Study to Evaluate the Efficacy and Safety of AMG 301 in Migraine Prevention

A migraine day is any calendar day from the eDiary in which the participant experienced a migraine headache. A migraine headache is a headache with or without aura, lasting for >= 4 hours, and meeting >=1 of the criteria:

• >= 2 pain features (unilateral, throbbing, moderate to severe, exacerbated with exercise/physical activity)
• >= 1 symptoms (nausea and/or vomiting, photophobia and phonophobia) If the participant took a migraine-specific medication during aura or to treat headache, it was counted as a migraine day.

Days without eDiary data in each monthly interval are handled by proration.

Negative change from baseline values indicated improvement (i.e. fewer migraine days after treatment as compared to baseline).

Responders are participants who had at least a 50% reduction from baseline in monthly migraine days during the last 4 weeks of treatment in the 12-week double blind period.

Number of days on which acute headache medications (triptans and ergotamine-derivatives, alone or in combination) are used as recorded in eDiary. Monthly acute headache medication treatment days at baseline are the number of acute headache medication treatment days in the baseline period. Days without eDiary data are handled by proration.

Negative change from baseline values indicate improvement (i.e. fewer days requiring acute migraine-specific medications after treatment as compared to baseline).

Participants complete the MPFID every day during baseline (Days -28 to Day -1) and the 12-week Double Blind Treatment Period. The MPFID has 2 domains, Impact on Everyday Activities (7 items) and Physical Impairment (5 items), and 1 stand-alone global question that provides an assessment of the overall impact of migraine on participants' everyday activities. The recall period for each item is the past 24 hours.

The Physical Impairment Domain Score is reported here. A participant's response to the difficulty of the 5 physical impairment items is measured using a 5-point scale, with difficulty measurements ranging from 1 to 5. The sum was rescaled to a 0 to 100 scale, with 0=no difficulty and 100=unable to do (maximum burden). Negative change from baseline values indicate improvement in migraine impact.

Participants complete the MPFID every day during baseline (Days -28 to Day -1) and the 12-week Double Blind Treatment Period. The MPFID has 2 domains, Impact on Everyday Activities (7 items) and Physical Impairment (5 items), and 1 stand-alone global question that provides an assessment of the overall impact of migraine on participants' everyday activities. The recall period for each item is the past 24 hours.

The Impact on Everyday Activities Domain Score is reported here. A participant's response to the Impact on Everyday Activities 7 items is measured using a 5-point scale, with difficulty measurements ranging from 1 to 5. The sum was rescaled to a 0 to 100 scale, with 0=no difficulty and 100=unable to do (maximum burden). Negative change from baseline values indicate improvement in migraine impact.

Adverse events (AEs) were graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 4, where:

Grade 1 = Mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated; Grade 2 = Moderate; minimal, local or noninvasive intervention indicated; limiting age-appropriate instrumental activities of daily living (ADL); Grade 3 = Severe or medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; limiting self care ADL; Grade 4 = Life-threatening consequences; urgent intervention indicated Grade 5 = Death related to AE.

Hy's law predicts potential for drug-related hepatotoxicity. Hy's Law cases have three components:

• The drug causes hepatocellular injury, generally defined as an elevated alanine aminotransferase (ALT) or aspartate aminotransferase (AST) by 3-fold or greater above the upper limit of normal (ULN).
• Among participants showing such aminotransferase elevations, they also have elevation of their serum total bilirubin of greater than 2 times the ULN, without findings of cholestasis (defined as serum alkaline phosphatase activity less than 2 times the upper limit of normal).
• No other reason can be found to explain the combination of increased aminotransferase and serum total bilirubin, such as viral hepatitis, alcohol abuse, ischemia, preexisting liver disease, or another drug capable of causing the observed injury.

Aminotransferase tests included alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Percentage of participants with results that were greater than 3 * ULN for either test are reported.

Percentage of participants with total bilirubin results that were greater than 2 * ULN are reported.

Participant was expected to be in a supine position (or the most recumbent position possible) in a rested and calm state for at least 5 minutes before blood pressure assessments were conducted. Blood pressure units are millimeters of mercury (mmHg).

Participant was expected to be in a supine position (or the most recumbent position possible) in a rested and calm state for at least 5 minutes before blood pressure assessments were conducted. Blood pressure units are millimeters of mercury (mmHg).

Participant was expected to be in a supine position (or the most recumbent position possible) in a rested and calm state for at least 5 minutes before pulse assessments were conducted. Pulse rate units are beats per minute (BPM)

Participant was expected to be in a supine position (or the most recumbent position possible) in a rested and calm state for at least 5 minutes before vital sign assessments were conducted. Temperature units are reported in degrees Celsius (C).

Participant was expected to be in a supine position (or the most recumbent position possible) in a rested and calm state for at least 5 minutes before vital sign assessments were conducted. Respiratory rate (RR) is reported in breaths/minute.