Real-Life Response to Erenumab in a Therapy-Resistant Case Series of Migraine Patients From the Province of Québec, Eastern Canada

Background and objective: Erenumab is the first migraine-specific preventive therapy approved by Health Canada since the approval of onabotulinumtoxinA 10 years ago. It is one of four calcitonin gene-related peptide antagonist monoclonal antibodies that have been commercialized worldwide for use in the headache pipeline. The objective of our study was to determine real-life efficacy of monthly erenumab for the prevention of migraine in a small case series of difficult-to-treat patients followed at a tertiary headache clinic from the Canadian province of Québec.

Methods: We performed a retrospective chart audit of patients having failed four or more conventional migraine oral preventive therapies and who were treated with monthly self-administered subcutaneous erenumab (70 or 140 mg/mL dose) over a 1-year period. We assessed the patients' baseline characteristics, response to treatment, and tolerability.

Results: A total of 18 patients with a diagnosis of high-frequency episodic migraines or chronic migraine met criteria (83.3% female; mean age: 48.7 years; mean duration of migraine condition: 32.9 years). Patients self-administered erenumab using a prefilled disposable autoinjector on a monthly basis; 16 patients received a 140 mg/mL dosage, two patients received a 70 mg/mL dosage. At 1 year follow-up, 50% of patients reported ≥ 50% reduction in migraine frequency and were deemed responders. Patients attempted six doses of erenumab therapy prior to discontinuation for non-response, except for two patients with other concomitant chronic pain conditions, who required ten doses to reach a 50% response. For the overall cohort, there was a decrease of 5.2 monthly migraine days; 9 days for responders and 1.3 days for non-responders (t-test (df = 16) = - 2.77, p = 0.014). There was an additional decrease of 7 monthly non-migraine days amongst patients with unremitting daily headaches; 8 days for responders and 5 days for non-responders (p > 0.05). There was a decrease of 5.4 monthly days using acute analgesics; 8.9 days for responders and 2 days for non-responders (T(16) = - 2.33, p = 0.033). The overall mean reduction in disability using the Headache Impact Test (HIT-6) score was 5.6 points; only responders showed a reduction in HIT-6 severity category (p > 0.05). The most commonly reported adverse event was constipation (16.7%), which did not lead to treatment discontinuation and was successfully managed in all patients with early counselling and intervention.

Conclusion: This study supports the efficacy of erenumab in a case series of therapy-resistant migraine patients from the region of Québec. A high rate of previously failed preventive oral agents and medication overuse did not predict response in our patient cohort. In the presence of real-world complexity factors, such as psychological distress, regular opioid consumption and concomitant chronic pain conditions, a longer therapy trial may be warranted in obtaining optimal response.