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), a biopharmaceutical company focused on developing human viral disease treatments, plummeted 35% after the Food and Drug Administration requested more information on preclinical hepatitis-C drug candidate IDX20963.

So what: According to the update provided by Idenix, the FDA requested additional safety information from preclinical studies of IDX20963, its uridine nucleotide drug candidate, before it will let the company proceed to human clinical trials. Until Idenix is able to respond and meet the FDA's requests for additional safety data, all clinical trials will remain on hold and Idenix's expected clinical trial launch timeframe will be pushed back.

Now what: No, this isn't deja vu, but it is another clinical hold of sorts placed on Idenix. If you recall, the company had two of its leading nucleotide inhibitors placed on clinical hold while the FDA reviewed their safety last summer (IDX184 and IDX19368). The impetus was the death of a patient who was taking Bristol-Myers Squibb's (NYSE:BMY) experimental hep-C drug, BMS-986094, which is now discontinued. Idenix's two nucleotide inhibitors shared similar chemistry on paper with Bristol's drug, and thus were also put on hold. Investors can now chalk up a third pipeline candidate that has been held up by the FDA in less than a year. All the while, Idenix's peers are marching ever closer to introducing all-oral and much improved forms of hep-C drugs. This looks like a desperate biopharmaceutical company that's quickly running out of options and time.

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