Evaluation of the change in efficacy of erenumab when used long-term for migraine prevention after initial established benefit in a veteran population.

Introduction: With the increased use of erenumab and other calcitonin gene-related peptide antagonists for migraine prevention, increased evidence on long-term efficacy and real-world effectiveness is needed. Some reports of a wearing-off effect or waning efficacy over time have been observed with erenumab use.

Objective: This study evaluated the change in efficacy of erenumab after initial established benefits for migraine prevention in a veteran population.

Methods: This retrospective chart review evaluated patients who were prescribed erenumab for migraine prevention at a Veterans Affairs neurology clinic between June 1, 2018, and May 31, 2021. Patients with an initial 50% or greater reduction in mean monthly headache days (MHDs) by 12 weeks after erenumab 70 mg initiation were then followed forward to determine the change in MHDs until erenumab dose was increased, changed to galcanezumab, or by November 30, 2021, to ensure a minimum 6-month follow-up for all patients.

Results: Ninety-three patients were included for analysis. A significant reduction in mean MHDs from 16.1 to 5.7 days was found by 12 weeks after erenumab 70 mg initiation (p < 0.0001). Following this initial response to erenumab, 69% of patients experienced a significant increase in MHDs over an average time of 7.8 months and required a subsequent dose increase to erenumab 140 mg or change to galcanezumab. The remaining 31% of patients continued erenumab 70 mg monthly with a further nonstatistically significant decline in MHDs.

Conclusions: A decrease in efficacy with the long-term use of erenumab was observed for the majority of patients evaluated in this analysis. This suggests that patients with initial benefits on lower dose erenumab should be monitored for change to effectiveness.