• 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