Hypomethylating Agent and Venetoclax After Allo-HSCT in Patients With High-risk Myeloid Malignancies.

Inclusion Criteria:

* Patients with AML or MDS and have received allogeneic hematopoietic cell transplantation;
* Patients with AML must have one of the following high-risk factors: Cytogenetics and molecular features consistent with adverse risk group by European LeukemiaNet classification for AML； require more than 2 courses of induction chemotherapy to reach complete remission； Extramedullary myeloid malignancy；≥CR2； Presence of measurable residual disease at the time of HSCT. \*
* Patients with MDS must have one of the following high-risk factors: IPSS-R scores are high-risk or very high-risk； Presence of TP53 mutation； Presence of measurable residual disease at the time of HSCT. \*
* CBC: ANC ≥ 1.0 × 10e9/L, Hb ≥ 80g/L, and PLT ≥ 50 × 10e9/L；
* Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2.

  * Presence of measurable residual disease at the time of HSCT is defined as the following: Blast percentage in bone marrow detected by flow cytometry ≥0.01%； Presence of fusion gene or mutated gene by qPCR.

Exclusion Criteria:

* Concurrent use of targeted drugs ;
* Resistant to Venetoclax before transplantation;
* Allergic to decitabine , Azacitidine or venetoclax;
* Active grade II or higher acute GVHD ;
* Active moderate or severe chronic GVHD ;
* Diseases recurrence (abnormal myeloid cells detected by flow cytometry \>0.01%, presence of WT1 or other genes, or extramedullary malignancy ), percentage of donor cells in bone marrow \<90% or graft rejection:
* CBC: ANC \< 1.0 × 10e9/L, or PLT \< 50 × 10e9/L；
* Severe organ dysfunction: Elevated Aspartate transaminase (AST) /alanine transaminase (ALT), or direct bilirubin \>3 times upper limit of normal; Creatinine clearance (Ccr)\<50mL/min or serum creatinine \>1.5 times upper limit of normal, whether hemodialysis treatment is performed;
* Active uncontrolled systemic fungal, bacterial, or viral infection
* Pregnant or lactating women;
* Other severe complications and not suitable judged by researchers.