Pfizer is voluntarily withdrawing Thelin (sitaxentan) for the treatment of pulmonary arterial hypertension (PAH) in the EU, Canada and Australia, where the drug is approved. The company will also discontinue clinical studies of Thelin worldwide.

The decision was based on emerging safety information from clinical trials and post-marketing reports that a new potentially life-threatening risk of liver injury with Thelin has been observed. While liver toxicity is a known complication of the class of drugs to which Thelin belongs, Pfizer has concluded that the overall benefit of Thelin no longer outweighs the risk in the general population of PAH patients. The company has notified health authorities and will stop clinical studies.

“Pfizer’s priority is to ensure the safety and well-being of patients, and we are in the process of communicating all of this information to the appropriate medical professionals and regulatory authorities in all regions as quickly as possible,” said Cara Cassino, MD, vice president, Clinical Development and Medical Affairs for Pfizer’s Pulmonary Vascular Disease unit.