Mr. Market savaged the biotech sector yesterday. Specifically, 92% of small-caps were losers, 94% of mid-caps painted the tape red, and large caps saw a single winner, Gilead Sciences. Given the broad-based downtrend in the sector, I think it's important to look at the names that were able to swim upstream in this turbulent environment and end the day green. With that in mind, let's take a closer look at why Achillion Pharmaceuticals (NASDAQ:ACHN), Exact Sciences Corp. (NASDAQ:EXAS) and NewLink Genetics Corp. (NASDAQ:NLNK) bucked yesterday's downtrend.

Achillion marches upwards on upgrade
Despite its experimental hepatitis C drug sovaprevir being placed on an indefinite clinical hold by the U.S. Food and Drug Administration, or FDA, last year, shares of this developmental stage biotech have pushed higher by 8.7% year to date. And yesterday, it was the sector's biggest winner, gaining 6.8% after Maxim Group upgraded the stock from hold to buy. That said, I am personally not optimistic about Achillion's chances to continue to defy the broader market going forward.

On the clinical front, Achillion's remaining clinical candidates are still in the early stages of their development. So, the company's valuation is likely to be directly tied to sovaprevir's fate for the time being. Yet, even if the FDA decides to lift the hold on sovaprevir later this year and the drug went on successfully complete clinical testing, it would face immediate competition from Gilead, Johnson & Johnson, and most likely AbbVie's respective drugs in the marketplace. Turning to Achillion's fundamentals, the company exited 2013 with $159.1 million in cash and cash equivalents. Even so, you need to keep in mind that the company has no revenue and is expecting to burn between $5 to $7 million per month in 2014. In sum, I don't see much value in Achillion shares from either a clinical or fundamental perspective.

Exact Sciences gets boost from FDA 
Shares of the molecular diagnostic company Exact Sciences continue to head higher ahead of its upcoming meeting with the FDA for Cologuard, a stool-based colorectal cancer test. The FDA's Molecular and Clinical Advisory Committee Panel will review Cologuard's clinical data March 27.

What sent shares higher yesterday was a comment in the briefing documents stating that Cologuard met its primary objectives with respect to both required sensitivity and specificity compared to colonoscopy. Although briefing documents are far from the final word in terms of regulatory approval, they sometimes offer valuable insight into the FDA's view of a device or drug going into a formal review. So, this note would appear to bode well for Cologuard's chances.

Looking ahead, Cologuard is projected to see peak sales between $1 to $2 billion if approved as a less invasive alternative to a colonoscopy. As such, Exact Sciences may have more upside, despite sporting a billion-dollar market cap.  

NewLink Genetics remains strong in a down market
NewLink Genetics continued its strong run yesterday moving higher by 3.4%. The stock is now up 37% year to date. NewLink's bull run this year has been triggered by a late-stage study for its HyperAcute Pancreatic cancer vaccine. Earlier this month, the company reported an interim analysis that warranted continuing the study, although some investors were hopeful the study would be halted early due a strong efficacy signal. What's key to understand is that NewLink does have other ongoing trials based on this same platform, but the late-stage study for pancreatic cancer will either validate this technology, or send the company back to the drawing board. Put simply, NewLink is a speculative immunotherapy company that is rising based on the hope that its lead clinical candidate will achieve a significant breakthrough this year.

Foolish wrap-up
What's interesting about these three particular winners is that they are all squarely on the speculative side. To my mind, this could mean investors still have a healthy appetite for risk. Indeed, we didn't see a flight to safety yesterday, to bigger names in health care that pay a stable dividend, or to companies with growing revenues. Instead, the few winners in the sector were primarily in the developmental stage of their life cycle. Time will tell if this trend continues, but you should keep in mind the wisdom of taking the long view in any type of market.

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.