Direct switch from an efavirenz-based regimen to intramuscular long-acting cabotegravir plus rilpivirine: A case report

Switching from oral antiretroviral treatment to intramuscular (IM) cabotegravir (CAB) + rilpivirine (RPV) has an optional oral lead-in to ensure tolerability. The British HIV Association guidelines advise against directly switching from oral antiretroviral (ART) combinations containing strong/moderate cytochrome inducers like efavirenz (EFV) to IM CAB + RPV. EFV has a prolonged elimination half-life, leading to a residual induction of UGT1A1 and CYP3A4 after discontinuation. These enzymes are responsible for CAB and RPV metabolism and their induction might lead to sub-optimal concentrations of CAB and RPV, risking drug resistance. When switching from EFV to oral CAB + RPV, the ATLAS and ATLAS 2M studies showed reduced RPV concentrations but with maintained viral suppression during the oral lead-in and subsequent long-acting injectable (LAI) phases. Also, a recent pharmacokinetic modelling study indicated reduced RPV concentrations, without viral implication, when switching from EFV to IM CAB + RPV. However, there are limited real-world data on direct switching from EFV-based therapy to long-acting IM CAB + RPV. We describe a case where oral intake was impossible in a critical care scenario, switching from emitricitabine/tenofovir-DF (FTC/TDF) 200/245 mg + 600 mg EFV to IM CAB + RPV for treatment optimisation.