Bcl-2 inhibitor, Venetoclax, increases the effector activity of anti-leukemic T cells without inducing T cell apoptosis
Venetoclax increases T cell effector function in ROS-dependent manner
Venetoclax, a Bcl-2 inhibitor, in combination with the hypomethylating agent, Azacytidine, achieves complete response with or without count recovery in approximately 70% of treatment-naïve elderly patients unfit for conventional intensive chemotherapy. However, the mechanism of action of this drug combination is not fully understood. We discovered that Venetoclax directly activated T cells to increase their cytotoxicity against AML in vitro and in vivo. Venetoclax enhanced T cell effector function by increasing ROS generation through inhibition of respiratory chain supercomplexes formation. In addition, Azacytidine induced a viral-mimicry response in AML cells by activating the STING/cGAS pathway, thereby rendering the AML cells more susceptible to T-cell mediated cytotoxicity. Similar findings were seen in patients treated with Venetoclax as this treatment increased ROS generation and activated T cells. Collectively, this study demonstrates a new immune mediated mechanism of action for Venetoclax and Azacytidine in the treatment of AML and highlights a potential combination of Venetoclax and adoptive cell therapy for patients with AML.