Bone mineral density and fractures in antiretroviral-naive persons randomized to receive abacavir-lamivudine or tenofovir disoproxil fumarate-emtricitabine along with efavirenz or atazanavir-ritonavir: Aids Clinical Trials Group A5224s, a substudy of ACTG A5202.

BACKGROUND: Long-term effects of abacavir (ABC)-lamivudine (3TC), compared with tenofovir (TDF)-emtricitabine (FTC) with efavirenz (EFV) or atazanavir plus ritonavir (ATV/r), on bone mineral density (BMD) have not been analyzed.

METHODS: A5224s was a substudy of A5202, in which HIV-infected treatment-naive participants were randomized and blinded to receive ABC-3TC or TDF-FTC with open-label EFV or ATV/r. Primary bone end points included Dual-emission X-ray absorbtiometry (DXA)-measured percent changes in spine and hip BMD at week 96. Primary analyses were intent-to-treat. Statistical tests used the factorial design and included linear regression, 2-sample t, log-rank, and Fisher's exact tests.

RESULTS: Two hundred sixty-nine persons randomized to 4 arms of ABC-3TC or TDF-FTC with EFV or ATV/r. At baseline, 85% were male, and 47% were white non-Hispanic; the median HIV-1 RNA load was 4.6 log(10) copies/mL, the median age was 38 years, the median weight was 76 kg, and the median CD4 cell count was 233 cells/μL. At week 96, the mean percentage changes from baseline in spine and hip BMD for ABC-3TC versus TDF-FTC were -1.3% and -3.3% (P = .004) and -2.6% and -4.0% (P = .024), respectively; and for EFV versus ATV/r were -1.7% and -3.1% (P = .035) and -3.1% and -3.4% (P = .61), respectively. Bone fracture was observed in 5.6% of participants. The probability of bone fractures and time to first fracture were not different across components.

CONCLUSIONS: Compared with ABC-3TC, TDF-FTC-treated participants had significantly greater decreases in spine and hip BMD, whereas ATV/r led to more significant losses in spine, but not hip, BMD than EFV. Clinical Trials Registration. NCT00118898.