Bone outcomes in virally suppressed youth with HIV switching to tenofovir disoproxil fumarate

Background: Tenofovir disoproxil fumarate (TDF) is included in first-line antiretroviral treatment (ART) for adolescents living with HIV (ALWH). Associated toxicities remain a concern. Objective: We evaluated bone and renal safety outcomes in virologically suppressed South African ALWH after switching to TDF. Method: We recruited virally suppressed (< 100 copies/mL) adolescents, aged 15-20 years, who switched from an abacavir (ABC)-based to a TDF-based efavirenz regimen. Bone mass and renal function were assessed at Week 0 and at Week 24 after the switch to TDF using dual-energy X-ray absorptiometry (DXA) and serum renal markers. A change in the lumbar spine (LS) and the whole-body less head (WBLH) bone mineral density (BMD) Z-scores and the estimated glomerular filtration rate (eGFR) between the two measures were compared (paired t-tests) and stratified by sex. Results: Fifty participants (48% male), with a median duration of prior ART of 11.4 years, were enrolled. Among 47 participants with 24-week DXA results, 15 (32%) had either no change or a decreased LS-BMD after the switch, with a mean change of -1.6%. Overall, more female participants experienced this outcome: 58% versus 4%, P < 0.0001. The mean change (standard deviation) in the LS-Z-score was -0.03 (0.25) and in the WBLH-Z-score was 0.02 (0.24). A decrease in the eGFR from 132.2 to 120.4 was observed (P = 0.0003); however, the levels remained clinically acceptable. Conclusion: South African ALWH switching from abacavir to TDF-based ART experienced statistically significant decreases in eGFR but not in LS and WBLH BMD. Female ALWH were more likely to experience a decrease in LS-BMD and may require closer monitoring.