HIV: Dual Therapy With Twice-Yearly Injections on the Horizon

One year into treatment with an every-6-month dose of the investigational drug lenacapavir (LEN, Gilead Sciences) in a dual-treatment combination, 88% of treatment-naive people living with HIV had undetectable viral loads.

The findings, presented at the Conference on Retroviruses and Opportunistic Infections (CROI) 2022 Annual Meeting, also showed the drug was well tolerated, with 2 of 182 people developing drug-resistant mutations to lenacapavir and one person developing a nodule at the injection site.

Laura Waters, MD, consulting physician in HIV and sexual health at Central and Northwest London NHS Trust, who was not involved in the trial, called the findings "hugely exciting," especially given its unique mode of administration. Right now it's formulated as a subcutaneous injection, not an intramuscular injection like cabotegravir and rilpivirine (Cabenuva, ViiV Healthcare).

"Clearly it's incredibly exciting to have the option for a subcutaneous drug that could be given at home every 6 months," Waters told Medscape Medical News. With phase 3 trials and long-term follow-up still to come, she said she's looking forward to how the treatment evolves.

The Study to Evaluate the Safety and Efficacy of Lenacapavir in Combination With Other Antiretroviral Agents in People Living With HIV (CALIBRATE) is a phase 2, four-arm, open-label, active-control study. Twenty-five of the 182 participants were randomized to the active control arm, in which participants took daily oral bictegravir, emtricitabine, and tenofovir alafenamide (Biktarvy, Gilead Sciences) as standard of care. The rest of the 182 participants were divided evenly between three arms. In one of those, treatment group three, participants took a daily oral version of 50-mg LEN with emtricitabine and tenofovir alafenamide (F/TAF, Descovy, Gilead Sciences).

The other two arms, treatment groups one and two, were the arms in which Samir K. Gupta, MD, of the Indiana School of Medicine, and colleagues tried the twice-yearly subcutaneous shots of LEN (LEN SC). Participants in those arms underwent a 2-week lead-in period in which they took 600 mg of LEN orally on days 1 and 2 and then a 300-mg pill on day 8 before starting the shots on day 15. As currently formulated, LEN SC shots can be given into the stomach and are designed to be simple enough to administer at home.

"It's like doing an insulin shot," Gupta told Medscape Medical News.

In addition to LEN SC, participants in treatment group one took a daily Descovy lead-in and then engaged in dual therapy of LEN plus TAF. In group two, they took a daily Descovy lead-in and then switched to LEN SC plus bictegravir (BIC) daily at 28 weeks.

Study results presented at CROI were the results at 54 weeks. Researchers had previously presented 28-week results for CALIBRATE at the International AIDS Society Conference on HIV Science 2021.

Of the participants, 7% were cisgender women, 52% were Black, and 45% were Latinx. A total of 15% of participants had baseline viral loads of more than 100,000 copies, and median CD4 counts were 437. None of the participants in either the active-control arm or the LEN SC plus Descovy group had a history of AIDS, defined as fewer than 200 cells/μL. In the LEN SC plus Biktarvy group, two did, and there were six people with a history of AIDS in the oral LEN plus Descovy group.

At 54 weeks, 88% of participants in groups one and two — the LEN SC arms — had undetectable viral loads (viral loads below 50 copies/mL). Specifically, 90% those in the subQ LEN plus TAF arm had viral loads below 50 copies. Those taking LEN SC plus BIC had an 85% viral suppression rate. The best performing of all was the control arm, in which 92% had undetectable viral loads. The protocol didn't allow for analysis of statistical significance between the arms, so it's unclear if any of the treatments really surpassed the others, Gupta said.

When they looked only at people whose viral loads became undetectable early, by week 28, the results were slightly better, with 93% people between the two subQ arms having undetectable viral loads at week 54. Again, the results were slightly higher in the LEN SC plus TAF arm (94%) than the LEN SC plus BIC (92%). People taking daily oral LEN plus Descovy had the lowest rate of viral suppression, but it was still at 90% if they were virally suppressed early. Again, it's unclear whether those differences were statistically significant.

Well Tolerated, With a Chance of a Nodule

Regarding safety, LEN was well tolerated across treatment arms, though the oral LEN group had as many people develop resistance mutations as the other three groups combined. Still, that was only three people, with one each in the two subcutaneous arms and one in the control arm.

Two people developed resistance to LEN — one in the LEN SC plus BIC arm and one in the oral LEN plus Descovy arm. In the LEN SC plus BIC arm, the mutations Q67H and K70R emerged at week 10, following a mutation that's common when people don't take integrase inhibitors as they're supposed to (M184M/I). This led Gupta to conclude that lack of adherence to the oral part of the regimen may have contributed to the development of resistance, rather than an issue with LEN SC itself.

In the oral LEN plus Descovy arm, mutation Q67H didn't emerge until week 54, when pill counts and drug levels revealed that that participant hadn't been taking his Descovy as prescribed. In both cases, viral loads in those participants returned to undetectable after switching to an integrase inhibitor-based three-drug regimen.

Most safety concerns were mild and included nausea, diarrhea, and vomiting. But that was for non-injection-site reactions. There were more side effects of that sort, with most of them being pain, hardening of the site, and swelling. But 11% of participants developed more serious side effects, including nodules. Only one nodule was considered a grade 3 reaction; that person didn't leave the trial because of it.

"These phase 2 data from the ongoing CALIBRATE trial support the further evaluation of lenacapavir for treatment and prevention of HIV-1," he said.

Finding the Right Partner

In short, the findings are promising, Gupta told Medscape Medical News. But the question now, as Gilead prepares to begin a phase 3 efficacy trial, is, what would be a good combination with LEN SC?

"Lenacapavir in a two-drug regimen should work," he said. "The question now, though, is you have to find a suitable, potent, second agent to pair it with."

Indeed, the long-acting HIV treatment pipeline sustained a blow in December when the US Food and Drug Administration halted all trials for Merck's investigational, long-acting drug islatravir. This led NHS's Waters to tweet, "Is it just me or are the islatravir abstracts at #CROI2022 quite sad to read?" She ended the tweet with, "I just hope it recovers!"

Indeed, Merck and Gilead have entered into an agreement to co-develop lenacapavir and islatravir as a weekly oral tablet. Islatravir seemed like the obvious choice as a partner to lenacapavir if phase 3 trials are successful, said Gupta. But now, it's anyone's guess as to what will happen. And while it's too soon to say that lenacapavir is a success, it does leave the field wondering about how to use LEN SC without another, equally long-acting agent.

"When I talk about LEN, I show a picture of a man standing solo at a party, leaning against the wall looking a bit lonely, with 'lenacapavir' written over his head," she told Medscape Medical News. "Right now, lenacapavir is the only drug at the 6-monthly party. It's going to need some other guests if that party is going to rock."

The study was funded by Gilead Sciences. Gupta has received research funding from ViiV Healthcare and advisory board fees from Gilead Sciences and ViiV Healthcare. Waters has received speaker or advisory fees from Gilead Sciences, ViiV Healthcare, Merck, Janssen, Theratech, Sipla, and Mylan.

Conference on Retroviruses and Opportunistic Infections (CROI) 2022 Annual Meeting: Abstract 138. Presented February 16, 2022.

Heather Boerner is an infectious disease and disparities reporter based in Pittsburgh, PA. Her book, Positively Negative: Love, Pregnancy, and Science's Surprising Victory Over HIV, came out in 2014.

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