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 developer of therapies to treat infectious diseases, advanced as much as 10% after announcing a poster presentation for preclinical drug ACH-3422 over the weekend and following a large insider purchase within the company.

So what: According to Achillion's press release from Saturday, ACH-3422 -- an NS5B polymerase inhibitor that could be a potential treatment for hepatitis C -- showed impressive preclinical activity with in vitro human cells and in a two-week animal toxicity study. The plan is for Achillion to advance ACH-3422 to proof-of-concept human trials by no later than mid-2014 and use it in combination with other direct-acting antiviral agents.

Also stirring the pot was an SEC filing that RA Capital Management, an owner of roughly 10% of Achillion's outstanding shares, purchased an additional 1.186 million shares at a price of $2.45. Insider buys can be an important tool for shareholders to keep their eyes on as insiders have a keen understanding of the company they're investing in. If they're bullish, it could mean good news is on the long-term horizon.

Now what: Whereas I see why investors are excited today, this is really much ado about nothing in my book. Achillion's preclinical portfolio has never been much of an issue; it's the fact that its lead drug is on hold by the Food and Drug Administration and that two new oral hepatitis-C medications from competitors are likely to be approved by the FDA within the next year. That's the real concern! I'm worried that Achillion has fallen so far behind in the hep-C race that even if it does manage to get one of its product candidate in front of the FDA that it may not matter. I would suggest tempering your optimism after some extremely early stage results on ACH-3422 and an insider buy from RA Capital.