What happened

Shares of the clinical-stage biotech Inovio Pharmaceuticals (INO 7.79%) gained a respectable 10.9% over the course of May, according to data provided by S&P Global Market Intelligence. The DNA vaccine company's shares rallied last month on the news that its pan-COVID-19 vaccine candidate, INO-4802, showed strong signs of efficacy across multiple strains of the virus in preclinical studies.

So what

Despite being one of the first American biotech companies to develop a COVID-19 vaccine candidate last year, Inovio has fallen woefully behind the leaders in the space over the last year. In fact, there probably won't be a significant need for another vaccine in the U.S. by the time Inovio pushes its lead COVID-19 vaccine candidate, INO-4800, into late-stage testing this summer. 

A female researcher inspecting vials of COVID-19 vaccine.

Image source: Getty Images.

A pan-COVID-19 vaccine, however, may still serve a purpose in the fight against this global pandemic. Investors, in turn, appear to be betting that the company may yet derive a relatively healthy revenue stream from its COVID-19 vaccine platform. 

Now what

Is Inovio's stock worth buying after last month's double-digit uptick? Although the biotech exited the first quarter of 2021 with over $500 million in cash, Inovio's future remains murky at best.

The company's lead product candidate, VGX-3100 for precancerous cervical dysplasia caused by high-risk HPV 16/18, needs a strong showing in its upcoming confirmatory phase 3 trial readout. What's more, there's no way to predict how the second-tier COVID-19 vaccine market will shape up over the next two years.

In short, Inovio's stock doesn't sport a particularly compelling investing thesis as things stand now.