(AP) -- Pfizer Inc. said Friday it is pulling its blood pressure drug Thelin off the market and stopping all clinical trials because the drug can cause fatal liver damage.
Thelin is sold in the European Union, Canada, and Australia as an oral treatment for severe pulmonary arterial hypertension, or high blood pressure in the pulmonary artery. Pfizer said a review of data from clinical trials and post-marketing reports showed a new link to liver injury. It also consulted with experts about the link between Thelin and the deaths of two patients.
Liver damage was a known side effect of Thelin and similar drugs, the company said. Pfizer said the withdrawal was voluntary and added that it has withdrawn its filing for marketing approval in the U.S.
Since there are other treatment options, Pfizer said the benefits of Thelin don't outweigh the risks. It is stopping all studies of the oral drug, which Pfizer acquired in 2008 when it bought Encysive Pharmaceuticals Inc. Encysive had been trying to win marketing approval for Thelin since 2005, but the Food and Drug Administration said it was not effective enough. Other agencies only approved the drug for hypertension that was so debilitating that patients' physical activity was severely limited.
The chemical name of Thelin is sitaxsentan.
In premarket trading, shares of Pfizer shed 9 cents to $16.67 from Thursday's close of $16.76.
Explore further: Merck ends development of Parkinson's disease drug