Clinical Study on the Safety and Efficacy of PID23 Injection in Patients With Relapsed/Refractory Acute Leukemia

Inclusion Criteria: 1. Patient or legal guardian voluntarily signs the informed consent form (ICF), demonstrating understanding of the study purpose and procedures, and willingness to participate. 2. Age 3 to 75 years, inclusive, male or female. 3. Diagnosis of relapsed or refractory acute leukemia per guideline criteria: Relapsed: reappearance of leukemic cells in peripheral blood or bone marrow blasts ≥5% after achieving complete remission (CR); Refractory: failure to achieve CR after 2 courses of standard induction chemotherapy; relapse within 12 months after consolidation/intensification therapy; relapse after 12 months with no response to conventional chemotherapy; 2 or more relapses; extramedullary leukemia relapse or persistence; relapse after allogeneic hematopoietic stem cell transplantation. 4.Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2. 5.Life expectancy ≥12 weeks. 6.Bone marrow morphology showing ≥5% primitive/immature lymphocytes (blasts). 7.Tumor cells positive for CD19, BCMA, or CD70 expression by flow cytometry. 8.Adequate major organ function, defined as: 1. Cardiac: left ventricular ejection fraction (LVEF) ≥40% by echocardiogram; 2. Renal: serum creatinine ≤2.0× upper limit of normal (ULN), or creatinine clearance ≥50 mL/min (Cockcroft-Gault formula); 3. Hepatic: ALT and AST ≤3.0×ULN (≤5.0×ULN if with liver involvement); total bilirubin ≤2.0×ULN (≤3.0×ULN for Gilbert's syndrome); 4. Pulmonary: oxygen saturation ≥92% on room air; 5. Hematologic: absolute neutrophil count (ANC) ≥1.0×10⁹/L, platelets ≥50×10⁹/L, hemoglobin ≥80 g/L (with bone marrow involvement, ANC ≥0.5×10⁹/L, platelets ≥20×10⁹/L permitted) - assessments allowed after transfusion or hematopoietic growth factor support. 9\. For women of childbearing potential, negative serum pregnancy test; all participants agree to use reliable (non-rhythm) contraceptive methods from ICF signing through 1 year post-PID23 infusion. Exclusion Criteria: 1. Prior treatment with CAR-T or other genetically modified cell therapies, unless the investigator determines that safety risks have been adequately excluded. 2. Received the following anti-tumor therapies prior to PID23 infusion: Chemotherapy or molecular targeted therapy within 14 days or 5 half-lives (whichever is longer) (excluding conditioning chemotherapy and intrathecal chemotherapy; intrathecal therapy must be stopped ≥1 week prior to PID23 infusion); Radiotherapy to non-hematopoietic sites within 7 days; Radiotherapy to hematopoietic sites within 14 days. 3. Any of the following cardiac conditions: (1) New York Heart Association (NYHA) Class III or IV congestive heart failure; (2) Myocardial infarction or coronary artery bypass grafting (CABG) within 6 months prior to enrollment; (3) Clinically significant ventricular arrhythmia, or unexplained syncope (excluding vasovagal or dehydration-related); (3) History of severe non-ischemic cardiomyopathy. 4.Active or uncontrolled infection requiring systemic therapy within 1 week prior to screening. 5.Grade 2-4 acute graft-versus-host disease (GVHD) or moderate-to-severe chronic GVHD within 4 weeks prior to screening. 6.Cerebrovascular accident or seizure within 6 months prior to screening. 7.Deep vein or arterial thrombosis event within 6 months prior to screening. 8.Active malignancy other than acute leukemia (excluding: inactive disease with treatment completed \>2 years; adequately treated cervical carcinoma in situ, basal/squamous cell skin carcinoma, localized prostate cancer post-curative surgery, ductal carcinoma in situ post-curative surgery). 9.Received (attenuated) live vaccine within 4 weeks prior to screening. 10.Any other condition that, in the investigator's judgment, makes the patient unsuitable for participation in this study.