Real-world use and effectiveness of fostemsavir in a US clinical setting: Insights from Trio Health HIV Research Network.

OBJECTIVE: To describe real-world patterns of use, virologic and immunologic outcomes and treatment persistence among people with HIV (PWH) initiating fostemsavir (FTR) in a diverse US cohort. DESIGN: Retrospective cohort study of adults receiving FTR in clinical practice, stratified by baseline viral suppression status. METHODS: Adults with ≥1 FTR prescription between July 2020 and August 2023 were included and followed for 12 months. Individuals with trial participation were excluded. Outcomes included virologic suppression (<50 and <200 copies/mL), confirmed virologic failure, viral blips, CD4 changes and immunologic recovery among those with baseline CD4 <350 cells/mm3. Persistence and adherence were assessed using dispensing data and proportion of days covered. RESULTS: Seventy-seven PWH were included (60% viremic, 40% suppressed). Multidrug resistance was observed in a subset (31%). At 12 months, most individuals remained on FTR, with high adherence among the subset with available dispensing data. Among viremic initiators, a minority achieved viral suppression, though reductions in viral load were observed. Among suppressed initiators, most maintained suppression. CD4 counts increased in both subgroups, with greater gains among those suppressed at initiation. Modifications to optimized background therapy were infrequent. CONCLUSIONS: In this real-world, diverse cohort, FTR was well tolerated, with high persistence and, in the dispensing-data subset, high adherence. It effectively maintained viral suppression among suppressed individuals and provided immunologic benefits across subgroups, including viremic initiators. These findings support FTR as a valuable treatment option for heavily treatment-experienced PWH.