Fremanezumab, a fully humanized monoclonal antibody (IgG2∆a) that selectively targets calcitonin gene-related peptide (CGRP), is approved in the United States and the European Union for the preventive treatment of migraine in adults [14, 15]. The 12-week, double-blind, placebo-controlled, phase 3 HALO CM trial demonstrated that subcutaneous administration of fremanezumab significantly reduced headache days of at least moderate severity in patients with CM [16]. To understand the impact of fremanezumab in patients with MO, data from patients with CM with and without MO were assessed post hoc to examine the reduction of headache and migraine days and acute headache medication use. Outcomes were also examined in patients who either did or did not revert from MO at baseline to no MO during the study.