This study is to investigate the therapeutic efficacy and side effect of venetoclax based regimen for relapsed or refractroy T cell acute lymphoblastic leukemia.

Inclusion Criteria:

1. Patients aged ≥ 15 and ≤ 70 years.

2. Patients diagnosed with T-ALL/LBL according to 2017 WHO lymphoid malignant disease diagnosis standard.

3. Patients with T-ALL/LBL must meet one of the following criteria, A or B.

   A: Refractory T-ALL/LBL disease was defined as follows: Failure to achieve CR at the end of induction.

   B: Relapsed T-ALL/LBL disease was defined as follows: Reappearance of blasts in the blood or bone marrow (>5%) or in any extramedullary site after a CR.

4. ECOG performance status score less than 3.

5. Expected survival time >3 months.

6. Patients without serious heart, lung, liver, or kidney disease.

7. Ability to understand and voluntarily provide informed consent.

Exclusion Criteria:

1. Patients who are allergic to the study drug or drugs with similar chemical structures.
2. Pregnant or lactating women, and women of childbearing age who do not want to practice effective methods of contraception.
3. Active infection.
4. Active bleeding.
5. Patients with new thrombosis, embolism, cerebral hemorrhage, or other diseases or a medical history within one year before enrollment.
6. Patients with mental disorders or other conditions whereby informed consent cannot be obtained and where the requirements of the study treatment and procedures cannot be met.
7. Liver function abnormalities (total bilirubin > 1.5 times the upper limit of the normal range, ALT/AST > 2.5 times the upper limit of the normal range or patients with liver involvement whose ALT/AST > 1.5 times the upper limit of the normal range), or renal anomalies (serum creatinine > 1.5 times the upper limit of the normal value).
8. Patients with a history of clinically significant QTc interval prolongation (male > 450 ms; female > 470 ms), ventricular heart tachycardia and atrial fibrillation, II-degree heart block, myocardial infarction attack within one year before enrollment, and congestive heart failure, and patients with coronary heart disease who have clinical symptoms and requiring drug treatment.
9. Surgery on the main organs within the past six weeks.
10. Drug abuse or long-term alcohol abuse that would affect the evaluation results.
11. Patients who have received organ transplants (excepting bone marrow transplantation).
12. Patients not suitable for the study according to the investigator's assessment.