DURBAN, SOUTH AFRICA – Long-acting injectable antiretroviral therapy with cabotegravir and rilpivirine in nanosuspension successfully suppressed HIV-infected patients’ plasma viral load to fewer than 50 copies/mL for 48 weeks as maintenance therapy in the LATTE-2 trial, David A. Margolis, MD, reported at the 21st International AIDS Conference.
The intramuscular gluteal injections given every 4 or 8 weeks also proved safe and extremely well tolerated. At week 48, more than 97% of patients on injectable maintenance antiretroviral therapy (ART) reported a high degree of satisfaction with their treatment regimen on a structured questionnaire and expressed a willingness to continue on injectable therapy in the future, according to Dr. Margolis of Viiv Healthcare in Research Triangle Park, N.C.
Cabotegravir is an HIV integrase inhibitor, rilpivirine a nonnucleoside reverse transcriptase inhibitor. Rilpivirine is already approved as Edurant, a once-daily 25-mg tablet for oral therapy. Cabotegravir is under development as a 30-mg once-daily tablet. As oral agents, each has a half-life of roughly 40 hours. The two-drug oral combination showed a high degree of safety and efficacy through 96 weeks of follow-up in the LATTE-1 study, previously reported by Dr. Margolis (Lancet Infect Dis. 2015 Oct;15):1145-55) .
In addition, the two antiretroviral agents are being developed as long-acting injectables with half-lives of 20-90 days. LATTE-2 was a phase IIb, open-label, multicenter study that began with 309 HIV-positive, ART-naive subjects who participated in a 20-week induction phase during which they received 30 mg/day of oral cabotegravir plus abacavir/lamivudine to induce HIV viral suppression. During the last 4 weeks of the induction phase, participants also received oral rilpivirine at 25 mg once daily to ensure they could tolerate the drug.
At the end of the 20-week induction phase, 228 patients with an HIV viral load below 50 copies/mL were randomized 2:2:1 to maintenance therapy with intramuscular injections of long-acting cabotegravir at 200 mg/mL and long-acting rilpivirine at 300 mg/mL in nanosuspension every 4 or 8 weeks or to the oral once-daily versions of the two drugs.
After 48 weeks of maintenance therapy, an HIV RNA load of less than 50 copies/mL was present in 92% of subjects on injections every 8 weeks, 91% with injections every 4 weeks, and 89% of those on oral daily therapy. Moreover, of the eight virologic nonresponders at 48 weeks in the 8-week-injection schedule, six remained in the study and five of them have consistently achieved a viral load below 50 copies/mL in subsequent visits through week 72.
Viral failure defined as an HIV RNA viral load greater than 200 copies/mL on two occasions occurred in 1% of patients on the 8-week interval schedule, 1% of those on oral therapy, and no one on IM injections every 4 weeks. One patient on every-8-week schedule developed treatment-emergent viral resistance.
More than 80% of patients in both IM injection study arms experienced painful injection site reactions after their first treatment session, 82% of which were mild and 17% moderate. Ninety percent of these reactions resolved within 7 days; median duration was 3 days. Two patients withdrew from the study as a result of these reactions. After the first round of injections, the incidence of injection site reactions fell to 25%-30%.
Other adverse events consisted of fever, fatigue, headache, rash, and flu-like symptoms, each with an incidence of 2%-4%.
Based upon the LATTE-2 outcomes, the once-per-month injection regimen has been selected for the forthcoming pivotal phase III randomized clinical trials of long-acting cabotegravir/rilpivirine for ART, Dr. Margolis said.
The pharmaceutical industry is pursuing long-acting injectable ART both for pre-exposure prophylaxis (PrEP) and for treatment of HIV-infected patients. Clinicians and patients alike are eager for this option, especially for PrEP, where adherence to daily oral therapy has been suboptimal in many studies.
But there is a fly in the ointment. One of the most talked about studies presented at AIDS 2016 was Dr. Ian McGowan’s report that low levels of rilpivirine were found in plasma and female genital tract fluids more than 18 months after a single IM 1,200-mg dose of rilpivirine in seven participants in a long-acting PrEP study.
“There is certainly the possibility that extended periods of drug availability at perhaps subtherapeutic concentrations might increase the risk of ART resistance in individuals who seroconvert after exposure to long-acting PrEP,” cautioned Dr. McGowan, professor of medicine at the University of Pittsburgh.
No similar studies have as yet been done with other candidate long-acting injectables, he said.
“It’s clear, I think, that as we move forward with this exciting field of long-acting injectables we really need to better characterize the terminal half-life of these products so that we can better inform management of the pharmacokinetic tail and hopefully avoid the potential for ART resistance,” Dr. McGowan added.