Many African-Americans may not be getting effective doses of the HIV drug maraviroc, a new study from Johns Hopkins suggests

The initial dosing studies, completed before the drug was licensed in 2007, included mostly European-Americans, who generally lack a protein that is key to removing maraviroc from the body. The current study shows that people with maximum levels of the protein - including nearly half of African-Americans - end up with less maraviroc in their bodies compared to those who lack the protein even when given the same dose. "Because African-Americans are disproportionately affected by HIV infection, it is doubly important that we get the dosing right," says Namandje Bumpus, Ph.D., an assistant professor of pharmacology and molecular sciences at the Johns Hopkins University School of Medicine. CYP3A5 is a protein found in abundance in liver and intestinal cells. It adds an oxygen molecule to various drugs to make them more water-soluble so they can ultimately enter the urine and leave the body. Between 80% and 90% of European-Americans have no CYP3A5, because they have inherited two dysfunctional copies of the CYP3A5 gene. The study highlights the importance of designing clinical trials in which the participants are as ethnically diverse as the population to be treated.