Weight Change and Predictors of Weight Change Among Patients Initiated on Darunavir/Cobicistat/Emtricitabine/Tenofovir Alafenamide or Bictegravir/Emtricitabine/Tenofovir Alafenamide: A Real-World Retrospective Study

**Background:** Recent evidence suggests that integrase strand transfer inhibitors are associated with greater weight gain than protease inhibitors in patients with human immunodeficiency virus (HIV-1). **Objectives:** To describe demographic and clinical characteristics of insured patients with HIV-1 in the United States initiating darunavir/​cobicistat/​emtricitabine/​tenofovir alafenamide (DRV/c/FTC/TAF) or bictegravir/FTC/TAF (BIC/FTC/TAF), assess the differences in weight and body mass index (BMI) change between cohorts up to one year after treatment initiation, and identify the predictors of weight gain associated with each treatment. **Methods:** The Symphony Health, IDV® database (July 17, 2017 – September 30, 2019) was used to identify treatment naïve or virologically suppressed stable switchers who initiated DRV/c/FTC/TAF or BIC/FTC/TAF (index date) on or after July 17, 2018, were ≥18 years of age on the index date, and had ≥12 months of continuous clinical activity pre-index (baseline period). To account for differences in baseline characteristics, inverse-probability of treatment weighting (IPTW) was used. Mean weight and BMI change from pre- to post-index measurements were compared between weighted cohorts at 3, 6, 9, and 12 months post-index using mean differences. Predictors of weight or BMI gain ≥5% were evaluated at last measurement, for each treatment cohort separately. **Results:** After IPTW, 452 and 497 patients were included in the DRV/c/FTC/TAF and BIC/FTC/TAF cohorts, respectively. Baseline characteristics were generally well-balanced (mean age=\~50 years, female: \~30%), except for the type of antiretroviral therapy from which patients switched. Patients initiated on BIC/FTC/TAF experienced greater weight and BMI increases between the pre-index period and each measurement of the post-index period than patients initiated on DRV/c/FTC/TAF, although results were only statistically significant at 9 months post-index (weight: mean difference=2.50 kg, *P*=0.005; BMI: mean difference=0.66 kg/m^2^, *P*=0.027). A common predictor of weight or BMI gain ≥5% among patients in both cohorts was female gender (DRV/c/FTC/TAF: odds ratio \[OR\]=5.92, *P*=0.014; BIC/FTC/TAF: OR=2.00, *P*\