Abstract 2871: NM28-2746, a reduced affinity bivalent mesothelin-binding MATCH4 T cell engager, with half-life extension, increases selectivity for killing of mesothelin-overexpressing cells

Abstract

CD3-based T cell engagers are highly potent therapeutic molecules which enable T cell-mediated cytotoxic activity toward cells expressing selected tumor-associated antigens. Alongside a highly potent anti-tumor activity, is the risk of on-target off-tumor side effects due to low levels of expression of the target antigen in normal tissue. We have sought to overcome this issue with the design and generation of a target-density-dependent activation mechanism. We have generated reduced-affinity antibody fragments to the tumor associated antigen mesothelin and constructed a multi-domain MATCH4 molecule encompassing bivalent mesothelin binding domains, a CD3 binding domain, and a human serum albumin (HSA)-binding domain for half-life extension. Here we report the design of the MATCH4 molecule and the preclinical activity of the molecule in vitro and in vivo. We also report the biochemical characteristics of the therapeutic candidate molecule showing its highly favorable properties for clinical development. We demonstrate that the bivalent mesothelin T cell engager has increased in vitro potency in T cell activation and tumor cell killing in the presence of high mesothelin expressing cells, when compared to a higher-affinity monovalent counterpart. We also demonstrate that the activity on low mesothelin expressing cells, such as healthy mesothelial cells, is reduced for the bivalent molecule compared to the higher affinity monovalent molecule. Due to the shedding of mesothelin from the surface of cancer cells and the high circulating levels of soluble mesothelin in patient sera, we also demonstrate that the bivalent molecule is still highly potent in cytotoxic activity in the presence of concentrations of soluble mesothelin up to 500 ng/ml. We also demonstrate dose dependent anti-tumor activity in in vivo efficacy studies in PBMC-reconstituted mice, and combination therapeutic activity with an anti-PD-L1, anti-4-1BB bispecific molecule (NM21-1480). Collectively, these data demonstrate an increased selectivity to mesothelin-overexpressing cells by this novel MATCH4 reduced affinity bivalent T cell engager. These data indicate the potential of this molecule to increase the therapeutic window by reducing safety concerns on normal tissue where mesothelin expression is low, and yet promote cytotoxicity on mesothelin over-expressing cancer cells. Citation Format: Bithi Chatterjee, Christian Hess, Daniel Snell, Tea Gunde, Stefan Warmuth, Alexandre Simonin, Matthias Brock, Fabio Spiga, Maria Johansson, Christopher Weinert, Julia Tietz, Niels Kirk, Nicole Bassler, Dana Mahler, Dania Diem, Alessandra Carrella, Noreen Giezendanner, Alessandra Alberti, Giorgio Gambino, Belinda Wickihalder, Bettina Bommer, Simone Muntwiler, Yasemin Yaman, Naomi Flueckiger, Robin Heiz, Sandro Wagen, David Urech. NM28-2746, a reduced affinity bivalent mesothelin-binding MATCH4 T cell engager, with half-life extension, increases selectivity for killing of mesothelin-overexpressing cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2871.