Abstract PR015: Determining the mechanism of action of the anti-ENTPD2 antibody, KAZ954
Authors: Zaharevitz Samantha , Salamone Richard , Jackson Carie , Grove Kerri , Briones Sergio , Kim David , Shi Jian , Ng Kenneth , Harris Marina , Lee Chris , Peters Eric , Galkin Anna , Guerrettaz Lisa , Knee Deborah A 
Published: December 2023

Abstract
Background: Ectonucleoside triphosphate diphosphohydrolase 2 (ENTPD2) is expressed in gastrointestinal malignancies and catalyzes the hydrolysis of adenosine triphosphate (ATP), creating an immunosuppressive microenvironment by reducing the cytotoxic antitumor immune response, enhancing the proliferation and polarization of immunosuppressive cells, and increasing neovascularization. Blocking the hydrolase activity of ENTPD2 increases extracellular ATP and triggers a sustained proinflammatory response in the tumor microenvironment. In this report, we describe the development and characterization of a first-in-class monoclonal anti-ENTPD2 antibody, KAZ954, and surrogate anti-mouse ENTPD2 (mENTPD2) antibody, capable of potently inhibiting the ATP hydrolase activity of ENTPD2 and inducing antibody-dependent cellular cytotoxicity (ADCC).
Methods: The ability of KAZ954 to inhibit ENTPD2-induced conversion of ATP to adenosine diphosphate (ADP) was evaluated. In vitro, NIH/3T3 cells engineered to express human or cyno-ENTPD2 and RKO cancer cell lines with endogenous ENTPD2 expression were used. In vivo, 4T1 syngeneic cell lines expressing mENTPD2 were generated, which have a luciferase molecule attached to the plasma membrane to measure extracellular ATP. The shift in ATP:ADP ratio was verified by matrix-assisted laser desorption/ionization imaging analysis. To assess the ADCC-inducing ability of KAZ954, a lactate dehydrogenase release assay was run using peripheral blood mononuclear cell (PBMCs) and RKO as effector and target cells, respectively. Two different ENTPD2-engineered syngeneic tumor models were used to study pharmacodynamics and the potential for single agent, and combinatorial, efficacy. Endpoint measurements included flow cytometry of tumor and blood and serum cytokine analysis. RASLseq was used to further identify RNA changes in mouse syngeneic tumor models treated with anti-mENTPD2.
Results: KAZ954 potently inhibited the hydrolysis of ATP to ADP in NIH/3T3 cells, expressing exogenous human or cyno ENTPD2, and in RKO cell lines. KAZ954 IgG was able to bind ENTPD2 on RKO cell lines and Fcγ receptors on PBMCs, inducing RKO cell lysis and LDH release by ADCC. However, the KAZ954 F(ab’)2 fragment, although able to bind ENTPD2, was unable to induce RKO cell lysis due to its inability to bind to Fcγ receptors. Preclinical syngeneic tumor models treated with a surrogate mENTPD2 antibody demonstrated that the blockade of ENTPD2 hydrolase activity results in a delay in tumor growth which is further augmented in combination with immune checkpoint inhibitors or further blockade of the adenosine pathway. Evaluation of the in vivo responses to KAZ954 treatment revealed an increase in ATP:ADP ratio; an increase in intra-tumoral monocytes, NK cells, peripheral CD8+ T cells, macrophages, and CD11b+ dendritic cells, and a gene signature consistent with immune activation in the tumor.
Conclusion: KAZ954 binds to and inhibits the hydrolase activity of ENTPD2, leading to an increased intratumoral ATP:ADP ratio and a systemic inflammatory response.
Citation Format: Samantha Zaharevitz, Richard Salamone, Carie Jackson, Kerri Grove, Sergio Briones, David Kim, Jian Shi, Kenneth Ng, Marina Harris, Chris Lee, Eric Peters, Anna Galkin, Lisa Guerrettaz, Deborah A Knee. Determining the mechanism of action of the anti-ENTPD2 antibody, KAZ954 [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr PR015.