An experimental oral coronavirus vaccine has shown promising results in an early-stage clinical trial of 35 healthy adults, South San Francisco-based Vaxart said Wednesday. Despite the results, Vaxart’s stock fell 50% just before the opening bell.
Vaxart scientists divided volunteers between the ages of 18 and 54 into three groups. The first received two small doses of the vaccine – called VXA-CoV2-1 – 29 days apart, while the remaining groups received a single low or high dose.
The vaccine, which is in a small tablet, generated a type of T cell responsible for killing virus-infected cells in about 75 percent of volunteers who received a single low or high dose, the company said. He said the reported responses were higher than those seen in the Moderna and Pfizer vaccines.
However, neutralizing antibodies were not detected in volunteers after a single dose, Vaxart said. Researchers believe that antibodies play an important role in defending cells against the virus. The company said it is now evaluating second-dose antibody responses after antibodies were detected in two-dose volunteer nasal swab samples.
Isaac Bogoch, an infectious disease specialist and professor at the University of Toronto, said the company’s stock could decline due to a lack of neutralizing antibodies after the first dose.
“The immune response is multilateral,” he said, adding that one aspect of the immune response is the creation of antibodies, especially neutralizing antibodies. While it is great to see that there seems to be a decent T cell response, the lack of detected antibodies is problematic and may reduce its effectiveness as a vaccine.
The company said no serious adverse events were reported in the phase one study, with side effects generally mild. Volunteers reported frequent side effects, such as headaches and fatigue, and there was a “slight increase” in the group with high doses of loose stool cases, the company said.
The data will be presented Wednesday afternoon at the New York Academy of Sciences Symposium.
“The most interesting thing about [phase one data] we can get a very, very strong T cell response even after a single dose, “Sean Tucker, Vaxart’s chief scientific officer, 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 have said in recent days that their vaccines may be less potent against B.1.351, an extremely contagious strain found in South Africa. US officials have expressed concern that Covid could continue to move and evade the protection of existing vaccines.
The Vaxart vaccine contains DNA instructions for making spike protein, which allows the virus to enter human cells, as well as instructions for making N protein, which is involved in other processes. Tucker said the inclusion of N protein can keep the vaccine able to work against emerging strains.
Many other developing vaccines have chosen spike protein as a “major target,” he said. “But the problem with [spike] Protein is definitely moving more over time. What we did is add protein N, which is very much preserved in the virus. “
Vaxart said his vaccine is the only oral tablet in the United States that has been tested in humans. A similar technology is used to develop flu and norovirus vaccines.
The company underwent federal scrutiny and investigations late last year for allegedly exaggerating its involvement in Operation Warp Speed, former President Donald Trump’s program for vaccines and treatments. In June, in a press release, he said that “Vaxart’s Covid-19 vaccine selected for the US government’s Warp Speed operation”, sending his actions growing.
But it turned out that the company did not receive financial support from the federal government for vaccine doses and only participated in preliminary US studies to determine potential areas for a possible partnership and support for Warp Speed, 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 to collaborate on its vaccine.
If the Vaxart vaccine is done through other clinical trials and US approval, it could offer advantages over needle-based vaccines.
Dr. Paul Offit, a member of the FDA’s Advisory Committee on Vaccines and Related Biological Products, said an orally administered vaccine could be better accepted by the public who may be anxious about needles. Two US-authorized Covid-19 vaccines – from Pfizer and Moderna – are injected into the arm and require two shots at about three to four weeks.
Vaxart said his vaccine is also stable at room temperature and does not require a freezer, which means it can be “stored and shipped to mass populations around the world.” By comparison, the Pfizer vaccine should be stored in ultra-cold freezers, which keep it between 112 and 76 degrees Fahrenheit negative. The Moderna vaccine should be transported between 13 and 5 degrees Fahrenheit negative.
Vaxart also said the vaccine does not require special medical training for administration and can be given at home. He said this would help adhere to the guidelines on social distancing, while reducing the burden on the health system.
The company said it is still deciding whether it will be a one- or two-dose regimen.
A second phase study is expected “in the next few months,” Tucker said. In its “fastest time”, the company expects the second and third phase studies to be completed by early 2022.
–CNBC Hugh Son contributed to this report.