What happened

Shares of Inovio Pharmaceuticals (NASDAQ:INO) were sinking 11.8% lower as of 11:01 a.m. EDT on Tuesday. The decline came after the biotech announced interim results from an early-stage clinical study of COVID-19 vaccine candidate INO-4800. Inovio referred to the data as "positive." However, industry observers didn't think the company disclosed enough information to draw any meaningful conclusions about the efficacy of the experimental vaccine.

So what

Inovio stated that 94% of the 40 participants in its early-stage study "demonstrated overall immune responses" six weeks after receiving two doses of INO-4800. The problem, though, is that the biotech didn't provide any details about how many patients produced neutralizing antibodies. These antibodies prevent infection by the novel coronavirus.

Gloved hands holding COVID-19 vaccine syringe

Image source: Getty Images.

It even seemed that Inovio could be attempting to downplay the importance of neutralizing antibodies. In the company's press release announcing the interim phase 1 results for INO-4800, Inovio referenced two studies published earlier this year that found between 33% and 40% of individuals who recovered from COVID-19 had low levels of neutralizing antibodies.

Investors appear to be concerned that INO-4800 might not be as effective as other COVID-19 vaccines in development. Moderna, for example, disclosed information about the number of patients producing binding antibodies and neutralizing antibodies in its interim phase 1 results.

Safety didn't appear to be a serious concern for INO-4800, though. Inovio reported that the experimental vaccine was "generally safe and well-tolerated in all participants." There were 10 adverse events reported. Each was grade 1 in severity, the lowest severity level. Most were related to injection site redness. Inovio said that there were no serious adverse events reported.

Now what

Inovio hopes to begin a phase 2/3 clinical study evaluating the efficacy of INO-4800 this summer assuming it gets a green light from the FDA. INO-4800 has also been selected to be part of a preclinical trial funded by Operation Warp Speed, the U.S. government's program to rapidly develop a COVID-19 vaccine. The biotech stock could be highly volatile, however, until investors are more comfortable about the efficacy of Inovio's coronavirus vaccine candidate.

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