Image source: Getty Images.

Two biotech stocks have received plenty of buzz lately for very different reasons. Medivation (NASDAQ:MDVN) attempted to jump-start a bidding war after rejecting Sanofi's (NASDAQ:SNY) second acquisition offer. Inovio (NASDAQ:INO) has made headlines recently with its sprint to develop a vaccine for the feared Zika virus. Both Medivation and Inovio have posted impressive gains so far in 2016, but which stock's hype is more justified? Let's see how the biotechs stack up.

The case for Medivation

There's nothing like interest from a big suitor to do wonders for a stock. At the end of March, Medivation's shares traded at less than $38. One month later, the biotech's stock was up to almost $58 per share after Medivation's board rejected Sanofi's first offer of $52.5 per share in cash. Medivation isn't opposed to selling, but only for the right price. The company announced on July 5 that it had "entered into confidentiality agreements with a number of parties that have expressed interest" in a deal.  

So what's so attractive about Medivation? Put Xtandi at the top of the list. The prostate cancer drug generated $547 million worldwide in the first quarter of 2016, a 53% year-over-year jump. Medivation's partner Astellas (OTC:ALPMY) kept a lot of that amount, but Medivation still made $182.5 million from Xtandi.

Medivation and Astellas appear likely to rake in plenty more cash in the coming years. Analysts estimate peak annual sales of Xtandi could reach close to $5 billion. Hitting that mark, though, depends in part on success from approval for other indications, including earlier-stage prostate cancer, advanced breast cancer, and liver cancer. 

Sanofi's most recent bid was $58 per share plus an extra $3 per share in the form of a contingent value right (CVR) of Medivation's next potential winner, talazoparib. That amounts to pegging the price tag of the experimental cancer drug at just under $500 million. Considering that estimates of peak annual sales for talazoparib range from $200 million to $850 million, it's not surprising that Medivation didn't like Sanofi's CVR offer.

Medivation's other pipeline candidate, pidilizumab, is in a phase 3 study for treatment of relapsed or refractory diffuse large B-cell lymphoma. Pidilizumab could reach peak annual sales of over $400 million.

The case for Inovio

A biotech's lead drug usually gets the most attention. For Inovio, however, that hasn't proven to be the case recently. While the company's cervical dysplasia vaccine VGX-3100 will soon be in a late-stage study, lately more interest has been shown for Inovio's experimental Zika virus vaccine. And that vaccine just received approval in June to begin phase 1 testing.

It certainly hasn't hurt Inovio that the Zika virus has received considerable news coverage across the world. Several celebrity athletes have opted out of the summer Olympic games in Rio de Janeiro over fears about Zika. The World Health Organization issued an advisory urging pregnant women to avoid traveling to areas with Zika outbreaks, including Rio. Meanwhile, more cases of Zika virus infection have been reported across the U.S.

So far, Inovio appears to be in a leading position in the race to develop a Zika vaccine. However, several other larger drugmakers have their own vaccine programs underway. It's still uncertain which company will ultimately emerge as the biggest winner -- or how long it will take for a successful vaccine to be developed.

But don't forget that Inovio isn't just about Zika. VGX-3100 could potentially bring peak annual sales of $500 million if the vaccine gains regulatory approval and analysts' estimates are right. If the cervical dysplasia vaccine indeed clears regulatory hurdles, that should bode well for Inovio's INO-3112 vaccine, which is in one early-stage study focusing on cervical cancer and another for head and neck cancer. INO-3112 combines VGX-3100 with a DNA-based immune activator.

For a small biotech, Inovio's pipeline looks quite robust. The company has several other early-stage clinical studies in progress for experimental vaccines targeting hepatitis B, hepatitis C, HIV, influenza, Ebola, and MERS.

Better buy

I like the potential for both of these stocks. However, I'd go with Medivation as the better buy right now for one reason: risk.

Inovio doesn't have any products on the market yet. While there's a good chance that VGX-3100 could win regulatory approval in the not-too-distant future, there's also always a risk that some issue could derail the vaccine. Likewise, Inovio's current leadership in developing a Zika virus vaccine could prove fleeting if one of the other companies in the hunt achieves a major breakthrough. I'm not saying this will happen, but it could happen.

On the other hand, Medivation has a bona fide blockbuster with Xtandi. The biotech's pipeline comes with some risks, but both of its candidates are already in phase 3 while Inovio has yet to launch a late-stage study. There's also a risk that no deal materializes for a larger company to buy Medivation. That outcome would probably hurt the stock, at least temporarily.

I still see Medivation as the less risky pick, though. The companies with interest in potentially buying the biotech know they'll have to beat Sanofi's last offer. I expect Medivation to sell for a price tag that should reward even those investors who buy shares now.  

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.