Dual therapy with Erenumab and onabotulinumtoxinA: No synergistic effect in chronic migraine: A retrospective cohort study

Objective To assess whether dual therapy with erenumab and onabotulinumtoxinA (BoNTA) was more effective than erenumab alone in chronic migraine. Background Calcitonin gene‐related peptide (CGRP) is crucial in migraine. Erenumab binds to the canonical CGRP receptor in Aδ‐fibers, and BoNTA prevents the release of CGRP from meningeal and extracranial C‐fibers. It is still unknown whether dual therapy is more effective. Methods This was a retrospective study in a Headache Unit. There was a thorough revision of charts of patients receiving erenumab from December 2019 to March 2021. The cohort was divided into three groups according to BoNTA at the start of erenumab: (1) WBT: were on BoNTA and maintained it as dual therapy; (2) WoBT: were on BoNTA and discontinued; (3) NoBT: were not on BoNTA. Primary endpoint was reduction in monthly headache days (MHD) at 12 weeks. Secondary endpoints were percent improvement and ≥50% reduction in MHD. Results Of 237 charts reviewed, 187 met the inclusion criteria. Seventy‐three (39%) were included in WBT, 44 (23.5%) in WoBT, and 70 (37.4%) in NoBT. The reduction in MHD was less with dual therapy [WBT 4.7 ± 7.68, WoBT 5.12 ± 7.98 (p = 0.80), NoBT 8.21 ± 7.84 p = 0.009]. The percentage of improvement was higher in the erenumab‐alone group [NoBT 35%, WoBT 22.3% (p = 0.92), WBT 21.7% (p = 0.001)]. The probability of achieving a ≥ 50% reduction in MHD was lower in WBT than in WoBT (OR 0.66, p = 0.35) and in the NoBT group (OR 0.57, p = 0.14). Conclusions Our findings suggest that dual therapy is less effective than erenumab alone. However, since the design has multiple limitations, further prospective studies are required to validate these data.