The prognosis of acute leukaemias of ambiguous lineage is poor. The effect of chemotherapy regimen and hematopoietic stem cell transplantation are still unclear. Therefore, we will explore new therapy to improve the remission rate of acute leukaemias of ambiguous lineage. Venetoclax can significantly improve the remission rate and prolong PFS and OS. At present, venetoclax combined with azacitidine or decitabine has become the preferred treatment regimen for elderly AML patients. It also shows a high response rate in relapsed/refractory AML or MDS patients. There are few clinical studies on the treatment of ALAL. The purpose of this study is to explore the efficacy and safety of venetoclax combined with azacitidine in the treatment of newly diagnosed ALAL patients.

Inclusion Criteria:

1. Patients aged ≥ 15 years.
2. Patients diagnosed with ALAL according to 5th edition of WHO Acute Leukaemias of Ambiguous Lineage diagnosis standard.
3. New diagnosed patients.
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.