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. A simple genetic test for the gene that makes the CYP3A5 protein could be used to determine what doses would achieve effective levels in individuals, the researchers say.
“Because African-Americans are disproportionately affected by HIV infection, it is doubly important that we get the dosing right,” says Namandje Bumpus, PhD, an assistant professor of pharmacology and molecular sciences at the Johns Hopkins University School of Medicine.
Normally, the absence of CYP3A5 is not noticeable; a very similar protein, CYP3A4, acts on most of the same drugs. But, for a few drugs, like maraviroc and the cancer drug vincristine, CYP3A5 seems to play a particularly prominent role in helping to remove them from the body. In those cases, the presence or absence of CYP3A5 would likely affect the amount of a drug in the bloodstream, the Johns Hopkins team predicted. And since 85 percent of participants in the maraviroc dosing study were European-Americans, who typically lack functional CYP3A5, the researchers surmised that the recommended dose for maraviroc could be too low for anyone with two functional copies of the gene — including 45 percent of African-Americans.
Read the full, original story: Dosage of HIV drug may be ineffective for half of African-Americans