Merck (NYSE:MRK) today announced positive results from a Phase 1 study of its subdermal drug-eluting implant for preventing HIV-1 infection.

The investigational implant has the potential for extended administration of islatravir for pre-exposure prophylaxis (PrEP) of HIV-1 infection, according to a news release.

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Merck (NYSE:MRK) today announced positive results from a Phase 1 study of its subdermal drug-eluting implant for preventing HIV-1 infection.

The investigational implant has the potential for extended administration of islatravir for pre-exposure prophylaxis (PrEP) of HIV-1 infection, according to a news release.

Islatravir is an investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) being valuated for both the treatment of HIV-1 infection in combination with other antiretroviral agents, as well as for the prevention of HIV-1 infection as a single agent.

Study results, presented by Merck at the 2021 Conference on Retroviruses and Opportunistic Infections showed that the implant achieved active drug concentrations above the pre-specified pharmacokinetics (PK) threshold at 12 weeks across the three doses (48 mg, 52 mg and 56 mg) studied.

The study included eight participants in each dosage group, plus 12 in the placebo group, with the implant removed after 12 weeks and an evaluation continuing for eight weeks thereafter. At 12 weeks, all three doses resulted in mean islatravir triphosphate concentrations above the target threshold.

Results also showed that the implant is projected to provide drug concentrations likely above the threshold for one year at the 56 mg dose. In the study, 67% of participants reported at least one implant site adverse event, although all were mild or moderate in severity and none resulted in discontinuations. Common adverse events included erythema, tenderness/pain, pruritus and induration. The most common one not related to the implant site was headache, which affected six participants.

The findings in the study have led to Merck’s plans to initiate a Phase 2 trial to continue exploring the potential of a subdermal implant containing islatravir as a long-acting option for PrEP for up to 12 months.

“We are delighted to share our early data at CROI 2021 supporting the potential for a once-yearly dosing regimen for islatravir using a subdermal implant,” Merck Research Laboratories VP of global clinical development Dr. Joan Butterton said in the news release. “We know that PrEP can have a positive impact in curbing the spread of HIV and are looking forward to evaluating our implant further with the goal of developing new long-term options for HIV prevention.”