This is a prospective, single-arm, investigator-initiated clinical trial evaluating the safety and efficacy of a BCMA/CD3 bispecific antibody (CM336) in patients with POEMS syndrome.

Inclusion Criteria:

1. Age ≥ 18 years.
2. Diagnosed with POEMS syndrome according to the 2025 Chinese Expert Consensus.
3. Deemed suitable for BCMA/CD3 bispecific antibody therapy by the investigator.
4. ECOG performance status 0-2.
5. Adequate organ function.
6. Provided written informed consent.

Exclusion Criteria:

1. Not meeting the diagnostic criteria for POEMS syndrome, including:

   • Chronic inflammatory demyelinating polyneuropathy (CIDP),
   • MGUS, multiple myeloma, amyloidosis, or other plasma cell disorders not meeting POEMS diagnostic criteria.

2. History of prior anti-plasma cell therapy, such as melphalan, cyclophosphamide, proteasome inhibitors, IMiDs, monoclonal antibodies, CAR-T, or bispecific antibodies (except:

   1. Immunosuppressants used for autoimmune neuropathy;
   2. Bisphosphonates used for bone disease;
   3. Topical or low-dose steroids ≤20 mg/day for rheumatic disease).

3. Investigator judges the patient unsuitable for BCMA/CD3 bispecific therapy (e.g., severe cardiopulmonary dysfunction).

4. Known allergy or intolerance to BCMA/CD3 bispecific antibody or any component.