Inclusion Criteria:

- Participant must be ≥ 18 to ≤ 89 years of age, at the time of signing the informed consent

- Confirmed diagnosis of MOG-AD consistent with published diagnostic criteria for MOG-AD

- Participant has history of relapsing MOG-AD with at least 1 documented relapse over the last 12 months and a documented positive serum MOG Ab test using a cell-based assay (CBA) within 6 months prior to randomization

- Participant must be clinically stable at the time of the Screening Visit and during the Screening Period

Exclusion Criteria:

- Participant has been diagnosed with a neurological autoimmune disease (including multiple sclerosis (MS) and aquaporin-4 positive neuromyelitis optica spectrum disorder (NMOSD)), or a systemic autoimmune disease that in the opinion of the investigator can interfere with the safety of the participant

- Participant has a clinically important active infection (including unresolved or not adequately treated infection) as assessed by the investigator

- Participant has a current or medical history of primary immunodeficiency

- Participant tests positive for aquaporin-4 antibodies at Screening

- Participant has a serum total IgG level ≤ 5.5g/L

- Study participant has positive TB test at the Screening Visit unless it is determined by a TB specialist that the positive result is related to an adequately treated latent TB infection).

Participant meets any of the following TB exclusion criteria:

• Known active TB disease;
• History of active TB involving any organ system unless adequately treated according to World Health Organization (WHO)/Centers for Disease Control and Prevention (CDC) therapeutic guidance and proven to be fully recovered upon consult with an appropriate specialist;
• Latent TB infection (LTBI) (unless appropriate treatment is initiated at least 4 weeks prior to IMP dosing and will be continued to completion). Tuberculosis preventive therapy should be in accordance with applicable clinical guidelines and appropriate specialist judgment.

- High risk of exposure to TB infection, as assessed by the investigator

- Current pulmonary nontuberculous mycobacterial (NTM) infection or history of pulmonary NTM infection unless proven to be fully recovered. For further information relating to definitions of known active TB, past history of TB, LTBI, high risk of acquiring TB infection and NTM infection, see Appendix 12, Section 10.12.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 12/7/23. Questions regarding updates should be directed to the study team contact.