Twice-yearly injections are 100% effective in preventing new infections, according to the final results from the PURPOSE 1 trial of lenacapavir.
For weeks, the HIV community has been talking about this highly anticipated clinical trial and whether the strong — and to many, surprising — interim results would hold at final presentation at the International AIDS Conference 2024 in Munich, Germany.
Presenting the results, Linda-Gail Bekker, MD, director of the Desmond Tutu HIV Center at the University of Cape Town, South Africa, reported zero new infections in those who got the shots in the study of about 5000 young women. In the group given daily oral preexposure prophylaxis (PrEP), roughly 2% contracted HIV from infected partners.
“A twice-yearly PrEP choice could overcome some of the adherence and persistence challenges and contribute critically to our quest to reduce HIV infection in women around the world,” Dr. Bekker said about the results, which were published simultaneously in The New England Journal of Medicine.
PURPOSE 1 confirmed that lenacapavir is a “breakthrough” for HIV prevention, said International AIDS Society president Sharon Lewin, PhD, MBBS. It has “huge public health potential,” said Dr. Lewin, the AIDS 2024 conference cochair and director of the Peter Doherty Institute for Infection and Immunity at the University of Melbourne in Australia.
Lenacapavir is a novel, first-in-class multistage HIV-1 capsid inhibitor with a long half-life, which enables the twice-yearly dosing.
PURPOSE 1 enrolled women aged 15-25 years who were at risk for HIV in South Africa and Uganda, with a primary endpoint of HIV infection. Because of the previously announced interim results, which showed the injection was preventing infections, study sponsor Gilead Sciences discontinued the randomized phase of the trial and shifted to an open-label design for lenacapavir.
“One hundred percent efficacy is more that we could ever have hoped for a potential prevention efficacy,” said Christoph Spinner, MD, MBA, an infectious disease specialist at the University Hospital of the Technical University of Munich and AIDS 2024 conference cochair.
Dr. Spinner added that while this is the first study of lenacapavir for PrEP, it’s also the first to explore outcomes of emtricitabine-tenofovir in cisgender women.
Strong Adherence Rates
The twice-yearly injection demonstrated adherence rates above 90% in the trial for both the 6- and 12-month injection intervals.
“Adherence was 91.5% at week 26 and 92.8% at week 52,” Dr. Bekker reported.
The trial compared three PrEP options including the lenacapavir injection to once-daily oral emtricitabine 200 mg and tenofovir-alafenamide 25 mg (F/TAF) and once-daily emtricitabine 200 mg and tenofovir–disoproxil fumarate 300 mg (F/TDF).
“Most participants in both the F/TAF and F/TDF groups had low adherence, and this declined over time,” Dr. Bekker reported. At 52 weeks, the vast majority of patients on both oral therapies had low adherence with dosing, defined at less than two doses a week.
Dr. Bekker called the adherence to the oral agents in this trial “disappointing.”
Findings from the trial underscore the challenges of adherence to a daily oral medication, Rochelle Walensky, MD, and Lindsey Baden, MD, from the Harvard Kennedy School of Government and Harvard Business School in Cambridge, Massachusetts, wrote in an editorial accompanying the published results.
With almost 92% attendance for the twice-yearly lenacapavir injections, the “well-done,” large, randomized, controlled trial “exemplifies not only that women can dependably adhere to this administration schedule, but also that levels of an HIV-1 capsid inhibitor can remain high enough over a period of 6 months to reliably prevent infection,” they added.
Another key focus of the presentation was adverse events. The rate of adverse events grade 3 or more in the lenacapavir arm was 4.1%, Bekker said, which is slightly lower than the rates in the oral arms. The rates of serious adverse events were 2.8% for lenacapavir, 4% for F/TAF and 3.3% for F/TDF.