Long-term safety and continued clinical benefit of erenumab 70 mg in Asian patients with chronic migraine: an open-label extension of the phase 3 DRAGON study

BACKGROUND: Erenumab is a fully human monoclonal antibody targeting the calcitonin gene-related peptide receptor. Several double-blind studies have demonstrated the clinical benefits of erenumab in migraine prevention. However, long-term studies on safety and effectiveness of erenumab are lacking in Asian population. OBJECTIVES: To evaluate the long-term safety and continued clinical benefit of erenumab 70 mg in adult patients with chronic migraine (CM) in China and other Asian countries. METHODS: This was an open-label extension of the Phase 3 DRAGON study. Upon completion of the 12-week, double-blind treatment phase (DBTP) of the DRAGON study, randomized patients who met the inclusion criteria and provided consent transitioned into an open-label treatment phase (OLTP) lasting until erenumab approval in the patient's country. During OLTP, patients received once-monthly subcutaneous injection of erenumab 70 mg, irrespective of their initial treatment allocation in DBTP. Safety was assessed by collecting all adverse events (AEs) and serious AEs (SAEs) including their severity and relationship to study treatment. Effectiveness outcomes included clinical global impression (CGI) [severity (CGI-S), improvement (CGI-I), and efficacy index (CGI-E)]. RESULTS: Of the 557 randomized patients (DBTP), 456 from 50 centers participated and 226 (49.6%) completed OLTP. The median duration of exposure to erenumab was 79.9 weeks (interquartile range: 39.9-130.5). Overall, 328 (71.9%) patients reported at least one AE during OLTP. AEs suspected to be related to treatment were reported in 69 (15.1%) patients, with constipation (34 [7.5%]) being the most frequent treatment-related AE. There were 13 (2.9%) patients who discontinued the study drug due to AEs. Breast cancer was reported as an AE leading to discontinuation in 2 (0.4%) patients (not treatment related). SAEs were reported in 45 (9.9%) patients during OLTP, of which only 3 (0.7%) were treatment-related (all resolved). Continued clinical benefit with erenumab 70 mg as assessed by CGI E/I/S scores were observed for participating patients during OLTP. CONCLUSION: Erenumab 70 mg showed a consistent and well-tolerated safety profile observed over a longer treatment duration along with sustained clinical benefit. No new safety signals were observed versus DBTP and prior global phase 3 studies. TRIAL REGISTRATION: ClinicalTrials.gov ID (DRAGON) NCT03867201 (registration date 2019-03-07).