This study is a single-arm, prospective, single-center phase IIb clinical efficacy study evaluating the therapeutic effects of azacitidine and venetoclax in combination with granulocyte colony-stimulating factor for the treatment of newly diagnosed acute myeloid leukemia (AML).

Acute myeloid leukemia (AML) is a malignant disease originating from myeloid hematopoietic stem/progenitor cells. It is highly aggressive, and patients have a very low survival rate. The 5-year survival rate for diagnosed AML patients is approximately 29%, with only 5-15% for patients aged 60 and above. Currently, the 3+7 regimen is the first-line induction chemotherapy for newly diagnosed AML patients, with about 60-80% of young patients (\<60 years old) and 40-60% of elderly patients (≥60 years old) achieving complete remission (CR). However, among AML patients receiving the 3+7 regimen, those with poor physical condition or high-risk cytogenetics have a worse prognosis. Therefore, there is a need to explore new treatment regimens that are less intensive but still effective.

Venetoclax is an oral selective Bcl-2 inhibitor. Multiple studies and clinical trials have demonstrated that Venetoclax, in combination with demethylating agents or low-dose cytarabine (LDAC), has synergistic anti-tumor effects and achieves higher treatment response and disease-free survival rates in AML patients. The results of the VIALE-A study showed that the median overall survival (OS) time with Venetoclax plus Azacitidine (AZA) was 14.7 months compared to 9.6 months with Azacitidine alone (P\<0.001). The median duration of remission was 17.5 months with Venetoclax plus Azacitidine compared to 13.4 months with Azacitidine alone, and the CR+CRi rates were 66.4% and 28.3%, respectively (P\<0.001). This combination significantly improves the overall survival of AML patients, with high response rates and good safety profile. In October 2020, the U.S. Food and Drug Administration approved the use of Venetoclax in combination with Azacitidine, Decitabine, or LDAC for the treatment of newly diagnosed AML patients aged 75 years or older or those who are unfit for intensive induction chemotherapy due to comorbidities. The Venetoclax plus Azacitidine regimen was also included in the AML NCCN guidelines in 2020. However, while Venetoclax in combination with demethylating agents is recommended for the treatment of elderly AML patients, there is currently a lack of research data for its use in young AML patients. The results of a phase II clinical trial presented at the 2022 ASH Annual Meeting, evaluating Venetoclax plus hypomethylating agents in young adults with newly diagnosed AML and adverse ELN risk, showed a complete remission with incomplete hematologic recovery (CRc) rate of 78% after one cycle of treatment, with a minimal residual disease (MRD) negativity rate of 77%. After two cycles of treatment, the CRc rate was 91.9% with an MRD negativity rate of 82.3%. The CRc rates for favorable, intermediate, and adverse risk groups were 69.6%, 75.4%, and 61.3%, respectively. Although the combination of Venetoclax and demethylating agents has shown promising efficacy, there are still limitations such as adverse events including thrombocytopenia (46%), nausea (44%), constipation (43%), neutropenia (42%), febrile neutropenia (42%), diarrhea (41%), and tumor lysis syndrome (TLS), as well as suboptimal achievement of MRD negativity and depth of remission after induction therapy.

Granulocyte colony-stimulating factor (G-CSF) is expressed by almost all AML cells and binds to its receptor, G-CSFR. In pre-activation regimens, G-CSF induces tumor cells in the quiescent phase (G0/G1) to enter the proliferative phase (S phase), enhancing the cytotoxic effect of chemotherapy drugs on tumor cells, improving the efficacy of chemotherapy, and reducing adverse reactions. A study conducted by Tang Xiaowen's team at the First Affiliated Hospital of Soochow University on the efficacy and safety of decitabine (DAC) combined with HAAG in the treatment of newly diagnosed acute myeloid leukemia showed that after one cycle of DAC+HAAG induction therapy in 50 patients, 48 patients (96%) achieved complete remission (CR)/CR with incomplete blood count recovery (CRp)/CR with incomplete count recovery and incomplete marrow recovery (CRi), and 2 patients (4%) achieved partial remission (PR). The median time to recovery of white blood cell count, platelet count, and hemoglobin was 17.5 days, 19.0 days, and 20.0 days, respectively. Only 16% (8/50) and 6% (3/50) of patients experienced grade 3-4 infections and bleeding, while non-hematologic toxicities were mainly grade 1-2 and resolved after symptomatic treatment.

The combination of venetoclax and hypomethylating agents is the most common approach, which synergistically induces cell apoptosis and reduces MCL-1 levels, thereby overcoming resistance to BCL-2 inhibitors. Additionally, the combination interferes with the energy metabolism of leukemia cells and targets leukemia stem cells. However, there is currently no research on the combination of azacitidine, venetoclax, and G-CSF. The investigators has conducted a preliminary clinical study on the VAG regimen (azacitidine, venetoclax, and granulocyte colony-stimulating factor) for newly diagnosed AML, which has shown promising results. We plan to expand the sample size and further investigate its mechanism of tumor cell killing.