A Study to Evaluate the Safety, Tolerability, Efficacy, Pharmacokinetics and Pharmacodynamics of M281 Administered to Adults With Generalized Myasthenia Gravis

An adverse event (AE) is any untoward medical event that occurs in a participant administered an investigational product and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. TEAE are defined as any AE occurring during or after the initiation of the first infusion of study drug.

An AE is any untoward medical event that occurs in a participant administered an investigational product and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. TEAEs are defined as any AE occurring during or after the initiation of the first infusion of study drug. An SAE is defined as any AE occurring at any dose that results in any of the following outcomes: death, life-threatening AE, hospitalization or prolongation of existing hospitalization, a persistent or significant disability/incapacity, or a congenital anomaly/birth defect.

An AE is any untoward medical event that occurs in a participant administered an investigational product and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. TEAEs are defined as any AE occurring during or after the initiation of the first infusion of study drug. For this study, any common terminology criteria for adverse events (CTCAE) Grade 3 or higher event of severe infection or hypoalbuminemia was considered as AESI.

The MG-ADL was used to assess the participant's MG symptom severity. It assesses 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, and eyelid droop) which were rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). The total score is the sum of the eight function scores and ranges from 0 to 24. Higher scores indicated greater symptom severity/difficulty in performing daily living activities.

Estimate of additional change from baseline in MG-ADL total score for every 10 percent (%) additional reduction in IgG based on a linear regression of change from baseline in MG-ADL total score on percent reduction in IgG at Day 57. The MG-ADL was used to assess the participant's MG symptom severity. It assesses 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, and eyelid droop) which were rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). The total score is the sum of the eight function scores and ranges from 0 to 24. Higher scores indicated greater symptom severity/difficulty in performing daily living activities.

Estimate of additional change from baseline in MG-ADL total score for every 10% additional reduction in IgG based on a linear regression of change from baseline in MG-ADL total score on percent reduction in IgG at Day 57 in anti-AChR positive participants. The MG-ADL was used to assess participant's MG symptom severity. It assesses 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, and eyelid droop) which were rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). Total score is sum of eight function scores and ranges from 0 to 24. Higher scores indicated greater symptom severity/difficulty in performing daily living activities.

Estimate of additional change from baseline in QMG total score for every 10% additional reduction in IgG based on a linear regression of change from baseline in QMG total score on percent reduction in IgG at Day 57. The QMG test was used to assess the participant's strength. The quantitative results of each of the 13 strength components were mapped to a 4-point scale where 0 equals to (=) none, 1= mild, 2= moderate and 3= severe. The total score is the sum of the 13 scale scores and ranges from 0 to 39. Higher scores indicated more severe impairment.

Estimate of additional change from baseline in QMG total score for every 10% additional reduction in IgG based on a linear regression of change from baseline in QMG total score on percent reduction in IgG at Day 57 in anti-AChR positive participants. The QMG test was used to assess the participant's strength. The quantitative results of each of the 13 strength components were mapped to a 4-point scale where 0 equals to (=) none, 1= mild, 2= moderate and 3= severe. The total score is the sum of the 13 scale scores and ranges from 0 to 39. Higher scores indicated more severe impairment.

The MG-ADL was used to assess the participant's MG symptom severity. It assesses 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, and eyelid droop) which were rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). The total score is the sum of the eight function scores and ranges from 0 to 24. Higher scores indicated greater symptom severity/difficulty in performing daily living activities.

The QMG test was used to assess the participant's strength. The quantitative results of each of the 13 strength components were mapped to a 4-point scale where 0 equals to (=) none, 1= mild, 2= moderate and 3= severe. The total score is the sum of the 13 scale scores and ranges from 0 to 39. Higher scores indicated more severe impairment.

The QMG test was used to assess the participant's strength. The quantitative results of each of the 13 strength components were mapped to a 4-point scale where 0 equals to (=) none, 1= mild, 2= moderate and 3= severe. The total score is the sum of the 13 scale scores and ranges from 0 to 39. Higher scores indicated more severe impairment.

The MG-QoL15r was used to assess the participant's limitations related to living with MG. Each of the 15 questions were rated by the participant on a 3-point scale (0= Not at all, 1= somewhat, 2=very much) based on a recall period of "over the past few weeks". The total score is the sum of the 15 question scores and ranges from 0 to 30. Higher scores indicated more limitation.

Change from baseline in total serum IgG was reported. Blood samples were collected for analysis of total serum IgG.

The MG-ADL was used to assess the participant's MG symptom severity. It assesses 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, and eyelid droop) which were rated on a 4-point scale: 0 (no impairment) to 3 (severe impairment). The total score is the sum of the eight function scores and ranges from 0 to 24. Higher scores indicated greater symptom severity/difficulty in performing daily living activities.

The QMG test was used to assess the participant's strength. The quantitative results of each of the 13 strength components were mapped to a 4-point scale where 0 equals to (=) none, 1= mild, 2= moderate and 3= severe. The total score is the sum of the 13 scale scores and ranges from 0 to 39. Higher scores indicated more severe impairment.

The MG-QoL15r was used to assess the participant's limitations related to living with MG. Each of the 15 questions were rated by the participant on a 3-point scale (0= Not at all, 1= somewhat, 2=very much) based on a recall period of "over the past few weeks". The total score is the sum of the 15 question scores and ranges from 0 to 30. Higher scores indicated more limitation.

The MGFA was used to assess the participant's MG severity. MGFA classification identifies the subgroup participants with MG who share distinct clinical features or severity of disease: Class I (ocular MG), classes II, III and IV generalized MG with mild, moderate and severe disease, respectively; Class V MG crisis. Separate subclasses under classes II, III and IV are designed: "a" if the predominant weakness is affecting limb/axial weakness or both; subclass "b" if the predominant weakness is affecting oropharyngeal or respiratory muscles or both. In the MGFA classification, lower roman numerals mean less severity. Changes in MGFA classification (regardless of subclass) are categorized as "Improved" (example, III to II), "Same" (example, II to II), or "Worsened" (example, II to III).

The MGFA was used to assess the participant's MG severity. MGFA classification identifies the subgroup participants with MG who share distinct clinical features or severity of disease: Class I (ocular MG), classes II, III and IV generalized MG with mild, moderate and severe disease, respectively; Class V MG crisis. Separate subclasses under classes II, III and IV are designed: "a" if the predominant weakness is affecting limb/axial weakness or both; subclass "b" if the predominant weakness is affecting oropharyngeal or respiratory muscles or both. In the MGFA classification, lower roman numerals mean less severity. Changes in MGFA classification (regardless of subclass) are categorized as "Improved" (example, III to II), "Same" (example, II to II), or "Worsened" (example, II to III).

Change from baseline in total serum IgG at Day 85 and Day 113 was analyzed. Blood samples were collected for analysis of total serum IgG.

Serum concentrations of nipocalimab were reported. Concentrations below the lowest quantifiable concentration (< LLOQ) that is <0.15 microgram/milliliter (mcg/mL) was treated as zero in calculating the summary statistics.