A Clinical Study to Evaluate DNTH103 in Adults With Multifocal Motor Neuropathy

Inclusion Criteria: 1. Must have given written informed consent before any study-related activities are carried out 2. Adult males and females, 18 to 75 years of age (inclusive). 3. Weight range between 40 to 120 kilograms (kg). 4. Confirmed diagnosis of definite or probable MMN. 5. Evidence of: 1. Responsiveness to Ig treatment; and 2. Receiving a stable Ig regimen 6. Documented vaccinations against encapsulated bacteria in accordance with local requirements and vaccine availability. 7. Female participants must be of nonchildbearing potential or if of childbearing potential, must agree not to donate ova, not to attempt to become pregnant and, if engaging in sexual intercourse with a male partner, must agree to use a highly effective method of contraception. 8. Male participants must agree not to donate sperm and, if engaging in sexual intercourse with a female partner who could become pregnant, must agree to use an acceptable method of contraception or be surgically sterile for at least 90 days prior to Screening. Exclusion Criteria: 1. History or presence of significant medical/surgical condition including any acute illness or major surgery considered to be clinically significant or that could impact efficacy assessments. 2. Any coexisting conditions which may interfere with outcome assessments (eg, severe diabetic neuropathy). 3. Concurrent or previous use of rituximab, cyclophosphamide, mycophenolate mofetil, azathioprine, or cyclosporine. If a participant has previously used these medications, the last dose must be at least 6 months prior to randomization. 4. Currently or previously on complement inhibitors including in a clinical trial setting. 5. Prior history (at any time) of N. meningitidis infection. 6. Diagnosis of an autoimmune disorder other than MMN. 7. Positive test results for active human immunodeficiency virus (HIV-1 or HIV-2), hepatitis B surface antigen (HBsAg), or hepatitis C virus (HCV) antibodies during Screening. 8. History of active malignancy within 5 years prior to Screening, except basal cell carcinoma of the skin, curatively resected squamous cell carcinoma of the skin, cervical carcinoma in situ curatively treated or low-grade prostate adenocarcinoma for which appropriate management is observation alone. 9. Participation in another clinical study of an investigational drug within 90 days or 5 half-lives of the investigational agent (whichever is longer) prior to randomization (Day 1). 10. Any other overlapping condition for which the condition or treatment of the condition may affect the study assessments or outcomes. 11. Any other condition, including mental illness or prior therapy, that in the opinion of the Investigator would make the participant unsuitable for this study, including inability to cooperate fully with the requirements of the study protocol or likelihood of noncompliance with any study requirements.