Gritstone Oncology (GRTS -1.85%) started the week as a little-known player in the coronavirus vaccine space. Its shares were trading at less than $10 apiece, and the market value totaled well under $1 billion. And then, in a blink of an eye, all of that changed. Its shares -- and market capitalization -- soared.

Why so much excitement? This clinical-stage company announced something that could address the biggest problem vaccine makers face right now: new strains of the coronavirus. Gritstone said its vaccine candidate targets that very problem. And the company aims to start a phase 1 trial this quarter. So, is Gritstone following Moderna's (MRNA -1.56%) footsteps to stock market stardom? Let's take a look.

An investor, standing in front of skyscrapers, draws a red line in the air with her finger to indicate a stock rising.

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Far behind many players

Gritstone's specialty is immunotherapy, or helping a person's immune system fight disease. But until recently, its focus has been uniquely on cancer immunotherapies. Gritstone has four oncology programs in the pipeline. The two most advanced are in phase 1/2 trials.

With the arrival of the coronavirus pandemic, the company decided to try its technology in this new area. Of course, Gritstone is far behind many players in the vaccine race. Moderna and Pfizer have already commercialized their vaccines through Emergency Use Authorizations (EUA). And 14 programs worldwide are in phase 3 trials. So, it's clear that if Gritstone's vaccine candidate makes it successfully through clinical trials, it will be a latecomer to the market.

But if Gritstone's potential product can handle current and future variants of the coronavirus, the company could score a major win -- and billions of dollars in revenue. So far, Moderna and Pfizer have said their vaccines can handle recently discovered variants of the coronavirus. That includes the U.K. and South African strains.

These strains include mutations within the coronavirus's spike protein. The spike protein is key because it attaches itself to cells and infects them. Vaccine makers have been focusing on this particular protein. In the case of Moderna and Pfizer, their vaccines give the body instructions to make a copy of the spike protein. That way, the body produces antibodies that can fight it. Moderna recently said that the spike protein in new strains is only 1% different from the original spike encoded in its vaccine.

The spike protein and other antigens

With that said, no one knows how the virus may evolve in the coming months or years. And that's where Gritstone comes in. Gritstone's vaccine candidate contains material from the spike protein like its rivals. But it also includes other antigens from the coronavirus. That way, if future mutations significantly change the spike, the body still will recognize the virus -- because the body will be familiar with other components of the virus too.

Preclinical studies indicate Gritstone's investigational vaccine can generate lasting, high levels of neutralizing antibodies and killer T-cell responses against the spike protein. The vaccine candidate also can prompt killer T-cell responses against a range of antigens from the virus, the research showed. Neutralizing antibodies block infection, while killer T-cells recognize and kill cells that have been infected by the virus.

Now, Gritstone must show its vaccine can do the same in humans. Gritstone has signed a clinical trial agreement with the National Institutes of Health's National Institute of Allergy and Infectious Diseases. The next step: filing an Investigational New Drug Application with the U.S. Food and Drug Administration (FDA). If the FDA doesn't oppose, the company can begin human trials.

Shares and market capitalization soar

Investors celebrated news of this imminent trial. In one trading session this week, the shares soared nearly 249%. And market value surged from $300 million to more than $1 billion -- again, in just one day.

GRTS Chart

GRTS data by YCharts

Moderna climbed more than 400% in all of last year, and its market cap rose more than six-fold, from $6 billion to $41 billion.

MRNA Chart

MRNA data by YCharts

Of course, Gritstone is starting out with a much lower market value than Moderna -- so it's easier for that market value to grow.

Beyond those numbers, can Gritstone also follow in Moderna's footsteps when it comes to success in the coronavirus field? Time -- and data -- will tell. Gritstone remains a risky investment. It doesn't have products on the market. And a failure in the coronavirus vaccine program would surely bring the stock back to where it started -- or lower.

But Gritstone is working on a game-changing potential product. It could protect populations against an ever-evolving coronavirus. If Gritstone's path through clinical testing is smooth and the FDA offers it emergency authorization or formal approval down the road, this biotech stock could indeed reach the heights of bigger rival Moderna.