Overview

The main purpose of this study is to evaluate the safety and efficacy of nipocalimab compared to placebo in delaying relapse in adults with chronic inflammatory demyelinating polyneuropathy (CIDP) who initially respond to nipocalimab in Stage A.

Eligibility

Inclusion Criteria:

• Adults greater than or equal to (>=) 18 years of age at the time of consent and as applicable, must also meet the legal age of consent in the jurisdiction in which the study is taking place
• Diagnosed with Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) according to criteria of the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) 2021, progressing or relapsing forms. CIDP diagnosis to be adjudicated by independent committee during screening period
• Inflammatory Neuropathy Cause and Treatment (INCAT) disability score between 2 and 9 at the Run-In Baseline visit for participants entering Run-In, or Stage A Baseline visit for participants directly entering Stage A. Participants with an INCAT score of 2 at trial entry must have this score exclusively from the leg disability score
• Fulfilling any of the following treatment conditions: a) Currently treated with oral corticosteroids (CS) less than or equal to (<=) 20 milligrams (mg)/day; or b) Currently treated with pulsed CS, and/or intravenous immunoglobulin (IVIg) or subcutaneous immunoglobulin (SCIg) and the participant is willing to discontinue no later than the run-in baseline visit; or c) Currently treated with oral CS greater than (>) 20 mg/day and the participant is willing to taper to <=20 mg/day during the run-in period; or d) Without previous treatment (treatment naive); or treatment with CS and/or IVIg or SCIg discontinued at least 3 months prior to screening (untreated)
• Active disease as determined by CIDP Disease Activity Status (CDAS) score >= 3
• Other protocol-defined inclusion criteria will apply

Exclusion Criteria:

• Has a history of severe and/or uncontrolled hepatic (example, viral/alcoholic/autoimmune hepatitis/cirrhosis and/or metabolic liver disease), gastrointestinal, renal, pulmonary, cardiovascular, psychiatric, neurological or musculoskeletal disorder, hypertension and/or any other medical or uncontrolled autoimmune disorder(s) (example, diabetes mellitus) or clinically significant abnormalities in screening laboratory that, might interfere with the participants full participation in the study, or might jeopardize the safety of the participant or the validity of the study results
• Pure sensory CIDP or chronic immune sensory polyradiculopathy (CISP) (EAN/PNS definition)
• Any other disease that could better explain the participant's signs and symptoms, such as significant persisting neurological deficits from stroke or central nervous system (CNS) trauma or peripheral neuropathy from another cause such as connective tissue disease or systemic lupus erythematosus
• Polyneuropathy of other causes, including the following: Multifocal motor neuropathy (MMN); Monoclonal gammopathy of uncertain significance with antimyelin associated glycoprotein (anti-MAG) immunoglobulin M (IgM) antibodies; Hereditary motor neuropathy; Hereditary neuropathy with liability to pressure palsies (HNPP); Polyneuropathy, organomegaly, endocrinopathy, monoclonal protein and skin change syndromes; Lumbosacral radiculoplexus neuropathy; Polyneuropathy most likely due to diabetes mellitus; Polyneuropathy most likely due to systemic illnesses; Drug- or toxin-induced polyneuropathy Note: A concomitant polyneuropathy of other causes (example, a mild, stable diabetic polyneuropathy) is not necessarily exclusionary if chronic inflammatory demyelinating polyneuropathy (CIDP) is confirmed as the main diagnosis, as determined by the investigator and confirmed by the adjudication committee
• Has known allergies, hypersensitivity, or intolerance to nipocalimab or its excipients
• Other protocol-defined exclusion criteria will apply