Inclusion criteria
1. Be a Japanese person.
2. The participant is male or female \>=18 years old at the time of screening.
3. Participant has a documented diagnosis of definite or probable CIDP (focal atypical CIDP and pure sensory atypical CIDP will be excluded) or definite or probable MMN, as confirmed by a neurologist specializing/experienced in neuromuscular diseases to be consistent with the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) 2010 criteria.
4. Participant has responded to IgG treatment in the past (partial or complete resolution of neurological symptoms and deficits), and must currently be on stable doses of IVIG treatment within the dose range equivalent to a cumulative monthly dose of 0.4 to 2.4 g/kg BW (inclusive) administered intravenously for at least 12 weeks prior to screening. The dosing interval of intravenous immunoglobulin (IVIG) treatment must be between 2 and 6 weeks (inclusive). Variations in the dosing interval of up to ±7 days or monthly dose amount of up to +or-20% between participant's pre-study IgG infusions are within acceptable limits.
5. CIDP participants only - INCAT disability score between 0 and 7 (inclusive). Participants with INCAT scores of 0, 1 (whether from upper or lower extremities), or 2 (if at least 1 point is from an upper extremity) at screening and/or baseline will be required to have a history of significant disability as defined by an INCAT disability score of 2 (must be exclusively from the lower extremities) or greater documented in the medical record. Participants will be eligible if one of the below eligibility criteria are met:
1. Screening and Baseline INCAT disability score between 3 and 7 inclusive.
2. Screening and/or Baseline INCAT disability score of 2 (both points are from lower extremities)
3. Screening and/or Baseline INCAT disability score of 2 (both points are not from lower extremities) AND has at least a score of 2 or greater documented in the medical record prior to screening. If a score was greater than 2 documented in the medical record prior to screening at least 2 points must be from lower extremities.
4. Screening and/or Baseline INCAT disability score of 0 or 1 AND has at least a score of 2 or greater (both from lower extremities) documented in the medical record prior to screening, at least 2 points must be from lower extremities.
6. If female of childbearing potential, the participant must have a negative pregnancy test at screening and agree to employ a highly effective contraceptive measure throughout the course of the study and for at least 30 days after the last administration of IP.
7. The participant is willing and able to sign an Informed Consent Form (ICF).
8. The participant is willing and able to comply with the requirements of the protocol.
Exclusion Criteria CIDP patients
1. Participants with focal atypical CIDP or pure sensory atypical CIDP or multifocal acquired demyelinating sensory and motor neuropathy (MADASAM).
2. Participants with any neuropathy of other causes, including:
1. Hereditary demyelinating neuropathies, such as hereditary sensory and motor neuropathy (HSMN) (Charcot-Marie-Tooth \[CMT\] disease), and hereditary sensory and autonomic neuropathies (HSANs).
2. Neuropathies secondary to infections, disorders, or systemic diseases such as Borrelia burgdorferi infection (Lyme disease), diphtheria, systemic lupus erythematosus, POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes) syndrome, osteosclerotic myeloma, diabetic and non-diabetic lumbosacral radiculoplexus neuropathy, lymphoma, and amyloidosis.
3. Multifocal motor neuropathy (MMN).
4. Drug-, biologic-, chemotherapy-, or toxin-induced peripheral neuropathy. MMN patients
3. Participant with other neuropathies (eg, diabetic, lead, porphyric or vasculitic neuropathy, chronic inflammatory demyelinating polyradiculoneuropathy, Lyme neuroborreliosis, post radiation neuropathy, hereditary neuropathy with liability to pressure palsies, CMT neuropathies, meningeal carcinomatosis).
CIDP/MMN Patients
4. Participant with immunoglobulin M (IgM) paraproteinemia, including IgM monoclonal gammopathy with high titer antibodies to myelin-associated glycoprotein.
5. Participant with presence of prominent sphincter disturbance.
6. Participant with any central demyelinating disorders such as multiple sclerosis.
7. Participant with any chronic or debilitating disease, or central nervous disorder that causes neurological symptoms or may interfere with assessment of endpoint measures, including (but not limited to) arthritis, stroke, Parkinson's disease, and diabetic peripheral neuropathy.
(Participants with clinically diagnosed diabetes mellitus who do not have diabetic peripheral neuropathy and who have adequate glycemic control with hemoglobin A1c \[HbA1c\] level of \<7.5% at screening will be eligible for the study, provided the electrodiagnostic criteria are consistent with the diagnosis of a definite or probable CIDP consistent with the EFNS/PNS 2010 criteria and the participant agrees to maintain adequate glycemic control.)
8. Participant with congestive heart failure (New York Heart Association \[NYHA\] class III/IV), unstable angina, unstable cardiac arrhythmias, or uncontrolled hypertension (defined as diastolic blood pressure \>100 mmHg and/or systolic blood pressure \>160 mmHg).
9. Participant with a history of deep vein thrombosis or thromboembolic events (eg, cerebrovascular accident, pulmonary embolism) within 12 months prior to screening.
10. Participant with condition(s) which could alter protein catabolism and/or IgG utilization (eg, protein-losing enteropathies, nephrotic syndrome).
11. Participant with a known history of chronic kidney disease, or glomerular filtration rate of \<60 mL/min/1.73m\^2 estimated based on the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation at the time of screening.
12. Participant with active malignancy requiring chemotherapy and/or radiotherapy, or history of malignancy with less than 2 years of complete remission prior to screening. Exceptions to this exclusion are: adequately treated basal cell or squamous cell carcinoma of the skin, carcinoma in situ of the cervix, and stable prostate cancer not requiring treatment.
13. Participant with clinically significant anemia that precludes repeated blood sampling during the study, or hemoglobin (Hgb) level of \<10.0 g/dL at the time of screening.
14. Participant with a known history of hypersensitivity or ARs such as urticaria, breathing difficulty, severe hypotension, or anaphylaxis following administration of human blood products such as human IgG, albumin, or other blood components.
(Clinically non-significant skin reactions, as per the investigator's and the sponsor medical monitor's discretion, do not meet this exclusion criterion. Clinically non-significant skin reactions may include local reactions to injection such as injection site's itching, redness, erythema, or swelling.)
15. Participant has a known allergy to hyaluronidase of human (including recombinant human hyaluronidase) or animal origin such as bee or wasp venom.
16. Participant with immunoglobulin A (IgA) deficiency and antibodies against IgA and a history of hypersensitivity.
17. Participant with an abnormal laboratory values at screening meeting any one of the following criteria:
1. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \>2.5 x upper limit of normal (ULN).
2. Platelet count \<100,000 cells/microL.
3. Absolute neutrophil count (ANC) \<1000 cells/microL.
18. Participant has a known history of or is positive at screening for one or more of the following: hepatitis B surface antigen (HBsAG), polymerase chain reaction (PCR) for hepatitis C virus (HCV), PCR for human immunodeficiency virus (HIV) Type 1/2.
19. Participant has received or is currently receiving treatment with immunomodulatory/immunosuppressive agents within 6 months prior to screening.
20. Participant has received or is currently receiving treatment with any corticosteroids dose within 8 weeks prior to screening, regardless of indication.
21. Participant has undergone PE within 3 months prior to screening.
22. Participant has any disorder or condition that in the investigator's judgment may impede the participant's participation in the study, pose increased risk to the participant, or confound the results of the study.
23. Participant is nursing or intends to begin nursing during the course of the study.
24. Participant has participated in another clinical study involving an IP or investigational device within 30 days prior to enrollment, or is scheduled to participate in another clinical study involving an IP or investigational device during the course of this study.
25. Participant is a family member or employee of the investigator.
26. Participants with known acquired or inherited thrombophilic disorders. These will include the specific types of acquired or inherited thrombophilic disorders that could put participants at risk of developing thrombotic events. Examples include a. Hereditary thrombophilia: i. Factor V Leiden mutation. ii. Prothrombin 20210A mutation. iii. Protein C deficiency. iv. Protein S deficiency. v. Anti-thrombin deficiency. b. Acquired thrombophilia: i. Anti-phospholipid antibody syndrome. ii. Activated protein C Resistance acquired. iii. Homocystinemia.
