Study finds injectable PrEP to be more effective than daily oral PrEP

Data presented at AIDS 2020 Virtual has shown that in a recent study ViiV Healthcare’s long-lasting injectable Cabotegravir was more effective at preventing HIV than the already highly effective Truvada.

The HIV Prevention Trial Network (HPTN)’s Phase IIb/III randomised, double-blinded, placebo-controlled HPTN083 study enrolled 4,570 participants made up HIV negative of cisgender men who have sex with men (88%) and transgender women (12%) who were all deemed to be at an increased risk of HIV acquisition.

The participants of HPTN083 were enrolled in November 2016 where they were randomised to one of two treatment arms:

• Long-lasting cabotegravir (CAB) injections (once every eight weeks)
• Oral Truvada (taken daily)

Because this was a double-blinded trial all participants were given eight-weekly injections and daily pills. Those in the CAB arm received oral CAB for five weeks before starting injections, those in the Truvada arm received CAB placebo pills.

The data presented at the AIDS 2020 Virtual conference suggests that those taking CAB had a 66% lower chance of acquiring HIV than those taking Truvada, or the generic formulation of TDF/FTC.

Indeed, whilst the study was initially intended to run for 148 weeks, not including the five week lead-in period, in May 2020 the data and safety monitoring board’s interim review found that CAB was highly effective at preventing HIV acquisition and as such prematurely ended the placebo phase.

Participants are now being offered a choice of remaining on the arm they were randomised to or being offered to switch to either CAB (when it is available in their country) or to Truvada.

During HPTN083 52 participants contracted HIV with 13 in the CAB arm and 38 in the Truvada arm.

Kimberly Smith, M.D., MPH, Head of Research & Development at ViiV Healthcare, said:

“These data are truly ground-breaking, demonstrating that long-acting injectable cabotegravir dosed every two months is superior to daily oral FTC/TDF at preventing HIV in at-risk men and transgender women who have sex with men. This advancement has the potential to be a game-changer for HIV prevention, offering an option with very high rates of effectiveness and the convenience of reduced dosing from daily to just six times per year. We are thrilled with the results not only because of the high effectiveness of cabotegravir but also because this study adequately represents some of the populations most disproportionately impacted by HIV -- black MSM in the US, young MSM globally and transgender women.”

The researchers were eager to point out that the study’s findings in no way invalidate the efficacy of Truvada as PrEP. Number studies have shown that when taken daily, as directed, Truvada can lower a person’s risk of HIV by more than 99%.

Those taking part in HPTN083 who stopped receiving CAB injections were required to take 48 weeks of oral Truvada to cover the drug’s “tail”. The “tail” refers to the time that a drug is still in the body after you have stopped receiving in, in CAB’s case this is thought to be up to 76 weeks.

Currently the trial network is also conducting HPTN084 which is conducting a similar study into the efficacy of CAB as PrEP for over 3,000 cisgender women across seven African countries.