Short-cycle three-day-per-week efavirenz/emtricitabine/tenofovir disoproxil fumarate therapy: a seven-year extension study

BACKGROUND: Following a successful pilot study of a three-day-per-week regimen of efavirenz, emtricitabine, and tenofovir disoproxil fumarate, we hypothesized that this strategy would sustain virological efficacy and reduce long-term toxicities. METHODS: After a 24-week randomized phase, participants in the A-TRI-WEEK trial (ClinicalTrials.gov NCT01778413) were offered the three-day-per-week regimen. The extension was approved by the Institutional Review Board, and participants provided informed consent; follow-up continued until further participation no longer offered additional clinical or research value. HIV-RNA, CD4 and CD8 cells, blood and urine chemistries, and bone mineral density (BMD) were assessed every 6 months. Treatment failure was defined a priori as virological failure (HIV RNA >1000 copies/mL once or ≥50 copies/mL confirmed), discontinuation, or loss to follow-up. Secondary outcomes included changes in lipids, estimated glomerular filtration rate (eGFR), urine protein/creatinine, and BMD. RESULTS: Of 61 participants completing the 24-week phase, 59 (97%) entered the extension. After 7 years, 37 (63%) remained free of treatment failure. Only one participant experienced virological failure, following an unintentional treatment interruption, with no resistance mutations detected. All other failures were due to discontinuations (CNS symptoms, n = 7; BMD decline, n = 7; drug interactions, n = 2; regimen preference, n = 2; cancer, n = 1; death unrelated, n = 1; loss to follow-up, n = 1). Laboratory parameters showed biphasic patterns, with initial stability followed by modest late declines in eGFR and BMD and increases in triglycerides and proteinuria. Most discontinuations occurred in the latter half of follow-up (years 4-7). CONCLUSIONS: A three-day-per-week regimen of efavirenz, emtricitabine, and tenofovir disoproxil fumarate maintained durable long-term viral suppression, while mitigating but not fully preventing toxicities associated with EFV/TDF/FTC. These findings support reduced-exposure antiretroviral therapy and warrant evaluation of similar strategies with modern integrase inhibitor-based regimens.