A Study to Evaluate the Efficacy and Safety of Eptinezumab for the Prevention of Migraine in Participants That Are Not Helped by Previous Preventive Treatments

- The participant has a diagnosis of migraine, with a history of chronic or episodic migraines of at least 12 months prior to the Screening Visit

- The participant has a migraine onset of ≤50 years of age.

- The participant has ≥4 migraine days per month for each month within the past 3 months prior to the Screening Visit.

- The participant has demonstrated compliance with the Headache eDiary by entry of data for at least 24 of the 28 days following the Screening Visit.

- The participant fulfils the following criteria for chronic migraine (CM) or episodic migraine (EM) in prospectively collected information in the eDiary during the screening period:

- For participants with CM: Migraine occurring on ≥8 days and headache occurring on >14 days

- For participants with EM: Migraine occurring on ≥4 days and headache occurring on ≤14 days

- The participant has documented evidence of treatment failure (must be supported by medical record or by physician's confirmation specific to each treatment) in the past 10 years of 2-4 different migraine preventive medications.

- The participant has a history of either previous or active use of triptans for migraine.

- The participant has experienced failure on a previous treatment targeting the calcitonin gene-related peptide (CGRP) pathway.

- The participant has a treatment failure on valproate/divalproex or botulinum toxin A/B and the treatment is not the latest preventive medication prior to study inclusion. The medication is regarded as the latest if the medication start date is after the start date of the other preventive medications and the medication stop date is after the stop date of the other preventive medications.

- The participant has confounding and clinically significant pain syndromes, (for example, fibromyalgia, chronic low back pain, complex regional pain syndrome).

- The participant has a diagnosis of acute or active temporomandibular disorder.

- The participant has a history or diagnosis of 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), ophthalmoplegic migraine, and migraine with neurological accompaniments that are not typical of migraine aura (diplopia, altered consciousness, or long duration).

- The participant has a psychiatric condition that is uncontrolled and/or untreated for a minimum of 6 months prior to the Screening Visit. Participants with a lifetime history of psychosis and/or mania in the last 5 years prior to the Screening Visit are excluded.

- The participant has a history of clinically significant cardiovascular disease or vascular ischaemia or thromboembolic events (for example, cerebrovascular accident, deep vein thrombosis, or pulmonary embolism). Other in- and exclusion criteria may apply