Gilead Sciences (GILD -0.21%) has gotten a crucial nod for its Vitekta treatment. The company announced that the European Commission -- the executive arm of the European Union -- has granted marketing authorization for the drug. The approval is for two doses, 85 milligrams and 150 milligrams, both of which are offered in tablet form.

Vitekta belongs to a class of treatments called integrase inhibitors and is used in combination with other compounds to suppress HIV. It works by interfering "with HIV replication by blocking the virus from integrating into the genetic material of human cells," in Gilead's words. The company added that in clinical trials, Vitekta effectively suppressed HIV in patients carrying drug-resistant strands of the virus.

In spite of the positive news, Gilead's stock price fell in the wake of the announcement. The shares dropped by 1.3%, or $0.92, to close the day at $68.97.