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Once-a-month PrEP pill shows promising results

A man takes a medicine tablet
Posed by model (Photo: Shutterstock)

A once-a-month PrEP pill may be on its way.

For a new drug to come to market, it must pass at least three different trials before being submitted to the FDA for approval for use in the U.S.

Islatravir, formerly known as MK-8591, is being developed by the pharma company, Merck. It has already reached its second stage of trials. Following promising results, it looks likely to go to Phase 3 trials, bringing it one step closer to approval.

Among those studying its effects is 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. According to Healio,

Hillier told reporters during a virtual HIV prevention meeting that Islatravir was “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.”

Related: 5 ways to get PrEP delivered to your doorstep

In its phase 2 trial, 250 participants at low-risk of HIV were recruited to receive either six monthly doses of Islatravir or a placebo.

Those taking Islatravir were monitored to see how quickly the medicine entered their bodies and how long it remained potent.

The Islatravir participants were found to have levels of the drug, “well above the prespecified PK threshold for HIV-1”.

Further investigation revealed “rapid, sustained and adequate distribution” throughout all tissue samples (i.e. in the parts of the body where it’s needed).

Hillier said a Phase 3 trial will commence later this year, first on cisgender women in the US and Africa, and then on trans women and gay men globally.

Hillier said that because the drug has a long half-life (the amount of time it takes to decrease in potency by half), it would hopefully not matter too much if people were a little late taking their dose: they would probably still have protection for longer than just one month.

Although promising news, further success in Phase 3 trials will be critical for it to be approved by the FDA.

Last November, the FDA called a long-acting PrEP injection a “breakthrough therapy”. Cabotegravir has been designed to be administered by a health professional once every eight weeks. Designating a treatment as a ‘breakthrough’ means the FDA has been impressed by trial results and will work with a pharmaceutical company to speed up a therapy going through the approval process.

Related: FDA says injectable PrEP a ‘breakthrough’ therapy as it pends approval

Although many people are happy to take a daily PrEP pill, other people struggle, including those with mental health or substance abuse issues. Long-acting pills or injections, whether for convenience or necessity, may prove yet another tool in the ongoing battle to end the HIV epidemic.