Warning dropped from Gilead PAH drug

Gilead Sciences' once-daily pulmonary arterial hypertension (PAH) drug Letairis (ambrisentan) will no longer be required by the US Food and Drug Administration to carry information about the risk of liver injury in its boxed warning. In addition, patients taking the drug will no longer need to obtain monthly liver function tests.

Post-marketing data collected through the Letairis Education and Access Program (LEAP) following the drug's 2007 approval showed that the drug does not cause liver damage, according to the FDA.

In addition, further evaluation of the 12-week clinical trial data submitted as part of the original marketing application showed that the incidence of liver function abnormalities was 0 per cent on Letairis and 2.3 per cent on placebo.

Letairis will continue to be available only through LEAP, the restricted distribution program that was part of the Risk Evaluation and Mitigation Strategy that the FDA required for the drug.  The programme will no longer include a requirement for monthly serum liver enzyme tests, although monthly pregnancy tests will still be required in women of childbearing age before each shipment of Letairis due to serious risks to the fetus when Letairis is taken during pregnancy.

Letairis will still carry a boxed warning, which is the strongest type of warning that the FDA can require, regarding risk of serious birth defects and the contraindication for use during pregnancy remain in the Letairis label.

The warning about the risk of liver injury was included in the Letairis label based on experience with other drugs in the same class, known as endothelin receptor antagonists (ERAs), which have been linked to liver enzyme elevations, liver injury, and liver failure. In addition, there were a few observed instances of increased liver enzymes in people taking Letairis, but further evaluation showed that rates of liver problems in Letairis patients are consistent with rates within the general PAH population.

Other ERAs include Actelion's Tracleer (bosentan).

The FDA stressed that Letairis is still not recommended for use in patients with moderate or severe liver problems because adequate data does not exist for that population.