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 two patients who were taking Thelin died during a clinical trial, and a review of data from clinical studies and post-marketing reports showed a new link to liver injury.
Liver damage was a known side effect of Thelin and similar drugs, the company said, but the review uncovered a link to liver damage that was not tied to identifiable risk factors. It said the problem was unlikely to be detected by routine monitoring, and in some cases the problems did not go away after patients stopped taking Thelin.
Pfizer said the withdrawal was voluntary and added that it has withdrawn its filing for marketing approval in the United States.
Since there are other treatment options, Pfizer said the benefits of Thelin don't outweigh the risks. It is stopping all studies of the 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 New York company said worldwide sales of Thelin, or sitaxsentan, totaled $44.4 million in the first nine months of 2010.
Shares of Pfizer rose 26 cents to close at $17.02 on Friday.