Yesterday, Rule Breakers pick InterMune (NASDAQ:ITMN) announced preclinical data for its hepatitis C (HCV) compound, ITMN-191, at a major European medical conference.

Many investors are excited about ITMN-191, a HCV protease inhibitor compound, due to its similarity to Vertex's (NASDAQ:VRTX) potential blockbuster HCV drug candidate in the making. While the in vitro data that InterMune presented yesterday is not nearly as interesting as human in vivo data, it does form the basis for future human clinical trials with a drug and is therefore an important part of the drug development process.

InterMune plans on presenting the first human efficacy data from a phase 1 trial of ITMN-191 in the second half of this year. Investors won't have to wait that long for more information about the market potential of ITMN-191, though. Vertex and Schering-Plough (NYSE:SGP), which is developing its own HCV protease inhibitor, will be presenting loads of data at this same medical conference, which is running through the weekend.

Early stage drug development is strange in that good clinical trial data for its competitors can also be good news for InterMune, since success with Vertex's or Schering's compounds validate InterMune's drug target. The time to parse the data to see which compound has the best efficacy, safety, and dosing profile will come in the not-too-distant future once ITMN-191 human clinical study data starts to come out. Right now, though, InterMune shareholders should be rooting for positive data from Vertex and Schering over the weekend.

InterMune and Vertex Pharmaceuticals are Rule Breakers selections. Looking for more Foolish drug stock coverage? Check out the Fool's market-beating Rule Breakers newsletter. You can check out all our recommendations as well as get access to our message boards and exclusive content with a 30-day free trial.

Fool contributor Brian Lawler owns shares of InterMune but no other company mentioned in this article. The Fool has a disclosure policy.