Injections of cabotegravir (ViiV Healthcare) given every other month are more effective in blocking HIV transmission than is the once-a-day combination of tenofovir disoproxil fumarate and emtricitabine (Truvada, Gilead Science), new data from the HPTN 083 trial show.
The findings “could transform the HIV prevention landscape for so many people,” said Megan Coleman, DNP, from Whitman-Walker Health in Washington, DC, who regularly prescribes Truvada as pre-exposure prophylaxis (PrEP).
At Whitman-Walker alone, about 3000 people were taking the pill in early 2020, but “for some people, taking a pill every day just isn’t a viable option,” said Coleman. “To have something that can support a patient’s choice and a patient’s ability to reduce their own risk of HIV is amazing.”
Final results from the trial — which looked at the drug in cisgender men and transgender women who have sex with men — were presented at the International AIDS Conference 2020.
Early Study Termination
Half of the 4566 study participants — from 43 sites in Africa, Asia, Latin America, and the United States — were younger than 30 years, 12.4% were transgender women, 29.7% were black, and 46.1% were Hispanic.
By design, ViiV Healthcare, the study sponsor, required that 50% of American participants be black to reflect the population at risk for HIV in the United States, said Raphael Landovitz, MD, from the UCLA David Geffen School of Medicine in Los Angeles, who is protocol chair for HPTN 083. In fact, 49.7% of the American cohort was black and 17.8% was Hispanic.
Patients randomized to the cabotegravir group received daily oral cabotegravir plus daily oral placebo for 5 weeks, to assess safety, followed by a cabotegravir injection at weeks 5 and 9 and every 2 months thereafter out to week 153 plus daily oral placebo. Patients randomized to the Truvada group received daily oral Truvada plus daily oral placebo for 5 weeks, followed by daily oral Truvada plus placebo injection, on the same schedule, out to week 153.
After the final injection, all participants continued on daily oral Truvada for 48 weeks.
The researchers expected to wait until 172 participants acquired HIV; they decided at the outset that this number would be sufficient to power a decision on whether or not cabotegravir injections are better than daily oral Truvada. But by May 2020, when 52 of the study participants had acquired HIV, the results were so lopsided in favor of cabotegravir that the trial was stopped. At that point, all participants were offered cabotegravir injections every 2 months.
Thirty-nine of the 52 (75%) new HIV infections occurred in the Truvada group. In fact, (hazard ratio, 0.34).
“This definitively establishes the superiority of cabotegravir,” said Landovitz.
He and his colleagues had been legitimately concerned that HIV acquisition would be so low in the trial that they wouldn’t be able to show how effective the injectable was. The success of Truvada PrEP has made it difficult to design prevention trials.
“We know that Truvada works extremely well, so the fact that we were able to show that cabotegravir in this population works better” is a powerful observation, said Landovitz. This is especially true because the rates of sexually transmitted infections — which are thought to increase risk for HIV transmission — were so high. Overall, 16.5% of the participants tested positive for syphilis during the trial, 13.3% tested positive for gonorrhea, and 21.1% tested positive for Chlamydia.