I always figured management at formerly independent Encysive Pharmaceuticals was just incompetent in its failure to get its pulmonary arterial hypertension drug Thelin approved in the U.S. time and time and time again.

But now I'm thinking Thelin is just cursed.

The drug's new owner, Pfizer (NYSE: PFE), announced today that it's pulling Thelin off the market and withdrawing the marketing application with the Food and Drug Administration because a new side effect was discovered. It was always know that Thelin and the drugs in the same class had a risk of liver toxicity, but the new data suggest injury to the liver is more severe.

Bye-bye, Thelin; at least Pfizer didn't pay much for you.

With every loser, there's a winner. Or in this case a few, since there are a number of pulmonary arterial hypertension drugs on the market. Pfizer sells Revatio, which is just Viagra under a different name, so Pfizer isn't completely out of the market. Similarly, Eli Lilly's (NYSE: LLY) erectile dysfunction drug Cialis is marketed by United Therapeutics (Nasdaq: UTHR) under the trade name Adcirca. United Therapeutics also has a PAH drug Remodulin, which could benefit from a little less competition.

But the two drugs that will likely benefit most are Actelion's Tracleer and Gilead Sciences' (Nasdaq: GILD) Letairis, since they're in the same class of drugs. Doctors are more likely to switch between an endothelin receptor antagonist than into a new class if Thelin was actually working for the patient.

It's always a little sad to see a drug die in development, but considering the long and tumultuous road Thelin has been on, maybe it's only fitting to see it have a sudden heart attack and die before ever making it to the market in the U.S.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.