A PrEP pill which users would only need to take once a month is edging closer to FDA approval.

Islatravir, formerly known as MK-8591, is being developed by the pharma company, Merck. Islatravir is at the second stage of trials, with just a third to conquer following that.

Sharon L. Hillier, PhD, professor of reproductive infectious disease at the University of Pittsburgh School of Medicine told reporters, the novel drugs is “extremely potent [with] an extremely long half-life. Which means that it’s a long-acting agent that can be used for prevention or treatment.”

250 participants were tested, with 40% being given 60mg, 40% given 120mg and the remaining 20% a placebo.

192 of those receiving six doses over six months found it was able to “achieve thresholds thought to be enough to prevent HIV.”

At the third phase, Islatravir will be tested first on cisgender women in the US and Africa, and then on trans women and gay men globally.

The extended half-life of the drug means that users would not have to be as strict with their doses, and would relieve the pressure of remembering to take medication daily.

The FDA previously referred to long-acting PrEP as a “breakthrough” as it would act almost as a vaccine to HIV.