An experimental treatment may keep HIV suppressed with once-weekly dosing. Merck’s MK-8507 is a new non-nucleoside reverse transcriptase inhibitor (NNRTI). In a Phase I trial, 18 participants received a single oral dose of MK-8507. The drug reduced viral load by about 1.5 log, with HIV levels continuing to decline for seven days. At day 7, the decrease was comparable to reductions seen with once-daily NNRTIs. To be used for once-weekly treatment, MK-8507 would need to be paired with other long-acting antiretrovirals. One possible partner is Merck’s islatravir, the first nucleoside reverse transcriptase translocation inhibitor. In a Phase II trial, a combination of once-daily islatravir plus the NNRTI Pifeltro (doravirine) kept viral load suppressed in 90% of participants at 96 weeks. But islatravir has a long half-life in the body, and it may be suitable for less frequent dosing. Wendy Ankrom, PhD, of Merck, says the company will test MK-8507 plus islatravir as a potential once-weekly treatment.