A migraine day was endorsed when at least 1 of the following situations occurred: 1) A calendar day (0:00 to 23:59) demonstrating at least 4 consecutive hours of a headache endorsing criteria for migraine, or 2) a calendar day (0:00 to 23:59) demonstrating at least 4 consecutive hours of a headache endorsing criteria for probable migraine, a migraine subtype where only one migraine criterion is missing, or 3) the participant used acute migraine medication (triptans and ergot compounds) to treat a headache of any duration, or 4) any of the above days preceded or followed by a day with a headache of any duration. This calculation was defined as the change from baseline in the number of headache days during the 28-day post treatment period ending at week 12. Headache severity was rated daily by the participant as either no pain, mild, moderate, or severe.

An AE was defined as any untoward medical occurrence that develops or worsens in severity during the conduct of a clinical study and does not necessarily have a causal relationship to the study drug. Relationship of AE to treatment was determined by the Investigator. Serious AEs include death, a life-threatening adverse event, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, a congenital anomaly or birth defect, or an important medical event that jeopardized the participant and required medical intervention to prevent the previously listed serious outcomes. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

Adverse events were rated based on the investigator's clinical judgment. Mild: awareness of a sign or symptom that was easily tolerated Moderate: sign or symptom intense enough to interfere with usual activity Severe: interfered significantly with ability to do work or usual activity