An adverse event (AE) is defined as any untoward medical occurrence in a patient or clinical investigation participant administered a pharmaceutical product which does not necessarily have a causal relationship with this treatment. The investigator assesses the relationship of each event to the use of study drug. A serious adverse event (SAE) is an event that results in death, is life-threatening, requires or prolongs hospitalization, results in a congenital anomaly, persistent or significant disability/incapacity or is an important medical event that, based on medical judgment, may jeopardize the participant and may require medical or surgical intervention to prevent any of the outcomes listed above. Treatment-emergent adverse events/treatment-emergent serious adverse events (TEAEs/TESAEs) are defined as any event that began or worsened in severity on or after the first dose of study drug.

Safety population included all participants who received at least 1 dose of atogepant in this extension study.

Clinical laboratory test values are considered PCS if they meet either the lower-limit or higher-limit PCS criteria defined in the categories below. Percentage of participants with PCS laboratory values are summarized for chemistry, hematology, and urinalysis. Only those categories where at least 1 person had a non-PCS value at Baseline and met the PCS criterion at least once during post-baseline are reported.

Safety population included all participants who received at least 1 dose of atogepant in this extension study. Number analyzed are participants with data available for analyses of the specific category.

12-lead ECGs were performed at select study visits. Only those categories where at least 1 person had a non-PCS value at Baseline and met the PCS criterion at least once during postbaseline are reported.

Safety population included all participants who received at least 1 dose of atogepant in this extension study.

PCS postbaseline vital sign values are summarized for categories: systolic and diastolic blood pressures [sitting and standing], pulse rate [sitting and standing], respiratory rate, temperature, weight. Only those categories where at least 1 person had a non-PCS value at Baseline and met the PCS criterion at least once during postbaseline are reported.

Safety population included all participants who received at least 1 dose of atogepant in this extension study. Number analyzed are participants with data available for analyses of the specific category.

C-SSRS is a clinician-rated instrument that reports the severity of both suicidal ideation and behavior. Suicidal ideation is classified on a 5-item scale: 1 (wish to be dead), 2 (nonspecific active suicidal thoughts), 3 (active suicidal ideation with any methods [not plan] without intent to act), 4 (active suicidal ideation with some intent to act, without specific plan), and 5 (active suicidal ideation with specific plan and intent). Suicidal behavior is classified on a 5-item scale: 0 (no suicidal behavior), 1 (preparatory acts or behavior), 2 (aborted attempt), 3 (interrupted attempt), and 4 (actual attempt). More than 1 classification can be selected provided they represent separate episodes. Suicidal ideation: Minimum total score 1, maximum total score 5; higher total scores indicate more suicidal ideation. Suicidal behavior: Minimum total score 0, maximum total score 4; higher total scores indicate more suicidal behavior.

Safety population included all participants who received at least 1 dose of atogepant in this extension study. One Safety population was used for the entire study. If participants were eligible for the Safety Follow-up they were included in the analyses even if they did not participate in the Safety Follow-up Period.