A Study to Investigate the Efficacy, Safety and Tolerability of Remibrutinib Versus Placebo in Adult Patients With Generalized Myasthenia Gravis

This study is a randomized, double-blind, placebo-controlled, multicenter, Phase III study, to evaluate the efficacy, safety and tolerability of remibrutinib in gMG patients who are on stable SOC treatment. Approximately 180 eligible participants will be randomized in a ratio of 1:1, to receive either remibrutinib or matching placebo.

The study consists of a Core Part (6-months double-blind treatment) and an Extension Part (up to 60-month open-label treatment).

Primary Outcome Measures

1. Change from baseline to Month 6 in Myasthenia Gravis Activity of Daily Living (MG-ADL) total score
   The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24).

Secondary Outcome Measures

1. Change from baseline to Month 6 in Quantitative Myasthenia Gravis (QMG) total score
   The Quantitative Myasthenia Gravis (QMG) Score is a 13-item direct physician assessment scoring system that quantifies disease severity, based on impairments of body functions and structures. The total QMG score ranges from 0 to 39, where higher scores indicated greater disease severity. The QMG score is composed of the following items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item) and respiratory (1 item).
2. Proportion of participants with ≥ 5 points reduction from baseline to Month 6 of QMG total score without rescue medication and/or strongly confounding prohibited medication
   The Quantitative Myasthenia Gravis (QMG) Score is a 13-item direct physician assessment scoring system that quantifies disease severity, based on impairments of body functions and structures. The total QMG score ranges from 0 to 39, where higher scores indicated greater disease severity. The QMG score is composed of the following items: ocular (2 items), facial (1 item), bulbar (2 items), gross motor (6 items), axial (1 item) and respiratory (1 item).
3. Proportion of participants with ≥ 3 points reduction from baseline to Month 6 of Myasthenia Gravis Activity of Daily Living (MG-ADL) scale total score without rescue medication and/or strongly confounding prohibited medication
   The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24).
4. Proportion of participants achieving Minimal Symptom Expression (MSE) at Month 6, defined as MG-ADL score of 0 or 1 at Month 6 without rescue therapy and/or strongly confounding prohibited medication
   The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24).
5. Change from baseline to Month 6 in Myasthenia Gravis Composite score (MGC) total score
   The MGC is a 10-item instrument that measures the symptoms and signs of MG based on physician examination and patient history. Items relate to ptosis, double vision, eye closure, talking, chewing, swallowing, breathing, neck flexion, shoulder abduction, and hip flexion. Each item is scored on an ordinal scale with 4 possible categories and weighted. The total score ranges from 0 to 50, where higher scores indicating more severe impairments.
6. Change from baseline to Month 6 in revised Myasthenia Gravis Quality of Life Questionnaire (MG-QOL15r) survey score
   The revised MG-QoL15 is a 15-item health related quality of life questionnaire completed by participants, designed to measure quality of life in gMG. Items on the MG-QoL15 relate to physical, social, and psychological components and are scored from 0 (not at all) to 2 (very much). The cumulative scores range from 0 to 30, with higher scores representing worse quality of life and dissatisfaction with MG-related dysfunction.
7. Incidence of adverse events
   Incidence of adverse events including changes in clinical laboratory values, vital signs, electrocardiograms and suicidality results qualifying and reported as AEs.
8. Proportion of time during which participants showed a reduction of ≥ 2 points in MG-ADL total score, that was maintained up to Month 6
   The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24).
9. Proportion of early MG-ADL responders during treatment (early responders with first MG-ADL improvement from baseline of ≥ 2 points occurring by week 4）
   The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24). Participants with a first MG-ADL improvement from baseline of ≥ 2 points occurring by week 4 are considered early responders.
10. Change from baseline to Month 6 in EuroQol-5 Dimensions-5 Level (EQ-5D-5L)
    The EQ-5D-5L is a widely used questionnaire designed to assess health status in adults. The measure is divided into two distinct sections, the descriptive system and the EQ visual analogue scale (EQ VAS). The first section includes one item addressing each of five dimensions (mobility, self-care, usual activity, pain/discomfort, and anxiety/depression). Participants rate each of these items from 1 of the 5 levels: no problems, slight problems, moderate problems, severe problems, or unable to/extreme. A composite health state is then defined by combining the levels for each dimension into a 5-digit number. The second section includes the EQ visual analogue scale (EQ VAS) that measures self-rated (global) health status utilizing a vertically oriented visual analogue scale where 100 represents the "best imaginable health state" and 0 represents the "worst imaginable health state." Respondents are asked to rate their current health by placing a mark along this continuum.
11. Proportion of participants achieving a reduction from baseline of ≥ 3 points in MGC total score at Month 6
    The MGC is a 10-item instrument that measures the symptoms and signs of MG based on physician examination and patient history. Items relate to ptosis, double vision, eye closure, talking, chewing, swallowing, breathing, neck flexion, shoulder abduction, and hip flexion. Each item is scored on an ordinal scale with 4 possible categories and weighted. The total score ranges from 0 to 50, where higher scores indicating more severe impairments.
12. Change from baseline in MG-ADL total score
    The MG-ADL is a categorical scale that assesses MG symptoms and their effects on daily activities. MG-ADL is composed of items related to patient's assessment of functional disability secondary to ocular (2 items), bulbar (3 items), respiratory (1 item), and gross motor or limb (2 items) impairment related to effects from MG. Each item is assessed on a 4-points scale where a score 0 represents normal function and a score 3 represents loss of ability to perform that function (total score 0 to 24).
13. Proportion of participants achieving a reduction from core part in oral corticosteroids (OCS) dose till the end of extension part
    Participants receiving oral corticosteroids are required to be on a stable dose for at least 4 weeks prior to baseline. The dose can be reduced or discontinued during the open label extension period at investigator discretion. Oral corticosteroids use will be recorded.
14. Incidence of adverse events
    Incidence of adverse events including changes in clinical laboratory values, vital signs, electrocardiograms and suicidality results qualifying and reported as AEs.