A Study of Nipocalimab in Children Aged 2 to Less Than 18 Years With Generalized Myasthenia Gravis

Change from baseline in total serum IgG levels were reported.

Number of participants with infectious AEs will be reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study.

Number of participants with SAEs will be reported. A SAE is any AE that results in: death, persistent or significant disability/incapacity, requires inpatient hospitalization or prolongation of existing hospitalization, is life-threatening experience, is a congenital anomaly/birth defect, is suspected transmission of any infectious agent via a medicinal product, is medically important to prevent one of the outcomes listed above.

Number of participants with AESIs will be reported. Treatment-emergent AEs associated with the following situations are considered an AESI: a) infections that are severe or require intravenous (IV) anti-infective or operative/invasive intervention; b) hypoalbuminemia with albumin less than (<)20 grams per liter (g/L) [<] 2.0 grams per deciliter [g/dL]) c) opportunistic infections and d) Serious and non-serious deep-vein thrombosis (DVT) and/or pulmonary embolism (PE). Any AE occurring at or after the initial administration of study intervention through end of study is treatment emergent.

Number of participants with abnormalities in clinical laboratory tests (including chemistry, hematology, coagulation, and urinalysis) will be reported.

Number of participants with abnormalities in vital signs including sitting pulse/heart rate, sitting systolic and diastolic blood pressure, and oral temperature (degrees Celsius) will be reported.

Number of participants with abnormalities in physical examinations including height, weight, assessments of the skin, head, eyes, ears, nose, throat, neck, thyroid, lungs, heart, abdomen, lymph nodes and extremities will be reported.

Serum samples will be analyzed to determine concentrations of nipocalimab using a validated, specific, and sensitive immunoassay method.

CL is defined as the volume of serum from which nipocalimab is completely removed per unit time.

V is defined as the representation of nipocalimab's propensity to either remain in the serum or redistribute to other tissue compartments.

t1/2 is defined as the time it takes for nipocalimab's active substance in the body to reduce by half.

Cpeak,ss is defined as the peak serum concentration of nipocalimab at steady state.

Ctrough,ss will be reported. It is defined as the observed serum concentration of nipocalimab just prior to the beginning of a dosing interval at steady state.

AUCss is defined as the area under the curve for nipocalimab at steady state.

Change from baseline in MG-ADL score will be reported. The MG-ADL score provides a rapid assessment of the participant's myasthenia gravis (MG) symptom severity. Eight functions (talking, chewing, swallowing, breathing, impairment of ability to brush teeth or comb hair, impairment of ability to arise from a chair, double vision, eyelid droop) are rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). The total score will be sum of eight function scores and can range from 0 to 24. A higher score indicates greater symptom severity.

The QMG score is a standardized quantitative strength assessment comprising 13 components (and is administered by a trained qualified healthcare professional [HCP] eg, physician, physician assistant, nurse practitioner, nurse). The quantitative results of each strength component are mapped to the following 4-point scale: 0 equals to (=) none, 1 = mild, 2 = moderate and 3 = severe. The total score will be sum of 13 components scores and can range from 0 to 39. A higher score indicates greater weakness.

The EQ-5D-Y is a standardized child friendly instrument for use as a measure of health status, primarily designed for self-completion by children and adolescents, or via a proxy version to be completed by the child's caregiver. The EQ-5D-Y descriptive system comprises the following 5 dimensions: Mobility, looking after myself (washing and dressing), usual activities, pain or discomfort and feeling worried or unhappy. Each of the 5 dimensions is divided into 3 levels of perceived problems (Level 1 indicating no problem, Level 2 indicating some problems, Level 3 a lot of problems).

The Neuro-QoL pediatric fatigue score will be used to assess the impact of fatigue in participants aged 10 to less than (<) 18 years. The participant will rate each of the 11 items on a 5-point scale. Higher scores indicate greater fatigue.

The PGI-S score will be used to assess the severity of fatigue due to generalized myasthenia gravis (gMG) in participants aged 10 to < 18 years. Participants will be asked to rate their fatigue over the past 7 days using the following 5-point scale: 1 = None, 2 = Mild, 3 = Moderate, 4 = Severe, and 5 = Very severe. Higher scores indicate greater severity of fatigue.

The PGI-C score will be used to assess if there has been an improvement or decline in patient-reported fatigue since the beginning of the treatment in participants aged 10 to <18 years. Participants will be asked to rate their current fatigue as compared to when they started the study, using the following 7-point scale: 1 = Much better, 2 = Moderately better, 3 = A little better, 4 = No change, 5 = A little worse, 6 = Moderately worse, and 7 = Much worse. Higher scores indicate greater change in overall fatigue.

Number of participants with ADAs to nipocalimab will be reported.

Number of participants with NAbs to nipocalimab will be reported.

Number of participants with vaccine antibody titers to diphtheria or tetanus will be reported.