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

Open to people ages 18 years and up

1. Male or female participants ≥18 years of age at screening (or ≥ legal age of adulthood based on local regulations, whichever is older)
2. Participant 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-Lipoprotein Receptor-related Protein 4 (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 participant 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
10. For the optional PK sub-study: Must have a Body Mass Index (BMI) ≥ 18.5 kg/m² and ≤ 30 kg/m² at screening

1. Participants 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 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. Participants 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 Human Immunodeficiency Virus (HIV) infection or a positive test at screening per local requirements

NOTE: Other protocol-defined Inclusion/ Exclusion Criteria apply