Long-Acting Injectable Cabotegravir/Rilpivirine as a Second-Line ART Regimen for Pregnant and Breastfeeding Women in Kenya: Modeling the Potential Impact on Vertical Transmission.

Background: Switching to injectable long-acting cabotegravir and rilpivirine (LA-CAB/RPV) may improve viral suppression among pregnant and breastfeeding women (PBFW) who have persistent viremia on first-line antiretroviral therapy (ART), resulting in the prevention of vertical transmission (PVT). Methods: We used a microsimulation model of PBFW living with HIV in Kenya on dolutegravir-based first-line ART to evaluate the PVT potential of LA-CAB/RPV in 2 maternal populations-newly positive (NP) pregnant women who initiate ART during antenatal care, and known positive (KP) women who initiate ART prior to conception-during antenatal care through 18 months postpartum. For each population, we modeled a standard of care (SOC) without access to a second-line regimen, and a strategy with LA-CAB/RPV as a second-line regimen. Both strategies implement routine maternal viral load (VL) monitoring every 6 months and account for an imperfect cascade, including a 50% probability of regimen switching among eligible PBFW in the LA-CAB/RPV strategy. Results: The average time from having unsuppressed VL to switching regimens was over 8 months, and 5.1% of NP and 8.2% of KP women ultimately switched. Compared to SOC, the LA-CAB/RPV strategy reduced vertical transmission by 1.2% for NP and 4.2% for KP women. These reductions increased to 4.0% and 11.5%, respectively, when assuming perfect adherence to more frequent VL monitoring (3-month intervals) and 100% regimen switching when eligible. Conclusions: Supporting high switching rates and decreasing delays in switching will help optimize the PVT impact of second-line LA-CAB/RPV among PBFW who accept this regimen.