A Study With Eptinezumab in Adolescents (12-17 Years) With Chronic Migraine

Inclusion Criteria:

* The participant has a diagnosis of migraine (with or without aura) as defined by International Classification of Headache Disorders 3 (ICHD-3) guidelines with history of chronic migraine, of at least 6 months prior to the screening visit.
* During the 28-day screening period, the participant must adequately complete the headache eDiary on at least 23 of the 28 days following the screening visit.
* During the 28-day screening period, the participant must have ≥15 to ≤26 headache days, of which at least 8 are migraine days as documented in the eDiary.

Exclusion Criteria:

* The participant has previously been randomised in this study and exposed to eptinezumab.
* The participant has been exposed to any monoclonal antibody treatment (including exposure in a study) \<6 months prior to the screening visit.
* The participant has been exposed to another calcitonin gene-related peptide (CGRP) antibody (including exposure in a study investigating a CGRP antibody) \<6 months prior to the screening visit.
* The participant has a history or diagnosis of complicated migraine (ICHD-3 version, 2018), chronic tension-type headache, hypnic headache, cluster headache, hemicrania continua, new daily persistent headache, or unusual migraine subtypes such as hemiplegic migraine (sporadic and familial), migraine with brainstem aura, ophthalmoplegic migraine, or migraine with neurological accompaniments that are not typical of migraine aura (diplopia, altered consciousness, or long duration; for example \>60 minutes).