• Percentage of participants achieving Myasthenia Gravis-Activities of Daily Living (MG-ADL) response at Visit 10 [ Time Frame: Visit 10 (Day 43) ]
  The total MG-ADL score is obtained by summing the responses to each individual item (8 items; Grades: 0, 1, 2, 3). The score ranges from 0 to 24, with a higher score indicating more disability.
• Change from Baseline to Day 43 (Visit 10) in Myasthenia Gravis-Composite (MG-C) score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The total Myasthenia Gravis-Composite (MG-C) score is obtained by summing the responses to each individual item (10 items; Grade:0-9 depending on item). The score ranges from 0 to 50, with lower scores indicating lower disease activity.
• Change from Baseline to Day 43 (Visit 10) in Quantitative Myasthenia Gravis (QMG) score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The total QMG score is obtained by summing the responses to each individual item (13 items; Responses: None=0, Mild=1, Moderate=2, Severe=3). The score ranges from 0 to 39, with lower scores indicating lower disease activity.
• Change from Baseline to Day 43 (Visit 10) in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Muscle Weakness Fatigability' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Change from Baseline to Day 43 (Visit 10) in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Physical Fatigue' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Change from Baseline to Day 43 (Visit 10) in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Bulbar Symptoms' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Occurrence of treatment-emergent adverse events (TEAEs) [ Time Frame: From Baseline until End of Study Visit (up to Week 14) ]
  An adverse event (AE) is any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. A treatment-emergent adverse event (TEAE) is defined as any event that was not present prior to the first administration of IMP or any unresolved event already present before the first administration of IMP that worsens in intensity following exposure to treatment.
• Treatment-emergent adverse events (TEAEs) leading to withdrawal of investigational medicinal product (IMP) [ Time Frame: From Baseline until End of Study Visit (up to Week 14) ]
  One of the secondary outcome measures is to assess safety and tolerability of the IMP in the MG patients. This can be measured by treatment-emergent adverse events (TEAEs) leading to withdrawal of IMP. A TEAE is defined as any event that was not present prior to the first administration of IMP or any unresolved event already present before the first administration of IMP that worsens in intensity following exposure to treatment.

• Percentage of participants achieving Myasthenia Gravis-Activities of Daily Living (MG-ADL) response at Visit 10 [ Time Frame: Visit 10 (Day 43) ]
• Change from Baseline to Visit 10 in Myasthenia Gravis-Composite score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The total Myasthenia Gravis(MG)-composite score is obtained by summing the responses to each individual item (10 items; Grade:0-9 depending on item). The score ranges from 0 to 50, with lower scores indicating lower disease activity.
• Change from Baseline to Visit 10 in Quantitative Myasthenia Gravis (QMG) score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The total QMG score is obtained by summing the responses to each individual item (13 items; Responses: None=0, Mild=1, Moderate=2, Severe=3). The score ranges from 0 to 39, with lower scores indicating lower disease activity.
• Change from Baseline to Visit 10 in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Fatigability' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Change from Baseline to Visit 10 in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Physical Fatigue, Limb and Axial Weakness' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Change from Baseline to Visit 10 in the Myasthenia Gravis (MG) Symptoms Patient Reported Outcome (PRO) 'Bulbar' score [ Time Frame: Baseline and Visit 10 (Day 43) ]
  The MG symptoms PRO instrument consists of 42 items across 5 scales: ocular symptoms (items 1-5); bulbar symptoms (items 6-15); respiratory symptoms (items 16-18); physical fatigue (items 19-33) and muscle weakness fatigability (items 34-42). The study participant will be asked to choose the response option that best describes the severity of ocular, bulbar, and respiratory symptoms over the past 7 days using a 4-point Likert scale ("none" to "severe") and how frequently they experience physical fatigue and muscle weakness fatigability over the past 7 days using a 5-point Likert scale ("none of the time" to "all of the time"), respectively.
• Occurrence of treatment-emergent adverse events (TEAEs) [ Time Frame: From Baseline until End of Study Visit (up to Week 14) ]
  An adverse event (AE) is any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. A treatment-emergent adverse event (TEAE) is defined as any event that was not present prior to the first administration of IMP or any unresolved event already present before the first administration of IMP that worsens in intensity following exposure to treatment.
• Treatment-emergent adverse events (TEAEs) leading to withdrawal of investigational medicinal product (IMP) [ Time Frame: From Baseline until End of Study Visit (up to Week 14) ]
  One of the secondary outcome measures is to assess safety and tolerability of the IMP in the MG patients. This can be measured by treatment-emergent adverse events (TEAEs) leading to withdrawal of IMP. A TEAE is defined as any event that was not present prior to the first administration of IMP or any unresolved event already present before the first administration of IMP that worsens in intensity following exposure to treatment.

• Drug: Rozanolixizumab
  Rozanolixizumab will be administered by subcutaneous infusion in dosage regimen 1 or 2.
  Other Name: UCB7665
• Other: Placebo
  Subjects will receive placebo at pre-specified time points.
  Other Name: PBO

• Experimental: Dosage Regimen 1
  Study participants randomized to dosage regimen 1 will receive assigned dosage of rozanolixizumab at pre-specified time points during Treatment Period.
  Intervention: Drug: Rozanolixizumab
• Experimental: Dosage Regimen 2
  Study participants randomized to dosage regimen 2 will receive assigned dosage of rozanolixizumab at pre-specified time points during Treatment Period.
  Intervention: Drug: Rozanolixizumab
• Placebo Comparator: Placebo
  Study participants randomized to this arm will receive placebo.
  Intervention: Other: Placebo

Inclusion Criteria:

• Study participant must be ≥18 years of age, at the time of signing the informed consent
• Study participant has documented diagnosis of generalized myasthenia gravis (gMG) at Visit 1, based on study participant's history and supported by previous evaluations
• Study participant has a confirmed positive record of autoantibodies against acetylcholine receptor (AChR) or muscle-specific kinase (MuSK) at Screening (Visit 1).The presence of autoantibodies may be confirmed with repeat testing at Visit 1
• Study participant has Myasthenia Gravis Foundation of America (MGFA) Class II to IVa at Visit 1
• Study participant with a Myasthenia Gravis-Activities of Daily Living (MG-ADL) score of at least 3 (with >3 points from non-ocular symptom) AND a quantitative myasthenia gravis (QMG) score of at least 11 at Visit 1 and at Baseline (Visit 2)
• Study participant is considered for additional treatment such as intravenous immunoglobulin g (IVIg) or plasma exchange (PEX) by the Investigator

Exclusion Criteria:

• Study participant has a known history of hyperprolinemia
• Study participant has a clinically relevant active infection (eg, sepsis, pneumonia, or abscess) in the opinion of the Investigator, or had a serious infection (resulting in hospitalization or requiring parenteral antibiotic treatment) within 6 weeks prior to the first dose of investigational medicinal product (IMP)
• Study participant with a known tuberculosis (TB) infection, at high risk of acquiring TB infection, or latent tuberculosis infection (LTBI), or current/history of nontuberculous mycobacterial infection (NTMBI) will be excluded
• Study participant has experienced hypersensitivity reaction after exposure to other anti-neonatal Fc receptor (FcRn) drugs
• Study participant with severe (defined as Grade 3 on the Myasthenia Gravis-Activities of Daily Living (MG-ADL) scale) weakness affecting oropharyngeal or respiratory muscles, or who has myasthenic crisis or impending crisis at Visit 1 or Visit 2
• Study participant has a history of a solid organ transplant or hematopoietic stem cell/marrow transplant