Unmet clinical needs in chronic migraine: Rationale for study and design of COMPEL, an open-label, multicenter study of the long-term efficacy, safety, and tolerability of onabotulinumtoxinA for headache prophylaxis in adults with chronic migraine

Background: Chronic migraine is a neurological condition with a large individual and socioeconomic burden of disease. The recently completed Phase III REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical development program established the efficacy and safety of onabotulinumtoxinA as a prophylactic treatment for chronic migraine patients. However, clinical questions remain. A long-term evaluation study of onabotulinumtoxinA aims to address some of the remaining questions in the treatment of chronic migraine. The clinical rationale, study design, and treatment plan of this ongoing study are reviewed in this paper. Methods/Design: The Chronic migraine OnabotulinuMtoxinA Prolonged Efficacy open Label (COMPEL) study will enroll approximately 500 adult patients with chronic migraine at international sites. Patients will be evaluated over 108 weeks, following a 4-week baseline period. Qualified subjects will receive 155 U of onabotulinumtoxinA every 12 weeks for 9 open-label cycles. The primary endpoint will be mean change from baseline in frequency of headache days at 108 weeks. Other endpoints will include additional assessments of the efficacy and safety of onabotulinumtoxinA and the effect of onabotulinumtoxinA on quality-of-life measures, disability, and health economic outcomes. The impact of onabotulinumtoxinA on common comorbidities (eg, sleep, anxiety, and fatigue) will also be assessed. Discussion: Recruitment and enrollment are ongoing. Post-approval, open-label studies are often designed to more closely resemble clinical practice and provide an opportunity to continue the evaluation of the efficacy and safety of approved treatments. By creating a large database and analyzing a variety of outcome measures over an extended time frame, the COMPEL study will seek to contribute substantially to the existing knowledge of the chronic migraine population and the long-term management of this debilitating disorder.