The purpose of the study is to investigate how the body absorbs, distributes, and get rid of eptinezumab when given directly into a vein.

This is an interventional, open-label pharmacokinetic study with eptinezumab, consisting of a single-dose, 20-week main study period (Part A) and an optional 44-week multiple-dose extension period (Part B).

The main study period includes a single IV infusion of eptinezumab. The optional extension period includes 3 additional eptinezumab infusions 12 weeks apart (reflecting recommended dosing interval in adults), for a total of up to 4 infusions over the course of the study.

At least 32 patients with migraine will be enrolled: 16 patients aged 6 to 11 years, and 16 patients aged 12 to 17 years, inclusive.

Inclusion Criteria:

• The patient has a diagnosis of migraine with or without aura according to international classification of headache disorders (ICHD)-3 (in the opinion of the investigator) for ≥6 months prior to the Screening Visit and has a frequency of migraine ≥4 migraine days per month for at least 3 months prior to the Screening Visit.

Exclusion Criteria:

• The patient has been exposed to any monoclonal antibody treatment (including exposure in a study) <6 months prior to the Screening Visit.

Other in- and exclusion criteria may apply