As the coronavirus outbreak continues to spread throughout the world, investors have been loading up on shares of companies working on treatment or prevention. Gilead Sciences (NASDAQ:GILD) rose as much as 29% this year, but has since given up some gains and is now up 11%. Vir Biotechnology (NASDAQ:VIR) stock has surged 170% in the same time.

Gilead is the maker of remdesivir, the drug that recently received emergency use authorization from the U.S. Food and Drug Administration (FDA) for the treatment of severe coronavirus cases. Vir has partnered with pharma giant GlaxoSmithKline (NYSE:GSK) to pursue the discovery of antibodies to fight the coronavirus.

Pills and a syringe are shown against a folder labeled coronavirus.

Image source: Getty Images.

If you're looking to bet on a coronavirus player now, you might be wondering which of these two represents the best opportunity. Let's take a look.

The case for Gilead

Gilead has stood out in recent weeks with encouraging data from ongoing remdesivir trials. One clinical trial showed that patients treated with remdesivir recovered more quickly than those who received placebo. Another study showed similar improvement between patients treated with the drug for five days and those treated for 10. That's positive news for the ongoing supply levels of the drug. Following the trial data, the FDA said remdesivir may be used on an emergency basis, and Japan gave the drug its first-ever approval for use there.

So far, remdesivir isn't a source of revenue for Gilead. The company is donating its existing supply -- about 1.5 million individual doses. The question now is on pricing once Gilead begins selling the drug. The cost of production for one day's dose is $0.93, according to estimates in a Journal of Virus Eradication article. That means a 10-day treatment represents a little less than $10. But that's not including margin for Gilead. The Institute for Clinical and Economic Review, which evaluates the value of prescription drugs, estimates a price of $4,460 per five- or 10-day treatment course would be cost-effective. Gilead will have the challenge of setting a price that is profitable yet considered fair so that all those in need may access the drug.

In the meantime, the company is prepared to invest as much as $1 billion in remdesivir this year -- without yet knowing how much money it will make from the drug. That said, Gilead has nearly 30 commercialized drugs, including an HIV portfolio that brought in $4.1 billion last quarter for a 14% gain from the year-earlier period.

The case for Vir

Vir is a clinical-stage company focused on infectious diseases. Its pipeline includes seven candidates from pre-clinical to phase 2 in areas including HIV, hepatitis B, and influenza.

As for coronavirus research, Vir is involved in several collaborations. Vir recently published a paper in Nature detailing its identification of an antibody from a patient who recovered from severe acute respiratory syndrome. That antibody has demonstrated an ability to prevent coronavirus infection, according to the report. Vir and partner Glaxo plan to advance two monoclonal antibodies based on that research into a phase 2 trial this summer.

Vir has partnered with Alnylam Pharmaceuticals (NASDAQ:ALNY) on an RNA interference candidate targeting the coronavirus genome, and the two plan to seek authorization later this year to start human trials. That technology uses RNA molecules to interfere with gene expression. Vir is also working with the U.S. government on antibody development. And the company is collaborating with Generation Bio to explore how the latter's gene-therapy platform and Vir's antibodies may work together.

With all of these programs, it's clear that Vir is aggressively pursuing its coronavirus program. It's also positive to see that the U.S. government and a big player like Glaxo are confident in Vir's work. If Vir's studies progress and produce favorable data, this may be an opportunity for the company to bring its first product to market sooner rather than later. Governments and regulatory agencies are making efforts to accelerate development and approval of products addressing the pandemic.

Gilead or Vir?

I'm always wary about investing in a clinical-stage biotech company that hasn't yet brought a candidate into phase 3 trials. Phase 3 is where we see efficacy in larger patient groups, and that's when we might evaluate the product's chances of gaining regulatory approval. That factor, along with Vir's massive share increase, means I wouldn't buy the shares now.

Gilead's main problem is the question of remdesivir pricing at a time when it is investing heavily in the drug. And that may weigh on the share price in the near term. That said, I like the fact that Gilead has many products on the market, and the growth in its HIV business is a big plus. Gilead may not be a coronavirus stock that will bring triple-digit share gains overnight, but its product portfolio should drive revenue growth and lead shares higher over the long term.