An experimental coronavirus vaccine taken orally showed promising results in an early-stage clinical trial of 35 healthy adults, South San Francisco-based Vaxart said Wednesday. Despite the results, Vaxart shares fell 50% shortly before the opening bell.
Vaxart scientists divided the 18- to 54-year-old volunteers 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, contained in a small tablet, generated a type of T cell responsible for destroying virus-infected cells in approximately 75% of volunteers who received a single low or high dose, the company. He said the reported responses were higher than those seen in the Moderna and Pfizer vaccines.
However, no neutralizing antibodies were 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 antibody responses from second doses after antibodies were detected in nasal swab samples from two-dose volunteers.
Isaac Bogoch, an infectious disease specialist and professor at the University of Toronto, said the company’s stock could fall 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, particularly neutralizing antibodies. “While it’s great to see that there seems to be a decent T cell response, the lack of detected antibodies is problematic and can reduce the effectiveness of this as a vaccine.”
The company said no serious adverse events were reported in the first-phase trial, with generally mild side effects. Volunteers reported common side effects such as headaches and fatigue, and there was a “slight rise” in the high-dose group of loose stool cases, the company said.
The data will be presented Wednesday afternoon at the New York Academy of Sciences Symposium.
“The most exciting of the [phase one data] “We can get a very, very strong response from T cells even after a dose,” Sean Tucker, Vaxart’s scientific director, told CNBC in a telephone interview, adding that the cells T are probably “undervalued” compared to antibodies in the fight against the virus.
The biotech firm said the vaccine has the potential to be more protective of current and emerging strains of the virus than existing vaccines. Moderna, Johnson & Johnson and Novavax in recent days have said their vaccines may be less potent against the highly contagious B.1.351 strain found in South Africa. U.S. officials have expressed concern that Covid may further mutate and evade protection from existing vaccines.
The Vaxart vaccine contains instructions on DNA to make the ear 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 N protein can make the vaccine maintain its ability to work against emerging strains.
He said many other developing vaccines chose ear protein as their “main target.” “But the problem with [spike] protein is that it definitely mutates more over time. What we did is add the N protein, which is very much preserved in the virus. “
Vaxart said his vaccine is the only U.S. oral tablet that has been tested in humans. Similar technology is used to develop influenza and norovirus vaccines.
The company was the subject of federal investigations and investigations late last year for allegedly exaggerating its involvement in Operation Warp Speed, former President Donald Trump’s vaccine and treatment program. He said in a press release in June that “Vaxart’s Covid-19 vaccine selected for the U.S. government’s Operation Warp Speed” sent his shares on the rise.
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 U.S. studies to determine possible areas of possible association 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 possible opportunities to collaborate on its vaccine.
If the Vaxart vaccine is produced through other clinical trials and US approval, it could provide advantages over needle vaccines.
Dr. Paul Offit, a member of the FDA’s advisory committee on vaccines and related biological products, said an oral vaccine may have better acceptance by audiences who may be anxious about needles. Two vaccines against Covid-19 authorized in the United States (from Pfizer and Moderna) are injected into the arm and require two shots between three and four weeks apart.
Vaxart said his vaccine is also stable at room temperature and does not need a freezer, so it can be “stored and shipped to massive populations around the world.” In comparison, the Pfizer vaccine should be stored in ultra-cold freezers that keep it between 112 and 76 degrees Fahrenheit negative. The Moderna vaccine should be sent between 13 and 5 degrees Fahrenheit negative.
Vaxart said the vaccine also does not need special medical training to be administered and can be taken at home. He said this will help meet social distancing guidelines and reduce the burden on the healthcare system.
The company said it is still determining whether this will be a single dose regimen or two.
A second-phase study is expected “in the next two months,” Tucker said. In its “fastest time line,” the company expects phase two and phase three studies to be completed in early 2022.
–CNBC’s Hugh Son has contributed to this report.