An experimental coronavirus vaccine taken by mouth showed promising results in an early clinical trial involving 35 healthy adults, Vaxart of South San Francisco said Wednesday. Despite the results, Vaxart’s stock fell 50% shortly before the opening bubble.
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 remaining groups received a single low or high dose.
The vaccine, contained in a small tablet, generated a type of T cell responsible for destroying virus-infected cells in about 75% of the volunteers who received a single low or high dose, the company said. It said the reported responses were higher than those seen in Moderna and Pfizer’s vaccines.
However, neutralizing antibodies were not detected in volunteers after a single dose, Vaxart said. Researchers believe the antibodies play an important role in defending cells against the virus. The company said it is now assessing antibody responses from second doses after antibodies have been detected in nasal swabs from volunteers at two doses.
Isaac Bogoch, an infectious disease specialist and professor at the University of Toronto, said the company’s stock could decline due to the 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 production of antibodies, especially 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 may reduce the effectiveness of this vaccine as a vaccine.”
The company said no serious side effects were reported in the phase 1 study, with generally mild side effects. Volunteers reported common side effects, such as headaches and fatigue, and there was a “slight increase” in the high-dose group of loose stools, the company said.
The data will be presented Wednesday afternoon at the New York Academy of Sciences symposium.
“The most exciting thing about the [phase one data] is that we can have a very, very strong T cell response even after one dose, ” Sean Tucker, Vaxart’s chief scientific director told CNBC in a telephone interview, adding that T cells are likely to be ‘undervalued’ in comparison. with antibodies in fighting the virus. .
The biotech company said the vaccine has the potential to provide more protection 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, a highly contagious strain found in South Africa. US officials have expressed concern that Covid may continue to mutate and evade the protections of existing vaccines.
Vaxart’s vaccine contains DNA instructions to make the spike protein, which allows the virus to enter human cells, as well as instructions to make the N protein, which is involved in other processes. Tucker said the inclusion of the N protein could help the vaccine maintain its ability to work against emerging strains.
Many other vaccines in development have chosen the spike protein as a “prime target,” he said. “But the problem with the [spike] protein is definitely more mutating over time. What we have done is also add the N protein, which is much conserved in the virus. “
Vaxart said his vaccine is the only oral tablet in the US that is tested on humans. Similar technology is being used to develop influenza and norovirus vaccines.
The company came under scrutiny and a federal investigation late last year for exaggerating its involvement in Operation Warp Speed, former President Donald Trump’s vaccine and treatment program. It said in a June press release that “Vaxart’s Covid-19 vaccine has been selected for the US government’s Warp Speed operation,” boosting its stock dramatically.
But it turned out that the company had received no financial support from the federal government for vaccine doses and was only participating in preliminary US investigations to determine potential areas for potential cooperation and support with Warp Speed, according to The New York Times.
Tucker told CNBC the company is in talks with the US and other governments to find possible options to work together on the vaccine.
If Vaxart’s vaccine gets 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 a vaccine taken by mouth may be better accepted by people in the public who may be concerned about needles. Two US-approved Covid-19 vaccines – from Pfizer and Moderna – are injected into the arm and require two injections approximately three to four weeks apart.
Vaxart said his vaccine is also stable at room temperature and does not require a freezer, meaning it can be “stored and shipped to mass populations around the world.” In comparison, Pfizer’s vaccine should be stored in ultra-cold freezers that keep it between -112 and -76 degrees Fahrenheit. Moderna’s vaccine should be shipped with a temperature between 13 and 5 degrees Fahrenheit.
Vaxart said the vaccine also does not require any special medical training to administer and can be taken at home. It said this will help adhere to social distance guidelines while reducing the burden on the healthcare system.
The company said it is still determining whether this will be a one- or two-dose regimen.
A phase two study is expected “in the next few months,” said Tucker. In its “most accelerated timeline,” the company expects phase two and phase three studies to be completed by early 2022.
–CNBCs Hugh Son contributed to this report.