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 hepatitis C, soared as much as 62%, its second-straight day of huge gains considering that it jumped 48% yesterday, after announcing a pipeline update regarding sovaprevir and ACH-3422.

So what: According to the company's early morning press release -- and the primary reason the stock is soaring today -- the Food and Drug Administration has lifted its nearly year-long clinical hold on Achillon's lead drug, sovaprevir, an NS3/4A protease inhibitor. Originally the investigational drug was placed on clinical hold after elevated ALT liver enzyme levels were discovered in patients. Based on its press release, Achillion will be able to dose trial patients once-daily at 200 mg, the prior dose that was well-tolerated in previous studies.

In addition, Achillion announced that the company has begun dosing the initial cohort of patients with ACH-3422, a uridine-analog nucleotide polymerase inhibitor, in a proof-of-concept study. Results for this seven-day treatment on genotype-1 patients are expected to be reported in the fall of this year.

Now what: This big news of the day is the clinical hold lift on sovaprevir which has long been the bread and butter of Achillion's pipeline. Now the potential chatter that it could be a takeover candidate would definitely make a bit more sense, because the remainder of its pipeline simply wasn't as impressive. However, I would also strongly caution -- especially with shares having more than doubled in just the past two days -- that Achillion has yet to get a therapy past midstage trials. Even if sovaprevir meets its primary endpoint of a preset sustained virologic response in HCV patients, consider that it won't make it to market until 2016 or 2017, which is more than enough time for Gilead Sciences' Sovaldi or AbbVie's direct-acting antiviral combo (if it's approved) to establish themselves and claim practically all hepatitis C treatment market share. In my personal opinion, Achillion still remains a company that should be avoided.

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.

The Motley Fool owns shares of, and recommends Gilead Sciences. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.