The purpose of this study is to assess the safety, pharmacokinetics and efficacy of a single dose of ALD403 in the prevention of migraine headache in frequent episodic migraineurs for 24 weeks.

Inclusion Criteria

• Diagnosis of migraine at ≤ 50 years of age (ICHD-II, 2004 Section 1)

• History of migraine ≥ 12 months with

  • ≥ 5 and ≤ 14 migraine days in each 28 day period in the 3 months prior to screening
  • use of acute migraine medications ≤ 14 days per 28 day period and, within those days, ≤ 10 days of triptan use per 28 day period in the 3 months prior to screening and the 28 day period of completion of eDiary prior to randomization

• Women of child-bearing potential and males with partners of child-bearing potential must agree to use adequate contraception (oral or injectable [depot] estrogen, and/or progestogen, or selective estrogen receptor modulator contraceptive therapeutic, intrauterine contraceptive device, or double barrier method [e.g., condom and diaphragm or spermicidal gel]). Non-childbearing potential is defined as post-menopausal for at least 1 year or surgical sterilization or hysterectomy at least 3 months before screening

• Any hormonal therapy (e.g., oral contraceptives, hormone replacement therapy) use is stable and ongoing for at least 3 months prior to screening and during the 28 day period from screening to randomization

• Agree not to post any personal medical data related to the trial or information related to the trial on any website or social media site (e.g., Facebook, Twitter) until the trial has been completed

Exclusion Criteria

• Confounding pain syndromes including fibromyalgia, chronic musculoskeletal (e.g., low back pain), psychiatric conditions, dementia, or major neurological disorders other than migraine that interfere with the participation in the trial
• Diagnosis of complicated migraine, chronic tension-type headache, hypnic headache, hemicrania continua, new daily persistent headache, basilar, hemiplegic, or familial hemiplegic migraine
• Regular use (greater than 7 days) of prophylactic headache medication (any preventive medication or supplement with evidence of efficacy from at least 1 placebo-controlled trial) within 3 months, or onabotulinumtoxin A within 6 months prior to screening or during the 28 day period prior to randomization
• Cardiac surgery or cardiac symptoms within 3 months of screening and during the 28 day period prior to randomization
• Suspected or diagnosis of hypertension with or without antihypertensive treatment
• Any ongoing co-morbidity that in the opinion of the Investigator will interfere with the participation in the trial
• Body Mass Index (BMI) > 39 at screening
• Pregnant, breast-feeding, or planning to become pregnant during the trial
• Patients who have used opioids > 5 days for the treatment of pain in more than 2 of the 6 months prior to screening or in the 28 day period prior to randomization