A Study to Test if Fremanezumab is Effective in Preventing Migraine in Children and Adolescents

Inclusion Criteria: Inclusion Criteria for Participants Rolling Over from the Pivotal Efficacy Studies (TV48125-CNS-30082 or TV48125-CNS-30083): * Participants have completed the pivotal efficacy study and, in the opinion of the Investigator or the Sponsor, are able to complete the study in a safe and compliant way. * Participants may continue with a stable dose/regimen of the preventive medication they were taking during the pivotal efficacy studies. * The participant continues to meet appropriate criteria carried forward from the pivotal efficacy study/ * The participant has received all recommended age-appropriate vaccines according to local standard of care and schedule. * The participant weighs at least 17.0 kg on the day of study enrollment. NOTE: Additional criteria apply; please contact the investigator for more information. Inclusion Criteria for Participants Rolling Over from the Phase 1 Pediatric Pharmacokinetic Study (Study TV48125-CNS-10141): * The participant/caregiver has demonstrated compliance with the electronic headache diary during the 28-day baseline period by entry of headache data on a minimum of 21 out of 28 days (approximately 75% diary compliance). * The participant has received all recommended age-appropriate vaccines according to local standard of care and schedule. * The participant weighs at least 17.0 kg on the day of study enrollment. * The participant has a body mass index ranging from the 5th to 120% of the 95th percentile, inclusive, on the day of study enrollment. * Not using preventive medications or using no more than 2 preventive medications for migraine or other medical condition, as long as the dose and regimen have been stable for at least 2 months prior to screening (visit 1). NOTE: Additional criteria apply; please contact the investigator for more information. Inclusion Criteria for Participants Rolling Over from the Pivotal Efficacy Studies (TV48125-CNS-30082 and TV48125-CNS-30083) for Safety and antidrug antibody (ADA) Assessment Only: • Participants may be included in this study if they sign and date the informed consent document or upon consent of a parent or guardian, if the participant is younger than the age of consent, accompanied by assent of the participant. Exclusion Criteria: Exclusion Criteria for Participants Rolling Over from the Pivotal Efficacy Studies (TV48125-CNS-30082 or TV48125-CNS-30083): * In the judgment of the investigator, the participant has a clinically significant abnormal finding on study entry, including hematology, blood chemistry, coagulation tests, or urinalysis values/findings (abnormal tests may be repeated for confirmation). * The participant has a current history of a clinically significant psychiatric condition, at the discretion of the investigator. Any prior history of a suicide attempt, or a history of suicidal ideation with a specific plan within the past 2 years, must be excluded. * The participant has an ongoing infection or a known history of human immunodeficiency virus infection, tuberculosis, Lyme disease, or chronic hepatitis B or C, or a known active infection of coronavirus disease 2019 (COVID-19). * The participant has a history of hypersensitivity reactions to injected proteins, including mAbs, or a history of Stevens-Johnson Syndrome or toxic epidermal necrolysis syndrome, or the participant is concomitantly using lamotrigine. * The participant received a live attenuated vaccine (eg, intranasal flu vaccine, and measles, mumps, and rubella vaccine) within the 12-week period prior to screening. Note: If a medical need arises during the study, the participant may receive a live attenuated vaccine. * The participant is pregnant or nursing. * In the judgment of the investigator, the participant has an abnormal finding on the baseline 12-lead ECG considered clinically significant. * The participant has a current or past medical history of hemiplegic migraine. NOTE: Additional criteria apply; please contact the investigator for more information. Exclusion Criteria for Participants Rolling Over from the Phase 1 Pharmacokinetic Study (TV48125-CNS-10141): * The participant has any clinically significant cardiovascular (including congenital cardiac anomalies or thromboembolic events), endocrine, gastrointestinal, genitourinary, hematologic, hepatic, immunologic, neurologic, ophthalmic, pulmonary, renal disease, or complications of an infection, at the discretion of the investigator. * The participant has a current history of a clinically significant psychiatric condition, any prior history of a suicide attempt, or a history of suicidal ideation with a specific plan within the past 2 years, at the discretion of the investigator. * The participant has an ongoing infection or a known history of human immunodeficiency virus infection, tuberculosis, Lyme disease, or chronic hepatitis B or C, or a known active infection of coronavirus disease 2019 (COVID-19). * The participant has a history of hypersensitivity reactions to injected proteins, including mAbs, or a history of Stevens-Johnson Syndrome or toxic epidermal necrolysis syndrome, or the participant is concomitantly using lamotrigine. * The participant received a live attenuated vaccine (eg, intranasal flu vaccine, and measles, mumps, and rubella vaccine) within the 12-week period prior to screening. Note: If a medical need arises during the study, the participant may receive a live attenuated vaccine. * The participant is pregnant or nursing. * In the judgment of the investigator, the participant has an abnormal finding on the baseline 12-lead ECG considered clinically significant. * The participant has a current or past medical history of hemiplegic migraine. NOTE: Additional criteria apply; please contact the investigator for more information. Exclusion Criteria for Participants Rolling Over from the Pivotal Efficacy Studies (TV48125-CNS-30082 and TV48125-CNS-30083) for Safety and antidrug antibody (ADA) Assessment Only: Not Applicable