INTRODUCTIONFremanezumab, a humanized monoclonal antibody targeting calcitonin gene-related peptide, is indicated for preventive treatment of migraine in adults. Real-world evidence assessing the effect of fremanezumab on migraine-related medication use, health care resource utilization (HCRU), and costs in patient populations with comorbidities, acute medication overuse (AMO), and/or unsatisfactory prior migraine preventive response (UPMPR) is needed.METHODSData for this US, retrospective claims analysis were obtained from the Merative® MarketScan® Commercial and supplemental databases. Eligible adults with migraine initiated fremanezumab between 1 September 2018 and 30 June 2019 (date of earliest fremanezumab claim is the index date), had ≥ 12 months of continuous enrollment prior to initiation (preindex period) and ≥ 6 months of data following initiation (postindex period; variable follow-up after 6 months), and had certain preindex migraine comorbidities (depression, anxiety, and cardiovascular disease), potential AMO, or UPMPR. Changes in migraine-related concomitant acute and preventive medication use, HCRU, and costs were assessed pre- versus postindex.RESULTSIn total, 3193 patients met the eligibility criteria. From pre- to postindex, mean (SD) per patient per month (PPPM) number of migraine-related acute medication and preventive medication claims (excluding fremanezumab), respectively, decreased from 0.97 (0.90) to 0.86 (0.87) (P < 0.001) and 0.94 (0.74) to 0.81 (0.75) (P < 0.001). Migraine-related outpatient and neurologist office visits, emergency department visits, and other outpatient services PPPM decreased pre- versus postindex (P < 0.001 for all), resulting in a reduction in mean (SD) total health care costs PPPM from US$541 (US$858) to US$490 (US$974) (P = 0.003). Patients showed high adherence and persistence rates, with mean (SD) proportion of days covered of 0.71 (0.29), medication possession ratio of 0.74 (0.31), and persistence duration of 160.3 (33.2) days 6 months postindex.CONCLUSIONSPatients with certain migraine comorbidities, potential AMO, and/or UPMPR in a real-world setting had reduced migraine-related medication use, HCRU, and costs following initiation of fremanezumab. Graphical abstract available for this article.