CAR 70-BCMA CAR-T Cells for the Treatment of Relapsed or Refractory Plasma Cell Neoplasms

Inclusion Criteria: 1. The subject or their legally authorized representative has provided written informed consent and is willing and able to comply with scheduled visits, study treatment, laboratory tests, and other study procedures 2. Diagnosis of relapsed or refractory plasma cell neoplasms, defined as follows: * Clonal plasma cells positive for BCMA and/or CD70 expression as determined by flow cytometry or immunohistochemistry * Patients with multiple myeloma, plasmacytoma, or plasma cell leukemia who have received at least three prior lines of therapy, including a proteasome inhibitor (PI), an immunomodulatory agent (IMiD), and an anti-CD38 monoclonal antibody, and whose best response was less than partial response (PR) or who experienced disease progression after achieving at least PR * Patients with systemic light chain amyloidosis who have received at least two prior lines of therapy, including an anti-CD38 monoclonal antibody and either a proteasome inhibitor (PI) or an immunomodulatory agent (IMiD), and whose best response was less than partial response (PR) or who experienced disease progression after achieving at least PR 3. Aged 18 to 75 years (inclusive), male or female 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 5. Life expectancy greater than 3 months from the date of informed consent 6. Hemoglobin (HGB) ≥ 60 g/L (transfusion permitted) 7. Adequate hepatic, renal, cardiac, and pulmonary function meeting the following criteria: * Creatinine ≤ 2 × upper limit of normal (ULN) * Left ventricular ejection fraction (LVEF) ≥ 50% * Oxygen saturation \> 90% * Total bilirubin ≤ 1.5 × ULN; alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × ULN 8. The subject agrees to use contraceptive measures from the time of signing the informed consent form until 1 year after CAR-T cell infusion Exclusion Criteria: * Severe cardiac dysfunction with left ventricular ejection fraction (LVEF) \< 50% * History of severe pulmonary function impairment * Concurrent progressive malignancy * Concurrent severe infection that cannot be adequately controlled * Concurrent severe autoimmune disease or congenital immunodeficiency * Active hepatitis, defined as hepatitis B virus deoxyribonucleic acid (HBV-DNA) or hepatitis C virus ribonucleic acid (HCV-RNA) above the lower limit of detection * Human immunodeficiency virus (HIV) infection or known acquired immunodeficiency syndrome (AIDS), or syphilis infection * History of severe allergic reaction to biological products (including antibiotics) * Patients who have undergone allogeneic hematopoietic stem cell transplantation and still have acute graft-versus-host disease (GVHD) one month after discontinuation of immunosuppressive agents * Presence of any other serious physical or mental illness, or laboratory abnormality that may increase the risk of study participation, interfere with the interpretation of study results, or render the patient unsuitable for study enrollment in the opinion of the investigator * Female patients of childbearing potential who are pregnant or breastfeeding