Demethylating Agents Combined With Venetoclax for High-risk T-cell Lymphoblastic Lymphoma/Leukemia Post-Transplant Relapse Prevention

Inclusion Criteria: * 1.14-55 years old, male,or female. * 2.Patients with allo-HSCT due to T-LBL/ALL, the donor type is not limited. * 3.ECOG score is 0-2 points. * 4.Blood routine: ANC ≥ 1.0 × 109/L, PLT ≥ 50 × 109/L. * 5.One of the following high-risk factors: * a. Age of initial diagnosis ≥ 35 years old. * b. Initial diagnosis of WBC ≥ 100 × 109/L. * c. Initial diagnosis of LDH exceeding the upper limit of normal values. * d. Initial diagnosis of bone marrow involvement (blast cells ≥ 5%). * e. Initial diagnosis of a bulky in the mediastinum (longest diameter ≥ 10cm). * f. ETP immunophenotype. * g. During the induction chemotherapy process, 2 courses did not achieve partial remission and/or 4 courses did not achieve complete remission. * h. Residual lesions before transplantation: Flow cytometry analysis showed that the proportion of abnormal lymphoid cells in the bone marrow was greater than 0.01%; Positive detection of minimal residual lesions in molecular biology; PET-CT scan shows that residual lesions are still active. * i. Based on the ELN recommendation based on adult T-ALL: gene mutations involving myeloid related genes, RAS/PI3K/AKT, JAK/STAT signaling pathway, and epigenetics, such as FLT3, NRAS/KRAS, PTEN, IL7R, JAK1, JAK3, DNMT3A, IDH1, IDH2; TP53, BCL2 mutations; t (8; 14) (q24; q11)/MYC rearrangement; t (7; 19) (q34; p13)/TCR-LYL1，TCR-MEF2C; del(5q) (q14). * j. High risk subgroups based on NGS definition: PI3K signaling pathway/NRAS, KRAS/TP53/IKZF1/DNTM3A/IDH1, IDH2 gene mutation with or without NOTCH1, FBXW7/PHF6/EP300 gene mutation. Exclusion Criteria： * 1.Central involvement during any course of the disease. * 2.Patients who have not achieved complete remission before transplantation. * 3.Identify those with available targeted drugs. * 4.For those who are resistant to BCL-2 inhibitors before transplantation, if the disease progresses during the application process, or if 3-4 courses of induction therapy containing BCL2 inhibitors do not improve. * 5.Individuals who are known to be allergic to demethylating drugs or venetoclax. * 6.Individuals with grade 2 or more degrees of active acute GVHD. * 7.Individuals with moderate to severe chronic GVHD. * 8.T-LBL/ALL relapse (flow cytometry abnormal lymphocyte cell proportion\>0.01%, WT1 positive, fusion gene positive, or extramedullary recurrence), or transplant rejection, bone marrow donor cell chimerism\<95%. * 9.Blood routine: ANC\<1.0 × 109/L or PLT\<50 × 109/L. * 10.Combined with severe organ dysfunction; The ratio of aspartate aminotransferase (AST)/alanine aminotransferase (ALT) is more than 3 times the normal value or the normal value of direct bilirubin is more than 3 times; The endogenous creatinine clearance rate (Ccr) is less than 50mL/min or 1.5 times the normal value of blood creatinine, regardless of whether hemodialysis treatment is used. * 11.Merge severe active infections. * 12.Pregnant or lactating women. * 13\. Accepting other investigational drugs. * 14.According to the researchers' assessment, the patient may have complications that could lead to other dangers.