OBJECTIVES: Payers may grant coverage for bariatric surgery (BaS) for patients with BMI ≥ 40 or BMI 35-39.9 with ≥1 obesity-related comorbidities. Trial of weight loss (WL) medications before BaS may be beneficial to both payers and patients if some patients can avoid BaS. This analysis evaluated the cost impact of lorcaserin, a FDA- approved WL medication, in weight management prior to BaS from payer’s perspective. METHODS: Cost impact of lorcaserin for WL prior to BaS was assessed in a hypothetical US health plan of one million members over a 2-year horizon.  Key assumptions include: 1) Average cost per BaS is $29,517; 2) Patients with BMI reduced to below 35 with pre-BaS WL can avoid BaS; 3) Only BaS and lorcaserin drug costs are included; 4) Only patients who achieve ≥5% weight loss at week 12 continue lorcaserin treatment (WK-12 responders). For modeling purpose, WL data for lorcaserin were drawn from a subset of patients in three clinical trials (BLOSSOM, BLOOM, BLOOM-DM) evaluating the efficacy and safety of lorcaserin for WL. RESULTS: