This is a single arm study to evaluate the safety and efficacy of CAR19BCMA CAR-T cells in the treatment of relapsed/refractory CD19/BCMA positive plasma cell neoplasms.

This study is an exploratory clinical trial of a single-arm, open, single-center treatment of CAR19BCMA CAR-T cell. 20 subjects with relapsed or refractory CD19/ BCMA positive positive plasma cell neoplasms will be enrolled and received CAR19BCMA CAR T cells injection therapy, and related data such as adverse reactions and therapeutic effects after medication were followed up. To evaluate its safety and efficacy

Inclusion Criteria:

1. Relapsed/refractory CD19BCMA positive plasma cell neoplasms must be assured and meet all of the following conditions:

   1.1 Confirmation for either BCMA or CD19 positivity using immunohistochemistry or flow cytometry.

   1.2 Patients with multiple myeloma, plasma cell carcinoma, and plasma cell leukemia who have received at least three 3 lines treatment (including anti-CD38 monoclonal antibodies, protease inhibitors, immunosuppressants, etc.) but have failed or experienced relapse.

   1.3 Patients with system light chain amyloidosis who have received at least 2 lines treatments in the past [anti-CD38 monoclonal antibody, proteasome inhibitor (PI), or immunomodulatory drug (IMiD)], but have failed or experienced relapse.

2. Age 18-75 years,

3. no gender restrictions;

4. ECOG score ≤ 2 points;

5. Expected survival period is not less than 3 months;

6. HGB≥60g/L;

7. Liver and kidney function and cardiopulmonary function meet the following requirements: (1) Creatinine ≤ 2× ULN; (2)left ventricular ejection fraction≥50%; (3) Oxygen saturation >90%; (4)Total bilirubin ≤1.5×ULN, ALT and AST≤2.5×ULN;

8. Participants agreed to use contraception from the time of informed consent until 1 year after CAR-T cell infusion.

Exclusion Criteria:

1. Severe heart failure with left ventricular ejection fraction <50%;
2. A history of severe lung function impairment; Combined with other advanced malignant tumors;
3. Complicated with severe infection that could not be effectively controlled;
4. Severe autoimmune disease or congenital immune deficiency;
5. Active viral hepatitis (defined as positive hepatitis B virus DNA [HBV-DNA] or hepatitis C virus RNA [HCV-RNA] detection, with test results exceeding the lower limit of quantification); Human immunodeficiency virus (HIV) infection or known acquired immunodeficiency syndrome (AIDS), or syphilis infection;
6. History of severe allergy to biological products (including antibiotics);
7. Allogeneic hematopoietic stem cell transplant patients who still have an acute graft-versus-host response (GVHD) one month after discontinuation of immunosuppressants;
8. Patients with other serious physical or mental illnesses or laboratory abnormalities that could increase the risk of participating in the study or interfere with the results of the study, and those who were deemed by the investigator to be unsuitable for participation in the study;
9. Female patients (those with fertility) are in pregnancy or lactation.