92%) had a 2-fold or greater increase in BT50 titers after 2 doses. The GMT titer rose from 21.3 on day to 85.1 on day 28 for a 3.8 GMFR. The GMT at day 56 were measured to be 75.8, a GMFR of 3.6 over the baseline values. Other groups given lower doses of vaccine had lower response rates. Groups A and C had higher increases in the titers compared to Group B, although this is not statistically significant. An ANCOVA model was used to determine the statistical significance of the increases in GMFR. Least-squares (“LS”) geometric mean titers (“LSGMTs”) and LS geometric mean fold rises (“LSGMFRs”) were calculated by exponentiating the LSMs from the ANCOVA model, which included log-transformed post baseline titer or log-transformed change from baseline titer as a dependent variable, cohort as a factor, and baseline log-titer as a covariate. The significance in the different groups to increase the GMFR (test is LSGMFR=0), was found to be P=0.0008, 0.1224, 0.0004, and <0.0001 for groups A through D respectively at day 56. This means all groups had statistically significant increases in the GMT except for group B, which had a more modest increase in the titers.

102 Study. BT50 Titers, Le^b

Table 6. Study 102, Geometric Mean Titer (GMT) for Le^b BT50 assay roger.

ASCs. Additional immunological analysis was performed by comparing the ASC responders between groups. The high dose group had 14 out of 15 subjects respond to the vaccine, with an average IgA ASC count of 698 per 1X10⁶ cells. Following a second dose, the subject that didn’t respond the first time had a significant increase in ASC counts so all 15 subjects (100%) were able to elicit an ASC response following two doses. As typical, subjects that had a high number of ASC counts after the first immunization had a low response after the 2^nd dose. The low dose groups were compared by examining the overall response rate, since the dosing and the analysis were performed at different intermediate timepoints. Group A had the highest overall response rate where 12/14 subjects (86%) were able to induce meaningful ASC responses after one or two doses. Slightly lower responders were observed in group B, where only a few subjects had a response after the first dose, but more subjects responded after additional vaccine doses. Group C had the most variable responses of any group. The average number of spots was 839 per 1X10⁶ cells after the first dose, but this was the result of several subjects having extremely high numbers of spots (three subjects had greater than 1500 per 1X10⁶), mixed with many subjects that didn’t respond at all.

By Fisher’s Exact test, the high dose group induced a higher number of responders than group C p=0.02), but only trended higher than groups A and B (0.22, 0.07). Similar results were observed for the IgG ASC responses, with slightly lower values on average.

Fig. 12. IgA ASC Counts for the 102 study.

Caption. The different groups were assessed for IgA ASC counts at each time point taken for each group. Because there were different dosing regiments for each group, there were different timepoints assessed. Response rates at each timepoint are indicated by a fraction and a percentage below each timepoint. The overall response rate (the total number of subjects that responded at any time point) is given near the top of each group. For example, in the last group, 15/15 (100%) subjects responded at either D7 or D35.

Fig. 13. IgG ASC Counts for the 102 Study.

Caption. The different groups were assessed IgG ASC counts at each time point taken for each group. Because there were different dosing regiments for each group, there were different timepoints assessed. Response rates at each timepoint are indicated by a fraction and a percentage below each timepoint. The overall response rate (the total number of subjects that responded at any time point) is given near the top of each group. For example, in the last group, 15/15 (100%) subjects responded at either D7 or D35.

Immunogenicity Results - Study 103

BT50 Titers. There was a significant increase in the titers of serum GI.1 HBGA blocking antibodies by BT50 at Day 29 in the Monovalent GI.1 and Bivalent GII.4/GI.1 from Day 1 values. There was a significant increase in the GMT of serum GII.4 HBGA blocking antibodies by BT50 at Day 29 in the Monovalent GII.4 and Bivalent GII.4/GI.1 from Day 1 values. Serum assays such as the BT50 showed a two- to three-fold increase in titer and a 50% seroconversion rate. No significant differences in the GMT of serum GI.1 HBGA blocking antibodies by BT50 were seen between the Monovalent GI.1 and Bivalent GII.4/GI.1 groups. No significant differences in the GMT of Serum GII.4 BT50 GMT were seen between the Monovalent GII.4 and Bivalent GII.4/GI.1 groups.

Antibody Secreting Cell (ASC). The ability of the vaccine to induce norovirus specific B cells in the peripheral blood was measured by ASC assay. This assay essentially counts the number of B cells that emerge after immunization and recognize norovirus in the peripheral blood. The number that circulate in the blood pre-immunization is very low, so the assay is a meaningful way to evaluate the vaccine specific effects.

The average counts of ASC GI.1 IgG were similar across treatment groups on Day 1. However, on Day 8, statistically significant increases in the average counts of ASC GI.1 IgG were seen in the Monovalent GII.4 group (p=0.0002), Monovalent GI.1 group (p=0.0019), and the Bivalent GII.4/GI.1 group (p<0.0001) compared with placebo. No significant differences in the average counts of ASC GI.1 IgG were seen between the Monovalent GI.1 and Bivalent GII.4/GI.1 groups (p=0.4172). The number of subjects with the ASC responses was highest in the Bivalent GII.4/GI.1 group (81.5%) compared with the Monovalent GI.1 group (57.1%), Monovalent GII.4 group (47.4%), and placebo group (6.7%).

The average counts of ASC GII.4 IgG were similar across treatment groups on Day 1. However, on Day 8, statistically significant increases in the average counts of ASC GII.4 IgG were seen in the Bivalent GII.4/GI.1 group (p<0.0001) and Monovalent GII.4 group (p<0.0001) compared with placebo. No significant differences in the average counts of ASC GII.4 IgG were seen between the Monovalent GII.4 and Bivalent GII.4/GI.1 groups (p=0.2694). Number of subjects with response was highest in the Bivalent GII.4/GI.1 group (92.6%) compared with Monovalent GII.4 group (84.2%) and Monovalent GII.4 group (14.3%).

Fig. 14. Plot of ASC GI.1 and GII.4 IgA and IgG response on Day 8 by Dose Group (PP Population).

Caption. The different groups were assessed for IgA and IgG ASC counts in the peripheral blood on Study Day 8 (seven days post immunization). Individual subjects were assessed for both GII.4 (purple) and GI.1 (orange) and plotted as a dot, with the average response for the group shown with a solid black line. These results show that the bivalent group could induce IgA and IgG responses to both GI.1 and GII.4, compared to the placebo group where no significant ASC responses were observed. Further, the monovalent and bivalent groups had similar average responses, demonstrating a lack of interference when the two vaccine strains were given together.

Norovirus Oral Tablet Vaccine Clinical Development Pathway

Phase 1 Bivalent Norovirus Trial Booster. The Phase 1 trial is designed to assess the safety and immunogenicity of a booster norovirus vaccine. The active portion of the bivalent Phase 1 trial was completed in the course of 2019, and topline results were reported in the third quarter of 2019. A booster dose for a subset of subjects was initiated in early 2021 to further evaluate safety and immunogenicity of the norovirus vaccine. In results announced on July 29, 2021, we reported that we were able to successfully boost immune responses with the G1.1 norovirus tablets in prior vaccinated subjects. These responses include IgA antibody secreting cells, as well as IgG and IgA serum antibody responses.

Phase 1 Norovirus Age Escalation Trial. The Monovalent Phase 1 age escalation trial is designed to assess the safety and immunogenicity of the norovirus vaccine in an older population. This trial has completed enrollment with data analysis underway and topline data expected in H1-2022.

Phase 2 Norovirus GI.1 Strain Challenge Study. We have initiated the conduct of a Phase 2 challenge study with our monovalent GI.1 norovirus vaccine candidate in young adult participants in Q1-2022. This study will evaluate the clinical efficacy of the GI.1 norovirus vaccine following viral challenge.

Phase 2 Dose Confirmation Trial. This trial will be designed to assess the safety and immunogenicity of the bivalent vaccine in an expanded population of adults age from 18 and older to allow confirmation of the dose with which to proceed into with larger Phase 3 trials.

Path to Approval. After completing the Phase 2 trials, we anticipate requesting an end-of-Phase 2 meeting with the FDA to discuss the design of a pivotal Phase 3 trial that would support licensure.

Additional Age Groups

Our Seasonal Influenza Program

Market Overview

Influenza is one of the most common global infectious diseases, causing mild to life-threatening illness with symptoms such as sore throat, nasal discharge, fever, and even death. It is estimated that at least 350 million cases of seasonal influenza occur annually worldwide, of which 3 million to 5 million cases are considered severe, causing 290,000 to 650,000 deaths per year globally. Very young children and the elderly are at greatest risk from death. In the United States, between 5% and 20% of the population contracts influenza, 226,000 people are hospitalized with complications of influenza, and between 3,000 and 49,000 people die from influenza and its complications each year, with up to 90% of influenza-related deaths occurring in adults older than 65.

According to a CDC commissioned-report based on 2003 population figures, in the United States seasonal influenza costs an average of over 600,000 life-years lost, 3.1 million hospitalized days, and 31.4 million outpatient visits annually. The total economic burden of seasonal influenza has been estimated to be $87.1 billion, including medical costs which average $10.4 billion annually, while lost earnings due to illness and loss of life amount to $16.3 billion annually.

The CDC generally recommends that individuals 6 months and older be vaccinated annually against influenza. In the U.S., this means an influenza vaccination is recommended for more than 300 million people. During the 2017/2018 influenza season, approximately 137 million doses of the influenza vaccine were delivered in the United States. Differentiated flu vaccines in the U.S. market continue to demonstrate the ability to ask for premium prices based on the additional value they provide to public health. According to a 2017 Datamonitor Healthcare report the seasonal influenza vaccines market within the United States and five major European markets (France, Germany, Italy, Spain and the UK) will increase from $2.7 billion in the 2016/17 season to $3.4 billion in the 2025/26 season. We believe, worldwide, the primary drivers of market growth include increasing awareness, increasing vaccination coverage in emerging countries, rising government support for immunization against seasonal influenza, pricing increases due to product differentiation and increased focus on the production and advancement of vaccination treatments.

Limitations of Current Seasonal Influenza Vaccines

Despite the number of cases of influenza diagnosed in the United States, according to the CDC, in the 2018/2019 seasonal influenza season, only approximately 49% of the total U.S. population was vaccinated against influenza, with particularly low vaccination rates among adults between ages 18 and 49. According to the CDC, less than 35% of adults between ages 18 and 49 were vaccinated during the 2018/2019 influenza season. We believe the low vaccination rates among this population are largely attributed to the following limitations of injectable vaccine administration:

Limitations for Providers

Limitations for Users

Our Seasonal Influenza Vaccine Candidate

We are developing a tablet vaccine candidate for the immunization of healthy adults against seasonal influenza. Our seasonal influenza vaccine candidate is being designed to cover the four-strain, or quadrivalent, seasonal influenza vaccine consisting of two circulating influenza A lineage viruses as well as two circulating influenza B lineage viruses, matching the seasonally updated recommendations by the FDA. We envision formulating our tablet vaccine candidate as one tablet per strain, or four tablets in total for the quadrivalent vaccine. We believe this modularity will allow for enhanced flexibility. For instance, in the event of a late season strain change, the tablet containing the obsolete strain could be easily replaced without having to discard the three correctly matched vaccine tablets. Alternatively, we have the option to formulate all four strains into a single tablet. This format would be the simplest to administer, but would take away some of the flexibility advantages that separate tablets would afford. We will assess the final formulation of our tablet vaccine candidates after conducting market studies to evaluate market acceptance closer to commercialization.

We believe our tablet vaccine candidates have the potential to address many of the limitations of current injectable, egg-based seasonal influenza vaccines. First, our tablet vaccine candidates are designed to create broad and durable immune responses, which may provide more effective immunity and protect against additional strain variants. Second, by providing a more convenient method of administration to enhance patient acceptance and simplify distribution and administration. Finally, by using recombinant methods, we believe our tablet vaccine candidates may be manufactured more rapidly than vaccines manufactured using egg-based methods, eliminate the risk of allergic reactions to egg protein, and alleviate issues caused by egg-adaptation of a mammalian virus.

Seasonal Influenza Clinical Trials

To date, we have completed two Phase 1 trials and have conducted the active portion of a Phase 2 challenge trial of our H1N1 influenza vaccine candidate. We have also completed a Phase 1 trial of an influenza B vaccine candidate.

Phase 1 Trial, VXA02-001, H1N1 Influenza Vaccine Candidate, 10⁹ and 10¹⁰ IU Doses

The first Phase 1 H1N1 trial was conducted at doses of 1 x 10⁹ and 1 x 10¹⁰ IU. Two doses were given one month apart. The tablet vaccine candidate generated a favorable safety and tolerability profile. The trial also demonstrated robust T cell responses and modest hemagglutination inhibition assay (“HAI”) responses, each dependent on the dosage level.

Phase 1 Trial VXA02-003, H1N1 Influenza Vaccine Candidate, 10¹¹ IU Dose

The second H1N1 trial was a tablet vaccine trial at a dose of 1 x 10¹¹ IU, delivered in a single administration. We observed a favorable safety and tolerability profile at this dose level. An HAI seroconversion rate of 75% was measured in the vaccine group, compared to 0% in the placebo group. 92% of subjects had a four-fold increase in Micro Neutralization (“MN”) titer after the single administration of tablets. Both the HAI seroconversion rate and the MN responses were substantially higher than the respective rates that we observed at lower doses in Trial VXA02-001. The side effects of the vaccine or placebo in the first seven days following administration were mild with no serious adverse effects. In the first seven days following administration, there were eight total solicited AEs reported in the vaccine and placebo groups (four in each group). All these AEs were grade 1 in severity. The most frequent AE was headache (two in placebo, and one in the vaccine group). There were no SAEs and no new onsets of chronic illnesses related to the adjuvant recorded during the entire one year follow up period of the study.

The table below summarizes the trial design and results (serum antibody responses) of our two placebo-controlled Phase 1 H1N1 clinical trials.

Table 7. Overview: H1 Influenza Phase 1 Placebo-Controlled Studies.

Phase 1 Trial. Influenza B

In 2015 and 2016, we conducted a randomized, double-blind, placebo-controlled Phase 1 trial to test the safety and immunogenicity of an influenza B tablet vaccine. A total of 54 healthy adults aged 18 to 49 were enrolled, with 38 receiving the vaccine and 16 receiving placebo. To participate in this trial, subjects were required to have an initial HAI measure of no greater than 1:20. The active phase of the trial was through day 28, with the follow-up phase for monitoring safety to continue for one year. All subjects who received the vaccine received a single dose of either 1 x 10¹⁰ IU or 1 x 10¹¹ IU on Day 0.

Safety. The side effects of the vaccine or placebo in the first seven days following administration were generally mild with no serious adverse events. There were no notable differences between the active dose groups and placebo in safety and tolerability.

HAI. In the placebo group, HAI GMT remained essentially unchanged (1:33) at day 28 post dosing. The GMFR of HAI titers both active treated groups at day 28 post dosing was about 2-fold, and independent of dose. For the vaccinated groups receiving either 1×10¹⁰ IU or 1×10¹¹ IU, seroconversion was observed in 5/19 subjects (26.3%) and 3/19 subjects (15.8%), respectively. There were no seroconversions in the placebo group.

Antibody Secreting Cells (ASCs). In order to measure total antibody responses to HA, the numbers of circulating B cells that recognize influenza HA in peripheral blood were measured by ASC assay on days 0 and 7 after immunization. Results show that ASCs could be reliably measured on day 7 in the vaccine-treated groups. Background ASCs were generally negligible on day 0. By IgG ASC, 68% of 1×10¹⁰ IU dose subjects responded, and 84% of subjects in the 1×10¹¹ IU dose group responded. For the 1×10¹¹ IU dose vaccine treated group, an average of 21 IgA ASCs (95% CI: 7 – 35) and 73 IgG ASCs (95% CI: 35 – 111) each per 1×10⁶ peripheral blood mononuclear cell (PBMC) were found at day 7. For the 1×10¹⁰ IU dose vaccine treated group, an average of 16 IgA ASCs (95% CI: 2 – 29) and 44 IgG ASCs (95% CI: 21 – 66) were found at day 7. The placebo group had no responders, and negligible average number of spots (1 or less) on Day 7 (95% CI: -0.6 – -2).

H1N1 Influenza Phase 2 Challenge Study Funded by BARDA

In 2015, we were awarded a $13.9 million contract by BARDA, part of the HHS. This two-year contract was awarded under a Broad Agency Announcement issued to support the advanced development of more effective influenza vaccines to improve seasonal and pandemic influenza preparedness. The contract primarily funded a Phase 2 challenge study in human volunteers, designed to evaluate whether our H1N1 tablet vaccine candidate offers broader and more durable protection than currently marketed injectable vaccines. The contract with BARDA was subsequently increased to $15.7 million and the term was extended until September 2018.

In this Phase 2 study, volunteers were randomized into three groups. One group received our oral H1N1 influenza tablet vaccine candidate, a second group received a commercially licensed inactivated influenza vaccine by intramuscular injection, and a third group received placebo. Three months following immunization, volunteers were challenged (deliberate experimental administration) with live H1N1 (A/H1N1 pdm09) influenza virus by intranasal administration. The placebo group served as the control group to determine how many unvaccinated volunteers became infected and how severe their influenza symptoms became. Data from our vaccine candidate group and the commercially licensed inactivated vaccine group were compared to placebo to determine each vaccine’s efficacy in this challenge study. Importantly, the two vaccines were also compared head-to-head. The goal of the study is to compare the efficacy of our vaccine to protect volunteers from illness caused by H1N1 influenza challenge, compared to both the injectable vaccine and placebo three months after immunization.

Clinical Trial Results VXA-CHAL-201

The Phase 2 challenge study was enrolled during 2016 and 2017. During this time, 179 subjects that cleared the screening requirements were randomized to receive a single dose of our tablet vaccine, the commercial injectable vaccine, or placebo. Of these 179 subjects, 143 subjects were subsequently challenged with live H1N1 influenza virus 90 to 120 days months after dosing.

Fig. 15. Maximum Severity of Solicited Local Symptoms.

Caption. Solicited local symptoms were collected for seven days following immunization. The severity of solicited symptoms is indicated for each treatment group over time. All events were mild.

Fig. 16. Maximum Severity of Solicited Systemic Symptoms.

Caption. Solicited systemic symptoms were collected for seven days following immunization. The severity of solicited symptoms is indicated for each treatment group over time.

Efficacy – Reduction of PCR Confirmed Influenza Illness.

The primary efficacy objective was to determine vaccine efficacy of our tablet vaccine following the challenge with the wild-type influenza A H1 virus strain (A/H1N1 pdm09). The primary efficacy endpoint was illness. The illness rate was 29% for our tablet vaccine, 35% for the commercial inactivated influenza vaccine, and 48% for subjects in the placebo group. Our tablet vaccine had a lower rate of illness than the commercial vaccine (-6% difference in illness rate in favor of our vaccine), although given the small size of the study, these differences were not statistically significant. Similarly, the difference in illness rates between our tablet vaccine and placebo (-19.1%) and the commercial injected vaccine and placebo (-13.2%) trended toward protection but were not statistically significant. These results suggest that our vaccine is no worse, and trended better than the commercial vaccine for protection. The ability to show clinical efficacy in humans is a major step forward for our oral influenza product. These results are summarized in the table below.

Table 8. H1 Influenza Phase 2 Challenge Study: Illness Rates*.

*Illness was defined as a combination of symptoms reported on a patient reported outcome tool (Flu-PRO^TM) and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) detectable shed influenza virus.

Efficacy – Flu-PRO symptom Scores

There were no statistically significant differences between the commercial inactivated influenza vaccine and our tablet vaccine for the Flu-PRO questionnaire, a validated patient recorded outcome tool used in influenza clinical trials in the community. However, our vaccine trended lower for overall symptom severity. Subjects in the VXA-A1.1 group showed a lower overall median Flu-PRO score (2.0 [0, 72]) than the QIV group (5.0 [0, 59]) or the placebo group (5.0 [0, 52]).

Efficacy – Shedding

Shedding represents influenza virus that is detected in nasal swabs post infection and is representative of viral infection and replication. In the study, 44.8% of subjects in VXA-A1.1 had at least one day positive for shedding, versus the commercial injected vaccine where 53.7% were positive for shedding and where 71.0% of placebo subjects were positive for shedding. There were no statistically significant differences observed between our tablet vaccine and the commercial inactivated influenza vaccine for viral shedding area under the curve (“AUC”). However, AUC was calculated using a standard logarithmic trapezoidal method and included only detectable shedding during the first five days of the duration of shedding, with subjects removed from the analysis that didn’t shed influenza for 5 days (a zero value cannot be used in log calculations and integrated). This may have led to an underestimate of the effect on viral shedding for the two vaccines relative to placebo. Therefore, in order to better determine the effect of the vaccines on shedding, an alternative method was used in which volunteers were defined as infected if they had detectable viral shedding at any time 36 hours after challenge. This approach eliminated possible issues related to calculations (log calculations of zero values) and of large doses of challenge virus (first 36 hours might be pass through rather than replicating influenza). In a Bayesian analysis, both vaccines significantly reduced the probability of shedding relative to placebo (Bayesian posterior p=0.001 for our tablet vaccine and p=0.009 for the commercial inactivated influenza vaccine). There is also trend toward greater efficacy for our vaccine with a posterior probability of approximately 80% (Table 8).

Table 9. H1 Influenza Phase 2 Challenge Study: Infection Rates*.

*Infection was defined as any positive quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) detectable shed influenza virus on any day after 36 hours from viral challenge. In a Bayesian analysis, both vaccines provide a statistically significant protection against infection. There is also trend toward greater efficacy for our vaccine with a posterior probability of approximately 80%.

Immunogenicity

HAI responses. HAI measures the ability of serum antibodies that can disrupt binding of influenza virus to red blood cells. Historically, HAI correlates to protection for injected influenza vaccines. HAI responses were measured 30 days following immunization to determine the number and percentage of volunteers that seroconverted. In our tablet vaccine group, 32% of volunteers achieved seroconversion. In the commercial inactivated influenza vaccine group 84% of volunteers achieved HAI seroconversion at 30 days post vaccination. This difference was statistically significant (P < 0.001, Fisher’s Exact test). There were no subjects in the placebo group who achieved seroconversion at 30 days post vaccination. Since 32% of subjects seroconverted in the Vaxart tablet vaccine group achieved HAI seroconversion, but 71% of subjects were protected from illness following influenza challenge, HAI seroconversion appeared not to be a reliable indicator of protection for the Vaxart vaccine. The table below summarizes the HAI data. The GMT, GMFR, percentage of volunteers who had a fourfold rise in their HAI and the percentage of subjects who seroconverted are reported.

Table 10. Hemagglutination Antibody Inhibition (HAI) Geometric Mean Titer (GMT) and Geometric Mean Fold Rise (GMFR) Results Post Dosing with 95% Confidence Intervals by Strain, Study Day and Treatment Group.

IgA Antibody Secreting Cells. B cells specific for influenza HA (IgA antibody secreting cells or IgA ASCs) were measured at baseline and eight days following immunization in order to determine the B cell responses to the vaccines. At eight days following vaccination, subjects in the commercial inactivated influenza vaccine group had significantly higher mean numbers of spots per 10⁶ cells (p<0.001, Wilcoxon test) and significantly higher percentages of subjects with greater than 8 spots per 10⁶ cells (p<0.001, Fisher exact). At Day 8, the commercial inactivated influenza vaccine group had mean spots 286 per 10⁶ cells compared to mean spots of 116 per 10⁶ cells for the Vaxart tablet vaccine. Additionally, the commercial inactivated influenza vaccine group had a 96% response rate compared to 71% in the Vaxart tablet vaccine group. The table below summarizes these data.

Table 11. ASC Response for IgA and IgG Assays by Study Day and Treatment Group – Vaccination Phase.

Correlation of IgA ASCs with Illness for the Vaxart Tablet Vaccine. As stated above, the absolute mean number of ASCs was higher for the commercial inactivated influenza vaccine group (286 spots per 10⁶ cells) than for the Vaxart tablet vaccine (116 spots per 10⁶ cells). However, when a comparison was made between the two vaccines of the ratio of IgA ASCs in volunteers that were not ill divided by volunteers that were ill following challenge, the Vaxart tablet vaccine group had a ratio of 4.7, compared to a ratio of 1.4 for the commercial injected vaccine. In a logistics fit model with illness compared to non-illness as the outcome, and IgA ASC as the independent variable, the model showed that the Vaxart tablet vaccine IgA ASC could predict ill versus non-ill, but the logistics fit model for the commercial inactivated influenza vaccine could not (p=0.0005 for our vaccine, p=0.3066 for the commercial injected vaccine for whole logistic model). These data suggest that IgA ASC is important for protection against influenza for our oral vaccine, but not for injected commercial vaccines. These data also suggest that there are qualitative differences between B cells induced post immunization by different methods. We are actively exploring these qualitative differences.

Fig. 17. IgA ASCs Correlate with Illness for Vaxart Tablet Vaccine.

                                Vaxart Tablet Vaccine                                                                       Commercial Inactivated Vaccine

Caption.  Logistic fit regression analysis demonstrates a statistically significant fit for the Vaxart Tablet Vaccine for IgA ASCs and illness. The correlation between higher ASCs and a lower rate of illness is observed. The same model fit is not observed with the commercial inactivated vaccine.

This work was funded in whole or in part with Federal funds from HHS, Office of the Assistant Secretary for Preparedness and Response and BARDA.

Preclinical Results

We have completed several animal challenge studies for influenza. In an H1N1 influenza challenge study, mice immunized orally with our tablet vaccine candidate were protected against sickness and death compared to unimmunized, control animals. Similarly, our oral H5N1 vaccine candidate protected ferrets and mice against a lethal avian influenza challenge compared to unimmunized animals when the vaccine construct expressed an avian influenza HA construct.

Cross Protection of Vaxart Quadrivalent Seasonal Flu Vaccine against Avian Flu in Ferret Challenge Model

A more recent ferret challenge experiment was completed in 2017 to compare an oral quadrivalent vaccine that we designed with the commercial vaccine Fluzone for protection against a virulent avian influenza strain. There are no components of seasonal influenza vaccines that are matched to the HA made by avian influenza virus, so the virus represents a severe case of vaccine mismatched to virus. Our quadrivalent vaccine was made by mixing four recombinant adenoviruses, each expressing a different HA that matches the HAs in the commercial vaccine, not the HA of the challenge. Two different doses were evaluated; the high dose was used at 1:10 of a Vaxart human dose (Vaxart Quad) and the low dose (Vaxart Quad Low) was used at 1:100 of the human dose. The Fluzone group (QIV) was given at 1:10 of the human dose to directly compare to the Vaxart quadrivalent high dose group. Vaxart animals and the negative control (PBS) animals were given vaccine delivered by endoscope. The QIV animals were intramuscularly injected. Animals were vaccinated on days 0 and 28. Animals were challenged on day 56 with approximately 10^2.69 TCID50/mL of wild type A/Vietnam/1203/2004 (A/VN). Results show that the Vaxart quadrivalent vaccines were able to protect against mismatched A/VN, trending better than Fluzone. The high dose group was able to protect all ferrets against death whereas the low dose Vaxart group protected 75% of ferrets.

Fig. 18.  Survival in ferrets vaccinated with seasonal influenza and challenged with H5N1 Vietnam.

Caption.  The percent survival was measured for each group at each time point. The Vaxart Quad vaccine group were 100% protected against mismatched avian influenza over the 14 days that survival was assessed. The other groups were not as well protected.

This work was funded in whole or in part with federal funds from HHS BARDA.

Our HPV Therapeutic Vaccine Candidate

In previous clinical studies with our H5 influenza vaccine candidate, we observed robust T-cell responses that appeared to compare favorably with published results of other flu vaccines, including an adjuvanted vaccine as well as an attenuated live viral vaccine. Specifically, our vaccine generated high levels of polyfunctional cytotoxic CD4 and CD8 cells, T-cells that are likely required to obtain a therapeutic benefit in chronic viral infection and cancer. It was based on these observations that we embarked on the development of our first therapeutic vaccine, targeting HPV-associated dysplasia and cervical cancer.

Medical Need, Commercial Opportunity

HPV is a family of more than 120 viruses which are extremely common globally. At least 13 HPV types are cancer-causing. HPV is primarily transmitted through sexual contact and infection is very prevalent following the onset of sexual activity. Nearly all cases of cervical cancer are attributable to HPV infection, with two HPV types – HPV-16 and HPV-18 – responsible for 70% of cervical cancers and precancerous cervical lesions. Cervical cancer is the fourth most common cancer in women worldwide, and about 13,000 new cases are diagnosed annually in the United States according to the National Cervical Cancer Coalition. Studies have indicated a high lifetime probability of any HPV infection by both men and women in the United States, with some estimates indicating at least 80% of women and men acquire HPV by age 45. The CDC estimates 80 million U.S. citizens are currently infected with HPV, representing 25% of the population, with about 14 million new infections per year. A report by BCC Research expects the global cervical cancer drug and diagnostic market to exceed $15 billion by 2018.

In women, many HPV infections of the cervix will spontaneously resolve and clear within two to three years, but women who have a persistent infection are at high risk of developing cellular abnormalities known as cervical intraepithelial neoplasia, or CIN, which can progress to invasive cancer over time. More than 400,000 women are diagnosed with CIN annually in the United States, with an annual incidence estimate for CIN1 and CIN2/3 at 1.6 and 1.2 per 1,000 women, respectively.

There are currently no approved therapeutic vaccines to treat HPV infection or cancer. Current treatment options for women infected with HPV (see below) include monitoring CIN status, surgical procedures to remove affected tissue, and chemotherapeutic or radiation therapies to treat localized or metastatic cervical cancer. Therefore, a medical need remains for a therapeutic vaccine to treat women with HPV-associated CIN and/or cervical cancer.

Our HPV Therapeutic Vaccine Candidate

We are in the early stages of developing a bivalent HPV vaccine against HPV-16 and HPV-18, the strains responsible for approximately 70% of cases of cervical cancer. We plan to target the E6 and E7 gene products of each strain, which are the primary oncogenic proteins responsible for progression through the stages of CIN to invasive cervical cancer. In pre-clinical studies, we have demonstrated immunogenicity for both our HPV-16 and our HPV-18 vaccine candidates. Specifically, mice given our HPV-16 or HPV-18 vaccines induced T cell responses to HPV as measured by IFN gamma ELISPOT. In addition, our HPV-16 vaccine has demonstrated tumor growth suppression as well as increased survival in a robust HPV tumor model in mice. We believe that our HPV vaccine has several advantages over current treatment options for both CIN and cervical cancer. Current treatment options for CIN are invasive and can lead to serious contraindications for pregnancy. In addition, surgical treatments for CIN do not treat the underlying HPV, but rather remove infected tissue. As a result, current CIN treatment options have a significant failure rate which can increase the risk for progression to cervical cancer. Our vaccines have demonstrated a favorable safety and tolerability profile in clinical subjects dosed to date. Current treatment options for cervical cancer, such as chemotherapy and radiation treatment, have multiple side effects such as hair loss, loss of appetite, and severe nausea.

T cells Responses to HPV-16 Can Shrink Solid Tumors Derived from Transformed HPV

The ability of T cell responses to HPV-16 to produce a therapeutic response was tested in a solid tumor growth model. TC-1 cells (an HPV-16 transformed cell-line) were injected subcutaneously into the hind flank of B6 mice and allowed to grow for several days before mice were immunized with vaccine or controls. In study 1, mice were immunized on days 7, 14, and 21. For groups 4 and 5, the vaccine expressed the HPV-16 antigens E6/E7 (Ad-HPV). A checkpoint inhibitor (an antibody to PD-1) was used along with the vaccine in group 5, and an isotype control (Iso) to the checkpoint inhibitor was used in group 4. A recombinant rAd vector identical to Ad-HPV, but which doesn’t express the HPV antigens (Ad-nr), was used in groups 1 or 2 to control for non-specific effects. Untreated animals were not given any vaccine.

The results in study 1 showed that Ad-HPV groups were able to the stop tumor growth and even shrink the tumor. This occurred whether the checkpoint inhibitor was used or not. The checkpoint inhibitor alone was not able to stop tumor progression, and eventually all these animals perished. Other control animals without Ad-HPV didn’t survive as well. The use of the checkpoint inhibitor with the Ad-HPV vaccine trended slightly better for survival (10/10 versus 9/10 survived), but this was not significant.

In study 2, the TC-1 tumor was transplanted as before, but allowed to grow longer before immunization occurred. Immunizations occurred on days 13, 20, and 27. In this study, mice that received the Ad-HPV vaccine plus the checkpoint inhibitor were able to control the tumor, up through day 40 before a few mice started to perish. More than 70% of animals in this group survived through the end of the experiment on day 80. Ad-HPV immunized mice in the absence of the checkpoint inhibitor were also able to substantially control the tumor through 60 days (33 days after the last immunization), before several additional animals perished. No control groups in the absence of the Ad-HPV were able to control any of the tumors, and all mice perished before day 40.

Fig. 19.  Small Tumor Vaccine Study.

Caption.  In the small tumor vaccine study (Study 1), tumors were allowed to grow for seven days before beginning the immunization schedule. Animals given the Vaxart HPV vaccine (Ad-HPV) were protected against tumor growth and survived better. This was the case whether or not a checkpoint inhibitor was used.

Fig. 20.  Large Tumor Vaccine Study.

Caption.  In the large tumor vaccine study (Study 2), tumors were allowed to grow for 13 days before the vaccines were given. Again, animals given the Ad-HPV were better protected against tumor growth. The addition of the checkpoint inhibitor improved survival.

The T cells induced post immunization in the tumor model were believed to traffic back to the solid tumor to attack and destroy the cancer cells. This was tested in an additional tumor model experiment. Tumors were transplanted as before, and immunizations were performed on days 13 and 21. Tumors were harvested from the experiment on day 24, and flow cytometry was used to enumerate the T cells infiltrating the tumors. The HPV-16 vaccine groups (with either the checkpoint inhibitor or an isotype control antibody) had T cell infiltrates of both CD4 and CD8 positive T cells. The CD8 T cell numbers from the Ad-HPV groups were significantly better than control treated animals in terms of infiltrating lymphocytes. The CD4 T cells were significantly better in the Ad-HPV + checkpoint group, and trended higher in the Ad-HPV + isotype control group.

Fig. 21.  The Ad-HPV vaccine induces T cells that migrate to the tumors.

Caption.  The number of CD4 and CD8 T cells found within the tumor were analyzed by flow cytometry. The Ad-HPV groups were found to elicit T cells that transited to the tumor, with the Ad-HPV plus checkpoint inhibitor creating slightly more T cell transit than the Ad-HPV vaccine alone.

Near Term HPV Vaccine Development Strategy

Preclinical

The next steps in the vaccine development are to complete the nonclinical studies, which may include a toxicology study using Good Laboratory Practices (“GLPs”) to support an IND filing for this vaccine. The exact nature of these studies will be determined in consultation with the appropriate regulatory authorities.

Clinical

We will propose to test the vaccine in subjects with cervical dysplasia related to HPV-16 or HPV-18, and to evaluate the ability of the vaccine to clear HPV infection, reduce the cervical dysplasia score, and induce T cells known to be important in the clearance of HPV. T cells will be measured by flow cytometry as well as by IFN-g ELISPOT. The primary endpoint will be safety and the secondary endpoint will be immunogenicity by examining T cell responses. Although clinical responses will be tracked, it is expected that the first study may not be powered to obtain statistically significant efficacy readouts.

Other Indications

We currently have preliminary data in animal models for indications such as RSV, Chikungunya, Hepatitis B and HSV-2.

Manufacturing

Manufacturing our oral tablet vaccines consists of two main stages, the production of bulk vaccine (drug substance), and the formulation and tableting thereof (drug product). Drug substance manufacturing consists primarily of the production and purification of the active ingredient. Bulk drug substance is then lyophilized, formulated and subsequently tableted and coated using a proprietary formulation and tableting process that we developed.

Bulk Vaccine Manufacturing (Drug Substance)

From inception through December of 2017, we relied on third-party contract manufacturers to manufacture clinical cGMP bulk drug substance for our influenza and norovirus tablet vaccine candidates. Starting in 2017, we invested in developing our own bulk vaccine manufacturing process with the aim to establish a small cGMP bulk manufacturing facility at our corporate headquarters in California for manufacturing cGMP product for our Phase 1 and small Phase 2 trials. During the fourth quarter of 2019, a decision was made to discontinue all activities related to in-house bulk manufacturing and revert to relying on third-party contract manufacturers, so the Company terminated all of its manufacturing staff. Following a reassessment due to the COVID-19 pandemic, we resumed small scale in-house manufacturing in 2020.

In July 2019 we entered into a relationship with Lonza Houston, Inc. (“Lonza”) to manufacture bulk norovirus GI.1 and GII.4 vaccine under cGMP. In late 2019, Company suspended the Lonza manufacturing agreement, pending the outcome of the norovirus partnering discussions. Vaxart settled all of its remaining obligations under its agreement with Lonza by paying $2.3 million in September 2020.

In March 2020, we entered into an agreement with Emergent BioSolutions Inc. for the development and manufacture of SARS-CoV-2 vaccine. In May 2020, we entered into an agreement with Kindred Biosciences, Inc. (“KindredBio”) for the manufacture of our SARS CoV-2 vaccine. In September 2020 we executed two statements of work with KindredBio for the bulk manufacture of our SARS-CoV-2 and norovirus vaccines. In November 2021 we cancelled the two statements of work and subleased one of their GMP manufacturing facilities which we will use to perform the same bulk manufacturing processes in-house. In addition, in October 2020 and January 2021 we executed agreements with Attwill Vascular Technologies, LP (“Attwill”) for manufacturing, including lyophilization of drug substance at a larger scale.

Vaccine Tablet Manufacturing (Drug Product)

From inception through December of 2017, we contracted with third-party contract manufacturers for the manufacture, labeling, packaging, storage and distribution of our drug product. During 2016, we established drug product manufacturing capabilities at our corporate headquarters. Our facility is licensed by the State of California Department of Public Health Food and Drug Branch to manufacture drug product for clinical trials. In addition, in January 2021 we executed an agreement with Attwill for further drug product manufacturing (tableting and coating) at a larger scale.

We have limited experience with process development, and the manufacture, testing, quality release, storage and distribution of drug substance and drug product according to cGMP and regulatory filings. The cGMP regulations include requirements relating to the organization of personnel, buildings and facilities, equipment, control of components and drug product containers and closures, production and process controls, packaging and labeling controls, holding and distribution, laboratory controls, records and reports, and returned or salvaged products. Our facility, and our third-party manufacturers, are subject to periodic inspections by FDA and local authorities, which include, but are not limited to procedures and operations used in the testing and manufacture of our vaccine candidates to assess our compliance with applicable regulations. If we or our third-part manufacturers fail to comply with statutory and regulatory requirements we and they could be subject to possible legal or regulatory action, including warning letters, the seizure or recall of products, injunctions, consent decrees placing significant restrictions on or suspending manufacturing operations and civil and criminal penalties. These actions could have a material adverse impact on the availability of our tablet vaccine candidates. Similar to contract manufacturers, we have in the past encountered difficulties involving production yields, quality control and quality assurance, and if we are not able to produce drug product or drug substance in sufficient quantities our ability to conduct our clinical trials and commercialize our tablet vaccine candidates, if approved, will be impaired.

Research and Development

In the ordinary course of business, we enter into agreements with third parties, such as clinical research organizations, medical institutions, clinical investigators and contract laboratories, to conduct our clinical trials and aspects of our research and preclinical testing. These third parties provide project management and monitoring services and regulatory consulting and investigative services.

Competition

The pharmaceutical and vaccine industries are characterized by intense competition to develop new technologies and proprietary products. In general, competition among pharmaceutical products is based in part on product efficacy, safety, reliability, availability, price and patent position.

While we believe that our proprietary tablet vaccine candidates provide competitive advantages, we face competition from many different sources, including biotechnology and pharmaceutical companies, and we may also face competition from academic institutions, government agencies, as well as public and private research institutions. Any products that we may commercialize will have to compete with existing products and therapies as well as new products and therapies that may become available in the future.

There are other organizations working to improve existing therapies, vaccines or delivery methods, or to develop new vaccines, therapies or delivery methods for their selected indications. Depending on how successful these efforts are, it is possible they may increase the barriers to adoption and success of our vaccine candidates, if approved.

We anticipate that we will face intense and increasing competition as new vaccines enter the market and advanced technologies become available. We expect any tablet or other oral delivery vaccine candidates that we develop and commercialize to compete on the basis of, among other things, efficacy, safety, convenience of administration and delivery, price, availability of therapeutics, the level of generic competition and the availability of reimbursement from government and other third-party payors.

Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we can obtain approval for our vaccine candidates, which could result in our competitors establishing a strong market position before we are able to enter the market. In addition, our ability to compete may be affected in many cases by insurers or other third-party payors seeking to encourage the use of generic products.

We face competition from smaller companies who, like us, rely on investors to fund research and development and compete for co-development and licensing opportunities from large and established pharmaceutical companies. We may also face significant competition in pursuing partnership opportunities and strategic acquisitions from other companies, financial investors and enterprises whose cost of capital may be lower than ours. Competition for future partnerships or asset acquisition opportunities in our markets is intense and we may be forced to increase the price we pay for such assets.

We also depend upon our ability to attract and retain qualified personnel, obtain patent protection or otherwise develop proprietary products or processes and secure sufficient capital resources for the development and commercialization of our products.

Seasonal Influenza Vaccine Candidate

We believe our seasonal influenza vaccine candidate would compete directly with approved vaccines in the market, which include non-recombinant and recombinant products that are administered via injection or intranasally. The major global non-recombinant injectable vaccine competitors include Astellas Pharma Inc., Abbott Laboratories, AstraZeneca UK Limited, Baxter International Inc., Research Foundation for Microbial Diseases of Osaka University, Seqirus-bioCSL Inc., GSK, Sanofi S.A. (“Sanofi”), Pfizer Inc., and Takeda Pharmaceutical Company Limited (“Takeda”). Non-recombinant intranasal competition includes MedImmune, Inc. (“MedImmune”), and potentially others. Recombinant injectable competitors include Sanofi, Medicago and Novavax, Inc. (“Novavax”). Many other groups are developing new or improved flu vaccine or delivery methods.

Norovirus Vaccine Candidate

There is currently no approved norovirus vaccine for sale globally. We believe that HilleVax is developing a norovirus vaccine (originally developed by Takeda) that would be delivered by injection. There may be other development programs that we are not aware of.

HPV Therapeutic Vaccine Candidate

There is currently no approved HPV therapeutic vaccine for sale globally; however, a number of vaccine manufacturers, academic institutions and other organizations currently have, or have had, programs to develop such a vaccine. We believe that several companies are in various stages of developing an HPV therapeutic vaccine including Inovio Pharmaceuticals, Inc. (“Inovio”), Advaxis, Genexine, and several others.

Coronavirus Vaccine Candidate

Pfizer-BioNTech, Moderna and Johnson & Johnson have already developed a COVID-19 vaccine approved for emergency use in the United States and elsewhere, and many more, including several that have progressed further than us, including Oxford-AstraZeneca, Sanofi, Inovio, Takara Bio and Novavax, are in various stages of development.

Inavir

Other anti influenza antivirals are marketed in Japan, including Tamiflu and Relenza. On February 23, 2018, Osaka-based drug maker Shionogi gained marketing approval for Xofluza, a new drug to treat influenza in Japan. The drug was approved for use against type A and B influenza viruses and requires only a single dose regardless of age. Since its launch, Xofluza has gained significant market share from Inavir in Japan, substantially reducing the sales of Inavir in Japan by Daiichi Sankyo. This has had a significant negative impact on the royalty payments we have received from Daiichi Sankyo and may continue to have a significant negative impact on our future royalty revenues.

Intellectual Property

We strive to protect and enhance the proprietary technology, inventions and improvements that are commercially important to our business, including seeking, maintaining, and defending patent rights. We also rely on trade secrets relating to our platform and on know-how, continuing technological innovation to develop, strengthen and maintain our proprietary position in the vaccine field. In addition, we rely on regulatory protection afforded through data exclusivity, market exclusivity and patent term extensions where available. We also utilize trademark protection for our company name and expect to do so for products and/or services as they are marketed.

Our commercial success will depend in part on our ability to obtain and maintain patent and other proprietary protection for commercially important technology, inventions and know-how related to our business; defend and enforce our patents; preserve the confidentiality of our trade secrets; and operate without infringing the valid enforceable patents and proprietary rights of third parties. Our ability to stop third parties from making, using, selling, offering to sell or importing our tablet vaccine candidates may depend on the extent to which we have rights under valid and enforceable patents or trade secrets that cover these activities. With respect to company-owned intellectual property, we cannot be sure that patents will be granted with respect to any of our pending patent applications or with respect to any patent applications we may file in the future, nor can we be sure that any of our existing patents or any patents that may be granted to us in the future will be commercially useful in protecting our commercial products and methods of manufacturing the same.

We have developed numerous patents and patent applications and own substantial know-how and trade secrets related to our platform and tablet vaccine candidates.

In addition to the above, we have established expertise and development capabilities focused in the areas of preclinical research and development, manufacturing and manufacturing process scale-up, quality control, quality assurance, regulatory affairs and clinical trial design and implementation. We believe that our focus and expertise will help us develop products based on our proprietary intellectual property.

The term of individual patents depends upon the legal term of the patents in the countries in which they are obtained. In most countries in which we file, the patent term is 20 years from the date of filing the non-provisional application. In the United States, a patent’s term may be lengthened by patent term adjustment, which compensates a patentee for administrative delays by the U.S. Patent and Trademark Office in granting a patent, or may be shortened if a patent is terminally disclaimed over an earlier-filed patent.

The term of a patent that covers an FDA-approved drug may also be eligible for patent term extension, which permits patent term restoration of a U.S. patent as compensation for the patent term lost during the FDA regulatory review process. The Hatch-Waxman Act permits a patent term extension of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review. A patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval and only one patent applicable to an approved drug may be extended. Moreover, a patent can only be extended once, and thus, if a single patent is applicable to multiple products, it can only be extended based on one product. Similar provisions are available in Europe and other foreign jurisdictions to extend the term of a patent that covers an approved drug. When possible, depending upon the length of clinical trials and other factors involved in the filing of a new drug application, or NDA, we expect to apply for patent term extensions for patents covering our vaccine candidates and their methods of use.

Trade Secrets

We rely, in some circumstances, on trade secrets to protect our technology. However, trade secrets can be difficult to protect. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with our employees, consultants, scientific advisors and contractors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these procedures, agreements or security measures may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. To the extent that our consultants, contractors or collaborators use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions.

Government Regulation and Product Approval

Federal, state and local government authorities in the United States and in other countries extensively regulate, among other things, the research, development, testing, manufacturing, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, post-approval monitoring and reporting, marketing and export and import of biological and pharmaceutical products such as those we are developing. Our vaccine candidates must be approved by the FDA before they may be legally marketed in the United States and by the appropriate foreign regulatory agency before they may be legally marketed in foreign countries. Generally, our activities in other countries will be subject to regulation that is similar in nature and scope as that imposed in the United States, even though it may differ in certain respects. The process for obtaining regulatory marketing approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources. The rules and regulations that apply to our business are subject to change and it is difficult to foresee whether, how, or when such changes may affect our business.

U.S. Product Development Process

In the United States, the FDA regulates pharmaceutical and biological products under the Federal Food, Drug and Cosmetic Act, Public Health Service Act, or PHSA, and implementing regulations. Products are also subject to other federal, state and local statutes and regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process or after approval, may subject an applicant to administrative or judicial sanctions. FDA sanctions could include, among other actions, refusal to approve pending applications, withdrawal of an approval, a clinical hold, warning letters, product recalls or withdrawals from the market, product seizures, total or partial suspension of production or distribution injunctions, fines, refusals of government contracts, restitution, disgorgement or civil or criminal penalties. Any agency or judicial enforcement action could have a material adverse effect on us. The process required by the FDA before a drug or biological product may be marketed in the United States generally involves the following:

Before testing any biological vaccine candidate, including our tablet vaccine candidates, in humans, the vaccine candidate enters the preclinical testing stage. Preclinical tests, also referred to as nonclinical studies, include laboratory evaluations of product chemistry, toxicity and formulation, as well as toxicological and pharmacological studies in animal species, to assess the potential safety and activity of the vaccine candidate. The conduct of the preclinical tests must comply with federal regulations and requirements including GLPs for certain animal studies and the Animal Welfare Act, which is enforced by the Department of Agriculture. The clinical trial sponsor must submit the results of the preclinical tests, together with manufacturing information, analytical data, any available clinical data or literature and a proposed clinical protocol, to the FDA as part of the IND. Some preclinical testing may continue even after the IND is submitted. Any person or entity sponsoring clinical trials in the United States to evaluate a product candidate’s safety and effectiveness must submit to the FDA, prior to commencing such trials, an IND application, which provides a basis for the FDA to conclude that there is an adequate basis for testing the product in humans. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA raises concerns or questions regarding the proposed clinical trials and places the trial on a clinical hold within that 30-day time period. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. The FDA may also impose clinical holds on a biological product candidate at any time before or during clinical trials due to safety concerns or non-compliance. If the FDA imposes a clinical hold, trials may not recommence without FDA authorization and then only under terms authorized by the FDA. Accordingly, we cannot be sure that submission of an IND will result in the FDA allowing clinical trials to begin, or that, once begun, issues will not arise that suspend or terminate such trials.

Clinical trials involve the administration of the biological product candidate to healthy volunteers or patients under the supervision of qualified investigators, generally physicians not employed by or under the trial sponsor’s control. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial, dosing procedures, subject selection and exclusion criteria, and the parameters to be used to monitor subject safety, including stopping rules that assure a clinical trial will be stopped if certain adverse events should occur. Each protocol and any amendments to the protocol must be submitted to the FDA as part of the IND. Clinical trials are subject to extensive regulation. Clinical trials must be conducted and monitored in accordance with the FDA’s bioresearch monitoring regulations and regulations composing the GCP requirements, including the requirement that all research subjects provide informed consent. Further, each clinical trial must be reviewed and approved by an independent institutional review board, or IRB, at or servicing each institution at which the clinical trial will be conducted. An IRB is charged with protecting the welfare and rights of trial participants and considers such items as whether the risks to individuals participating in the clinical trials are minimized and are reasonable in relation to anticipated benefits. The IRB also approves the form and content of the informed consent that must be signed by each clinical trial subject or his or her legal representative and must monitor the clinical trial until completed.

Foreign studies conducted under an IND must meet the same requirements applicable to studies conducted in the United States. However, if a foreign study is not conducted under an IND, the data may still be submitted to the FDA in support of a product application, if the study was conducted in accordance with GCP and the FDA is able to validate the data.

The sponsor of a clinical trial or the sponsor’s designated responsible party may be required to register certain information about the trial and disclose certain results on government or independent registry websites, such as clinicaltrials.gov.

Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

Post-approval clinical trials, sometimes referred to as Phase 4 clinical trials, may be conducted after initial marketing approval. These clinical trials are used to gain additional experience from the treatment of patients in the intended therapeutic indication, particularly for long-term safety follow-up.

During all phases of clinical development, regulatory agencies require extensive monitoring and auditing of all clinical activities, clinical data, and clinical trial investigators. Annual progress reports detailing the results of the clinical trials must be submitted to the FDA. Written IND safety reports must be promptly submitted to the FDA and the investigators for serious and unexpected adverse events, any findings from other studies, tests in laboratory animals or in vitro testing that suggest a significant risk for human subjects, or any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. The sponsor must submit an IND safety report within 15 calendar days after the sponsor determines that the information qualifies for reporting. The sponsor also must notify the FDA of any unexpected fatal or life-threatening suspected adverse reaction within seven calendar days after the sponsor’s initial receipt of the information. Phase 1, Phase 2 and Phase 3 clinical trials may not be completed successfully within any specified period, if at all. The FDA or the sponsor or its data safety monitoring board may suspend or terminate a clinical trial at any time on various grounds, including a finding that the research subjects are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the biological product has been associated with unexpected serious harm to subjects.

Concurrently with clinical trials, companies usually complete additional studies and must also develop additional information about the physical characteristics of the biological product as well as finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. To help reduce the risk of the introduction of adventitious agents with use of biological products, the PHSA emphasizes the importance of manufacturing control for products whose attributes cannot be precisely defined. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other criteria, the sponsor must develop methods for testing the identity, strength, quality, potency and purity of the final biological product. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the biological product candidate does not undergo unacceptable deterioration over its shelf life.

U.S. Review and Approval Processes

After the completion of clinical trials of a biological product, FDA approval of a BLA must be obtained before commercial marketing of the biological product. The BLA must include results of product development, laboratory and animal studies, human trials, information on the manufacture and composition of the product, proposed labeling and other relevant information. The FDA may grant deferrals for submission of data, or full or partial waivers. The testing and approval processes require substantial time and effort and there can be no assurance that the FDA will accept the BLA for filing and, even if filed, that any approval will be granted on a timely basis, if at all.

Under the Prescription Drug User Fee Act, or PDUFA, as amended, each BLA must be accompanied by a significant user fee. The FDA adjusts the PDUFA user fees on an annual basis. PDUFA also imposes an annual program fee for biological products. Fee waivers or reductions are available in certain circumstances, including a waiver of the application fee for the first application filed by a small business.

Within 60 days following submission of the application, the FDA reviews a BLA submitted to determine if it is substantially complete before the agency accepts it for filing. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission, and may request additional information. In this event, the BLA must be resubmitted with the additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once the submission is accepted for filing, the FDA begins an in-depth substantive review of the BLA. FDA performance goals generally provide for action on a BLA within 12 months of submission. That deadline can be extended under certain circumstances, including by the FDA’s requests for additional information. The FDA reviews the BLA to determine, among other things, whether the proposed product is safe, potent, and/or effective for its intended use, and has an acceptable purity profile, and whether the product is being manufactured in accordance with cGMP to assure and preserve the product’s identity, safety, strength, quality, potency and purity. The FDA may refer applications for novel biological products or biological products that present difficult questions of safety or efficacy to an advisory committee, typically a panel that includes clinicians and other experts, for review, evaluation and a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions. During the biological product approval process, the FDA also will determine whether a Risk Evaluation and Mitigation Strategy, or REMS, is necessary to assure the safe use of the biological product. If the FDA concludes a REMS is needed, the sponsor of the BLA must submit a proposed REMS. The FDA will not approve a BLA without a REMS, if required.

Before approving a BLA, the FDA will inspect the facilities at which the product is manufactured. The FDA will not approve the product unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure that the clinical trials were conducted in compliance with IND trial requirements and GCP requirements. To assure cGMP and GCP compliance, an applicant must incur significant expenditure of time, money and effort in the areas of training, record keeping, production, and quality control.

Notwithstanding the submission of relevant data and information, the FDA may ultimately decide that the BLA does not satisfy its regulatory criteria for approval and deny approval. Data obtained from clinical trials are not always conclusive and the FDA may interpret data differently than we interpret the same data. If the agency decides not to approve the BLA in its present form, the FDA will issue a complete response letter that describes all of the specific deficiencies in the BLA identified by the FDA. The deficiencies identified may be minor, for example, requiring labeling changes, or major, for example, requiring additional clinical trials. Additionally, the complete response letter may include recommended actions that the applicant might take to place the application in a condition for approval. The complete response letter may also request additional information, including additional preclinical or clinical data, for the FDA to reconsider the application. If a complete response letter is issued, the applicant may either resubmit the BLA, addressing all of the deficiencies identified in the letter, or withdraw the application.

If a product receives regulatory approval, the approval may be significantly limited to specific diseases and dosages or the indications for use may otherwise be limited, which could restrict the commercial value of the product.

Further, the FDA may require that certain contraindications, warnings or precautions be included in the product labeling. The FDA may impose restrictions and conditions on product distribution, prescribing, or dispensing in the form of a risk management plan, or otherwise limit the scope of any approval. In addition, the FDA may require post marketing clinical trials, sometimes referred to as Phase 4 clinical trials, designed to further assess a biological product’s safety and effectiveness, and testing and surveillance programs to monitor the safety of approved products that have been commercialized.

In addition, under the Pediatric Research Equity Act, a BLA or supplement to a BLA must contain data to assess the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The FDA may grant deferrals for submission of data or full or partial waivers.

Obtaining approval can take years, requires substantial resources and depends on a number of factors, including the severity of the targeted disease or condition, the availability of alternative treatments, and the risks and benefits demonstrated in clinical trials.

Post-Approval Requirements

Any products for which we receive FDA approvals are subject to continuing regulation by the FDA, including, among other things, record-keeping requirements, reporting of adverse experiences with the product, providing the FDA with updated safety and efficacy information, product sampling and distribution requirements, and complying with FDA promotion and advertising requirements, which include, among others, standards for direct-to-consumer advertising, restrictions on promoting products for uses or in patient populations that are not described in the product’s approved uses, known as ‘off-label’ use, limitations on industry-sponsored scientific and educational activities, and requirements for promotional activities involving the internet. Although physicians may prescribe legally available products for off-label uses, if the physicians deem to be appropriate in their professional medical judgment, manufacturers may not market or promote such off-label uses. If ongoing regulatory requirements are not met, or if safety problems occur after a product reaches market, the FDA may take actions to change the conditions under which the product is marketed, including limiting, suspending or even withdrawing approval.

In addition, quality control and manufacturing procedures must continue to conform to applicable manufacturing requirements after approval to ensure the long-term stability of the product. cGMP regulations require among other things, quality control and quality assurance as well as the corresponding maintenance of records and documentation and the obligation to investigate and correct any deviations from cGMP. Manufacturers and other entities involved in the manufacture and distribution of approved products are required to register their establishments with the FDA and certain state agencies, and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP and other laws. Accordingly, manufacturers must continue to expend time, money, and effort in the area of production and quality control to maintain cGMP compliance. Discovery of problems with a product after approval may result in restrictions on a product, manufacturer, or holder of an approved BLA, including, among other things, recall or withdrawal of the product from the market. In addition, changes to the manufacturing process are strictly regulated, and depending on the significance of the change, may require prior FDA approval before being implemented. Other types of changes to the approved product, such as adding new indications and claims, are also subject to further FDA review and approval.

Discovery of previously unknown problems with a product or the failure to comply with applicable FDA requirements can have negative consequences, including adverse publicity, judicial or administrative enforcement, warning letters from the FDA, mandated corrective advertising or communications with doctors, and civil or criminal penalties, among others. Newly discovered or developed safety or effectiveness data may require changes to a product’s approved labeling, including the addition of new warnings and contraindications, and also may require the implementation of other risk management measures. Also, new government requirements, including those resulting from new legislation, may be established, or the FDA’s policies may change, which could delay or prevent regulatory approval of our tablet vaccine candidates under development.

Other U.S. Healthcare Laws and Compliance Requirements

In the United States, our activities are potentially subject to regulation by various federal, state and local authorities in addition to the FDA, including but not limited to, the Centers for Medicare and Medicaid Services, or CMS, other divisions of the U.S. Department of Health and Human Services, for instance the Office of Inspector General, the U.S. Department of Justice, or DOJ, and individual U.S. Attorney offices within the DOJ, and state and local governments. For example, sales, marketing and scientific/educational grant programs must comply with the anti-fraud and abuse provisions of the Social Security Act, the false claims laws, the physician payment transparency laws, the privacy and security provisions of the Health Insurance Portability and Accountability Act, or HIPAA, as amended by the Health Information Technology and Clinical Health Act, or HITECH, and similar state laws, each as amended.

The federal Anti-Kickback Statute prohibits, among other things, any person or entity, from knowingly and willfully offering, paying, soliciting or receiving any remuneration, directly or indirectly, overtly or covertly, in cash or in kind, to induce or in return for purchasing, leasing, ordering or arranging for the purchase, lease or order of any item or service reimbursable under Medicare, Medicaid or other federal healthcare programs. The term remuneration has been interpreted broadly to include anything of value. The Anti-Kickback Statute has been interpreted to apply to arrangements between pharmaceutical manufacturers on one hand and prescribers, purchasers, and formulary managers on the other. There are a number of statutory exceptions and regulatory safe harbors protecting some common activities from prosecution. The exceptions and safe harbors are drawn narrowly and practices that involve remuneration that may be alleged to be intended to induce prescribing, purchasing or recommending may be subject to scrutiny if they do not qualify for an exception or safe harbor. Our practices may not in all cases meet all of the criteria for protection under a statutory exception or regulatory safe harbor. Failure to meet all of the requirements of a particular applicable statutory exception or regulatory safe harbor, however, does not make the conduct per se illegal under the Anti-Kickback Statute. Instead, the legality of the arrangement will be evaluated on a case-by-case basis based on a cumulative review of all of its facts and circumstances.

Additionally, the intent standard under the Anti-Kickback Statute was amended by the Affordable Care Act to a stricter standard such that a person or entity no longer needs to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation. In addition, the Affordable Care Act codified case law that a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the federal False Claims Act (“FCA”), as discussed below.

The civil monetary penalties statute imposes penalties against any person or entity that, among other things, is determined to have presented or caused to be presented a claim to a federal health program that the person knows or should know is for an item or service that was not provided as claimed or is false or fraudulent.

The federal FCA prohibits, among other things, any person or entity from knowingly presenting, or causing to be presented, a false claim for payment to, or approval by, the federal government or knowingly making, using, or causing to be made or used a false record or statement material to a false or fraudulent claim to the federal government. As a result of a modification made by the Fraud Enforcement and Recovery Act of 2009, a claim includes “any request or demand” for money or property presented to the U.S. government. Recently, several pharmaceutical and other healthcare companies have been prosecuted under these laws for allegedly providing free product to customers with the expectation that the customers would bill federal programs for the product. Other companies have been prosecuted for causing false claims to be submitted because of the companies’ marketing of the product for unapproved, and thus non-reimbursable, uses.

HIPAA created new federal criminal statutes that prohibit knowingly and willfully executing, or attempting to execute, a scheme to defraud or to obtain, by means of false or fraudulent pretenses, representations or promises, any money or property owned by, or under the control or custody of, any healthcare benefit program, including private third-party payors and knowingly and willfully falsifying, concealing or covering up by trick, scheme or device, a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items or services. Similar to the federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation.

Also, many states have similar fraud and abuse statutes or regulations that apply to items and services reimbursed under Medicaid and other state programs, or, in several states, apply regardless of the payor.

We may be subject to data privacy and security regulations by both the federal government and the states in which we conduct our business. HIPAA, as amended by the HITECH Act, imposes requirements relating to the privacy, security and transmission of individually identifiable health information. Among other things, HITECH makes HIPAA’s privacy and security standards directly applicable to business associates independent contractors or agents of covered entities that receive or obtain protected health information in connection with providing a service on behalf of a covered entity. HITECH also created four new tiers of civil monetary penalties, amended HIPAA to make civil and criminal penalties directly applicable to business associates, and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce the federal HIPAA laws and seek attorneys’ fees and costs associated with pursuing federal civil actions. In addition, state laws govern the privacy and security of health information in specified circumstances, many of which differ from each other in significant ways, thus complicating compliance efforts.

Additionally, the Federal Physician Payments Sunshine Act under the Affordable Care Act, and its implementing regulations, require that certain manufacturers of drugs, devices, biological and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program, with certain exceptions, to report information related to certain payments or other transfers of value made or distributed to physicians and teaching hospitals, or to entities or individuals at the request of, or designated on behalf of, the physicians and teaching hospitals and to report annually certain ownership and investment interests held by physicians and their immediate family members. Failure to submit timely, accurately, and completely the required information may result in civil monetary penalties of up to an aggregate of $150,000 per year and up to an aggregate of $1 million per year for “knowing failures”. Certain states also mandate implementation of compliance programs, impose restrictions on pharmaceutical manufacturer marketing practices and/or require the tracking and reporting of gifts, compensation and other remuneration to healthcare providers and entities.

In order to distribute products commercially, we must also comply with state laws that require the registration of manufacturers and wholesale distributors of drug and biological products in a state, including, in certain states, manufacturers and distributors who ship products into the state even if such manufacturers or distributors have no place of business within the state. Some states also impose requirements on manufacturers and distributors to establish the pedigree of product in the chain of distribution, including some states that require manufacturers and others to adopt new technology capable of tracking and tracing product as it moves through the distribution chain. Several states have enacted legislation requiring pharmaceutical and biotechnology companies to establish marketing compliance programs, file periodic reports with the state, make periodic public disclosures on sales, marketing, pricing, clinical trials and other activities, and/or register their sales representatives, as well as to prohibit pharmacies and other healthcare entities from providing certain physician prescribing data to pharmaceutical and biotechnology companies for use in sales and marketing, and to prohibit certain other sales and marketing practices. All of our activities are potentially subject to federal and state consumer protection and unfair competition laws.

If our operations are found to be in violation of any of the federal and state healthcare laws described above or any other governmental regulations that apply to us, we may be subject to penalties, including without limitation, civil, criminal and/or administrative penalties, damages, fines, disgorgement, exclusion from participation in government programs, such as Medicare and Medicaid, injunctions, private “qui tam” actions brought by individual whistleblowers in the name of the government, or refusal to allow us to enter into government contracts, contractual damages, reputational harm, administrative burdens, diminished profits and future earnings, and the curtailment or restructuring of our operations, any of which could adversely affect our ability to operate our business and our results of operations.

Coverage, Pricing and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of any tablet vaccine candidates for which we obtain regulatory approval. In the United States and markets in other countries, sales of any products for which we receive regulatory approval for commercial sale will depend, in part, on the extent to which third-party payors provide coverage, and establish adequate reimbursement levels for such products. In the United States, third-party payors include federal and state healthcare programs, private managed care providers, health insurers and other organizations. The process for determining whether a third-party payor will provide coverage for a product may be separate from the process for setting the price of a product or for establishing the reimbursement rate that such a payor will pay for the product. Third-party payors may limit coverage to specific products on an approved list, also known as a formulary, which might not include all of the FDA-approved products for a particular indication. Third-party payors are increasingly challenging the price, examining the medical necessity and reviewing the cost-effectiveness of medical products, therapies and services, in addition to questioning their safety and efficacy. We may need to conduct expensive pharmaco-economic studies in order to demonstrate the medical necessity and cost-effectiveness of our tablet vaccine candidates, in addition to the costs required to obtain the FDA approvals. Our tablet vaccine candidates may not be considered medically necessary or cost-effective. A payor’s decision to provide coverage for a product does not imply that an adequate reimbursement rate will be approved. Further, one payor’s determination to provide coverage for a product does not assure that other payors will also provide coverage for the product. Adequate third-party reimbursement may not be available to enable us to maintain price levels sufficient to realize an appropriate return on our investment in product development.

Different pricing and reimbursement schemes exist in other countries. Some jurisdictions operate positive and negative list systems under which products may only be marketed once a reimbursement price has been agreed. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical trials that compare the cost-effectiveness of a particular product candidate to currently available therapies. Other countries allow companies to fix their own prices for medicines, but monitor and control company profits. The downward pressure on health care costs has become very intense. As a result, increasingly high barriers are being erected to the entry of new products. In addition, in some countries, cross-border imports from low-priced markets exert a commercial pressure on pricing within a country.

The marketability of any tablet vaccine candidates for which it receives regulatory approval for commercial sale may suffer if the government and third-party payors fail to provide adequate coverage and reimbursement. In addition, emphasis on managed care in the United States has increased and we expect the pressure on healthcare pricing will continue to increase. Coverage policies and third-party reimbursement rates may change at any time. Even if favorable coverage and reimbursement status is attained for one or more products for which we receive regulatory approval, less favorable coverage policies and reimbursement rates may be implemented in the future.

US Healthcare Reform

We anticipate that current and future U.S. legislative healthcare reforms may result in additional downward pressure on the price that we receive for any approved product, if covered, and could seriously harm our business. Any reduction in reimbursement from Medicare and other government programs may result in a similar reduction in payments from private payors. The implementation of cost containment measures or other healthcare reforms may prevent us from being able to generate revenue, attain profitability or commercialize our tablet vaccine candidates. In addition, it is possible that there will be further legislation or regulation that could harm our business, financial condition and results of operations.

Foreign Regulation

In order to market any product outside of the United States, we would need to comply with numerous and varying regulatory requirements of other countries and jurisdictions regarding quality, safety and efficacy and governing, among other things, clinical trials, marketing authorization, commercial sales and distribution of our products. Whether or not we obtain FDA approval for a product, we would need to obtain the necessary approvals by the comparable foreign regulatory authorities before we can commence clinical trials or marketing of the product in foreign countries and jurisdictions. Although many of the issues discussed above with respect to the United States apply similarly in the context of the European Union, the approval process varies between countries and jurisdictions and can involve additional product testing and additional administrative review periods. The time required to obtain approval in other countries and jurisdictions might differ from and be longer than that required to obtain FDA approval. Regulatory approval in one country or jurisdiction does not ensure regulatory approval in another, but a failure or delay in obtaining regulatory approval in one country or jurisdiction may negatively impact the regulatory process in others.

Employees and Human Capital Resources

Our management and scientific teams possess considerable experience in vaccine and anti-infective research, clinical development and regulatory matters. Our research and development team includes Ph.D.-level scientists with expertise in mucosal immunology, T cells, viral vectors and virology. General and administrative includes finance, human resources, administration, business and general management. In the year ended December 31, 2021, our employee rollforward, excluding interns, was as follows:

We also had 15 full-time equivalent contractors as of December 31, 2021. We do not have collective bargaining agreements with our employees and we have not experienced any work stoppages. We consider our relations with our employees to be good.

Our human capital resources objectives include identifying, recruiting, training, retaining, and incentivizing our existing and new employees. We maintain an equity incentive plan, the principal purpose of which is to attract, retain and reward personnel through the granting of stock-based compensation awards, in order to increase stockholder value and the success of our company by motivating such individuals to perform to the best of their abilities and achieve our objectives. To facilitate talent attraction and retention, we strive to make Vaxart a safe and rewarding workplace, with opportunities for our employees to grow and develop in their careers, supported by competitive compensation, benefits and health and wellness programs, and by programs that build connections between our employees.

In addition, as a result of the COVID-19 pandemic, we have taken steps to protect the health and safety of our employees by generally adopting a work from home policy in line with directives from the State of California and the applicable local governments, and guidance from the CDC. On-site activities have been restricted to certain essential facility and laboratory support functions and various safety protocols have been implemented.

Item 1A.  Risk Factors

You should carefully consider the following risk factors, as well as the other information in this Annual Report on Form 10-K, including our financial statements and the related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations”, as well as our other public filings. The occurrence of any of the following risks could harm our business, financial condition, results of operations and/or growth prospects or cause our actual results to differ materially from those contained in forward-looking statements we have made in this Annual Report on Form 10-K and those we may make from time to time. You should consider all of the risk factors described when evaluating our business.

We operate in a rapidly changing environment that involves a number of risks, some of which are beyond our control. This discussion highlights some of the risks that may affect future operating results. These are the risks and uncertainties we believe are most important to consider. We cannot be certain that we will successfully address these risks. If we are unable to address these risks, our business may not grow, our stock price may suffer and we may be unable to stay in business. Additional risks and uncertainties not presently known to us, which we currently deem immaterial or which are similar to those faced by other companies in our industry or business in general, may also impair our business operations.

Summary of Risk Factors

Our business is subject to numerous risks and uncertainties, discussed in more detail in the following section. These risks include, among others, the following key risks:

Risks Related to Our Business, Financial Position and Capital Requirements

Risks Related to Clinical Development, Regulatory Approval and Commercialization

Risks Related to Dependence on Third Parties

Risks Related to Our Business, Financial Position and Capital Requirements

Our business may be adversely affected by the ongoing coronavirus pandemic.

In December 2019, a novel strain of coronavirus, COVID-19, was reported to have surfaced in Wuhan, China. This virus continues to spread globally and efforts to contain the spread of COVID-19 have intensified. The outbreak and any preventative or protective actions that governments or we may take in respect of COVID-19 may result in a period of business disruption and reduced operations. Any resulting financial impact cannot be reasonably estimated at this time but may materially affect our business, financial condition and results of operations. The extent to which COVID-19 impacts our results will depend on future developments, which are highly uncertain and cannot be predicted, including new information which may emerge concerning the severity of COVID-19 and the actions to contain COVID-19 or treat its impact, among others. There may be interruptions to our supply chain due to the inability of manufacturers to continue normal business operations and to ship products. In addition, a significant outbreak of COVID-19 or other infectious diseases could result in a widespread health crisis that could adversely affect the economies and financial markets worldwide, resulting in an economic downturn that could impact our business, financial condition and results of operations. We are currently working to enhance our business continuity plans to include measures to protect our employees in the event of infection in our corporate offices, or in response to potential mandatory quarantines.

In light of the COVID-19 pandemic, it is possible that one or more government entities may take actions that directly or indirectly have the effect of abrogating some of our rights or opportunities. If we were to develop a COVID-19 vaccine, the economic value of such a vaccine to us could be limited.

Various government entities, including the U.S. government, are offering incentives, grants and contracts to encourage additional investment by commercial organizations into preventative and therapeutic agents against coronavirus, which may have the effect of increasing the number of competitors and/or providing advantages to known competitors. Accordingly, there can be no assurance that we will be able to successfully establish a competitive market share for our COVID-19 vaccine, if any.

We have a limited operating history and have generated only limited product revenue.

Even though we generate royalty revenue from Inavir, our commercialized influenza product, we are at an early stage in our clinical development process and have not yet successfully completed a large-scale, pivotal clinical trial, obtained marketing approval, manufactured our tablet vaccine candidates at commercial scale, or conducted sales and marketing activities that will be necessary to successfully commercialize our product candidates. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing and commercializing product candidates.

Our ability to generate significant revenue and achieve and maintain profitability will depend upon our ability to successfully complete the development of our tablet vaccine candidates for the treatment of coronavirus, norovirus, seasonal influenza, respiratory syncytial virus (“RSV”), cervical cancer and dysplasia caused by human papillomavirus (“HPV”) and other infectious diseases, and to obtain the necessary regulatory approvals.

Even if we receive regulatory approval for the sale of any of our product candidates, we do not know when we will begin to generate significant revenue, if at all. Our ability to generate significant revenue depends on a number of factors, including our ability to:

Because of the numerous risks and uncertainties associated with vaccine development and manufacturing, we are unable to predict the timing or amount of increased development expenses, or when we will be able to achieve or maintain profitability, if at all. Our expenses could increase beyond expectations if we are required by the FDA, or comparable non-U.S. regulatory authorities, to perform studies or clinical trials in addition to those we currently anticipate. Even if our product candidates are approved for commercial sale, we anticipate incurring significant costs associated with the commercial launch of and the related commercial-scale manufacturing requirements for our product candidates. If we cannot successfully execute on any of the factors listed above, our business may not succeed.

We have incurred significant losses since our inception and expect to continue to incur significant losses for the foreseeable future and may never achieve or maintain profitability.

We have generated only limited product revenues and we expect to continue to incur substantial and increasing losses as we continue to pursue our business strategy. Our product candidates have not been approved for marketing in the United States and may never receive such approval. As a result, we are uncertain when or if we will achieve profitability and, if so, whether we will be able to sustain it. Our ability to generate significant revenue and achieve profitability is dependent on our ability to complete development, obtain necessary regulatory approvals, and have our product candidates manufactured and successfully marketed. We cannot be sure that we will be profitable even if we successfully commercialize one of our product candidates. If we do successfully obtain regulatory approval to market our tablet vaccine candidates, our revenues will be dependent, in part, upon the size of the markets in the territories for which regulatory approval is received, the number of competitors in such markets, the price at which we can offer our product candidates and whether we own the commercial rights for that territory. If the indication approved by regulatory authorities is narrower than we expect, or the treatment population is narrowed by competition, physician choice or treatment guidelines, we may not generate significant revenue from sales of our product candidates, even if approved. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become and remain profitable, the market price of our common stock and our ability to raise capital and continue operations will be adversely affected.

We expect overall research and development expenses to increase significantly for any of our tablet vaccines, including those for the prevention of coronavirus, norovirus, influenza and RSV infection, as well as those for the treatment of HPV-related dysplasia and cancer, although we intend to fund a significant portion of these costs through partnering and collaboration agreements. In addition, even if we obtain regulatory approval, significant sales and marketing expenses will be required to commercialize the tablet vaccine candidates. As a result, we expect to continue to incur significant and increasing operating losses and negative cash flows for the foreseeable future. These losses have had and will continue to have an adverse effect on our financial position and working capital. As of December 31, 2021, we had an accumulated deficit of $219.4 million.

We are largely dependent on the success of our tablet vaccines for the prevention of coronavirus and norovirus infection, which are still in early-stage clinical development, and if one or both of these tablet vaccines do not receive regulatory approval or are not successfully commercialized, our business may be harmed.

None of our product candidates are in late-stage clinical development or approved for commercial sale and we may never be able to develop marketable tablet vaccine candidates. We expect that a substantial portion of our efforts and expenditures over the next few years will be devoted to our tablet vaccine candidates for coronavirus and norovirus. We are committing financial resources to the development of a COVID-19 vaccine, which may cause delays in or otherwise negatively impact our other development programs. In addition, our management and scientific teams have dedicated substantial efforts to our COVID-19 vaccine development. Accordingly, our business currently depends heavily on the successful development, regulatory approval and commercialization of our coronavirus and norovirus tablet vaccine. These tablet vaccines may not receive regulatory approval or be successfully commercialized even if regulatory approval is received. The research, testing, manufacturing, labeling, approval, sale, marketing and distribution of tablet vaccine candidates are and will remain subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries that each have differing regulations. We are not permitted to market our tablet vaccines in the United States until we receive approval of a Biologics License Application (“BLA”) from the FDA, or in any foreign countries until we receive the requisite approval from such countries. To date, we have only completed Phase 1 clinical trials for our bivalent norovirus tablet vaccine candidate. As a result, we have not submitted a BLA to the FDA or comparable applications to other regulatory authorities and do not expect to be in a position to do so for the foreseeable future. Obtaining approval of a BLA is an extensive, lengthy, expensive and inherently uncertain process, and the FDA may delay, limit or deny approval of our tablet vaccines for many reasons, including:

Our development of a COVID-19 vaccine candidate is at an early stage. We may be unable to produce an effective vaccine that successfully immunizes humans against SARS-CoV-2 in a timely manner, if at all.

We are in the business of developing oral vaccines that are administered by tablet rather than by injection. In response to the global outbreak of COVID-19, in January 2020 we announced that we had initiated a program to develop a coronavirus vaccine candidate based on our Vector-Adjuvant-Antigen Standardized Technology (“VAAST”) proprietary oral vaccine platform. In addition, on October 13, 2020, we announced that the first subject has been dosed in our Phase 1 study of VXA-CoV2-1, a non-replicating Ad5 vector oral tablet COVID-19 vaccine candidate. Our development of the vaccine is at an early stage, and we may be unable to produce an effective vaccine that successfully immunizes humans against SARS-CoV-2 in a timely manner, if at all.

We have also entered into an agreement with certain manufacturing partners to help develop and manufacture our experimental oral COVID-19 vaccine. If we are unsuccessful in maintaining our relationships with these and other critical third parties, our ability to develop our oral COVID-19 vaccine candidate and consequently compete in the marketplace could be impaired, and our results of operations may suffer. Even if we are successful, we cannot assure you that these relationships will result in successful development and commercialization of our oral COVID-19 vaccine candidate. Our failure, or the failure of such partners or potential partners, to comply with applicable regulations could result in sanctions being imposed on us, including clinical holds, delays, suspension or withdrawal of approval to conduct clinical investigations, license revocation, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect supplies of our potential COVID-19 vaccine.

Manufacturing any drug product with recombinant technology such as our adenovirus type 5 based vaccines presents technical challenges. Our manufacturing partners may not be able to successfully manufacture any vaccine with our VAAST platform, or to comply with cGMP, regulations or similar regulatory requirements. To date, our manufacturing partners have manufactured clinical supply for our planned clinical investigations. The number of doses of our potential vaccine that we are able to produce is dependent on the ability of our contract manufacturers to successfully and rapidly scale-up manufacturing capacity. The number of doses that we will be able to produce is also dependent in large part on the dose of the vaccine required to be administered to patients which will be determined in our clinical trials. To properly scale-up and develop a commercial process, we may need to expend significant resources, expertise, and capital.

Scale up can present problems such as difficulties with production costs and yields, quality control, including stability of the product candidate and quality assurance testing, shortages of qualified personnel or key raw materials, and compliance with strictly enforced federal, state, and foreign regulations. Our contract manufacturers may not perform as agreed. If any manufacturer encounters these or other difficulties, our ability to provide product candidates to patients in our clinical trials could be jeopardized.

Various government entities, including the U.S. government, are offering incentives, grants and contracts to encourage additional investment by commercial organizations into preventative and therapeutic agents against COVID-19, and this may have the effect of increasing the number of competitors and/or providing advantages to known competitors. We are aware of a substantial number of companies, individuals and institutions working to develop a vaccine against or treatment for COVID-19, many of which have substantially greater financial, scientific and other resources than us, and another party may be successful in producing a vaccine against COVID-19 or an effective treatment before we do. The rapid expansion of development programs directed at COVID-19 may also generate a scarcity of manufacturing capacity among contract research organizations that provide cGMP materials for development and commercialization of biopharmaceutical products.

We will require additional capital to fund our operations, and if we fail to obtain necessary financing, we may not be able to complete the development and commercialization of our tablet vaccine candidates.

We expect to spend substantial amounts to complete the development of, seek regulatory approvals for and commercialize our tablet vaccine candidates. We will require substantial additional capital to complete the development and potential commercialization of our tablet vaccine candidates for coronavirus, norovirus, seasonal influenza, RSV and HPV and the development of other product candidates. If we are unable to raise capital or find appropriate partnering or licensing collaborations, when needed or on acceptable terms, we could be forced to delay, reduce or eliminate one or more of our development programs or any future commercialization efforts. In addition, attempting to secure additional financing may divert the time and attention of our management from day-to-day activities and harm our development efforts.

As of December 31, 2021, we had $182.7 million of cash, cash equivalents and marketable securities. Since then, we have received net proceeds of $1.0 million from the sale of common stock under our Controlled Equity Offering Sales Agreement (the “September 2021 ATM”).

Although we believe these funds are sufficient to fund our operations under our current operating plan for at least one year from the date of issuance of this Annual Report, our estimate as to what we will be able to accomplish is based on assumptions that may prove to be inaccurate, and we could exhaust our available capital resources sooner than is currently expected. Because the length of time and activities associated with successful development of our product candidates is highly uncertain, we are unable to estimate the actual funds we will require for development and any approved marketing and commercialization activities. Our future funding requirements, both near and long-term, will depend on many factors, including, but not limited to:

Additional funding may not be available on acceptable terms, or at all. If we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may have to significantly delay, scale back or discontinue the development or commercialization of our product candidates or potentially discontinue operations.

Raising additional funds by issuing securities may cause dilution to existing stockholders, and raising funds through lending and licensing arrangements may restrict our operations or require us to relinquish proprietary rights.

We expect that significant additional capital will be needed in the future to continue our planned operations. Until such time, if ever, as we can generate substantial product revenues, we expect to finance our cash needs through a combination of equity offerings, royalties, debt financings, strategic alliances and license and development agreements in connection with any collaborations. We do not currently have any committed external source of funds. To the extent that we raise additional capital by issuing equity securities, our existing stockholders’ ownership may experience substantial dilution, and the terms of these securities may include liquidation or other preferences that adversely affect our common stockholders’ rights. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures, declaring dividends, creating liens, redeeming our stock or making investments.

If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, or through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties on acceptable terms, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise develop and market ourselves.

The price of our common stock has been volatile and fluctuates substantially, which could result in substantial losses for stockholders.

Our stock price has been, and in the future may be, subject to substantial volatility. As a result of this volatility, our stockholders could incur substantial losses. The stock market in general, and the market for biopharmaceutical companies in particular, has experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, you may not be able to sell your common stock at or above your initial purchase price.

The market price for our common stock may be influenced by many factors, including the results of clinical trials of our products or those of our competitors, regulatory or legal developments, developments, disputes, or other matters concerning patent applications, issued patents, or other proprietary rights, our ability to recruit and retain key personnel, public announcements by us or our strategic collaborators regarding the progress of our development candidates similar public announcements by our competitors, and other factors set forth in this quarterly report and our other reports filed with the SEC.

If our quarterly or annual results fall below the expectations of investors or securities analysts, the price of our common stock could decline substantially. Furthermore, any quarterly or annual fluctuations in our results may, in turn, cause the price of our stock to fluctuate substantially. We believe that period-to-period comparisons of our results are not necessarily meaningful and should not be relied upon as an indication of our future performance.

In addition, public statements by us, government agencies, the media or others relating to the coronavirus outbreak (including regarding efforts to develop a coronavirus vaccine) have in the past resulted, and may in the future result, in significant fluctuations in our stock price. Given the global focus on the coronavirus outbreak, any information in the public arena on this topic, whether or not accurate, could have an outsized impact (either positive or negative) on our stock price. Information related to our development, manufacturing and distribution efforts with respect to our vaccine candidates, or information regarding such efforts by competitors with respect to their potential vaccines, may also impact our stock price.

Our stock price is likely to continue to be volatile and subject to significant price and volume fluctuations in response to market and other factors, including the other factors discussed in our filings incorporated by reference herein or in future periodic reports; variations in our quarterly operating results from our expectations or those of securities analysts or investors; downward revisions in securities analysts’ estimates; and announcement by us or our competitors of significant acquisitions, strategic partnerships, joint ventures or capital commitments.

Market prices for securities of early-stage pharmaceutical, biotechnology and other life sciences companies have historically been particularly volatile. Some of the factors that cause the market price of our common stock to fluctuate include:

If we fail to obtain or maintain adequate reimbursement and insurance coverage for our product candidates, our ability to generate significant revenue could be limited.

The availability and extent of reimbursement by governmental and private payors is essential for most patients to be able to afford expensive treatments. Sales of any of our product candidates that receive marketing approval will depend substantially, both in the United States and internationally, on the extent to which the costs of our product candidates will be paid by health maintenance, managed care, pharmacy benefit and similar healthcare management organizations, or reimbursed by government health administration authorities, private health coverage insurers and other third-party payors. If reimbursement is not available, or is available only on a limited basis, we may not be able to successfully commercialize our product candidates. Even if coverage is provided, the approved reimbursement amount may not be high enough to allow us to establish or maintain adequate pricing that will allow us to realize a sufficient return on our investment.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in Europe, Canada and other countries may cause us to price our product candidates on less favorable terms that we currently anticipate. In many countries, particularly the countries of the European Union, the prices of medical products are subject to varying price control mechanisms as part of national health systems. In these countries, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a product. To obtain reimbursement or pricing approval in some countries, we may be required to conduct a clinical trial that compares the cost-effectiveness of our product candidates to other available therapies. In general, the prices of products under such systems are substantially lower than in the United States. Other countries allow companies to fix their own prices for products, but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the United States, the level of reimbursement for our products is likely to be reduced compared with the United States and may be insufficient to generate commercially reasonable revenues and profits.

Moreover, increasing efforts by governmental and third-party payors, in the United States and internationally, to cap or reduce healthcare costs may cause such organizations to limit both coverage and level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. We expect to experience pricing pressures in connection with the sale of any of our product candidates due to the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative changes. The downward pressure on healthcare costs in general, particularly prescription drugs and surgical procedures and other treatments, has become very intense. As a result, increasingly high barriers are being erected to the entry of new products into the healthcare market.

Our future success depends on our ability to retain executive officers and attract, retain and motivate qualified personnel.

We rely on our executive officers and the other principal members of the executive and scientific teams, particularly our President and Chief Executive Officer, Andrei Floroiu and our Chief Scientific Officer, Sean N. Tucker, Ph.D. The employment of our executive officers is at-will and our executive officers may terminate their employment at any time. The loss of the services of any of our senior executive officers could impede the achievement of our research, development and commercialization objectives. We do not maintain “key person” insurance for any executive officer or employee.

Recruiting and retaining qualified scientific, clinical and sales and marketing personnel is also critical to our success. We may not be able to attract and retain these personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. Our industry has experienced an increasing rate of turnover of management and scientific personnel in recent years. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in devising our research and development and commercialization strategy. Our consultants and advisors may be employed by third parties and have commitments under consulting or advisory contracts with other entities that may limit their availability to advance our strategic objectives. If any of these advisors or consultants can no longer dedicate a sufficient amount of time to us, our business may be harmed.

We will need to expand our organization, and may experience difficulties in managing this growth, which could disrupt operations.

Our future financial performance and our ability to commercialize our product candidates, continue to earn royalties and compete effectively will depend, in part, on our ability to effectively manage any future growth. As of December 31, 2021, we had 110 full-time employees, which we believe would be insufficient to commercialize our vaccine product candidates. We may have operational difficulties in connection with identifying, hiring and integrating new personnel. Future growth would impose significant additional responsibilities on our management, including the need to identify, recruit, maintain, motivate and integrate additional employees, consultants and contractors. Also, our management may need to divert a disproportionate amount of its attention away from our day-to-day activities and devote a substantial amount of time to managing these growth activities. We may not be able to effectively manage the expansion of our operations, which may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. Our expected growth could require significant capital expenditures and may divert financial resources from other projects, such as the development of our product candidates. If we are unable to effectively manage our growth, our expenses may increase more than expected, our ability to generate and/or grow revenues could be reduced, and we may not be able to implement our business strategy.

Many of the other pharmaceutical companies that we compete against for qualified personnel and consultants have greater financial and other resources, different risk profiles and a longer history in the industry than us. They may also provide more diverse opportunities and better chances for career advancement. Some of these characteristics may be more appealing to high-quality candidates and consultants than what we are able to offer. If we are unable to continue to attract and retain high-quality personnel and consultants, the rate and success at which we can select and develop our product candidates and our business will be limited.

We are subject to multiple legal proceedings, and may be subject to additional legal proceedings, which may result in substantial costs, divert management’s attention and have a material adverse effect on our business, financial condition and results of operations.

We are currently subject to multiple pending legal proceedings, as described in this report. We may become involved in additional legal proceedings relating to the aforementioned matters or, from time to time, we may become involved in legal proceedings involving unrelated matters. Due to the inherent uncertainties in legal proceedings, we cannot accurately predict their ultimate outcome. Our stock price has been extremely volatile, and we may become involved in additional securities class action lawsuits in the future. Any such legal proceedings, regardless of their merit, could result in substantial costs and a diversion of management’s attention and resources that are needed to successfully run our business, could impair the Company’s ability to recruit and retain directors, officers, and other key personnel, could impact its ability to secure financing, insurance, and other transactions (or the terms of any such financings, insurance, or other transactions), and for these and other reasons could have a material adverse impact on our business, financial condition, results of operations, and prospects.

We could face risks related to the potential outcomes of the investigation by the U.S. Attorney’s office and/or SEC informal inquiry, including potential fines, penalties, damages or other remedies that could be imposed on us, substantial legal costs and expenses, significant management distraction, and potential reputational damages that we could suffer as a result of adverse findings.

In July 2020, the U.S. Attorney’s Office for the Northern District of California provided a grand jury subpoena to the Company seeking information pertaining to the Company’s participation in, and disclosure of, an Operation Warp Speed-funded (“OWS”) non-human primate study of the Company’s oral COVID-19 vaccine and certain corporate, financing and stock transactions. In October 2020, the Company was informed that the investigation was being transferred to the Office of the U.S. Attorney for the Eastern District of New York and the Fraud Section of Main Justice (collectively, “DOJ”), and that the Office of the U.S. Attorney for the Northern District of California required no further response or action from the Company. In November 2020, the Company received a grand jury subpoena from DOJ that seeks substantially the same information as the earlier subpoena from the Northern District of California. In August 2020, the Enforcement Division of the SEC requested that the Company provide, on a voluntary basis, certain documents and information relating to the Company’s participation in the aforementioned OWS-funded nonhuman primate study. The SEC has advised us that this informal, non-public fact-finding inquiry should not be construed as an indication that we or anyone else has violated the law or that the SEC has any negative opinion of any person, entity or security. The Company is cooperating with the SEC and DOJ and has provided them both with information and documents. We do not intend to comment further on these matters until they are closed or further action is taken by the SEC or the DOJ that, in our judgment, merits further comment or public disclosure. We could face risks related to the potential outcomes of these inquiries, including legal costs and expenses, potential regulatory action, penalties, damages or other remedies that could be imposed on us, management distraction, and potential reputational damage that we could suffer as a result of potential adverse findings.

If securities or industry analysts do not publish research, or publish inaccurate or unfavorable reports about our business, our stock price and trading volume could decline.

The trading market for our common stock is influenced by independent research and reports that securities or industry analysts publish about us or our business from time to time. If one or more of the analysts who cover us should downgrade our shares or change their opinion of our business prospects, our share price would likely decline.

Risks Related to Clinical Development, Regulatory Approval and Commercialization

The regulatory pathway for coronavirus vaccines is evolving and may result in unexpected or unforeseen challenges.

To date, VXA-CoV2-1 has moved rapidly through the FDA regulatory review process. The speed at which all parties are acting to create and test therapeutics and vaccines for COVID-19 is unusual, and evolving or changing plans or priorities within the FDA, including changes based on new knowledge of COVID-19 and how the disease affects the human body, may significantly affect the regulatory timeline for VXA-CoV2-1. Results from clinical testing may raise new questions and require us to redesign proposed clinical trials, including revising proposed endpoints or adding new clinical trial sites or cohorts of subjects. Results from our vaccine (and other COVID-19) trials may require us to perform additional preclinical studies in order to advance our vaccine candidate. Discussions with FDA regarding the design of the anticipated Phase 2 and 3 studies for VXA-CoV2-1 are ongoing and important aspects of the trial design have yet to be determined, including the number of patients to be enrolled, the specific endpoints of the trial and the methods for obtaining and testing samples in the trial. The incidence of COVID-19 in the communities where our studies might be conducted will vary across different locations. If the overall incidence of COVID-19 in those locations is low, it may be difficult for us to recruit subjects or for any study we might perform to demonstrate differences in infection rates between participants in the study who receive placebo and participants in the study who receive VXA-CoV2-1. The availability of other authorized vaccines may decrease the population of clinical trial subjects willing to participate in our future trials.

The FDA has the authority to grant an Emergency Use Authorization to allow unapproved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions when there are no adequate, approved, and available alternatives. If we are granted an Emergency Use Authorization for VXA-CoV2-1, we would be able to commercialize VXA-CoV2-1 prior to FDA approval. Furthermore, the FDA may revoke an Emergency Use Authorization where it is determined that the underlying health emergency no longer exists or warrants such authorization, and we cannot predict how long, if ever, an Emergency Use Authorization would remain in place. Such revocation could adversely impact our business in a variety of ways, including if VXA-CoV2-1 is not yet approved by the FDA and if we and our manufacturing partners have invested in the supply chain to provide VXA-CoV2-1 under an Emergency Use Authorization.

In addition, any success in preclinical testing we might observe for our COVID-19 vaccine candidates may not be predictive of the results of later-stage human clinical trials. Factors such as efficacy, immunogenicity, and adverse events can emerge at any time in clinical testing and have the potential to have adverse consequences for our ability to proceed with clinical trials. Other factors such as manufacturing challenges, availability of raw materials, and slow-downs in the global supply chain may delay or prevent us from receiving regulatory approval of our vaccine candidate or, if we do receive regulatory approval, prevent a successful product launch. We may not be successful in developing a vaccine, or another party may be successful in producing a more efficacious vaccine or other treatment for COVID-19.

If we fail to continue to develop and refine the formulations of our tablet vaccine candidates, we may not obtain regulatory approvals, and even if approved, the commercial acceptance of our tablet vaccine candidates would likely be limited.

In our H1N1 influenza Phase 2 trial we used vaccine tablets that contained approximately 1.5 x 10¹⁰ IU of vaccine. Accordingly, subjects in this trial were required to take 7 tablets in a single setting to reach the aggregate dose of 1 x 10¹¹ IU, the target dose for this trial. We believe that in order to fully capture the commercial success of our seasonal influenza vaccine candidate, we will need to continue to refine our formulation and develop influenza vaccine tablets that contain the desired dose for each vaccine strain in a single tablet, resulting in a vaccination regime of no more than four tablets. Increasing the potency of the vaccine tablets may affect the stability profile of the vaccine and we may not be able to reduce the vaccination regime for an influenza strain to a single tablet or combine the four influenza strains into one vaccine tablet. In addition, increasing the potency of the vaccine tablets or combining the influenza strains necessary to create a quadrivalent vaccine may adversely affect manufacturing yields and render such tablets too costly to manufacture at commercial scale. Our efforts to develop tablet vaccine candidates for norovirus and RSV face similar formulation challenges. If we are unable to further develop and refine the formulations of our tablet vaccine candidates, we may be unable to obtain regulatory approval from the FDA or other regulatory authorities, and even if approved, the commercial acceptance of our tablet vaccine candidates would likely be limited.

Clinical trials are very expensive, time-consuming, difficult to design and implement and involve an uncertain outcome, and if they fail to demonstrate safety and efficacy to the satisfaction of the FDA, or similar regulatory authorities, we will be unable to commercialize our tablet vaccine candidates.

Our tablet vaccine candidates for norovirus and seasonal influenza are still in early-stage clinical development. Both will require extensive additional clinical testing before we are prepared to submit a BLA for regulatory approval for either indication or for any other treatment regime. Such testing is expensive and time-consuming and requires specialized knowledge and expertise. We cannot predict with any certainty if or when we might submit a BLA for regulatory approval for any of our tablet vaccine candidates, which are currently in clinical development, or whether any such BLAs will be approved by the FDA. Human clinical trials are very expensive and difficult to design and implement, in part because they are subject to rigorous regulatory requirements. For instance, the FDA may not agree with our proposed endpoints for any clinical trial we propose, which may delay the commencement of our clinical trials. The clinical trial process is also time-consuming. We estimate that the clinical trials we need to conduct to be in a position to submit BLAs for our tablet vaccine candidates for seasonal influenza, norovirus and RSV will take several years to complete. Furthermore, failure can occur at any stage of the trials, and we could encounter problems that cause us to abandon or repeat clinical trials. Our vaccine candidates in the later stages of clinical trials may fail to show the desired safety and efficacy traits despite having progressed through preclinical studies and initial clinical trials. Also, the results of early clinical trials of the tablet vaccine candidates for seasonal influenza, norovirus and RSV may not be predictive of the results of subsequent clinical trials. Furthermore, the FDA may impose additional requirements to conduct preclinical studies to advance the HPV therapeutic vaccine candidates which could delay initiation of Phase 1 studies. A number of companies in the biopharmaceutical industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or adverse safety profiles, notwithstanding promising results in earlier trials.

Moreover, preclinical and clinical data are often susceptible to multiple interpretations and analyses. Many companies that have believed their vaccine candidates performed satisfactorily in preclinical studies and clinical trials have nonetheless failed to obtain marketing approval of their products. Additionally, success in preclinical testing and early clinical trials does not ensure success in later clinical trials, which involve many more subjects and, for influenza, all four strains rather than the one strain we have studied in Phase 1 clinical trials to date. Accordingly, the results of later clinical trials may not replicate the results of prior clinical trials and preclinical testing or may be interpreted in a way that may not be sufficient for marketing approval.

We may experience numerous unforeseen events during, or as a result of, clinical trials that could delay or prevent our ability to receive marketing approval or commercialize our tablet vaccine candidates, including that:

If we are required to conduct additional clinical trials or other testing of our tablet vaccine candidates beyond those that we currently contemplate, if we are unable to successfully complete clinical trials of our tablet vaccine candidates or other testing, if the results of these trials or tests are not positive or are only modestly positive or if there are safety concerns, we may:

Product development costs will also increase if we experience delays in testing or in receiving marketing approvals. We do not know whether any clinical trials will begin as planned, will need to be restructured or will be completed on schedule, or at all. Significant clinical trial delays also could shorten any periods during which we may have the exclusive right to commercialize our tablet vaccine candidates, could allow our competitors to bring products to market before we do, and could impair our ability to successfully commercialize our tablet vaccine candidates, any of which may harm our business and results of operations.

COVID-19 could adversely impact our preclinical studies and clinical trials.

Since the initial report of a novel strain of coronavirus, SARS-CoV-2, in China in December 2019, COVID-19 has spread to multiple countries, including the United States. We have active and planned preclinical studies and clinical trial sites in the United States. On October 13, 2020, we announced that the first subject has been dosed in our Phase 1 study of VXA-CoV2-1, a non-replicating Ad5 vector oral tablet COVID-19 vaccine candidate.

As COVID-19 continues to spread around the globe, we will likely experience disruptions that could severely impact our planned and ongoing preclinical studies and clinical trials, including preclinical and clinical studies and manufacturing of VXA-CoV2-1 and clinical trials of our vaccine candidate for the GI.1 and GII.4 norovirus strains. Effects on our preclinical studies and clinical trial programs include, but are not limited to: