Multifocal motor neuropathy (MMN) is a rare but serious chronic disorder that affects the nerves responsible for controlling muscle movement, mainly in the hands, forearms, and lower legs. Over time, it causes progressive muscle weakness that could eventually lead to considerable disability. This may result in irreversible functional impairment and fatigue, which often impacts a person’s physical health, psychological health, social life, and occupation.

*The investigational study drug has not been approved by any regulatory agency for use in MMN as efficacy and safety have not been established.

You may be eligible to participate if you:

• Have been diagnosed with MMN
• Are at least 18 years old
• Are not pregnant or actively trying to become pregnant
• Be willing to have close medical care and follow-up examinations throughout the study.
• Meet other criteria that the study staff will discuss with you

The study will be conducted in two parts, Part A and Part B.

In Part A, enrolled participants will be randomly assigned to two separate treatment groups to receive either:

•  Empasiprubart plus placebo IVIg, or
• IVIg plus placebo empasiprubart.

In Part B, all participants will receive empasiprubart.

Study Part A is blinded, meaning that neither the study participant nor the study team will know which study treatment the participant is receiving. Participants never receive placebo-only treatments. Placebos are always combined with either empasiprubart or IVIg. Enrolled participants will be asked to remain in the study for up to 49 months (nearly 4 years). During this period, study participants will need to visit the study site up to 48 times. This will include up to 15 weeks of screening, a 24-week treatment period (Part A), a 24-month open-label extension period (Part B), and a 15-month safety follow-up period after the last dose of the study drug is administered. The investigational study drug will be administered monthly, the IVIg treatment schedule will remain the same as the standard treatment routine the participant was on prior to starting the study. Both are given intravenously (in a vein in your arm).