Late Response to Anti-CGRP Monoclonal Antibodies in Migraine: A Multicenter Prospective Observational Study

Objectives: To assess the frequency and characteristics of late responders (>12 weeks) to monoclonal antibodies (mAbs) targeting the calcitonin gene-related peptide (CGRP). Methods: This is a multicenter (n = 16) prospective real-life study considering all consecutive adults with high-frequency or chronic migraine treated with anti-CGRP mAbs for ≥24 weeks. We defined responder patients with a ≥50% reduction from baseline in monthly migraine/headache days at weeks 9-12 and late responders as those achieving a ≥50% reduction only afterward. Results: A total of 771 people with migraine completed ≥24 weeks of anti-CGRP mAb treatment. Responders at 12 weeks were 65.6% (506/771) of the patients, while nonresponders were 34.4% (265/771). A total of 146 of the 265 nonresponders (55.1%) at 12 weeks responded afterward (late responders): they differed from responders for a higher BMI (+0.78, 95% CI [0.10; 1.45]; p = 0.024), more frequent treatment failures (+0.52, 95% CI [0.09; 0.95]; p = 0.017) and psychiatric comorbidities (+10.1%, 95% CI [0.1; 0.20]; p = 0.041), and less common unilateral pain, alone (-10,9%, 95% CI [-20.5; -1.2]; p = 0.025) or in combination with unilateral cranial autonomic symptoms (-12.3%, 95% CI [-20.2;-3.9]; p = 0.006) or allodynia (-10.7, 95% CI [-18.2; -3.2]; p = 0.01). Discussion: Half of nonresponders to anti-CGRP mAbs at 12 weeks are indeed late responders. Efficacy of anti-CGRP mAbs should be assessed at 24 weeks while treatment duration should be extended beyond 12 months.