A Study to Assess the Efficacy and Safety of Empasiprubart Versus IVIg in Adults With Multifocal Motor Neuropathy

Inclusion Criteria: * Is at least 18 years of age and the local legal age of consent for clinical studies * Has a confirmed diagnosis of definite or probable MMN at screening according to the EFNS/PNS 2010 guidelines * Has responded to IVIg in the past 5 years. * Is receiving IVIg at a treatment interval of once every 2, 3, 4, or 5 weeks, and a dose of 0.4 to 2.0 g/kg body weight per cycle * Is receiving a maintenance regimen (no change in frequency, and no change in dose \>10%) of IVIg for at least 8 weeks before screening (or at least 10 weeks for participants receiving IVIg once every 5 weeks) * Minimum converted weekly IVIg dose of ≥0.125 g/kg * Has documented immunization against encapsulated bacterial pathogens (N meningitidis and S pneumoniae) within 5 years of screening or is willing to receive immunization at least 14 days before first study drug administration Exclusion Criteria: * Besides the indication under study, known autoimmune disease (eg, SLE) or any other medical condition that would confound the study results or put the participant at undue risk * Clinical signs or symptoms suggestive of neuropathies other than MMN, such as motor neuron disease (eg, bulbar signs, brisk reflexes) or other inflammatory neuropathies (eg, sensory neuropathy)