Pfizer Pulls PAH Drug Due to Liver Toxicity


December 10, 2010

December 10, 2010 (New York, New York) — Pfizer is to voluntarily withdraw sitaxentan (Thelin), a drug for pulmonary arterial hypertension (PAH), following two cases of fatal liver toxicity [1]. The drug has been marketed in 16 countries in the European Union and in Australia and Canada; clinical trials with the compound will also be discontinued, and the company no longer plans to file a US new drug application.

Pfizer says its decision is based on "a review of emerging safety information from clinical trials and postmarketing reports." While liver toxicity is a known complication of the class of drugs to which sitaxentan belongs, the company says a new potentially life-threatening idiosyncratic risk of liver injury has been observed. "Given the availability of alternative treatments, Pfizer has concluded that the overall benefit of Thelin no longer outweighs the risks in the general population of PAH patients," the company says in a statement [2].

Alternative treatments for PAH include the dual endothelin antagonist bosentan (Tracleer, Actelion Pharmaceuticals), the endothelin A receptor antagonist ambrisentan (Letairis, Gilead Sciences), and two phosphodiesterase type-5 inhibitors better known for their treatment of erectile dysfunction but repackaged with new brand names for PAH, sildenafil (Revatio; Pfizer) and tadalafil (Adcirca, United Therapeutics)

Don't Stop Drug Without Consulting a Healthcare Professional

PAH is a rare and incurable condition that often lies undetected until it reaches the most severe stages. It can occur in isolation (primary pulmonary hypertension); related to other diseases, such as connective-tissue disorders like scleroderma and systemic lupus erythematosus; or as a result of the use of appetite suppressants, cocaine, or other drugs of abuse.

The firm recommends that no new patients be prescribed sitaxentan and that patients already receiving it be transitioned to appropriate alternative treatments as soon as is safely possible; it stresses that people should not stop taking the drug until they speak with a healthcare professional.

The European Medicines Agency says its scientific Committee for Medicinal Products for Human Use (CHMP) will look at this issue during its plenary meeting next week, December 13-16, "and will provide detailed advice for patients and prescribers."


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