Ultra-late response (> 24 weeks) to anti-CGRP monoclonal antibodies in migraine: a multicenter, prospective, observational study

Objective: Nearly 60% of migraine patients treated with monoclonal antibodies (mAbs) targeting the calcitonin gene-related peptide (CGRP) pathway experience a ≥ 50% reduction in monthly migraine days (MMD) at 12 weeks compared to baseline (responders). However, approximately half of the patients not responding to anti-CGRP mAbs ≤ 12 weeks do respond ≤ 24 weeks (late responders). We assessed frequency and characteristics of patients responding to anti-CGRP mAbs only > 24 weeks (ultra-late responders). Methods: In this multicenter (n = 16), prospective, observational, real-life study, we enrolled all consecutive adults affected by high-frequency episodic migraine (HFEM: ≥ 8 days/month) or chronic migraine (CM), with ≥ 3 prior therapeutic failures, treated with any anti-CGRP mAbs for ≥ 48 weeks. We defined responders patients with a ≥ 50% response rate ≤ 12 weeks, late responders those with a ≥ 50% response rate ≤ 24 weeks, and ultra-late responders those achieving a ≥ 50% response only > 24 weeks. Results: A total of 572 migraine patients completed ≥ 48 weeks of anti-CGRP mAbs treatment. Responders accounted for 60.5% (346/572), late responders for 15% (86/572), and ultra-late responders for 15.7% (90/572). Among ultra-late responders, 7.3% (42/572) maintained the ≥ 50% response rate across all subsequent time intervals (weeks 28, 32, 36, 40, 44, and 48) and were considered persistent ultra-late responders, while 8.4% (48/572) missed the ≥ 50% response rate at ≥ 1 subsequent time interval and were classified as fluctuating ultra-late responders. Fifty patients (8.7%) did not respond at any time interval ≤ 48 weeks. Ultra-late responders differed from responders for higher BMI (p = 0.033), longer duration of medication overuse (p < 0.001), lower NRS (p = 0.017) and HIT-6 scores (p = 0.002), higher frequency of dopaminergic symptoms (p = 0.002), less common unilateral pain—either alone (p = 0.010) or in combination with UAS (p = 0.023), allodynia (p = 0.043), or UAS and allodynia (p = 0.012)—a higher number of comorbidities (p = 0.012), psychiatric comorbidities (p = 0.010) and a higher proportion of patients with ≥ 1 comorbidity (p = 0.020). Conclusion: Two-thirds of patients not responding to anti-CGRP mAbs ≤ 24 weeks do respond later, while non-responders ≤ 48 weeks are quite rare (8.7%). These findings suggest to rethink the duration of migraine prophylaxis and the definition of resistant and refractory migraine, currently based on the response after 2–3 months of treatment.