Immune recovery in tumor microenvironment of TP53-mutated AML following venetoclax combination therapy

The BCL-2 inhibitor venetoclax combined with the hypomethylating agent azacitidine or with low-dose cytarabine significantly improves response rates and overall survival (OS) for newly diagnosed unfit and relapsed / refractory (R/R) acute myeloid leukemia (AML) patients. We retrospectively analyzed our experience with venetoclax combination therapy in 41 unfit AML patients (23 untreated, 18 R/R). Overall response rates were 78.3% for untreated patients and 61.1% for R/R patients. TP53 alterations were observed in 13 patients (31.7%) and were identified as an independent predictor of poor outcome (p=0.0008). We further conducted single-cell RNA sequencing in bone marrow, sampled before and after venetoclax and azacitidine treatment, of three TP53-mutated AML patients who achieved complete remission (CR) or CR with incomplete hematologic recovery. After treatment, numbers of cells expressing anti-apoptotic genes such as BCL2 and MCL1 decreased. CD4 T cells, cytotoxic CD8 T cells, and NK cells significantly increased both in number and in levels of gene expression associated with cytotoxicity post-treatment, confirming immune recovery in the tumor microenvironment. Residual AML cells expressed CD47 and CLEC12A (CLL1). These results indicate that venetoclax combination therapy of AML is promising in real-world clinical practice and suggest a role for ancillary treatment targeting antigens expressed on residual AML cells as a therapeutic strategy in TP53-mutated AML.