Efficacy and Safety of Erenumab in Pediatric Subjects With Chronic Migraine

Inclusion Criteria: * Children (6 to less than 12 years of age) or adolescent (12 to less than 18 years of age) at the time of signing, if developmentally appropriate, the formal assent to participate to the study. * Participant's parent or legal representative has provided written informed consent before initiation of any study-specific activities/procedures. * History of migraine (with or without aura) for ≥ 12 months before screening according to the IHS Classification ICHD-3 (Headache Classification Committee of the International Headache Society, 2013) ICHD-3 specifications for pediatric migraine (participants aged less than 18 years), should be considered for the diagnosis of migraine. * History of ≥ 15 headache days per month of which ≥ 8 headache days were assessed by the participant as migraine days per month in each of the 3 months prior to screening. * Migraine frequency: greater than or equal to 8 migraine days based on the eDiary data during the last 28 days of the baseline phase if more than 28 days in duration. * Headache frequency of greater than or equal to 15 headache days based on the eDiary data during the last 28 days of the baseline phase if more than 28 days in duration. * Demonstrated at least 80% compliance with the eDiary based on the last 28 days of the baseline period, if more than 28 days in duration (eg, completing eDiary items for at least 23 out of the last 28 days of the baseline phase). Key Exclusion Criteria: * History of cluster headache or hemiplegic migraine headache. * Chronic migraine with continuous pain, in which the participant does not have any pain free periods (of any duration) during the 1 month prior to screening. * No therapeutic response with greater than 3 medication categories for prophylactic treatment of migraine after an adequate therapeutic trial. No therapeutic response is defined as no reduction in headache frequency, duration, or severity after administration of the medication for at least 6 weeks at the generally-accepted therapeutic dose(s) based on the investigator's assessment. * History of suicidal behavior or the participant is at risk of self-harm or harm to others. * History of major psychiatric disorder. Participants with anxiety disorder and/or mild major depressive disorder (Patient Health Questionnaire Modified for Adolescents \[PHQ-A\] score 9 for adolescents or based on medical judgement of the investigator for children) are permitted in the study if they are considered by the investigator to be stable and are taking no more than 1 medication for each disorder. Participants must have been on a stable dose within the 3 months before the start of the baseline phase.