Safety and Efficacy of NPS 1776 in the Acute Treatment of Migraine Headaches

Inclusion Criteria: 1. Diagnosis of migraine for at least a year prior to screening. 2. Experiences 2-10 migraine headaches per month (with at least 24 hours between episodes) and no more than 15 headache days per month in the 3 months prior to screening. 3. Ability and willingness to arrive at the investigator's center within 1 hour (±5 min) of migraine pain onset (defined as pain that is consistent with the subject's usual migraine and is of at least moderate severity). 4. Ability and willingness to abstain from taking medications not allowed by the protocol and to meet phone and check-in criteria. 5. Ability and willingness to undergo a comprehensive urine toxicology screen for both licit and illicit drugs. 6. Ability and willingness to complete a migraine-history diary from screening to treatment with study drug and a migraine-treatment diary from discharge through the remainder of the 24-hour period following study-drug treatment. Exclusion Criteria: 1. Unstable or uncontrolled significant metabolic, hepatic, renal, hematological, pulmonary, gastrointestinal, urological, neurological (except migraine headaches), or psychiatric disorders. 2. Severe or acute cardiovascular or cerebrovascular disease, uncontrolled hypertension, or basilar or hemiplegic migraines. 3. History of hypersensitivity, allergies, or nonresponse to valproic acid. 4. Have taken VPA or other AED in the 30 days prior to screening, or are taking a migraine prophylaxis treatment other than a stable dose of propranolol or tricyclic antidepressant. 5. Migraine attacks that in the investigator's opinion are associated with intractable nausea and/or vomiting. 6. Any acute or chronic condition that in the investigator's opinion would limit the subject's ability to complete and/or participate in this clinical study or would place the subject at increased risk. 7. Have newly started or changed the dose of either feverfew or magnesium (above 200 mg, the amount in common daily supplements) within 3 months prior to screening.