The HIV protease inhibitor Crixivan indinavir causes signs of potential liver side effects in up to 25% of patients taking the product, causing physicians to change treatment. Researchers now have identified the mechanism responsible for the side effect, providing both a genetic polymorphism that can be used to screen patients, as well as a target for screening new HIV protease inhibitors.

Crixivan, which is marketed by Merck & Co. Inc. (MRK, Whitehouse Station, N.J.), is used in combination with other antiretroviral agents to treat HIV/AIDS. However a large proportion of patients treated with indinavir develop indirect hyperbilirubinemia (increased plasma levels of unconjugated bilirubin