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 Idenix Pharmaceuticals (Nasdaq: IDIX) got a positive diagnosis today and climbed 43% after the company released positive data for its hepatitis C drug.

So what: The company said that in a phase 2b trial of IDX184, the drug achieved rapid virologic response in 73% of patients using 100 mg and 63% of patients using 50 mg. The stock also got some of its boost after Bristol-Myers Squibb (NYSE: BMY) bought Inhibitex (Nasdaq: INHX) for $2.5 billion, a 163% premium from its Friday close.

Now what: Makers of hepatitis C drugs are hot today, and analysts think this could lead to more activity in the sector. Baird and Bernstein analysts were among those who think this could pump up these stocks as companies compete to find treatments for the virus. If you own shares, I would take some profit today just to reduce risk, but these stocks appear to be at the beginning of a run-up right now.

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