A genetics study found that certain people have genes which would make an HIV antiretroviral drug ineffective.

The drug, tenofovir, is used for preventing as well as treating an HIV infection.

At first, it was unclear why the drug did not protect everyone from HIV infection, but it was later concluded that rare genetic variants can undermine tenofovir's effect, as reported by pharmacologist Namandjé Bumpus of Johns Hopkins University School of Medicine.

Enzymes adenylate kinase 2 and creatine kinase can activate the drug, Bumpus and his colleagues have discovered.