A Study to Test How Safe Pozelimab and Cemdisiran Combination Therapy and Cemdisiran Alone Are and How Well They Work in Adult Patients With Generalized Myasthenia Gravis

Eligibility Criteria

• 1. Male or female patients ≥18 years of age at screening (or ≥ legal age of adulthood based on local regulations, whichever is older)
• 2. Patient with documented diagnosis of myasthenia gravis (MG) based on medical history and supported by previous evaluations as described in the protocol
• 3. Documented prior history of positive serologic test or a positive result during screening of anti-acetylcholine receptor (AChR) antibodies or anti-LRP4 antibodies.
• 4. Myasthenia Gravis Foundation of America (MGFA) Clinical Classification Class II to IVa at screening
• 5. Myasthenia Gravis-Activities of Daily Living (MG-ADL) score ≥6 at screening. Ocular items should not contribute more than 50% of MG-ADL total score as described in the protocol
• 6. Currently receiving an acetylcholinesterase inhibitor or documented reason for not using acetylcholinesterase inhibitor therapy per investigator
• 7. Currently receiving an immunosuppressive therapy (IST) for MG, or documented reason why the patient is not taking an IST per investigator
• 8. If currently receiving an IST, not anticipated to have IST dosage changed before randomization or during double-blind treatment period (DBTP).
• 9. Willing and able to comply with clinic visits and study-related procedures, including completion of the primary series of the meningococcal vaccinations required per protocol
• 1. Patients with antibody profile that is only positive for muscle specific tyrosine kinase (MuSK) (MuSK positivity is based on a documented prior history of positive serologic test for antibodies to MuSK or a positive result during screening
• 2. History of thymectomy within 12 months prior to screening or planned during the study
• 3. History of malignant thymoma (patients with stage 1 may be enrolled), or history of cancer within the past 5 years, except for adequately treated basal cell skin cancer, squamous cell skin cancer, or in situ cervical cancer
• 4. Myasthenic crisis or Myasthenia Gravis Foundation of America (MGFA) Class V within 1 month of screening
• 5. Not meeting meningococcal vaccination requirements and, at a minimum, documentation of quadrivalent meningococcal vaccination within 5 years prior to randomization and serotype B vaccine (when available) within 3 years prior to randomization as described in the protocol
• 6. Known contraindication to meningococcal vaccines (group ACWY conjugate and group B vaccines) as described in the protocol
• 7. Patients who require antibiotics for meningococcal prophylaxis and have a contraindication, warning, or precaution precluding the use of penicillin class and penicillin-alternative antibiotics planned to be used for prophylaxis, or a history of intolerance leading to the discontinuation of these antibiotics
• 8. Positive hepatitis B surface antigen or hepatitis C virus ribonucleic acid (RNA) during screening. NOTE: Cases with unclear interpretation should be discussed with the medical monitor
• 9. History of HIV infection or a positive test at screening per local requirements