Therapy Areas: AIDS & HIV
Merck Presents New Data from Ongoing Phase 2a Clinical Trial Evaluating the Safety, Tolerability and Pharmacokinetics of Investigational, Once-Monthly, Oral Islatravir for HIV-1 Prevention
21 July 2021 - - US-based pharmaceutical company Merck (NYSE: MRK) has presented results from a Phase 2a clinical trial evaluating the safety, tolerability and pharmacokinetics of six monthly oral doses, over 24 weeks, of islatravir, the company's investigational nucleoside reverse transcriptase translocation inhibitor, versus placebo for pre-exposure prophylaxis of HIV-1 infection in adults at low-risk of contracting HIV-1.

After 24 weeks, once-monthly oral islatravir was generally well tolerated versus placebo. Most adverse events were mild and there were no serious drug-related AEs in people who received islatravir.

The levels of islatravir in peripheral blood mononuclear cells (PBMCs) also remained above the pre-specified efficacy PK threshold for PrEP at both doses studied (60 mg and 120 mg) eight weeks after the last study dose.

These data were shared as a late-breaking oral presentation during the virtual 11th International AIDS Society Conference on HIV Science (IAS 2021) and are a follow-up to the interim analysis that was presented earlier this year at the virtual 2021 HIV Research for Prevention Conference (HIVR4P 2021).

Islatravir is currently being evaluated across a variety of dosing regimens, for both the treatment of HIV-1 infection in combination with other antiretroviral agents and for the prevention of HIV-1 infection as a monotherapy.

An overview of the islatravir treatment and prevention development program is available here, which includes our two Phase 3 IMPOWER trials evaluating islatravir as once-monthly oral PrEP across diverse populations of people who may benefit from additional HIV-1 prevention options.

In the ongoing Phase 2a (NCT04003103) randomized, double-blind, parallel assignment, placebo-controlled, multicenter trial in adults at low-risk for acquiring HIV-1 infection, participants were randomly assigned (2:2: 1) to one of three oral once-monthly therapy groups: islatravir 60 mg, islatravir 120 mg or placebo.

Participants received once monthly oral doses of islatravir or placebo over a 24-week blinded therapy period, followed by a 12-week blinded follow-up in all groups and a 32-week unblinded follow-up in the islatravir groups to characterize the terminal elimination phase.

Outcome measures for safety, tolerability and PK will be analyzed through week 68.

Of the 242 randomized participants at this 24-week analysis, which concludes the dosing portion of the study, 92% (n=222/242) completed dosing and 8% (n=20/242) discontinued the study intervention before week 24.

Less than 1% of participants discontinued due to an AE. Of the total participants, 67.4% (n=163/242) were female, 52.9% (n=128/242) were white, 41.7% (n=101/242) were Black or African American and 14.9% (n=36/242) were Hispanic or Latino.

Unblinded safety data showed that both doses of islatravir were generally well tolerated versus placebo over 24 weeks and most AEs were mild (73.5%).

The most common AEs (occurring in >5% of participants) in the islatravir 60 mg, islatravir 120 mg and placebo groups respectively were headache (10.3% [n=10/97], 9.3% [n=9/97] and 4.2% [n=2/48]), diarrhea (5.2% [n=5/97], 5.2% [n=5/97] and 8.3% [n=4/48]) and nausea (5.2% [n=5/97]), 7.2% [n=7/97] and 4.2% [n=2/48]). There were no serious drug-related AEs in people who received islatravir.

The study enrolled a population at low-risk for HIV infection as evidenced by no confirmed HIV infections occurring during the treatment period.

The PK analysis showed that trough concentrations (the lowest level between doses) of islatravir triphosphate in PBMCs following either 60 mg or 120 mg monthly doses continue to remain above the pre-specified PK threshold for HIV-1 prophylaxis of 0.05 pmol/106 PBMCs and were sustained through eight weeks after the last dose of islatravir.

Islatravir (MK-8591) is Merck's investigational nucleoside reverse transcriptase translocation inhibitor 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 of HIV-1 infection as a single agent across a variety of formulations, including the IMPOWER clinical trials evaluating an oral once-monthly regimen.
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