A migraine day was defined as a calendar day where the participant reported either of the following: A calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for migraine with or without aura or; a calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for probable migraine, a migraine subtype where only 1 migraine criterion is missing; a calendar day (0:00 to 23:59) demonstrating a headache of any duration that was treated with migraine specific medications (triptans and ergot compounds). Monthly averages were derived and normalized to 28 days equivalent by formula: (number of days of efficacy variable over 12-week period/number of days with assessments recorded in e-diary for 12-week period) * 28. Least square (LS) mean was calculated using analysis of covariance (ANCOVA).

DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

A migraine day was defined as a calendar day where the participant reported either of the following: A calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for migraine with or without aura or; a calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for probable migraine, a migraine subtype where only 1 migraine criterion is missing; a calendar day (0:00 to 23:59) demonstrating a headache of any duration that was treated with migraine specific medications (triptans and ergot compounds). Monthly averages were derived and normalized to 28 days equivalent by formula: (number of days of efficacy variable over 4-week period/number of days with assessments recorded in e-diary for 4-week period) * 28.

DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

Participants recorded any headache medications (name of drug, number of tablets/capsules, and the dose in milligrams per tablet/capsule) taken each day in their electronic headache diary device. Acute headache medication included opioids, barbiturates, triptans, ergots, non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen and their combination products. Monthly averages were derived and normalized to 28 days equivalent by formula: (number of days of efficacy variable over 12-week period/number of days with assessments recorded in e-diary for 12-week period) * 28.

DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

A migraine day was defined as a calendar day where the participant reported either of the following: A calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for migraine with or without aura or; a calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of a headache meeting the criteria for probable migraine, a migraine subtype where only 1 migraine criterion is missing; a calendar day (0:00 to 23:59) demonstrating a headache of any duration that was treated with migraine specific medications (triptans and ergot compounds). Monthly averages were derived and normalized to 28 days equivalent by formula: (number of days of efficacy variable over 12-week period/number of days with assessments recorded in e-diary for 12-week period) * 28.

DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

A headache day of at least moderate severity was defined as a calendar day (00:00 to 23:59) where the participant reported either of the following: A calendar day (0:00 to 23:59) demonstrating at least 2 consecutive hours of headache of at least moderate severity; or a calendar day (0:00 to 23:59) demonstrating a headache of any duration that was treated with migraine-specific acute medications (triptans and ergot compounds). Monthly averages were derived and normalized to 28 days equivalent by formula: (number of days of efficacy variable over 12-week period/number of days with assessments recorded in e-diary for 12-week period) * 28.

DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

An adverse event (AE) was defined as any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. Serious AEs (SAEs) were defined as death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, a congenital anomaly or birth defect, or an important medical event that jeopardized participant and required medical intervention to prevent 1 of the outcomes listed in this definition. TEAEs were defined as AEs that occurred after the first dose of study drug was administered through end of the trial. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

DB safety analysis set included all randomized participants who received at least 1 dose of study drug during the DB treatment period.

An AE was defined as any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. SAEs were defined as death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, a congenital anomaly or birth defect, or an important medical event that jeopardized participant and required medical intervention to prevent 1 of the outcomes listed in this definition. TEAEs were defined as AEs that occurred after the first dose of study drug was administered through end of the trial. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

DB safety analysis set included all randomized participants who received at least 1 dose of study drug during the DB treatment period.

An AE was defined as any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. SAEs were defined as death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, a congenital anomaly or birth defect, or an important medical event that jeopardized participant and required medical intervention to prevent 1 of the outcomes listed in this definition. TEAEs were defined as AEs that occurred after the first dose of study drug was administered through end of the trial. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The OL safety analysis set included all participants who received at least 1 dose of study drug during the OL treatment period.

An AE was defined as any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. SAEs were defined as death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability or incapacity, a congenital anomaly or birth defect, or an important medical event that jeopardized participant and required medical intervention to prevent 1 of the outcomes listed in this definition. TEAEs were defined as AEs that occurred after the first dose of study drug was administered through end of the trial. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The OL safety analysis set included all participants who received at least 1 dose of study drug during the OL treatment period.

Concomitant medications included all medications taken while the participant was treated with the study drug. Any concomitant medication received by the participant for AEs was recorded on the case report form (CRF). Concomitant medications included: butalbital for migraine/headache, ergots for migraine/headache, NSAIDs for migraine/headache, NSAIDs for other reason than migraine/headache, opioids for migraine/headache, opioids for reasons other reason than migraine/headache, preventive medication as specified in the protocol for migraine/headache, preventive medication as specified in the protocol for other reason than migraine/headache, triptans for migraine/headache.

DB safety analysis set included all randomized participants who received at least 1 dose of study drug during the DB treatment period.

Concomitant medications included all medications taken while the participant was treated with the study drug. Any concomitant medication received by the participant for AEs was recorded on the case report form (CRF). Concomitant medications included: butalbital for migraine/headache, ergots for migraine/headache, NSAIDs for migraine/headache, NSAIDs for other reason than migraine/headache, opioids for migraine/headache, opioids for reasons other reason than migraine/headache, preventive medication as specified in the protocol for migraine/headache, preventive medication as specified in the protocol for other reason than migraine/headache, triptans for migraine/headache.

The OL safety analysis set included all participants who received at least 1 dose of study drug during the OL treatment period.

Participants who received fremanezumab were analyzed for ADA.

Participants who received fremanezumab were analyzed for ADA.