Changes in bone quality after switching from a TDF to a TAF based ART: A pilot randomized study

Area of Science:

• Bone Metabolism and HIV Therapeutics
• Pharmacological Impact on Skeletal Health
• Antiretroviral Therapy and Bone Complications

Background:

• Tenofovir disoproxil fumarate (TDF) antiretroviral therapy (ART) has known impacts on bone health, primarily assessed via bone mineral density (BMD).
• Emerging evidence suggests bone quality (BQ) is also affected by TDF-based ART.
• Understanding the skeletal effects of different tenofovir formulations is crucial for managing long-term HIV care.

Purpose of the Study:

• To assess changes in BMD and BQ after switching from TDF to tenofovir alafenamide (TAF) ART in individuals with HIV.
• To compare the effects of TAF versus continued TDF on bone health parameters.
• To evaluate the impact of ART regimen switch on bone turnover biomarkers.

Main Methods:

• Pilot study involving HIV individuals randomized to switch from TDF to Bictegravir-TAF-Emtricitabine or continue TDF-based ART.
• Bone mineral density (BMD) measured by DXA and bone quality (BQ) assessed via bone microindentation (bone material strength index, BMSi) at baseline and 24 weeks.
• Plasma bone turnover biomarkers measured by ELISA at the same time-points.

Main Results:

• No significant changes in lumbar or femoral BMD were observed in either the TAF or TDF groups at 24 weeks.
• Significant improvement in bone quality (BMSi) was observed in the TAF group (+5.1%, p=0.041), while the TDF group remained stable.
• A reduction in bone formation markers and bone resorption markers was noted with TAF, suggesting reduced bone turnover.

Conclusions:

• Switching from TDF to TAF-based ART leads to improved bone quality, independent of BMD changes.
• TAF may offer bone health benefits beyond BMD improvements in HIV individuals.
• Further research is needed to confirm these findings and elucidate the mechanisms of ART-related bone toxicity.