Merck Presents Results from Phase 1 Trial Evaluating Investigational Islatravir Subdermal Implant for the Prevention of HIV-1 Infection at CROI 2021 - Seite 2

At 12 weeks, all three doses resulted in mean islatravir triphosphate (the active form of islatravir) concentrations above the target PK threshold (0.05 pmol/10⁶ cells), the lowest level of islatravir triphosphate projected to have an antiviral effect as monotherapy in humans based on Phase 1 and Phase 2 data. The top two doses (52 mg and 56 mg) maintained islatravir triphosphate levels above the PK threshold in all individuals from implant insertion until the end of the study. The results of this study, along with previous assessments of islatravir implants, provide evidence for the potential of implants to generate levels of islatravir triphosphate projected to provide drug concentrations likely above the target PK threshold for at least one year.

In this study, 67% of (n=24/36) participants reported at least one implant site adverse event (AE). All AEs were mild or moderate in severity and there were no discontinuations due to an AE. Common AEs included erythema (3/12; 4/8; 2/8; 4/8), tenderness/pain (4/12; 2/8; 4/8; 4/8), pruritus (3/12; 5/8; 2/8; 6/8), and induration (2/12; 4/8; 4/8; 4/8) for the placebo, 48 mg, 52 mg, and 56 mg groups, respectively. The most common AE not related to the implant site was headache, affecting six individuals overall. There was no clear relationship between dose and implant site AE frequency or severity.

About Islatravir (MK-8591)

Islatravir (formerly MK-8591) is Merck’s investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) under evaluation in clinical trials for the treatment of HIV-1 infection in combination with other antiretrovirals, including the ILLUMINATE clinical trials program for once-daily treatment. Islatravir is also being studied for pre-exposure prophylaxis (PrEP) of HIV-1 infection as a single agent across a variety of formulations, including the IMPOWER clinical trials evaluating an oral once-monthly regimen.

Our Commitment to HIV

For more than 35 years, Merck has been committed to scientific research and discovery in HIV, and we continue to be driven by the conviction that more medical advances are still to come. Our focus is on pursuing research that addresses unmet medical needs and helps people living with HIV and their communities. We remain committed to working hand-in-hand with our partners in the global HIV community to address the complex challenges that hinder continued progress toward ending the epidemic.