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An experimental orally administered coronavirus vaccine has shown promising results in an early clinical trial in 35 healthy adults, South San Francisco-based Vaxart said on Wednesday. Despite the results, Vaxart’s stock plunged 60% in intraday trading.
Vaxart scientists divided the volunteers aged 18 to 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 comes in a small tablet, generated a type of T lymphocyte responsible for destroying cells infected with the virus in about 75% of volunteers who received a single low or high dose, the company said. He said the reported responses were higher than those seen in Moderna’s and Pfizer’s vaccines.
However, neutralizing antibodies were not detected in the volunteers after a single dose, Vaxart said. Researchers believe that antibodies play an important role in the defense of cells against the virus. The company said it is currently evaluating the antibody responses of the second doses after detecting antibodies 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 shares could drop 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 creation 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.”
The company said no serious adverse events were reported in the phase one trial, with side effects generally being mild. Volunteers reported common side effects such as headaches and fatigue, and there was a “slight increase” in the high-dose loose stool group of cases, the company said.
The data will be presented Wednesday afternoon at the New York Academy of Sciences Symposium.
“The most exciting thing about [phase one data] can we get a very, very, strong T cell response even after a dose, “Vaxart Scientific Director Sean Tucker told CNBC in a telephone interview, adding that T cells were probably “Underestimated” compared to antibodies in the fight against the virus.
The biotech firm 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, a highly contagious strain found in South Africa. U.S. officials have expressed concerns over the possibility of Covid mutating further and taking protection away from existing vaccines.
Vaxart’s vaccine contains DNA instructions for making the spike protein, which allows the virus to enter human cells, as well as instructions for making the N protein, which is involved in other processes. Tucker said the inclusion of the N protein could allow the vaccine to retain its ability to work against emerging strains.
Many other vaccines in development have chosen the spike protein as a “major target,” he said. “But the problem with the [spike] protein is certainly more mutated over time. What we did was also add the N protein, which is well conserved in the virus. “
Vaxart said its vaccine is the only oral tablet in the United States to be tested in humans. Similar technology is used to develop vaccines against influenza and norovirus.
The company came under scrutiny and federal investigation late last year for allegedly exaggerating its involvement in Operation Warp Speed, former President Donald Trump’s program for vaccines and treatments. He said in a press release in June that “Vaxart’s Covid-19 vaccine selected for the US government’s Operation Warp Speed”, skyrocketing its shares.
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 a possible partnership and Warp Speed support, according to the New York Times.
Tucker told CNBC the company is in talks with the United States and other governments to find potential opportunities to collaborate on its vaccine.
If Vaxart’s vaccine goes through further clinical trials and US approval, it may offer advantages over needle-based vaccines.
Dr Paul Offit, a member of the FDA’s Vaccines and Related Biologics Advisory Committee, said that an orally administered vaccine may be better accepted by those in the public who may be anxious about needles. Two Covid-19 vaccines licensed in the United States – from Pfizer and Moderna – are injected into the arm and require two injections about three to four weeks apart.
Vaxart said its vaccine is also stable at room temperature and does not require a freezer, meaning it can be “stored and shipped to massive populations across the world.” In comparison, Pfizer’s vaccine should be stored in ultra-cold freezers that keep it between negative 112 and negative 76 degrees Fahrenheit. Moderna vaccine should be shipped between 13 and 5 degrees Fahrenheit negative.
Vaxart said the vaccine also does not require special medical training to be given and can be taken at home. He said it would help meet social distancing guidelines while reducing the burden on the healthcare system.
The company said it is still in the process of determining whether this will be a single dose or a two dose regimen.
A phase two study is expected “within the next two months,” Tucker said. In its “most accelerated timeline,” the company expects phase two and phase three studies to be completed in early 2022.
–CNBC Hugh son contributed to this report.
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