Treatment failure with bictegravir/emtricitabine/tenofovir alafenamide in a treatment-naïve person with HIV under perfect adherence

We describe a treatment-naïve 30-year-old man with an advanced HIV infection who experienced virologic failure on bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) despite complete adherence. Initially, resistance testing revealed non-nucleoside reverse transcriptase inhibitor mutations but no baseline resistance to BIC/FTC/TAF. Despite an initial viral decline, rebound viremia occurred by day 77, accompanied by the emergence of the M184I mutation, which confers resistance to FTC. Switching to darunavir/cobicistat/TAF/FTC, followed by intensification with dolutegravir, achieved partial viral suppression. This case suggests a possible contribution of transmitted drug resistance or minority variants undetectable at baseline, with selective outgrowth under therapeutic pressure.