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Pill Vaccine Biotech Vaxart Suspends Covid-19 Trial, Keeps Norovirus Focus

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Vaccine developer Vaxart contends its pill vaccinations against Covid-19 will be preferable to patients, and potentially more effective than currently available injections. But a different virus offers the biotech a clearer and faster path to validating its still experimental oral vaccine technology, so it’s suspending plans for mid-stage clinical testing in Covid-19.

Vaxart will instead focus on clinical development of a pill vaccine for norovirus, which has no vaccine to protect against the serious gastrointestinal problems caused by the pathogen. As part of the strategy shift announced after Wednesday’s market close, South San Francisco-based Vaxart said it would lay off about 27% of its staff. At the end of 2022, the company had 164 employees, according to its annual report.

Speaking on a conference call to discuss full year 2022 financial results, Vaxart CEO Andrei Floroiu said prioritizing the norovirus program is the best way to position the company for long-term success. The emerging variants of SARS-CoV-2 present a constantly moving target that make it difficult to develop a vaccine, he said. But the key characteristics of norovirus have not changed and are not expected to change. Furthermore, the norovirus space is less competitive, and Vaxart stands apart with its oral vaccine candidate.

“Our goal with this strategy is to focus most of our investments on the programs that have the greatest near-term potential to validate and progress our oral pill technology platform,” Floroiu said.

The Vaxart vaccine platform is called Vector-Adjuvant-Antigen Standard Technology, or VAAST. Like some other vaccines, a Vaxart vaccine employs an engineered adenovirus to deliver an antigen that sparks an immune response. A short section of double-stranded RNA is included as an adjuvant to boost the immune response. Those components are incorporated into a tablet specifically designed to deliver adenovirus particles.

Vaxart aims to trigger mucosal immunity. Its pills have a coating that protects them until they reach the small intestine, where the vaccine is released, entering the mucosal cells lining the intestine. The mucosal cells become factories that manufacture antigen intended to lead to an immune response. Vaxart believes tablet delivery to the gut avoids neutralization by the blood or immune cells that can happen from intramuscular injection of a vaccine.

So far, Vaxart has reached the clinic with oral vaccines for Covid-19, influenza, and norovirus. The restructuring will shift the company’s resources to the norovirus program. Specifically, Vaxart is continuing a Phase 2 human challenge study; preliminary efficacy data are expected in the third quarter of this year. Last month, Vaxart started a Phase 2 dose-ranging study for its bivalent norovirus vaccine candidate. Preliminary data are expected by mid-year. Vaxart also plans a clinical test of its norovirus vaccine in breastfeeding mothers and their infants. The company expects that this study, which has support from the Bill & Melinda Gates Foundation, will start later this year.

Vaxart’s norovirus competition includes HilleVax, a biotech that spun out of Takeda Pharmaceutical and went public last year. The Boston-based company’s vaccine, which is based on a virus-like particle, is administered by injection. Late last year, HilleVax reported preliminary Phase 2b data showing the vaccine led to an immune response in infants. The company already has data from a Phase 2b test in adults.

While Vaxart has shelved the clinical trial plans for its Covid-19 vaccine, it is not ending all of its coronavirus vaccine research. Floroiu said one weakness of currently available injectable Covid-19 vaccines is their limited ability to provide cross-reactivity, which means broader protection against multiple variants and other coronaviruses. That kind of protection will be essential to address a virus that evolves rapidly, such as SARS-CoV-2, he said. Vaxart will continue preclinical research aiming that could lead to a vaccine protective protect against the novel coronavirus as well as other types of betacoronaviruses, such as SARS-CoV-1 and Middle East Respiratory Syndrome, or MERS-CoV.

Vaxart finished 2022 with a cash position of $95.7 million. With the restructuring, the company estimates it will have enough money to last until the second quarter of 2024, when it should have data readouts from its norovirus trials. The company also said it has access to cash and other deposits that were previously held at Silicon Valley Bank, whose failure affects companies across the life sciences sector. Vaxart said it has moved its deposits to larger financial institutions and does not expect SVB’s failure will have any material impact on the company.

Photo: Martin Barraud, Getty Images