Study of Sustained Benefit of AMG334 in Adult Episodic Migraine Patients

Inclusion Criteria:

   - Written informed consent must be obtained before any assessment is performed.

   - Adults greater than or equal to 18 years of age upon entry into screening.

   - Documented history of migraine (with or without aura) greater than or equal to 12
   months prior to screening according to the International Classification of Headache
   Disorders-3rd Edition (ICHD-3).

   - Greater than or equal to 4 and less than 15 days per month of migraine symptoms (based
   on ICHD-3 criteria) on average across 3 months prior to screening based on
   retrospective reporting.

   - Less than 15 days per month of headache symptoms (i.e., migraine and non-migraine).

   - Subjects in need for switching by documented failure of 1 or 2 prophylactic treatments
   in the last 6 months due to either lack of efficacy or poor tolerability. For subjects
   with 1 prior treatment failure, the failure should have occurred in the last 6 months.
   For subjects with 2 prior treatment failures, the second treatment failure should have
   occurred in the last 6 months.

   - During baseline: Confirmed migraine frequency of 4 to 14 migraine days and less than
   15 days of headache symptoms.

   - During baseline: greater than or equal to 80% compliance with the headache diary.

Exclusion Criteria:

   - Subjects meeting any of the following criteria are not eligible for inclusion in this
   study.

      - Older than 50 years of age at migraine onset.

      - History of cluster headache or hemiplegic migraine headache.

      - Unable to differentiate migraine from other headaches.

      - Lack of efficacy or poor tolerability with greater than 2 treatments from the 7
      medication categories for prophylactic treatment of migraine after an adequate
      therapeutic trial.

   - Efficacy failure is defined as no meaningful reduction in headache frequency,
   duration, and/or severity after administration of the medication for at least 6 weeks
   at the generally accepted therapeutic dose(s) based on the investigator's assessment.

   - Tolerability failure is defined as documented discontinuation due to adverse events of
   the respective medication during the last 6 months prior to screening.

   - The following scenarios do not constitute lack of therapeutic response:

   - Lack of sustained response to a medication.

   - Patient decision to halt treatment due to improvement.

   - Used a prohibited medication from the 7 categories of prior prophylactic medications
   within 3 months prior to the start of and during baseline for a non-migraine
   indication if dose is not stable

   - Exposure to botulinum toxin in the head and/or neck region within 4 months.

   - Taken the following for any indication in any month during the 2 months prior to the
   start of the baseline period:

      - Ergotamines or triptans on greater than or equal to 10 days per month, or Simple
      analgesics (non-steroidal anti-inflammatory drugs [NSAIDs], acetaminophen) on
      greater than or equal to 15 days per month, or

      - Opioid- or butalbital-containing analgesics on greater than or equal to 4 days
      per month.

   - Device, or procedure that potentially may interfere with the intensity or number of
   migraine days within 2 months prior to the start of or during baseline.

   - History of major psychiatric disorders (such as schizophrenia or bipolar disorder) or
   current evidence of depression. Subjects with anxiety disorder and/or major depressive
   disorders are permitted in the study if they are considered by the investigator to be
   stable and are taking no more than 1 medication for each disorder. Subjects must have
   been on a stable dose within the 3 months prior to the start of the baseline period.

   - History of seizure disorder or other significant neurological conditions other than
   migraine. Note: a single childhood febrile seizure is not exclusionary.

   - History of malignancy of any organ system (other than localized basal cell carcinoma
   of the skin or in situ cervical cancer), treated or untreated, within the past 5
   years, regardless of whether there is evidence of local recurrence or metastases.

   - Human immunodeficiency virus (HIV) infection by history.

   - History or evidence of any other unstable or clinically significant medical condition
   or clinically significant vital sign, laboratory, or electrocardiogram (ECG)
   abnormality during that could pose a risk to subject safety or interfere with the
   study evaluation.

   - Myocardial infarction, stroke, transient ischemic attack, unstable angina, or coronary
   artery bypass surgery or other re-vascularization procedures within 6 months prior to
   screening.

   - Score "yes" on item 4 or item 5 of the Suicidal Ideation section of the C-SSRS, if
   this ideation occurred in the past 6 months, or "yes" on any item of the Suicidal
   Behavior section, except for the "Non-Suicidal Self-Injurious Behavior" (item also
   included in the Suicidal Behavior section), if this behavior occurred in the past 2
   years.

   - Evidence of drug or alcohol abuse or dependence, based on Investigator discretion
   within 12 months.

   - Pregnant or nursing (lactating) women.

   - Women of child-bearing potential must use contraception during dosing with study
   treatment.

   - Use of other investigational drugs within 5 half-lives of enrollment, or until the
   expected pharmacodynamic effect has returned to baseline, whichever is longer.

   - History of hypersensitivity to any of the study drugs or its excipients or to drugs of
   similar chemical classes.

   - Previous exposure to AMG334 or exposure to any other prophylactic CGRP-targeted
   therapy (prior to the study).