A migraine day was defined as a day with any of the following: A day (0:00 to 23:59) with at least 2 hours of headache with ≥2 migraine symptom(s) or day (0:00 to 23:59) demonstrating a headache treated with migraine medications (e.g., non-steroidal anti-inflammatory drugs [NSAIDs], paracetamol etc.), or a headache associated with aura. 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 electronic diary (e-diary) for 12-week period) * 28. Least square (LS) mean was calculated using analysis of covariance (ANCOVA). The full analysis set (FAS) included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments on primary endpoint. Efficacy analysis was planned to be collected and evaluated combined for both fremanezumab dose treatment groups.

The full analysis set (FAS) included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments 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. AEs were considered TEAEs if onset occurred on or after the first dose date. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug.

The number of participants with a shift from Baseline (Normal, Abnormal CS [Clinically Significant], or Abnormal NCS [Not Clinically Significant]) in any of the following ECG parameters is reported by treatment group: Heart rate, PR interval, QRS interval, RR interval, QT interval, QT interval corrected using the Bazett's formula (QTcB), and QT interval corrected using the Fridericia formula (QTcF). Last assessment was defined as the last observed postbaseline interpretation. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug.

The number of participants with a shift from Baseline (Normal or Abnormal) in any of the following ECG parameters is reported by treatment group: Heart rate, PR interval, QRS interval, RR interval, QT interval, QTcB, and QTcF. Last assessment was defined as the last observed postbaseline interpretation. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug.

Potentially clinically significant abnormal vital signs findings included any one of the following: Pulse rate ≥120 beats per minute (bpm) and increase from baseline of ≥15 bpm, or ≤50 bpm and decrease from baseline of ≥15 bpm; Systolic blood pressure ≤85 millimeters of mercury (mmHg) and decrease from baseline of ≥20 mmHg; Diastolic blood pressure ≥100 mmHg and increase from baseline of ≥15 mmHg; Respiratory rate <15 breaths/minute. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug. Here, 'Overall number of participants analyzed' = participants with at least one Baseline and post-baseline vital sign assessment.

Serum chemistry tests with potentially clinically significant abnormal findings included: alanine aminotransferase (ALT) and aspartate aminotransferase (AST) both ≥2*upper limit of normal (ULN); and bilirubin ≥34.2 micromole/liter (umol/L). Hematology tests with potentially clinically significant abnormal findings included: hemoglobin ≤100 grams (g)/L, leukocytes ≤3*10^9 cells/L, neutrophils ≤1*10^9 cells/L, eosinophils/leukocytes ≥10%, and platelets ≥700*10^9 cells/L or ≤75*10^9 cells/L. Coagulation parameter test with potentially clinically significant abnormal findings included: prothrombin international normalized ratio (INR) >1.5. Urinalysis laboratory tests with potentially clinically significant abnormal findings included: urine protein ≥2 units (U) increase from baseline. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug. Here, 'Overall number of participants analyzed' and 'Number analyzed'= participants with at least one Baseline and post-baseline assessment of the specified laboratory parameters.

A complete physical examination included the following organ systems: general appearance; head, eyes, ears, nose, and throat (HEENT); chest and lungs; heart; abdomen; musculoskeletal; skin; lymph nodes; and neurological. Only the organ systems with abnormal physical findings in at least one treatment group have been reported. A summary of other non-serious AEs and all serious AEs, regardless of causality is located in Reported AE section.

The safety analysis set included all randomized participants who received at least 1 dose of study drug. Here, 'Overall number of participants analyzed' = participants with at least one Baseline and post-baseline physical examination.

C-SSRS is a questionnaire to assess suicidal ideation and suicidal behavior. Suicidal behavior was defined as a "yes" answer to any of 5 suicidal behavior questions: preparatory acts or behavior, aborted attempt, interrupted attempt, actual attempt, and completed suicide. Suicidal ideation was defined as a "yes" answer to any one of 5 suicidal ideation questions: wish to be dead, non-specific active suicidal thoughts, active suicidal ideation with methods without intent to act or some intent to act, without specific plan or with specific plan and intent, any self-injurious behavior with no suicidal intent.

The ITT analysis set included all randomized participants. Here, 'Overall number of participants analyzed' = participants with both Baseline and Month 3 assessment.

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 day with headache pain that lasted ≥2 hours with a peak severity of at least moderate severity or a day where the participant used acute medication (triptans, ergots, NSAIDs or paracetamol) to treat a headache of any severity or duration. 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. LS mean was calculated using ANCOVA.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments 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 that was accompanied by ≥1 migraine symptom(s) or a calendar day (0:00 to 23:59) demonstrating a headache of any duration that was treated with migraine specific medications (NSAIDs, paracetamol or 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.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments 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 triptans and ergot compounds, NSAIDs or paracetamol. 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. LS mean was calculated using ANCOVA.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

The PedMIDAS is a scale developed to assess headache-related disability which can be self-administered by the participant or administered by a caregiver. It has been validated in participants aged 4 to 18 years and includes 3 subscales: the impact of headache on school performance (range of scores 0-92), disability at home (range of scores 0-92), social/sport functioning (range of scores 0-92). The subscales are added to get the total score with a range 0 to 276. The total score was used for grading of disability, with 4 score categories of 0 to 10, 11 to 30, 31 to 50, and 51-276 interpreted as disability grades 1 (little or no disability), 2 (mild disability), 3 (moderate disability), and 4 (severe disability), respectively. Higher total scores indicated severe disability. LS mean was calculated using ANCOVA. The change from baseline score is reported with a range of -276 to 276 with higher scores indicating more severe disability.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

PedsQL 4.0 is a brief 23-item health-related quality of life (QoL) instrument that evaluates QoL in 4 areas of functioning: physical, emotional, social, and school functioning. For child and adolescent self-report (8 - 18 years) and parent report forms, respondents used a 5-point Likert scale to rate item severity (0=never a problem;1=almost never a problem; 2=sometimes a problem; 3=often a problem; 4=almost always a problem). For younger children (5 - 7 years), a simplified 3-point Likert scale, anchored with a happy and a sad face, was used (0=not at all a problem; 2=sometimes a problem; 4=a lot of a problem). PedsQL yields a total QoL score and 2 summary scores: Physical Health Summary Score and Psychosocial Health Summary Score. To obtain scores, items were reverse scored, transformed to a 0 through 100 scale (0=100, 1=75, 2=50, 3=25, 4=0), and averaged; total scores near 0 indicated lower QoL, while scores approaching 100 indicated higher QoL. LS mean was calculated using ANCOVA.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments on the primary endpoint. Efficacy analysis was planned to be evaluated combined for both fremanezumab dose treatment groups.

Number of participants who developed ADAs were reported.

The FAS included all randomized participants who received at least 1 dose of study drug and had at least 10 days of diary entries postbaseline for efficacy assessments on the primary endpoint. Here, 'Overall number of participants analyzed' = Participants who had Baseline and at least 1 postbaseline ADA assessment.