Newly announced results from a phase 2 clinical trial show that a drug combination—islatravir and lenacapavir—holds promise as the first-ever weekly oral pill for HIV treatment, comparable to a single-tablet regimen taken every day.
At 48 weeks, the drug combo had a 94.2% success rate in keeping adult participants “undetectable,” with an HIV viral load less than 50 copies/mL of blood. No one from either group had a viral load of 50 or greater.
The combo is a collaboration between Merck, manufacturer of islatravir (ISL), and Gilead Sciences, maker of lenacapavir (LEN).
The open-label study involved 104 virologically suppressed adults who were taking the brand name daily oral HIV medication Biktarvy; half of the adults were switched to a once-weekly ISL+LEN combination of islatravir 2 mg and lenacapavir 300 mg, while the other half remained on Biktarvy. Median age of the participants was 40, ranging 20–76 years of age. Of the participants, 18% were cis women, 50% were “non-white” (according to the press release) and 29% were Latiné.
Data from the study (known as NCT05052996) were presented on the last day of IDWeek 2024, the infectious disease medical conference that concluded Saturday, Oct. 19 in Los Angeles. Earlier this year, 24-week data had been presented at the 31st Conference on Retroviruses and Opportunistic Infections (known as CROI).
Both drugs are being tested individually and in combination with other HIV medications. Also known as MK-859, islatravir is a nucleoside reverse transcriptase translocation inhibitor (NRTTI). In studies, islatravir is being paired up with other antiretrovirals to determine dosing options for potential daily and once-weekly HIV treatments.
Lenacapvir is already approved as a six-month shot—but only as part of a treatment regimen that includes oral medications, and only for people living with HIV who are heavily treatment-experienced with few other treatment options left. While most HIV medications target a single step of HIV’s replication process, lenacapavir, the first-in-class HIV-1 capsid inhibitor, aims at different stages of the virus’ lifecycle. Lenacapavir made news recently with results from two PURPOSE clinical trials showing the drug to be highly effective in preventing HIV among cisgender women and in men and trans men who have sex with men.
“The future of HIV treatment is person-centered, with long-acting options tailored to help meet the needs and preferences of people affected by HIV,” said Jared Baeten, MD, PhD, Gilead’s senior vice president and head of virology therapeutic area head. “There is no ‘one size fits all’ approach.”
The most common side effects experienced by the ISL+LEN group were dry mouth (19%, or 10 out of 52), and nausea (3.8%, or 2 out of 52). In the Biktarvy group, 5.8% (3 out of 52) reported side effects, none serious. Two participants stopped taking ISL+LEN but the adverse events were unrelated to the medication.
There was no significant difference seen from baseline in CD4+ T cell counts or absolute lymphocyte counts in either group.
“We are pleased to see these encouraging 48-week data for this once-weekly oral combination regimen and advance to phase 3 clinical trials in collaboration with Gilead.” said Dr. Elizabeth Rhee, vice president of Merck’s Global Clinical Development.
This is still early days; more testing is needed before a weekly HIV medication becomes available. A combination of weekly oral ISL 2 mg + LEN 300 mg is being further evaluated as a fixed-dose regimen in two phase 3 studies, NCT06630286 and NCT06630299.