Background and importance Monoclonal antibodies targeting the calcitonin gene-related peptide (CGRP-mAbs) have been introduced into the therapeutic arsenal of chronic migraine (CM) prophylaxis. Clinical trials report similar efficacy between them. Some patients with CM and multiple treatment failures do not respond to a first treatment with CGRP-mAbs, but there is no evidence for switching to a second CGRP-mAbs. These treatments are dispensed in hospital pharmacies, where pharmacists follow up these patients and the efficacy of these treatments.

Aim and objectives We aimed to describe the effectiveness of CGRP-mAbs (erenumab and galcanezumab) switching in preventive treatment for CM in clinical practice.

Material and methods A retrospective case series including patients with CM treated with CGRP-mAbs and switched to another CGRP-mAb between August 2020 and September 2021 in a third-level hospital in Spain. Effectiveness was established with ≥50% reduction of monthly migraine days (MMD) in respect to baseline, or ≥30% reduction of MMD and ≥5 points reduction of the HIT-6 with respect to baseline.

Results Twenty patients were included: 14 were treated with erenumab as first CGRP-mAb and were switched to galcanezumab; 6 were treated with galcanezumab and were switched to erenumab. The median duration of the first CGRP-mAb treatment was 7.8 (5.0–9.7) months. The reason for treatment switching was non-response in 15 cases and adverse events in 5 cases. The adverse event was in all cases severe constipation in patients treated with erenumab.

Thirteen patients improved their response after CGRP-mAb switching with a median of 22.6% (12%–40%) reduction of MMD in respect to baseline; 4 patients had a worse response after CGRP-mAb switching with a median of 14.7% (12.5%–17.8%) increase of MMD with respect to baseline; and 3 patients did not respond to any CGRP-mAb treatment. Response to the second CGRP-mAb was observed in 10 patients switched from erenumab to galcanezumab and 3 patients switched from galcanezumab to erenumab. No patient presented unacceptable toxicity to the second CGRP-mAb treatment.

Conclusion and relevance Some patients with CM may benefit from switching between mAbs with the same mechanism of action. More studies are needed to describe which patients will respond to CGRP-mAb switching.

Conflict of interest No conflict of interest