An experimental orally administered coronavirus vaccine showed promising results in an early-stage clinical trial with 35 healthy adults, said Vaxart, based in South San Francisco, on Wednesday. Despite the results, Vaxart’s shares plunged 50% just before the opening bell.
Vaxart scientists divided volunteers between the ages of 18 and 54 into three groups. The first received two low doses of the vaccine – called VXA-CoV2-1 – 29 days apart, while the other groups received a single low or high dose.
The vaccine, which is in a small tablet, generated a type of T cell responsible for destroying virus-infected cells in about 75% of volunteers who received a single low or high dose, the company said. He said the reported responses were greater than those seen in Moderna and Pfizer vaccines.
However, neutralizing antibodies were not detected in volunteers after a single dose, said Vaxart. The researchers believe that antibodies play an important role in defending cells against the virus. The company said it is now evaluating antibody responses at second doses, after the antibodies were detected in nasal swab samples from volunteers at two doses.
Isaac Bogoch, an infectious disease specialist and professor at the University of Toronto, said the company’s stock may be falling due to a lack of neutralizing antibodies after the first dose.
“The immune response is multifaceted,” he said, adding that one aspect of the immune response is the creation of antibodies, in particular neutralizing antibodies. “While it is great to see that there appears to be a decent T cell response, the lack of detected antibodies is problematic and could reduce the effectiveness of this as a vaccine.”
The company said that no serious adverse events were reported in the phase one study, with generally mild side effects. The volunteers reported common side effects, such as headache and fatigue, and there was a “slight increase” in the group of high-dose soft stools, the company said.
The data will be presented on Wednesday afternoon at the New York Academy of Sciences Symposium.
“The most exciting thing about the [phase one data] is that we can get a very, very strong T cell response even after a dose, “Sean Tucker, Vaxart’s scientific director, told CNBC in a telephone interview, adding that T cells are probably” underestimated “compared to antibodies in the fight against the virus.
The biotechnology company said the vaccine has the potential to be more protective against current and emerging strains of the virus than existing vaccines. Moderna, Johnson & Johnson and Novavax in the past few days have said their vaccines may be less potent against B.1.351, a highly contagious strain found in South Africa. US officials have expressed concern that Covid may undergo further mutations and avoid protection existing vaccines.
The Vaxart vaccine contains DNA instructions for making the protein spike, which allows the virus to enter human cells, as well as instructions for making protein N, which is involved in other processes. Tucker said that the inclusion of protein N may cause the vaccine to retain its ability to act against emerging strains.
Many other vaccines in development have chosen the spike protein as a “primary target,” he said. “But the problem with the [spike] protein is definitely changes more with time. What we did was add protein N as well, which is very conserved in the virus. “
Vaxart said its vaccine is the only oral pill in the United States to be tested on humans. Similar technology is being used to develop vaccines against influenza and norovirus.
The company was under federal scrutiny and investigation last year for allegedly exaggerating its involvement in Operation Warp Speed, former President Donald Trump’s vaccine and treatment program. The company said in a press release in June that “Vaxart’s Covid-19 vaccine has been selected for the US government’s Operation Warp Speed”, causing its stock to skyrocket.
But it turned out that the company had not received financial support from the federal government for vaccine doses and was only participating in preliminary studies in the United States to determine potential areas for possible partnership and Warp Speed support, according to The New York Times.
Tucker told CNBC that the company is in talks with the United States and other governments to find potential opportunities for collaboration on its vaccine.
If the Vaxart vaccine passes other clinical tests and is approved by the United States, it may offer advantages over needle vaccines.
Dr Paul Offit, a member of the FDA’s Vaccine and Related Biological Products Advisory Committee, said that an orally administered vaccine may have better acceptance by the public who may be concerned about needles. Two Covid-19 vaccines authorized in the United States – from Pfizer and Moderna – are injected into the arm and require two injections every three to four weeks.
Vaxart said its vaccine is also stable at room temperature and does not require a freezer, meaning it can be “stored and shipped to large populations worldwide”. In comparison, the Pfizer vaccine needs to be stored in deep-frozen freezers that keep it between minus 112 and 76 degrees Fahrenheit. Moderna’s vaccine needs to be shipped between minus 13 and 5 degrees Fahrenheit.
Vaxart said the vaccine also does not require special medical training to be administered and can be taken at home. He said that this will help adhere to the social distancing guidelines, reducing the burden on the health system.
The company said it is still determining whether this will be a single-dose or two-dose regimen.
A phase two study is expected “in the coming months,” said Tucker. In its “faster timeline”, the company expects the phase two and three studies to be completed in early 2022.
–CNBC’s Hugh Son contributed to this report.