Testing TAK-411 for treating CIDP in adults

Key Inclusion Criteria

1. The participant is at least 18 years of age, inclusive, at the time of signing the Informed Consent Form (ICF).
2. The participant has a body weight of less than or equal to (\<=) 150 kilogram (kg).
3. The participant has a documented diagnosis of typical CIDP, as confirmed by a neurologist specializing/experienced in neuromuscular diseases and consistent with the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) 2021 criteria.
4. The participant has responded to IgG treatment in the past (documented partial or complete resolution of neurological symptoms and deficits).
5. The participant has had disease activation within 24 months before screening, as documented in medical records and in the opinion of the investigator, defined as one of the following:

   1. Clinically meaningful deterioration of symptoms on interruption or dose reduction of IgG treatment.
   2. Clinically meaningful deterioration of symptoms requiring IgG treatment dose increase with subsequent clinical improvement.
   3. Clinically meaningful deterioration of symptoms at the end of IgG treatment dose interval with improvement after next dose administration.
6. The participant is on a stable dose of immunoglobulin treatment intravenously (IGIV) treatment, (within the dose range of 0.4 to 2.4 grams per kilogram \[g/kg\] every 2 to 6 weeks \[inclusive\]). A stable dose is defined as no change greater than 10 percentage (%) in frequency or dose of IGIV therapy within the 3 months before and throughout screening.
7. The participant has an INCAT score between 0 and 7 (inclusive) at screening.

Key Exclusion Criteria

1. The participant has a documented diagnosis of a CIDP variant per EAN/PNS 2021 criteria.
2. The participant has any neuropathy of other causes, including the following:

   1. Hereditary demyelinating neuropathies, such as hereditary sensory and motor neuropathy, Charcot-Marie-Tooth disease, and hereditary sensory and autonomic neuropathies.
   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 nondiabetic lumbosacral radiculoplexus neuropathy, lymphoma, amyloidosis.
   3. Multifocal motor neuropathy.
   4. Drug-, biologic-, chemotherapy-, or toxin-induced peripheral neuropathy.
   5. Diabetic peripheral neuropathy.
3. The participant has any chronic or debilitating disease, or central nervous disorder that causes neurological symptoms or that may interfere with assessment of CIDP or outcome measures, including (but not limited to) multiple sclerosis, arthritis, stroke, and Parkinson's disease.
4. The participant is required to take or has taken either of the following for treatment of CIDP:

   1. Immunomodulatory/immunosuppressive agents (except IGIV) that include, but are not limited to, complement inhibitors, efgartigimod, and chemotherapeutic drugs, within 3 months or 5 half-lives, whichever is longer, of screening.
   2. B-cell affecting biologics (e.g. rituximab) within 6 months of screening.

   Note: Participants on a long-term, stable dosing regimen of certain immunomodulatory agents (eg, hydroxychloroquine) for any disease other than CIDP may be eligible, provided the dose regimen has been stable for 3 months before screening and is expected to remain stable throughout the study.
5. The participant has undergone plasma exchange within 3 months of screening.
6. The participant has a history of malignancy with less than 2 years of complete remission before screening, or active malignancy requiring chemotherapy and/or radiotherapy.

   Note: Participants with adequately treated basal cell or squamous cell carcinoma of the skin, carcinoma in situ of the cervix, or stable prostate cancer not requiring treatment are eligible.
7. The participant has experienced deep vein thrombosis or arterial thromboembolic events (example, cerebrovascular accident, pulmonary embolism) within 12 months of screening.
8. The participant has any medical condition, laboratory finding, or physical examination finding that precludes participation or with clinical evidence of any significant acute or chronic disease that, in the opinion of the investigator, may interfere with successful completion of the study or place the participant at undue medical risk.
9. The participant has participated in another clinical study involving an IP or investigational device within 30 days before screening or is scheduled to participate in another clinical study involving an IP or investigational device during the course of this study.