10-K

vxrt20201211_10k.htm

FORM 10-K

vxrt20191213_10k.htm

Table of Contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2020

For the transition period from to

Commission file number: 001-35285

Vaxart, Inc.

(Exact Name of Registrant as Specified in its Charter)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading symbol Name of each exchange on which registered

Common stock, $0.0001 par value VXRT The Nasdaq Capital Market

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☑ No ☐

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐ No ☑

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☑ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☑ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer ☑ Accelerated filer ☐

Non-accelerated filer ☐ Smaller reporting company ☐

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☑

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☑

The aggregate market value of the Registrant’s common stock held by non-affiliates of the Registrant as of the last business day of the Registrant’s most recently completed second fiscal quarter, June 30, 2020, based on the last reported sales price of the Registrant’s common stock of $8.85 per share, was $842,046,746. As of February 24, 2021, the registrant had a total of 117,766,672 shares of common stock issued and outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

The registrant intends to file a definitive proxy statement pursuant to Regulation 14A within 120 days after the end of the fiscal year ended December 31, 2020. Portions of such proxy statement are incorporated by reference into Part III of this Form 10-K.

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TABLE OF CONTENTS

Page

FORWARD-LOOKING STATEMENTS 1

PART I

ITEM 1. Business 2

ITEM 1A. Risk Factors 46

ITEM 1B. Unresolved Staff Comments 83

ITEM 2. Properties 84

ITEM 3. Legal Proceedings 84

ITEM 4. Mine Safety Disclosures 84

PART II

ITEM 6. Selected Financial Data 86

ITEM 7A. Quantitative and Qualitative Disclosures About Market Risk 97

ITEM 8. Financial Statements and Supplementary Data 98

ITEM 9A. Controls and Procedures 133

ITEM 9B. Other Information 134

PART III

ITEM 10. Directors, Executive Officers and Corporate Governance 135

ITEM 11. Executive Compensation 135

ITEM 14. Principal Accounting Fees and Services 135

PART IV

ITEM 15. Exhibits and Financial Statement Schedules 136

EXHIBIT INDEX 137

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FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K for the year ended December 31, 2020, 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.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

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.

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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 human dosing for our Phase 1 clinical trial for our SARS CoV-2 vaccine candidate, that commenced in October 2020 and met its primary and secondary endpoints. 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. Our monovalent H1 influenza vaccine protected participants against H1 influenza infection in a Phase 2 challenge study.

In addition, we are developing our first therapeutic vaccine targeting cervical cancer and dysplasia caused by human papillomavirus (“HPV”). Pending licensing, partnering or collaboration agreements, our seasonal influenza, RSV and HPV programs are currently on hold.

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.

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Our Product Pipeline

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

5. HPV therapeutic pre-IND feedback received. Program presently on hold.

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

According to the CDC, in late 2019 an outbreak of COVID-19, caused by the virus SARS-CoV-2, began in Wuhan, China. The disease spread rapidly and person-to-person transmission has been widely documented. Stay-at-home orders or similar mandates were issued in all 50 states in the U.S. and throughout Europe and restrictions on certain activities, especially those involving large gatherings of people, remain in place, with regional variations. By February 24, 2021, more than 112 million COVID-19 cases had been identified in over 200 countries and territories worldwide, including the United States, where the CDC had reported over 28 million infections and 501,000 deaths.

On September 14, 2020, we announced that the U.S. Food and Drug Administration (the “FDA”) had permitted our Investigational New Drug (“IND”) application to proceed. On October 13, 2020, we announced that a Phase 1 study had commenced and on February 3, 2021, we announced preliminary results.

The Phase 1 study utilized an open-label, dose-ranging design to evaluate the safety and immunogenicity of Vaxart’s tablet adenoviral-vector based COVID-19 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-CoV-2. Five subjects in the low dose group received a boost four weeks after their initial vaccination. Study subjects were 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.

Male and female volunteers who were between the ages of 18 to 54 years with body mass index (“BMI”) between 17 and 30 kg/m2 inclusive at screening, 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, were eligible to participate in this study. Post confirmation of eligibility, five sentinel subjects were enrolled into Cohort 1 and immunized with the low dose (1x1010 infectious units (“IU”) ± 0.5 log increase / reduction (“log”)) VXA-CoV2-1 oral vaccine.

The primary objective was to determine the safety of our VXA-CoV2-1 oral vaccine delivered by enteric tablet. Safety and tolerability were evaluated through the detection and documentation of solicited symptoms of reactogenicity (seven days post each vaccination), unsolicited Adverse Events (“AEs”) (through 28 days post last vaccination, or Day 29; Day 57 for Cohort 1), Serious Adverse Events (“SAEs”), Medically Attended Adverse Events (“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.

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 active study 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 of between four and five months post initial vaccinations. No serious AEs have been reported to date.

The secondary objective of this study was to determine the immunogenicity of the vaccine. The vaccine was immunogenic, and immune responses against SARS-CoV-2 were observed in approximately 85% of subjects. In particular, increases in Th1 cytokines and markers were observed in the T cells that recognize the SARS-CoV-2 S and N proteins in the clinical trial. Cytotoxic T cells, those that express the surface marker CD8, at day eight had a high percentage of cells that made IFNg, TNFa, and/or CD107a in response to stimulation with the S protein, with substantial increases compared to the first day of the study. B cell plasmablasts increased in subjects post immunization, as well as upregulation of the mucosal homing receptor and surface IgA on those B cells in a dose dependent manner. While no neutralizing antibody responses were observed in the serum of subjects, preliminary analysis showed that increases in IgA responses to the S protein, the receptor binding domain, and the N protein could be found in some subjects and several different compartments including nasal and saliva samples. Given the dose dependent manner in which the B cells of interest were activated, future studies of this candidate will focus on dose ranging and boosting to increase the mucosal immune responses to SARS-CoV-2.

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 a little 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.

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

Vaxart’s bivalent vaccine demonstrated robust immunogenicity in Phase 1 testing, 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, and 86% and 90%, respectively, for the two monovalent cohorts of the study. There was no interference observed in the bivalent arm of the study.

As previously disclosed, we suspended our norovirus program in late 2019. In October 2020 we recently restarted clinical development with our norovirus vaccine candidate. The next step in the clinical development program is administering a second dose to a subset of participants in the Phase 1b bivalent study. Additionally, a Phase 1b dose ranging study in elderly adult subjects aged 55 to 80 years old is currently in the start-up phase with enrollment expected to be initiated in April 2021. After this Phase 1b elderly study, we plan to initiate a Phase 2 safety and dose confirmation study with our bivalent norovirus vaccine in 2021. A Phase 2 challenge study may also be considered, and could be conducted in parallel with, before or after the Phase 2 dose confirmation study. The Phase 2 dose confirmation study would be followed by a Phase 3 efficacy study in subjects age 18 and over, after an End of Phase 2 Meeting to gain FDA concurrence.

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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 has the potential to address many of the limitations of current injectable egg-based influenza vaccines, because: our tablet vaccine candidates are designed to create broad and durable immune responses, which may provide immunity and protect against strain variants; our vaccine is delivered as a room temperature-stable tablet, which we believe would provide a more convenient method of administration to enhance patient acceptance, and should simplify distribution and administration; and, by using recombinant methods, we believe our tablet vaccine may be manufactured more rapidly than vaccines manufactured using egg-based methods and should eliminate the risk of allergic reactions to egg protein.

Clinical Trial Update. 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 the Assistant Secretary for Preparedness and Response; 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 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 provided evidence that our vaccines may protect through mucosal immunity, the first line of defense against mucosal infections such as flu, norovirus, RSV and others, a potential key advantage over injectable vaccines for these indications.

At this time, we aim to finance development and commercialization of our seasonal quadrivalent influenza oral tablet vaccine through third-party collaboration and licensing arrangements and/or non-dilutive funding. In the future, we may also consider equity offerings and/or debt financings to fund the program. Pending a licensing, partnering or collaboration agreement, the seasonal flu program is currently on hold.

In addition to our conventional seasonal flu vaccine, we entered into a research collaboration agreement with Janssen Vaccines & Prevention B.V. (“Janssen”) to evaluate our proprietary oral vaccine platform for the Janssen universal influenza vaccine program. Under the agreement, we produced non-GMP oral vaccine containing certain proprietary antigens from Janssen and tested the product in a preclinical challenge model. The study has been completed and we have submitted a report to Janssen. Janssen has an option to negotiate an exclusive worldwide license to our technology encompassing the Janssen antigens.

Based on the positive results of our cotton rat study, we believe our proprietary oral vaccine platform has the potential to be the optimal vaccine delivery system for RSV, offering potential advantages over injectable vaccines. We will seek to develop a tablet RSV vaccine by licensing one or more RSV protein antigens that have demonstrated protection against RSV infection in clinical studies, or by partnering with a third party with RSV antigens that can be delivered with our platform. Pending a licensing, partnering or collaboration agreement, the RSV program is currently on hold.

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 for our first therapeutic vaccine targeting HPV16 and HPV18 with the FDA, and we subsequently submitted a pre-IND briefing package. We received feedback from the FDA in January 2019. The HPV program is currently on hold while the Company is focusing its efforts on the COVID-19 vaccine.

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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:

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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.

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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.

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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 challenge study was recently 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 recently 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.

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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 through populations in the United Kingdom (B.1.1.7), South Africa (B.1.351) and Brazil (P.1). These particular 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. 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. Recent data from a Johnson & Johnson 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 Oxford-AstraZeneca vaccine campaign in Africa has recently been halted due to efficacy being only 25% against the dominant circulating strain. While laboratory experiments indicate that Moderna and Pfizer-BioNTech vaccines are effective against the U.K. variant B.1.1.7, it seems unlikely that substantial cross-protection will extend to P1 or B.1.351 mutants. These results indicate as novel S protein variants continue to emerge current vaccination approaches will need to be updated to offer immune protection against new SARS-CoV-2 mutants.

Our COVID-19 Vaccine Candidate

Our 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.

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.

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 1⁄2 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.

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-CoV-2. 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

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. N3c).

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. 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. N3

A B C

Figure N3. 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 N4A-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 N4c). 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 N4d).

Fig. N4

Figure N4. 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. N5

Figure N5.Fold rise in IgA in serum, nasal and saliva samples.

MesoScale Discovery (MSD) SARS-CoV-2 V-plex plates were used to measure spike (S), nucleoprotein (N) and receptor binding domain (RBD) in serum, nasal and saliva samples. Sera was measured at a dilution of 1:100, nasal and saliva samples measured at a dilution of 1:10. Fold rise was calculated by the division of day 8 over day 1 (baseline) MSD arbitrary units.

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

We plan to commence a Phase 2a study in the second quarter of 2021 utilizing 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 is currently being planned. Under this Phase 2a protocol 48 participants will be enrolled to receive either a low dose (n=16), mid dose (n=16) or a high dose (n=16) of the vaccine VXA-CoV-2. The study will be enrolled in six cohorts of eight subjects each, three cohorts will be aged 18 to 55 years old and three cohorts will enroll older adults aged 56 to 75 years old. 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 proposed study design is shown in the table below:

Table 1. VXA-COV2-201 Dose Proposal

Treatment Group Dose (±0.5 log) Population (yrs.) No. of Doses

After signing an informed consent, participants will undergo screening assessments to determine study eligibility over a 30-day screening period. Screening assessments will include a SARS-CoV-2 rapid antibody or antigen test. 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). 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) oral vaccine delivered by enteric tablet which 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.

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”).

Solicited Adverse Events*(1) Placebo N=20 Low Dose N=23 High Dose N=23

Number of Subjects with Any Symptoms 10 (50%) 11 (48%) 14 (61%)

Gastrointestinal disorders

General disorders and administration site conditions

Nervous system disorders

(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 vaccine study was an open labeled study, and enrolled sequentially from group A to group D. The primary endpoint of the study was to evaluate the safety of all dosing regimens and the secondary endpoint was to compare immunogenicity between groups by BT50 titers and antibody secreting cells (ASC) counts.

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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.

Solicited Adverse Events Group A N=15 Group B N=15 Group C N=15 Group D N=15

GASTROINTESTINAL DISORDERS

Abdominal Pain, Upper 0 1 (7%) 0 0

GENERAL DISORDERS

NERVOUS SYSTEM DISORDERS

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.

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

Number of Subjects with Any Symptoms 9 (45%) 8 (53%) 16 (53%) 4 (27%)

Gastrointestinal disorders

General disorders and Nervous system disorders

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 Leb synthetic glycan as the coating antigen. Titers rose in the vaccine recipients, and at all timepoints (Figure 6). By the Leb 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.

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GMT for Leb BT50 assays

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

HBGA Leb

Group D0 LSGMT (95 CI) D28 LSGMT (95 CI) LSGMR p value*

Overall significance 0.0017

*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.

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Fig. 6. Geometric Mean Titers vs. Time.

Caption. Geomean Serum BT50 Titers over time for Leb.

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.

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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.

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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, Leb

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

Group Description DO GMT D28 (or D36) GMFR GMT D56 GMFR D56

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 2nd 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.

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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.

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%).

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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 is planned for early 2021 to further evaluate safety and immunogenicity of the norovirus vaccine.

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.

Phase 2 Norovirus GI.1 Strain Challenge Study. We may conduct a challenge study with our monovalent GI.1 norovirus vaccine candidate dependent on the availability of resources and vaccine.

Phase 2 Efficacy and Safety Trial. This trial will be designed to assess the safety, immunogenicity and possibly the efficacy of the bivalent vaccine in an expanded population of adults ranging in age from 18 to 49 years and step up to adults age 50 to 64, and 65 and older.

Path to Approval. After completing the Phase 2 trial, 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

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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

● longer manufacturing, shipping and handling time for suppliers;

● cold storage requirement throughout the logistics chain;

● potential for needle injuries; and

● medical waste.

Limitations for Users

● fear of needles;

● pain at injection site; and

● potential for allergic reactions to the egg component of the vaccine.

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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.

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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 age 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 10 10 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.

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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.

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

VAXART Commercial VAXART-Commercial Placebo

n % (95% CI) n % (95% CI) Rate Difference (95% CI) n % (95% CI)

*Illness was defined as a combination of symptoms reported on a patient reported outcome tool (Flu-PROTM) 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*.

Treatment Arm N Number Infected Percent (95% CI) Posterior P

*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.

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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.

Full Analysis Set - Vaccination Phase

Baseline (Pre-Dosing) 30 Days Post Dosing

Strain: A/California/7/2009

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.

Vaccination Phase

Baseline (Pre-Dosing) Day 8 (Post-Dosing)

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.

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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 102.69 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.

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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.

Seasonal Influenza Clinical Development Strategy and Pathway

We aim to partner with and/or to obtain funding from the U.S. federal government to finance the development and commercialization of our seasonal quadrivalent influenza oral tablet vaccine. In the future, we may also consider equity offerings and/or debt financings to fund the program.

Our Human Papillomavirus (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 – HPV16 and HPV18 – 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.

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Our HPV Therapeutic Vaccine Candidate

Our plan is to develop a bivalent HPV vaccine against HPV 16 and 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 HPV16 and our HPV18 vaccine candidates. Specifically, mice given our HPV16 or HPV18 vaccines induced T cell responses to HPV as measured by IFN gamma ELISPOT. In addition, our HPV16 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 HPV16 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.

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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 HPV16 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.

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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 FDA.

Clinical

We will propose to test the vaccine in subjects with cervical dysplasia related to HPV16 or HPV18, 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.

General

Currently, all HPV development is on hold while the Company is focusing its efforts on the COVID-19 vaccine.

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 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.

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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 Takeda is developing a norovirus vaccine 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.

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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.

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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:

● FDA review and approval, or licensure, of the BLA.

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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.

VXRT US Equity

VXRT · 10-K · period ended 2020-12-31

Item 1. Business

VXRT US Equity☆

VXRT · 10-K · period ended 2020-12-31

Item 1. Business

VXRT US Equity