This single-arm, dose-escalation exploratory trial evaluates the safety and efficacy of Allogeneic CAR-T (UCAR-T) cell therapy in patients with relapsed or refractory CD19+/BCMA+ hematologic malignancies, including those with minimal residual disease (MRD). Eligible patients will receive lymphodepletion followed by a single infusion of UCAR-T cells, either post-transplant or without transplantation depending on disease status. The trial assesses overall response and disease control rates, treatment-emergent adverse events, and in vivo behavior of UCAR-T cells.

This single-arm, dose-escalation exploratory trial evaluates the safety and efficacy of Allogeneic CAR-T (UCAR-T) cell therapy in patients with relapsed or refractory CD19+/BCMA+ hematologic malignancies, including those with minimal residual disease (MRD). Eligible patients will receive lymphodepletion followed by a single infusion of UCAR-T cells, either post-transplant or without transplantation depending on disease status.Primary endpoints include treatment-emergent adverse events (TEAEs) and dose-limiting toxicities (DLTs). Secondary endpoints include objective response rate (ORR), disease control rate (DCR), pharmacokinetics, and pharmacodynamics of UCAR-T. This study aims to provide initial evidence for the safety and anti-tumor activity of UCAR-T in CD19+/BCMA+ hematologic malignancies.

Inclusion Criteria

1. Voluntary participation with signed informed consent.

2. Pathologically confirmed CD19-positive and/or B-cell maturation antigen (BCMA)-positive hematologic malignancy according to the WHO 2017 classification, including but not limited to multiple myeloma, B-cell acute lymphoblastic leukemia (B-ALL), mature B-cell lymphomas, and plasmablastic lymphoma.

3. Relapsed/refractory disease defined as failure to achieve complete remission after standard therapy, or relapse after an initial response during treatment or follow-up.

4. Measurable disease required:

   1. For B-ALL: persistent minimal residual disease (MRD) positivity despite hematologic remission.
   2. For lymphoma: at least one measurable lesion ≥1.5 cm in longest diameter per IWG revised criteria.
   3. For multiple myeloma: positive immunofixation electrophoresis or presence of extramedullary disease.

5. Age ≥18 years; both sexes eligible.

6. Expected survival ≥12 weeks.

7. Adequate organ function (exceptions for disease-related impairment are at the investigator's discretion):

   1. Total bilirubin <2× upper limit of normal (ULN); serum creatinine \