Candidate: VXA-CoV2-1
Category: VAX
Type: Oral recombinant vaccine administered by room temperature-stable tablet, and based on proprietary VAAST™ Platform. The vaccine is designed to target both the spike protein (S) and nucleoprotein (N).
2021 Status: Vaxart said February 25 that it will advance VXA-CoV2-1 into Phase II testing during the second quarter. Three weeks earlier, Vaxart reported preliminary data from its Phase I trial of VXA-CoV2-1 (NCT04563702) showing that its oral COVID-19 tablet vaccine candidate was generally well-tolerated, and immunogenic as measured by multiple markers of immune response to SARS-CoV-2 antigens.
VXA-CoV2-1 triggered multiple immune responses against SARS-CoV-2 antigens, including CD8+ cytotoxic T-cell response to the viral Spike (S) protein, which Vaxart said was higher than seen in any previous Vaxart clinical trial. The company also reported an increase in plasmablast cell number and an upregulation of the mucosal homing receptor; an increase in proinflammatory Th1 cytokines; and IgA responses in serum and/or nasal swab samples in 100% of participants receiving two doses.
However, the company also acknowledged that neutralizing antibodies were not detected in serum and IgG responses were not detected in most subjects. “It is very important to recognize that for our oral tablet vaccine, serum neutralizing antibodies are not an appropriate proxy for efficacy,” Vaxart CEO Andrei Floroiu said during a March 2 conference call. He cited an earlier study showing efficacy for VXA-CoV2-1 vs. an influenza vaccine based on B cell activity. Compared with injectable vaccines, he said, “our oral vaccine generated a broader adaptive immune response.”
Vaxart also said that because the N protein is less prone to mutations than the S protein, viral variants of SARS-CoV-2 may be less likely to escape protection.
2020 Status: Vaxart on October 14 announced topline results from its Hamster Challenge Study showing that all hamsters that received two oral doses of VXA-CoV2-1 showed neither systemic weight loss nor lung weight gain. By contrast, Vaxart said, all unvaccinated hamsters lost at least 8% of their body weight, and all showed lung weight as a percentage of body weight that was approximately twice that of the vaccinated hamsters. Full results will be published when data analysis is complete, the company added.
That same morning, the company acknowledged in a regulatory filing that it had provided documents to the U.S Attorney’s Office for the Northern District of California after it served the company with a grand jury subpoena. The subpoena sought information on Vaxart’s participation in, and disclosure of, an Operation Warp Speed-funded nonhuman primate study, as well as option grants, warrant transactions, “and other corporate and financing matters disclosed since March 2020.” Vaxart said it “voluntarily provided documents requested by the SEC and is cooperating with this informal inquiry.”
On October 13, Vaxart said the first subject has been dosed in its Phase I trial (NCT04563702) assessing VXA-CoV2-1. According to the company, VXA-CoV2-1 is the first oral tablet vaccine to reach human clinical trials. The open-label study is designed to enroll up to 48 healthy adults ages 18-54 years old, who will receive the low or high dose of the oral tablet at days 1 and 29. Safety, reactogenicity and immunogenicity assessments will be performed at set times during the active phase.
Vaxart founder and Chief Scientific Officer Sean Tucker, PhD, said VXA-CoV2-1 was advanced into the clinic based on preclinical data showing that the oral vaccine was capable of inducing both a robust systemic immune response and a strong mucosal immune response, specifically in the lungs.
The Phase I study is expected to be completed in December and will have a 12-month safety follow-up period post last vaccination, Vaxart said.
In September, Tucker and a team of Vaxart researchers posted a preprint in bioRxiv detailing preclinical studies in mice of Vaxart’s oral tablet vaccine. The vaccine and its full length, wild-type spike antigen induced significantly higher neutralizing antibodies in the periphery and in the lungs, the researchers reported, with antigen-specific CD4+ and CD8+ T cells induced by the vaccine candidate at low and high doses.
“These studies in mice represent our first step in creating a vaccine candidate, demonstrating the immunogenicity of the construct at even low vaccine doses and the elucidation of the full-length spike protein as a leading candidate antigen to induce T cell responses and superior systemic and mucosal neutralizing antibody,” the Vaxart researchers wrote. “Future work will focus on the immune responses in humans.”
In June, Vaxart said its oral COVID-19 vaccine candidate had joined the handful of experimental vaccines being studied as part of President Donald Trump’s commitment to delivering 300 million vaccine doses protecting against SARS-CoV-2 by January 2021—while the company gears up to manufacture as many as 1 billion doses a year.
The South San Francisco, CA, vaccine developer said Friday that its room temperature stable tablet vaccine had been selected for a non-human primate (NHP) challenge study organized and funded by Operation Warp Speed. The study is designed to demonstrate the efficacy of Vaxart’s COVID-19 vaccine candidate, which is based on the company’s proprietary Vector-Adjuvant-Antigen Standardized Technology (VAAST™) Platform.
“We are very pleased to be one of the few companies selected by Operation Warp Speed, and that ours is the only oral vaccine being evaluated,” Vaxart CEO Andrei Floroiu said in a statement.
Floroiu was appointed CEO effective June 14, in part to accelerate development of the COVID-19 vaccine candidate; he retains the seat on Vaxart’s board he has held since April.
A spokesman for the U.S. Department of Health and Human Services (HHS) told The New York Times that Vaxart was not selected for funding under Warp Speed: “[HHS] has entered into funding agreements with certain vaccine manufacturers, and we are negotiating with others. Neither is the case with Vaxart.” The newspaper
Vaxart announced its inclusion in Operation Warp speed a day after disclosing plans to ramp up manufacturing of its COVID-19 vaccine to 1 billion or more doses a year, through a Mamorandum of Understanding the company has signed with Attwill Medical Solutions Sterilflow (AMS). The agreement—whose value was not disclosed— affirmed the companies’ intent to establish AMS as a resource for lyophilization development and large scale manufacturing including tableting and enteric coating for Vaxart’s oral COVID-19 vaccine, Vaxart said.
AMS agreed to assign dedicated resources and equipment for scale-up and commercial production of the vaccine, based on finalizing a formal agreement.
In May, Vaxart said its oral vaccine candidate for COVID-19 will be manufactured by Kindred Biosciences, which agreed to provide manufacturing services from its biological development and cGMP manufacturing facility in Burlingame, CA. There, KindredBio will produce the candidate vaccine bulk drug substance under GMP, and provide it to Vaxart to be formulated into a vaccine tablet to be taken orally. KindredBio agreed to manufacture the vaccine for clinical trials beginning in the second half of 2020.
On April 30, Vaxart said it obtained positive preclinical results for its COVID-19 vaccine candidates, with “several” of the candidates generating immune responses in all tested animals after a single dose. “These preclinical results confirm that all constructs are immunogenic as measured by IgG antibodies in serum, and we observed a robust boosting effect after the second dose,” Vaxart Chief Scientific Officer Sean Tucker, PhD, stated.
Tucker said Vaxart will use the data to select a lead candidate for manufacturing: “We remain on track to start a first phase 1 study in the second half of this year.”
Earlier in April, Vaxart reported positive preclinical results for its five COVID-19 vaccine candidates, saying that several of them generated immune responses in all tested animals after a single dose. Additional data will determine which of the candidates Vaxart advances into clinical trials, Chief Scientific Officer Sean Tucker, PhD, stated, adding: “We are particularly interested in vaccine candidates that can generate mucosal immune responses in addition to serum antibody responses.”
In March, Vaxart disclosed it had produced five COVID-19 vaccine candidates for testing in preclinical models. Each vaccine construct is based on a different coronavirus antigen combination, Vaxart said, adding that it expects to advance the best performing vaccine to manufacturing for clinical trials.
Vaxart has agreed to use the “molecule-to-market” contract development and manufacturing (CDMO) services of Emergent BioSolutions in preparation for cGMP production of a vaccine. Provided Vaxart elects to proceed with cGMP manufacturing, Emergent is expected to produce bulk cGMP vaccine for use in a Phase I study that Vaxart said could be launched in the second half of 2020. Vaxart also said it was prioritizing development of the COVID-19 vaccine by putting several vaccine programs on hold, including its therapeutic HPV vaccine program and a norovirus vaccine program for which the company completed a successful Phase I study, and was actively seeking a development partner.
Emergent has said it will provide development services out of its Gaithersburg, MD location and manufacture drug substance at its Bayview facility in Baltimore, designated a Center for Innovation in Advanced Development and Manufacturing (CIADM) by the U.S. Department of Health and Human Services.
Vaxart disclosed plans in January to generate vaccine candidates based on the published genome of SARS-CoV-2, and evaluate them in preclinical models based on their ability to generate both mucosal and systemic immune responses. The company cited a study published in The Lancet Infectious Diseases, showing that the Vaxart oral H1 influenza tablet vaccine primarily protected against infection based on mucosal immunity, compared with the injectable flu vaccine that protected primarily through systemic immunity.
COVID-19: 300 Candidates and Counting
To navigate through the >300 potential therapeutic and vaccine options for COVID-19, GEN has grouped the candidates into four broad categories based on their developmental and (where applicable) clinical progress:
● FRONT RUNNER – the most promising therapeutics/vaccines based on clinical progress, favorable data or both.
● DEFINITELY MAYBE – earlier phases with promising partners, or more advanced candidates in development that have generated uneven data
● KEEPING AN EYE ON… – interesting technology, attracting notable partners, or both, but preliminary data.
● TOO SOON TO TELL – longshots pending additional experimental and/or clinical data.
GEN has also tagged the most common treatment types:
● ANTIVIRAL
● VAX
● ANTIBODY
● RNA
