Outcomes of participants switching from F/TDF to F/TAF for PrEP: week 48 results from the DISCOVER open label phase


BACKGROUND: DISCOVER is an ongoing, multinational, double-blind, randomized controlled trial of F/TAF vs F/TDF for PrEP which demonstrated noninferior efficacy and improved bone mineral density (BMD) and renal safety biomarkers at week (W) 48 and 96 of the blinded phase. Here we report the W48 outcomes of the open label (OL) phase, where participants initially randomized to F/TDF switched to F/TAF.
METHODS: After W96 of the blinded phase, participants could opt to receive F/TAF in the OL phase. We evaluated BMD, glomerular function (eGFR), biomarkers of proximal tubular injury (PTI; β2M/Cr, RBP/Cr), lipids and weight at OLW48 in participants who switched from F/TDF to F/TAF (switch group) and those remaining on F/TAF (stay group).
RESULTS: The F/TAF OL phase included 2,128 switch group and 2,080 stay group participants. Participants in the switch and stay groups had 2,076 and 2,075 person-years of F/TAF exposure in the OL phase, respectively. There were two HIV infections in the switch group and three in the stay group (Table). Hip and Spine BMD increased in the switch group. Switch group participants had lower eGFR at OL onset, which increased by OLW48. Both groups had improvements in PTI markers, which was greater in the switch group. LDL and HDL cholesterol increased in the switch group, with minimal change in total cholesterol:HDL ratio; fasting glucose change was small and not significantly different between groups. Weight gain was seen in both groups and was greater in the switch group.

CONCLUSIONS: Participants switching from F/TDF to F/TAF in the OL phase of DISCOVER had a low HIV incidence rate, increased BMD, and improved renal biomarkers. LDL, HDL and weight increased in these participants, consistent with removal of TDF's weight and lipid suppressive effects. These data support F/TAF as a safe and effective switch option for people currently taking F/TDF for PrEP.