Investigating the Dual Targeting of BCL-2 and CD38 in Models of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is correlated with poor prognosis and a high mortality. Current AML treatment often fails to achieve complete remission and relapse is common, highlighting the need for more targeted treatments. Overexpression of BCL2 is a hallmark of AML progression and is often associated with a poor response to cytotoxic treatment. BCL2 inhibition by the BH3 mimetic Venetoclax has been shown to be effective in promoting AML cell death and recently Venetoclax has received FDA approval for the treatment of AML. However, some patients do not respond or can develop resistance, therefore multiple studies for combinational therapies for Venetoclax have been researched. We have previously demonstrated CD38 inhibition by daratumumab treatment inhibits mitochondrial transfer from mesenchymal stromal cell (MSC) to AML blasts in the bone marrow (BM) microenvironment, which results in a reduction in AML derived oxidative phosphorylation and subsequent reduced leukemia growth and improved animal survival. We therefore investigated the consequences of inhibiting CD38 using daratumumab and BCL2 using Venetoclax on the AML survival.

Primary AML blasts were isolated from patient's BM. CD38 expression and BCL2 expression was assessed by flow cytometry analysis of AML. AML had significantly higher BCL2 expression and a slight increase in CD38 expression compared to CD34+ cells. Venetoclax alone caused a significant decrease in cell viability, however daratumumab or in combination with Venetoclax had no additive effect on AML survival. Since AML is highly reliant on the BM microevironment we cultured AML on MSC with either Venetoclax alone, daratumumab alone, or Venetoclax and daratumumab for 24 hours. Cells were then stained with Annexin V-FITC/PI and analysed using flow cytometry. Cells underwent significantly more apoptosis in the combination Venetoclax and daratumumab treatment when compared to control AML cells.

To determine the effect of Venetoclax and daratumumab treatment in preclinical models we used an NSG xenograft mouse model of AML, we transplanted MV411-luc or patient derived AML and treated the animals with either vehicle control (PBS) daratumumab (5mg/kg) on day 7 and 14 alone, Venetoclax (100mg/kg/day) alone, or both daratumumab and Venetoclax followed by bioluminescence imaging. In vivo, treatment with combination daratumumab and Venetoclax significantly reduced tumor burden and improved survival compared to control and either drug alone in the patient derived AML xenograft mouse model and in MV411.

These data support the further clinical investigation of Venetoclax and Daratumumab combination as a therapeutic approach for the treatment AML.