• Migraine attacks present for more than 1 year with the age of onset prior to 50 years of age.

• Migraine attacks, on average, lasting about 4 - 72 hours, if untreated.

• 4 to 14 migraine days per month, on average, across the 3 months prior to the Screening Visit (month is defined as 28-days for the purpose of this protocol).

• Less than15 headache days (migraine or non-migraine) per month in each of the 3-months prior to the Screening Visit and throughout the Screening Phase.

• Subjects must be able to distinguish migraine attacks from tension/cluster headaches. Prior inadequate response, within 10 years of the Screening Visit, to agents across 2-4 categories of recognized, orally-administered, migraine-preventive medications where at least one example of prior inadequate response is due to lack of efficacy or prior intolerance (not contraindication).