Sometimes, drugs that fail in clinical trials get a second life with a new company. Vilazodone, a depression treatment, seems to be one of those compounds.

Earlier this week, Clinical Data (NASDAQ:CLDA) announced positive phase 3 results for Vilazodone, its lead drug candidate. The drug met both its main and secondary goals of improving subjects' moods, as defined by two different rating scales compared against placebo.

While it's great that the drug improved individuals' moods compared to a sugar pill, Vilazodone really needs to be compared to drugs currently on the market, instead of placebo, before investors will know how much market share the drug could take.

The drug combines a Selective Serotonin Reuptake Inhibitor (SSRI), like Pfizer's (NYSE:PFE) Zoloft, with a 5HT1A partial agonist, which activates serotonin receptors, as found in drugs like Bristol-Myers Squibb's (NYSE:BMY) BuSpar.

Clinical Data acquired worldwide rights to the drug from Merck (NYSE:MRK) in 2004, after Vilazodone failed several clinical trials. The company realized that since one-half of depressed patients don't achieve satisfactory results with the first drug they take, the drug might still have promise for a subset of patients.

Clinical Data has experience in developing genetic markers, and since depression is believed to be genetic in at least some cases, the company guessed that it could find markers that would help determine the patients' likelihood of responding to the drug. In fact, part of the clinical trial was designed to find markers that would differentiate patients for whom the drug will work from those for whom it won't.

The company will need to do at least one more clinical trial to prove efficacy, perhaps only enrolling patients that its new markers predict will respond to the drug. That should give it stronger efficacy data, while supporting the use of its markers in a companion pharmacogenetic test.

In the new era of personalized medicine, Clinical Data is on track to deliver a test alongside a complementary drug. That would give it two forms of income, and it might put the drug on the fast track to gaining market share. Doctors may feel more confidence writing prescriptions after genetic tests have determined that the drug is likely to work.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Pfizer has been selected by the Inside Value newsletter. The Fool's disclosure policy works for everyone.