Vertex Pharmaceuticals (NASDAQ:VRTX) has had an especially good month. Actually, that might be understating the case a bit -- May has been one of the most exciting months in the company's history.

During the Digestive Disease Week meeting in late May, Vertex reported highly anticipated clinical trial results from a study that examined its hepatitis C (HCV) drug, VX-950. VX-950 is a small-molecule drug that directly hits the virus and stops it from replicating. Hepatitis C can be difficult to control with existing therapies, so innovative drugs like VX-950 are sorely needed.

The clinical trial data for VX-950 looks very good, particularly in the highest doses of the drug. Using highly sensitive assays to measure the presence of the HCV virus, four out of eight patients were HCV-RNA negative, and two of those four patients had undetectable levels. Considering that these patients took the drug for only two weeks, this is an incredible result.

While this data is exciting, the drug is still very early in development. The next big step is the initiation of phase 2 trials, which should start later this year. While the drug moves through further clinical trials, cautious optimism is warranted.

Vertex's VX-950 is potentially a multi-billion dollar product. I've long been a fan of Vertex, even before all this buzz. The promise of VX-950, as well as its HIV protease inhibitor Lexiva, which it co-promotes with GlaxoSmithKline (NYSE:GSK), led me to recommend Vertex in the February issue of Motley Fool Rule Breakers. The stock is up 34% since then.

For continuing coverage of Vertex and VX-950, as well as regular updates and insight into the biotech industry, test-drive Rule Breakers­ for 30 days-- for free.

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Motley Fool Rule Breakers biotech analyst Charly Travers owns shares of Vertex Pharmaceuticals. The Motley Fool has a disclosure policy.