Inclusion Criteria:  History of migraine headache disorder meeting International Classification of Headache Disorders (ICHD)-3 diagnostic criteria for migraine with aura or migraine without aura for >= 12 months. Onset of migraine before 50 years of age. History of 6 to 14 migraine days/month in each of the 3 months prior to Visit 1. Six to 14 migraine/probable migraine days during the 4-week screening/baseline phase. Less than 15 headache days/month in each of the 3 months prior to Visit 1 and during the 4-week screening/baseline phase.  Exclusion Criteria:  Current diagnosis of chronic migraine according to ICHD-3. History or current diagnosis of migraine with brainstem aura, retinal migraine, complications of migraine, tension-type headache, trigeminal autonomic cephalalgias, hypnic headache, hemicrania continua, or new daily persistent headache. History of headache attributed to another disorder (eg, secondary headaches), except medication overuse headache. History of an inadequate response to >4 medications (2 of which have different mechanisms of action) prescribed for the prevention of migraine. Pregnant or nursing females.