BackgroundMigraine is a debilitating neurological disorder that affects 14.1% of the US and 14.7% of the European populations. Chronic migraine (CM) is broadly defined as headache occurring on ≥15 days per month for ≥3 months, and has an estimated worldwide prevalence of 1.4% to 2.2%. OnabotulinumtoxinA is currently approved for the treatment of CM in most European countries, and is the only preventative treatment approved for adults with CM, based on results from the PREEMPT clinical trial programme. The ongoing prospective, observational REal-life use of botulinum toxin for the symptomatic treatment of adults with chronic migraine, measuring healthcare resource utilisation, and Patient-reported OutcomeS observed in practice (REPOSE) Study aims to describe real-world healthcare resource utilisation and patient-reported outcomes over a 2-year period in Germany, Italy, Norway, Russia, Spain, Sweden, and the United Kingdom, among patients with CM prescribed onabotulinumtoxinA.MethodsHerein, methodology and baseline characteristics of patients who participated for ≥6 months in REPOSE are reported. No outcomes data are presented, although the methods for collecting these data are detailed. In REPOSE, onabotulinumtoxinA is administered at baseline and each follow-up visit (approximately every 3 months) during the 24-month treatment period, according to the treating physician’s best clinical judgment and standard of care, guided by the terms of the marketing authorisation described in the Summary of Product Characteristics. Outcome assessments include Migraine-Specific Quality of Life Questionnaire (MSQ), EuroQol Group Questionnaire (EQ-5D), headache-day frequency, treatment satisfaction, headache-related healthcare resource utilisation (ie, healthcare professional visits, hospital admissions, medication use), onabotulinumtoxinA utilisation (ie, dose, sites), and safety/tolerability.ResultsAs of the interim assessment date for this analysis, the study has enrolled 644 patients from 78 sites throughout Europe, and baseline data are available for 336 patients from 61 sites who participated in the study for ≥6 months. Baseline measures indicate substantial disease burden and healthcare resource utilisation.ConclusionsFinal results from the REPOSE Study will provide the largest real-world, long-term analysis of the clinical use of onabotulinumtoxinA for the treatment of CM and will add important information to existing real-world findings. Future analyses will assess the long-term safety and efficacy of onabotulinumtoxinA in this population.