Radiation plus BCMA/CD3 bispecific antibody (CM336) for solitary bone plasmacytoma with mild marrow involvement

A Prospective Single-Arm Clinical Trial of Radiation Combined With BCMA/CD3 Bispecific Antibody Therapy for Solitary Bone Plasmacytoma With Mild Bone Marrow Infiltration

This will test whether adding the BCMA/CD3 bispecific antibody CM336 after radiotherapy can clear remaining cancer cells and lower the chance of progression in adults with solitary bone plasmacytoma and small amounts of bone marrow involvement.

Quick facts

• Phase: PHASE2
• Study type: Interventional
• Enrollment: 21 (estimated)
• Ages: 18 Years to 78 Years
• Sex: All
• Sponsor: Institute of Hematology & Blood Diseases Hospital, China (other)
• Drugs / interventions: CAR-T, chimeric antigen receptor, cyclophosphamide, radiation
• Locations: 1 site (Tianjin)
• Trial ID: NCT07115667 on ClinicalTrials.gov

What this trial studies

This is a prospective, single-arm, single-center Phase 2 study treating adults with solitary bone plasmacytoma and <10% clonal plasma cells in the marrow. Participants receive local radiotherapy followed by a planned 12-cycle course of the BCMA/CD3 bispecific antibody CM336. The study monitors safety, tolerability, and measures depth of disease clearance and markers of progression. The goal is to determine whether the addition of CM336 can eradicate residual clonal cells and reduce progression to multiple myeloma.

Who should consider this trial

Good fit: Adults (≥18) with histologically confirmed solitary bone plasmacytoma, less than 10% clonal plasma cells in bone marrow, ECOG 0–2, and no prior systemic anti-myeloma therapy are eligible.

Not a fit: Patients who have received prior systemic anti-plasma-cell therapies, have substantial marrow involvement, or have medical conditions making them unsuitable for the regimen are unlikely to benefit from this protocol.

Why it matters

Potential benefit: If successful, this approach could reduce progression to multiple myeloma and improve long-term disease control for high-risk solitary bone plasmacytoma patients.

How similar studies have performed: BCMA-targeted bispecific antibodies have shown promising activity in relapsed/refractory multiple myeloma, but combining a BCMA/CD3 bispecific with radiotherapy for solitary bone plasmacytoma is a novel approach with limited prior data.

Eligibility criteria

Inclusion Criteria:

* ≥18 years old
* Histologically confirmed SBP with \<10% clonal plasma cells in marrow
* ECOG ≤ 2
* No prior anti-myeloma therapy. Previous local radiotherapy for SBP is not an exclusion criterion.
* Meets laboratory and imaging criteria

Exclusion Criteria:

1. Patients who have previously received anti-plasma cell therapy, including melphalan, cyclophosphamide, proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, bispecific antibodies, or chimeric antigen receptor T-cell (CAR-T) therapy.
2. Any condition that, in the opinion of the investigator, would make the patient unsuitable for participation in this study.

Where this trial is running

Tianjin

• Institute of Hematology and Blood Diseases Hospital Chinese Academy of Medical Sciences — Tianjin, China (RECRUITING)

Study contacts

• Study coordinator: Gang An, MD

Conditions: Solitary Bone Plasmacytoma, Plasmacytoma of Bone, Plasma Cell Disorders, solitary bone plasmacytoma, BCMA/CD3 bispecific antibody