Metro Weekly

Monthly PrEP pill shows “potent” results in trials

Merck said results of a study into islatravir suggested it could be used to prevent and treat HIV

PrEP Truvada HIV
Merck’s new monthly PrEP pill produced encouraging results in phase 2 trials — Photo: Anastasiia Ostapovych / Unsplash

PrEP could soon become a monthly pill to prevent HIV infection, rather than a daily pill.

Pharmaceutical company Merck has released data from the second phase of trials into its antiretroviral drug islatravir, which has proven to be “extremely potent” when taken monthly, Healio reports.

PrEP, or pre-exposure prophylaxis, uses antiretroviral treatments for HIV to prevent an HIV-negative person from contracting the virus.

The most widely known form of PrEP is currently the once-per-day pill known as Truvada, manufactured by Gilead Sciences.

But that daily regimen could be transformed into just 12 pills per year if Merck’s trials continue to demonstrate the efficacy of islatravir.

Sharon L. Hillier, Ph.D., professor of reproductive infectious disease at the University of Pittsburgh School of Medicine and director of reproductive infectious disease research at UPMC Magee-Women’s Hospital in Pittsburgh, told reporters that islatravir was “extremely potent [with] an extremely long half-life,” according to data from Merck’s phase 2a trial.

Simply translated, Hillier said this “means that it’s a long-acting agent that can be used for prevention or treatment.”

The study involved 250 people between 18 and 65 who were considered at low risk for HIV. Of those 250, 192 participants received six monthly doses of islatravir and were found to have achieved “thresholds thought to be enough to prevent HIV,” according to Hillier.

Hillier also said that islatravir was “probably a little more forgiving” than daily PrEP because of its long-lasting nature and once-monthly requirement.

“That is, if the dose is taken late or people miss a dose, it may still in fact achieve that level that will allow for protection,” she said.

Merck plans to launch two phase 3 trials to test the efficacy of islatravir in preventing HIV — the first trial among cisgender women in the U.S. and Africa, and a second global trial among men who have sex with men and transgender women.

The outcome of the phase 3 trials will determine whether islatravir can be approved for use as PrEP by the U.S. Food and Drug Administration (FDA).

Islatravir isn’t the only once-monthly PrEP solution being developed. Last year, the FDA granted “breakthrough therapy” status to a form of PrEP that would require injections every two months — reducing a person’s PrEP regimen to just six doses per year.

ViiV Healthcare’s antiretroviral cabotegravir was f9und to be 69% more effective than Truvada when used as PrEP — despite Truvada already being up to 99% effective in preventing HIV transmission.

The results of ViiV’s trial were so conclusive that it stopped the trial early and offered those on Truvada its bimonthly injections instead.

The FDA’s breakthrough therapy designation helps the development of drugs that address serious or life-threatening medical conditions and expedites their review by the FDA.

This month, ViiV also announced that its injectable treatment for HIV, Cabenuva, was as effective when used every two months — potentially representing a “paradigm shift” in a person’s treatment regimen should it be approved by the FDA.

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Rhuaridh Marr is Metro Weekly's online editor. He can be reached at rmarr@metroweekly.com.

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