Novavax reports positive early results for experimental COVID-19 vaccine NVX-CoV2373

Novavax on Tuesday announced preliminary data from a Phase I/II study indicating that its recombinant coronavirus vaccine candidate NVX-CoV2373 triggered immune responses in healthy adults and was generally well-tolerated. According to findings in a paper Novavax submitted to the preprint server medRxiv, the vaccine induced neutralisation titers in all vaccinated participants, with antibody responses "numerically superior to that seen in human convalescent sera."

The Phase I portion of the randomised, placebo-controlled trial evaluated two doses of the vaccine at the 5 mcg and 25 mcg dose levels, in 131 participants aged 18 to 59 years in Australia. In addition to NVX‑CoV2373, a stable prefusion protein that will incorporate Novavax's Matrix-M adjuvant, the study also looked at a non-adjuvanted form of the vaccine.

Neutralising antibodies, T-cell responses

According to Novavax, all study subjects developed anti-spike IgG antibodies after a single dose, and many also had wild-type virus neutralising antibody responses, with the latter triggered in all participants after dose two. "Both anti-spike IgG and viral neutralisation responses compared favourably to responses from patients with clinically significant COVID‑19 disease," the company said, noting that IgG antibody response was also highly correlated with neutralisation titers, "demonstrating that a significant proportion of antibodies were functional."

Further, the company said the cellular immune responses seen in a subset of participants showed that adjuvanted NVX‑CoV2373 induced antigen-specific polyfunctional CD4+ T-cell responses "with a strong bias toward the Th1 phenotype." The Matrix-M adjuvant also allowed the lower 5-mcg dose of NVX‑CoV2373 to perform "comparably" with the 25-mcg dose, it added.

No serious adverse events

In terms of safety, Novavax said that more side effects occurred following the second dose, as expected, although the majority of symptoms were less than Grade 1 in severity, with the average duration of events being less than two days. There were no Grade 3 unsolicited adverse events or any serious adverse events observed. Earlier media reports cited eight possible hospitalisations related to the study, but Novavax said no patients involved with the study were hospitalised. Company shares were down as much as 32% before later recovering.

Novavax said the data have been submitted for peer-review to a scientific journal. Meanwhile, the Phase II portion of the study will be conducted in multiple countries, including the US.

Gregory Glenn, who heads R&D at Novavax, said the company will begin much larger late-stage clinical trials soon and could potentially glean enough data to obtain regulatory approvals as early as December. In July, the US government agreed to pay Novavax $1.6 billion to help cover costs related to testing and manufacturing the vaccine, with the aim of procuring 100 million doses by January 2021, or enough to give to 50 million people if administered in two doses. For related analysis, see ViewPoints: Novavax makes hay from government confidence in COVID vaccine.

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