Long-Term Safety and Tolerability of OnabotulinumtoxinA Treatment in Patients with Chronic Migraine: Results of the COMPEL Study

Introduction OnabotulinumtoxinA is approved in the USA for the prevention of headache in adults with chronic migraine, a debilitating neurologic disease characterized by headaches occurring on >= 15 days per month for > 3 months and including migraine features on >= 8 days per month. Objective The COMPEL Study (NCT01516892), a 108-week, multi-center, open-label study, evaluated the long-term efficacy and safety of onabotulinumtoxinA in adults with chronic migraine. The objective of this subanalysis was to examine the safety and tolerability of onabotulinumtoxinA after each of nine treatment cycles. Methods OnabotulinumtoxinA 155 U was administered every 12 weeks. Safety and tolerability, overall and by treatment cycle, were assessed. Treatment-emergent adverse events reported between successive treatments were attributed to the preceding treatment. The safety population received one or more doses of onabotulinumtoxinA. The primary efficacy outcome was the reduction in headache days at week 108 compared with baseline. Results Of 716 patients enrolled, 373 patients (52.1%) completed the study and 343 (47.9%) withdrew; 481 patients (67.2%) received 60 weeks of treatment and 402 (56.1%) received 108 weeks of treatment. In total, 436 (60.9%) patients reported treatment-emergent adverse events; most were mild/moderate in severity. Thirty-two patients (4.5%) discontinued the study after experiencing treatment-emergent adverse events. The incidence of treatment-emergent adverse events typically decreased with repeated onabotulinumtoxinA treatment: first cycle, 24.2%; fourth cycle, 18.4%; ninth cycle, 12.2%. Neck pain (2.7%), eyelid ptosis (1.8%), musculoskeletal stiffness (1.4%), injection-site pain (1.3%), and headache (1.3%) were the most common treatment-emergent adverse events after the first cycle. Seventy-five patients (10.5%) reported serious treatment-emergent adverse events, 13 (1.8%) withdrew. Treatment-related adverse events were reported by 131 patients (18.3%), one was considered serious. OnabotulinumtoxinA significantly reduced headache day frequency by 10.7 (6.4) days per 28-day period (p < 0.0001) at week 108. Conclusions OnabotulinumtoxinA treatment was well tolerated over 108 weeks; no new safety signals were identified. The overall incidence of treatment-emergent adverse events and the most common individual events decreased with repeated onabotulinumtoxinA administration.