Gilead Sciences and Merck & Co. have guided their once-weekly HIV combination therapy past another milestone, linking the cocktail to sustained suppression of the virus out to 48 weeks in a midphase clinical trial.
The collaborators reported a hit on the primary, 24-week endpoint in the study of 104 virologically suppressed adults in March. The combination of Merck’s islatravir and Gilead’s lenacapavir, which the biopharma sells as Sunlenca, kept HIV-1 RNA below 50 copies/mL in 98% of patients after 24 weeks of once-weekly dosing. The figure for Gilead’s once-daily Biktarvy, the control treatment, was 100%.
Gilead and Merck continued to track patients through Week 48 and shared the follow-up data during an oral session at IDWeek 2024. The rates of HIV suppression at Week 48 in the combination and Biktarvy arms were 94.2% and 92.3%, respectively. The figures for both cohorts were 94.2% at Week 24.
The potential advantage over the combination stems from its weekly, rather than daily, dosing.
“Daily single-tablet regimens have helped to transform HIV care but can be challenging for some people to maintain,” Elizabeth Rhee, vice president of global clinical development at Merck Research Laboratories, said. “Novel HIV treatment options that allow for less frequent oral dosing have the potential to help support adherence, and address stigma faced by some individuals taking daily oral therapy.”
Merck’s attempts to establish islatravir as the backbone of a new generation of HIV therapies hit trouble in 2021 when falls in total lymphocyte and CD4+ T-cell counts led the drugmaker to pause enrollment in studies of the molecule.
There were no significant differences between CD4+ T-cell counts or absolute lymphocyte counts in the combination and Biktarvy cohorts at Week 48 of the phase 2 trial. No participants discontinued because of a decrease in CD4+ T-cell or lymphocyte counts.
The combination is now entering phase 3. Gilead is starting up two pivotal trials that will each randomize 600 virologically suppressed adults to receive its once-weekly combination or the once-daily Biktarvy. The primary endpoints of the trials are looking at the proportion of participants with HIV-1 RNA of 50 copies/mL or fewer at Week 48.