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 Motley Fool Rule Breakers biotech pick Vertex Pharmaceuticals (Nasdaq: VRTX) rose more than 14% in early trading on nearly three times the average volume.

So what: Those investing in Vertex have long waited for the Food and Drug Administration to bless Telaprevir, the company's experimental treatment for Hepatitis C. The wait is almost over. This morning, the agency issued a favorable preliminary review of the drug.

Now what: The FDA's study of Telaprevir concludes that the drug does a better job curing patients of the blood-borne disease than current therapies, Bloomberg reports. Later this week, an advisory council will convene to weigh the risks and benefits of approving the drug for wider use.

Risks remain, of course. Merck (NYSE: MRK) also has a Hepatitis C treatment under review and could still beat Vertex to market. But after today's news, that outcome looks a lot less likely.

Interested in more info on Vertex Pharmaceuticals? Add it to your watchlist.

Interested in more info on Merck? Add it to your watchlist.

Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. Vertex is a Rule Breakers recommendation. You can try any of our Foolish newsletter services free for 30 days.

Tim didn't own shares in any of the companies mentioned in this article at the time of publication. Check out his portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. You can also get his insights delivered directly to your RSS reader. 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 is also on Twitter as @TheMotleyFool. Its disclosure policy is at least 10% better than other disclosure policies.