BCMA CAR-T for Dynamic High-risk Multiple Myeloma

Inclusion Criteria: 1. Be informed and voluntarily sign the Informed Consent Form (ICF). 2. Age between 18 and 75 years (inclusive). 3. Have measurable disease meeting at least one of the following criteria: Serum M-protein ≥1 g/dL (\>10 g/L) as detected by serum protein electrophoresis (SPEP), or quantifiable IgA or IgD levels for IgA or IgD-type myeloma; Urine M-protein ≥200 mg/24 hours; In cases where serum and urine M-protein do not meet the above thresholds, an abnormal free light chain (FLC) ratio (normal range: 0.26 to 1.65) and involved serum FLC ≥100 mg/L. 4. Have received only one line of standard anti-myeloma therapy, including: Induction therapy with at least one proteasome inhibitor, one immunomodulatory agent, and corticosteroids; Sequential autologous hematopoietic stem cell transplantation or consolidation therapy; Maintenance therapy based on either a proteasome inhibitor or an immunomodulatory agent. 5. Meet at least one of the following dynamic high-risk criteria: Early relapse: Disease progression or relapse within 18 months of starting first-line therapy, including progression or relapse within 12 months post-autologous hematopoietic stem cell transplantation; Primary refractory disease: Failure to achieve at least minimal response (MR) after four cycles of induction therapy; Relapse with new genetic abnormalities: Gain(1q), del(17p), or TP53 mutation. 6. Confirmed expression of the BCMA target antigen on MM cells by flow cytometry or bone marrow immunohistochemistry. Exclusion Criteria: 1. Primary plasma cell leukemia. 2. Concurrent amyloidosis. 3. Involvement of the central nervous system (CNS). 4. Previous treatment with BCMA-targeted therapy or CAR-T cell therapy. 5. Disease progression or relapse within 3 months of autologous hematopoietic stem cell transplantation.