Efficacy and Safety of Switching Between Anti-CGRP Monoclonal Antibodies: A Detailed Monthly and Long-term Follow-up Study and Literature Review

Objective Switching from one anti-calcitonin gene-related peptide monoclonal antibody (CGRP mAb) to another can be beneficial for treating patients with migraine who do not respond well to the first CGRP mAb. However, detailed and long-term follow-up reports of both efficacy and safety remain insufficient. We conducted a case-series analysis of patients with migraine who switched from galcanezumab to erenumab, both belonging to the class of CGRP mAbs. Methods We conducted a single-center retrospective real-world study. Patients with migraine who first received galcanezumab for ≥3 months and then switched to erenumab at Keio University Hospital were enrolled to investigate changes in monthly migraine days (MMD), response rate, and adverse effects (e.g., injection-site reactions). Additionally, we performed a narrative review of the literature on switching CGRP mAbs. Results Among the nine patients enrolled, the 50% response rate for MMD was 33% at 3 months after switching. Two patients (22%) initially responded at the 3-month assessment, but later reverted to baseline MMD levels. Switching from galcanezumab to erenumab increased the frequency of constipation, which was typically managed using laxatives. Participants who experienced injection-site reactions tended to exhibit similar reactions regardless of the type of CGRP mAb used. Five patients (56%) demonstrated an improvement in satisfaction after erenumab initiation at least once. A literature review revealed that the characteristics of the cohorts varied among studies. Conclusions Switching from galcanezumab to erenumab was effective in some patients, while it was associated with some tolerable side effects, and it improved patient satisfaction in approximately half of the patients, despite interindividual diversity in responses and fluctuating responses after switching, which warrants further investigation.