Virological outcomes with Bictegravir/Emtricitabine/Tenofovir alafenamide ( B/F/TAF ) in people previously treated with darunavir‐based antiretroviral therapy

Background Darunavir‐based antiretroviral therapy (ART) is commonly used in people with HIV who experience adherence challenges and/or have complex resistance patterns. Changes in ART commissioning have led to an increased use of Bictegravir/Emtricitabine/Tenofovir alafenamide (B/F/TAF) in these populations despite limited real‐world outcome data. Methods Single centre, retrospective analysis of virological outcomes in individuals previously treated with Darunavir who initiated B/F/TAF before 01/01/2025. Logistic regression was used to analyse associations with sustained virological suppression (HIV RNA <200 copies/mL) on B/F/TAF. Results Of the 223 individuals who initiated B/F/TAF, 207 (median age 52 [40–58] years, 38% female, 69% Black ethnicity, 24% with CD4 < 200 cells/mm 3 and 36% with HIV RNA ≥200 copies/mL) contributed virological outcome data. Over a median of 2.4 [1.3–3.3] years, 153 (74%) maintained or achieved sustained virological suppression, 11 (5.3%) had a single viral load ≥200 copies/mL and 43 (20.8%) experienced virological failure. Participants with CD4 < 200 cells/mm 3 (aOR 0.15 [95%CI 0.07–0.33]) and HIV RNA ≥200 copies/mL (aOR 0.17 [0.08–0.34]) at B/F/TAF initiation were less likely to achieve sustained virological suppression; historical resistance‐associated mutations (RAMs) were not associated with virological outcome. Of the 32 participants successfully genotyped, 3 had novel INSTI mutations (E157Q, L74LM) and 4 had not previously documented NRTI mutations (M184V/I, D67DN, Y115F) mutations. Conclusions Substituting of Darunavir‐based ART with B/F/TAF in this challenging population was associated with treatment‐emergent INSTI and NRTI resistance. Historical resistance did not predict virological outcomes and treatment‐emergent resistance did not preclude re‐suppression on B/F/TAF, suggesting that adherence remains a major barrier to achieving long‐term virological success.