DEFINE: A Prospective, Randomized, Phase 4 Trial to Assess a Protease Inhibitor-based Regimen Switch Strategy to Manage Integrase Inhibitor-related Weight Gain.

Background: Integrase strand transfer inhibitor (InSTI)-based antiretroviral therapies have been associated with greater weight gain in people living with HIV versus on protease inhibitor (PI)-based regimens. The DEFINE study investigated whether switching from an InSTI- to a PI-based regimen could mitigate/reverse weight gain.

Methods: DEFINE (NCT04442737) was a randomized, 48-week, open-label, prospective, phase 4 study in virologically suppressed adults with HIV-1 and ≥10% weight gain on InSTI+tenofovir alafenamide (TAF)/emtricitabine (FTC) (<36 months pre-screening). Participants either switched immediately to darunavir/cobicistat/emtricitabine/TAF (D/C/F/TAF) or continued InSTI+TAF/FTC during Weeks 0-24 then switched to D/C/F/TAF for Weeks 24-48. The primary endpoint was least squares (LS) mean (95% confidence interval [CI]) percent weight change from baseline to Week 24.

Results: Overall, 103 adults were randomized (D/C/F/TAF, n=53; InSTI+TAF/FTC, n=50); 30% female; 61% Black/African American. No significant difference in weight change was observed at Week 24 (LS mean change: D/C/F/TAF, 0.63% [95%CI: -0.44, 1.70] vs InSTI+TAF/FTC, -0.24% [-1.35, 0.87]; p=0.24); however, a trend towards weight loss was observed with extended time post-ARV switch to D/C/F/TAF (baseline to Week 48, -0.36% [-1.77, 1.06]), particularly in subgroups at higher weight gain risk (eg, females, Black/African Americans). Metabolic endpoints paralleled weight change over time. D/C/F/TAF was well tolerated, with comparable virologic efficacy between arms.

Conclusions: While no significant change in body weight was observed at 24 weeks after switching from InSTI+TAF/FTC to D/C/F/TAF among adults with weight gain, a trend towards weight loss emerged with longer time post-ARV switch, supporting further investigation of antiretroviral selection/switch for weight management.