UTAA17 Injection in the Treatment of Relapsed/Refractory Multiple Myeloma

Inclusion Criteria: * All subjects or legal representatives must sign an informed consent form approved by the Ethics Committee in person before commencing any screening process. * ≥18 years old, regardless of gender, diagnosed with relapsed or refractory multiple myeloma according to the Efficacy Evaluation Criteria for multiple myeloma (IMWG), where relapsed or refractory is defined as: Multiple myeloma that has failed or relapsed after at least 3 lines of therapy (including proteasome inhibitor and immunomodulator-based chemotherapy regimen) in which induction chemotherapy, stem cell transplantation, and maintenance therapy given consecutively are considered a treatment regimen if no disease progression occurs during treatment. * The presence of measurable lesions at the time of screening will be determined according to any of the following criteria: 1. Monoclonal plasma cells in bone marrow ≥ 10%. 2. Serum monoclonal protein (M-protein) level ≥10 g/L. 3. Urinary M protein level ≥200 mg/24 hours. 4. Light chain multiple myeloma with no measurable lesions in serum or urine: serum immunoglobulin free light chain ≥10 mg/dL and abnormal serum immunoglobulin κb /γ free light chain ratio. 5. There are extramedullary lesions. * BCMA expression on the cell membrane is positive by flow cytometry and/or immunohistochemistry. * Patients were unable to undergo autologous hematopoietic stem cell transplantation or relapsed after autologous hematopoietic stem cell transplantation and were determined by the investigators to require treatment. * Patients who have previously received CAR T cell therapy should not be included until at least 3 months after the last CAR T cell infusion and no previously used CAR T cells are detectable in peripheral blood or bone marrow. * The ECOG score is 0 or 1. * Expected survival ≥12 weeks. * Subjects must have appropriate organ function and meet all of the following laboratory test results prior to enrollment 1. Blood routine: Absolute neutrophil count (ANC) \>0.75×10\^9 /L; Absolute lymphocyte count (ALC) ≥0.3×10\^9 /L; Platelet ≥50×10\^9 /L; Hemoglobin \>60 g/L 2. Liver function: alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5 × upper limit of normal (ULN); Serum total bilirubin ≤1.5×ULN, except patients with Gilbert syndrome (patients with Gilbert syndrome ≤3.0 times the upper limit of normal and direct bilirubin ≤1.5 times the upper limit of normal can be included) 3. Renal function: serum creatinine ≤2.5×ULN 4. Coagulation function: fibrinogen ≥ 1.0g /L; Activated partial thromboplastin time, activated partial thromboplastin time ≤1.5×ULN, and prothrombin time (PT) ≤1.5×ULN 5. Must have a minimum level of lung reserve, blood oxygen saturation \> 92% * Hemodynamically stable and left ventricular ejection fraction (LVEF) ≥ 50% as determined by echocardiography. Exclusion Criteria: * Patients who were determined by the investigators to require long-term immunosuppressant use during screening. * Cerebrovascular accident or convulsive attack occurred within 6 months before signing the informed consent. * Other malignancies other than MM, except carcinoma in situ. * Hepatitis B surface antigen (HBsAg) positive; Hepatitis B core antibody (HBcAb) positive and peripheral blood hepatitis B virus (HBV) DNA titer detection is not within the normal reference value range; Hepatitis C virus (HCV) antibody positive and peripheral blood hepatitis C virus (HCV) RNA positive; Human immunodeficiency virus (HIV) antibody positive; cytomegalovirus (CMV) DNA test positive; EBV virus DNA and herpes virus DNA positive test; Syphilis test positive. * Serious heart disease: including, but not limited to, unstable angina, myocardial infarction (within 6 months prior to screening), congestive heart failure (NYHA classification ≥III), and severe arrhythmia. * Unstable systemic disease, as determined by the investigator: including, but not limited to, severe liver, kidney, or metabolic disease requiring medical treatment. * There are chronic progressive neurological disorders. * Patients who have not yet recovered from the acute toxic effects of prior treatment. * Presence of active or uncontrolled infections that require systemic treatment (except for mild genitourinary and upper respiratory tract infections). * Female subjects who are capable of becoming pregnant and plan to become pregnant within 2 years after cell transfusion; Or a male subject whose partner plans to become pregnant within 2 years of cell transfusion. * The researchers assessed that there were other conditions that were not suitable for inclusion.