Study identifies predictors of low-level viremia after switching to injectable cabotegravir/rilpivirine

Although one benefit of switching people living with HIV (PLWH) to long-acting injectable cabotegravir/rilpivirine (CAB/RPV) can be the removal of oral treatment adherence concerns, doing so does not always eliminate their chances of developing low-level viremia, a real-world U.S. study has found.

About This Study

“Predictors of post-switch viremia in people with HIV on injectable cabotegravir/rilpivirine“ was published online on Oct. 12, 2023, in Journal of Acquired Immune Deficiency Syndromes. The lead author is Lucas Hill, Pharm.D., of the Skaggs School of Pharmacy and Pharmaceutical Sciences and of the UC San Diego Owen Clinic in the Division of Infectious Diseases at the Department of Medicine, both at the University of California in San Diego. Data were presented at the 2023 Conference on Retroviruses and Opportunistic Infections in Seattle, Washington.

Key Research Findings

This 2021-2022 retrospective cohort study of 144 virally-suppressed PLWH who switched to long-acting injectable (LAI) CAB/RPV at a single U.S. clinic assessed whether and when participants experienced persistent low-level viremia (pLLV) or viral blips while on this regimen. Participants’ median age was 44 years, 11% of participants were women, 43% of participants were white, and 40% were Latinx.

Eighty-seven percent of participants started on oral CAB/RPV before moving to bi-monthly LAI CAB/RPV and 97% of participants had resistance testing results. None of the results indicated resistance to CAB or major RPV resistance, but 6% of participants had minor RPV resistance mutations. One participant developed virological failure on LAI CAB/RPV.

After switching, the viral load (VL) in 10% of participants rose above 50 copies/mL once but was still ≤200 copies/mL (a blip), and in another 7% of participants remained in that range (pLLV). Either type of elevated viral load was more common in PLWH who had experienced blips or pLLV prior to switching, although the number of such individuals was small: For example, four of nine participants with prior pLLV experienced pLLV after switching, compared to four of 112 participants with no prior pLLV.

Discussion Highlights and Implications for Practice

Study limitations reported by the authors included the limitations of using an electronic medical record, little information on reasons for the switch to LAI CAB/RPV, lack of an oral-only control group, no drug concentration measurements, no confirmation that longer needles were used for participants with body mass index (BMI) ≥ 30 kg/m² (to ensure intramuscular drug delivery), and a relatively short follow-up period.

The researchers concluded that despite increased adherence due to the drug’s long-acting nature and lack of major resistance mutations, some PLWH still have detectable viral loads on LAI CAB/RPV, especially if they had pLLV or viral blips in the year before switching. One possible explanation for the observed pLLV is clonal expansion of T cells with proviral expression, they said.

By Barbara Jungwirth