An investigational capsid inhibitor, GS-6207, has shown early promise as a new long-acting form of HIV treatment to be dosed only every three months. The drug, being developed by Gilead Sciences, proved safe and well tolerated in a Phase I placebo-controlled trial. The ongoing study included 40 HIV-negative participants randomized to receive various doses of GS-6207 in a single subcutaneous injection or a placebo injection. Gilead is also attempting to develop an oral formulation of the antiretroviral. After analyzing the levels of GS-6207 in the blood over time, researchers determined that a dose of 100 milligrams or greater should be sufficient for quarterly dosing. The study has seen no deaths or serious adverse health events. Most side effects were mild and resolved in time. Gilead has already begun a Phase Ib study of GS-6207 in HIV-positive participants.