Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Achillion Pharmaceuticals (NASDAQ:ACHN), a clinical-stage biopharmaceutical company focused on developing therapies to treat infectious diseases, jumped by as much as 13% after detailing positive clinical activity for experimental hepatitis-C drug ACH-3102 in an oral presentation at the Asian Pacific Association for the Study of the Liver conference in Australia. Shares have since backed off and are now up just 4% as of this writing.

So what: According to Achillion's findings in patients with genotype 1b hepatitis-C, ACH-3102, when given with sovaprevir and a ribavirin, demonstrated a sustained virologic response (i.e., undetectable levels of the hepatitis-C virus) at the 12-week mark in all eight patients -- even those with the Y93 mutation. Achillion's oral presentation also noted, via a second oral presentation, "Despite the presence of up to six linked mutations identified at baseline in the NS5A protein, ACH-3102, without the co-administration of interferon or a second direct-acting antiviral, was able to suppress viral replication with no virologic breakthrough observed during 12 weeks of treatment."

Now what: What we have here seems to be the trademark of Achillion Pharmaceuticals: rich and robust promise from early and perhaps even midstage data, but the inability thus far to move anything beyond midstage trials. Because Gilead Sciences already has Sovaldi approved to treat HCV, and it appears that an approval for AbbVie's direct-acting antiviral is likely as well, Achillion's window of opportunity is shrinking by the day. With that being said, I don't personally see much upside potential in Achillion's share price until it can successfully move its key HCV products into late-stage development.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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