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What: Shares of Idenix Pharmaceuticals (NASDAQ:IDIX), a clinical-stage biopharmaceutical company developing therapies to treat human viral diseases, jumped as much as 14% after reporting data and updating the progress of its nucleotide prodrug inhibitor development program for the treatment of hepatitis C.

So what: According to Idenix's press release, the most pertinent piece of information is that IDX21437, its lead nucleotide prodrug inhibitor, demonstrated "potent antiviral activity of mean maximum 4.2-4.3 log10 IU/mL reductions for patients infected with HCV genotype 1, 2 or 3 receiving 300 mg once daily of IDX21437 in the seven-day proof-of-concept portion of a phase I/II clinical trial." Following its positive proof-of-concept results Idenix announced plans to initiate a combination therapy trial involving IDX21437 and samatasvir by mid-2014. In addition, Idenix announced the initiation of enrollment in a phase 1 study involving IDX21459 which will be tested in varying doses of 10 mg to 300 mg in 40 treatment-naive genotype 1 HCV patients.

Now what: This has become sort of the modus operandi of Idenix Pharmaceuticals: get shareholders all worked up over the excitement of a phase 1 or phase 2 therapy, then have their dreams get crushed with a clinical hold that winds up with the company scrapping its drug. There have been numerous occasions since 2010 where Idenix has had one or more of its pipeline therapies put on hold due to safety concerns and eventually shelved. In fact, it's happened so often that I just assume investors' best course of action is to stick to the sidelines until the company successfully pushes a product beyond phase 2. Not to mention, with Gilead Sciences' Sovaldi now approved by the FDA and looking for additional indications, and AbbVie's direct-acting antiviral looking as if it has a very good shot at a late 2014 approval, the sands of time to even make a dent in the HCV space are beginning to blow away quickly for Idenix, making it an easily avoidable stock for investors.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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