Researchers have uncovered a way the malaria parasite becomes resistant to a key clinical trial drug. The parasite that causes malaria makes a class of molecules called isoprenoids. These play multiple roles in keeping organisms healthy whether plants animals or bacteria. In malaria the investigational drug fosmidomycin blocks isoprenoid synthesis killing the parasite. But over time the drug often becomes less effective. 'In trials testing fosmidomycin the malaria parasite returned in more than half the children by the end of the study' said Audrey R. Odom an assistant professor of pediatrics at Washington University's school of medicine in St. Louis.