ObjectiveTo evaluate the impact of fremanezumab on the severity and duration of remaining migraine attacks in patients with chronic migraine (CM) or episodic migraine (EM).BackgroundFremanezumab is a fully humanized monoclonal antibody (IgGΔa) that selectively targets calcitonin gene‐related peptide and is efficacious in reducing migraine frequency.MethodsThis exploratory post hoc analysis included data from three randomized, double‐blind, 12‐week, phase 3 studies (HALO CM, HALO EM, and FOCUS). In all three studies, patients with CM or EM were randomized 1:1:1 to receive subcutaneous quarterly fremanezumab (month 1/2/3: 675 mg/placebo/placebo), monthly fremanezumab (month 1/2/3: 675 mg [CM], 225 mg [EM]/225 mg/225 mg), or matched monthly placebo. Changes from baseline were evaluated in the proportion of headache days of at least moderate severity, peak severity of headache days, mean monthly headache hours (of any severity and at least moderate severity), and mean headache hours per headache day of any severity.ResultsA total of 2843 patients were randomized with 2823 patients included in the efficacy analyses across all studies (HALO CM, N = 1121; HALO EM, N = 865; FOCUS, N = 837). At study baseline, mean (standard deviation [SD]) monthly number of headache days rated moderate or severe in the quarterly fremanezumab, monthly fremanezumab, and placebo groups, respectively, were 13.2 (5.5), 12.8 (5.8), and 13.3 (5.8) in HALO CM; 7.2 (3.1), 6.8 (2.9), and 6.9 (3.1) in HALO EM; and 12.4 (5.8), 12.7 (5.8), and 12.8 (5.9) in FOCUS. Patients experienced significant least‐squares mean (LSM; 95% confidence interval) percent reductions from baseline in monthly number of headache days rated moderate or severe during the 12 weeks: HALO CM, quarterly fremanezumab, 34.5% (−39.8, −29.2) and monthly fremanezumab, 36.2% (−41.4, −31.0) vs. placebo, 19.6% (−20.0, −14.3); HALO EM, quarterly fremanezumab, 40.7% (−47.8, −33.5) and monthly fremanezumab, 43.4% (−50.4, −36.3) vs. placebo, 17.9% (−24.9, −11.0); and FOCUS, quarterly fremanezumab, 36.5% (−41.9, −31.1) and monthly fremanezumab, 38.6% (−44.0, −33.3) vs. placebo, 3.5% (−8.9, 1.8); all p < 0.0001. At study baseline, mean (SD) number of monthly headache hours rated moderate or severe in the quarterly fremanezumab, monthly fremanezumab, and placebo groups, respectively, were 66.4 (58.8), 68.0 (53.9), and 68.5 (57.0) in HALO CM; 33.3 (25.4), 31.7 (23.7), and 31.6 (23.2) in HALO EM; and 59.2 (54.7), 64.3 (65.2), and 65.9 (70.2) in FOCUS. Significant reductions were observed in LSM (standard error) number of monthly headache hours of at least moderate severity: HALO CM, quarterly fremanezumab, 24.4 (2.5) and monthly fremanezumab, 26.4 (2.3) vs. placebo, 14.1 (2.5); HALO EM, quarterly fremanezumab, 14.5 (1.4) and monthly fremanezumab, 15.5 (1.3) vs. placebo, 8.1 (1.3); and FOCUS, quarterly fremanezumab, 16.8 (3.0) and monthly fremanezumab, 18.3 (3.0) vs. placebo, 2.3 (3.0); all p < 0.001.ConclusionThese analyses demonstrated that quarterly or monthly treatment with fremanezumab significantly reduced headache severity and duration in patients with CM or EM, including in patients with documented inadequate response to two to four prior migraine preventive medication classes.