Abstract
Background
In the DISCOVER PrEP trial, emtricitabine/tenofovir alafenamide (F/TAF) was noninferior to emtricitabine/tenofovir disoproxil fumarate (F/TDF) for HIV prevention. Here we report the bone safety outcomes of F/TAF and F/TDF.
Methods
Men who have sex with men (MSM) and transgender women (TGW) at risk of HIV were randomized 1:1 to receive blinded F/TDF or F/TAF, taken once daily. Those on PrEP with F/TDF were eligible to enroll. Bone densitometry (DXA) of the hip and spine were performed in a subset of participants (BMD subset). Fracture events were compared in all study participants. Week 48 data are presented.
Results
5387 participants were enrolled in the main study, with 383 included in the BMD subset. In the BMD subset, the median age was 37 (IQR 29, 46); 0.8% were TGW, 9.4% were black, and 20.6% were Hispanic or Latinx. Fifty-three BMD subset participants were on baseline F/TDF PrEP at enrollment, 26 of whom were randomized to F/TAF. F/TAF was associated with more favorable changes in hip and spine BMD compared with F/TDF (Table 1); these differences were similar when participants on baseline PrEP were excluded. Participants age <35 on F/TAF gained BMD, whereas those on F/TDF lost BMD (Table 1). BMD decreases of ≥3% were less frequent in the F/TAF group than the F/TDF group at the hip (3.8% vs. 18.4%, P < 0.001) and spine (10.1% vs. 26.9%, P < 0.001). Osteopenia was more frequently diagnosed in the spine in participants on F/TDF compared with F/TAF (Figure 1, P = 0.007); but not in the hip. Fracture event frequency was the same (53 [2.0%] per group, P = 1.00). One pathological fracture was reported in the F/TAF group compared with two in the F/TDF group (P = 0.57). In participants on baseline F/TDF PrEP, those randomized to F/TAF had significantly improved hip BMD compared with baseline (median percent change 1.13 [IQR −0.86, 3.47], P = 0.027), while spine BMD was unchanged.
Conclusion
Through 48 weeks, DXA subset participants taking F/TAF for PrEP had significantly less change in BMD than those taking F/TDF, and were less likely to develop spine osteopenia. The incidence of fracture was similar, and pathological fractures were rare. F/TAF for PrEP is effective and has a superior bone safety profile compared with F/TDF.
Disclosures
All authors: No reported disclosures.
Session: 149. HIV: Prevention
Friday, October 4, 2019: 12:15 PM