LAUSR

Mesothelin (MSLN) is a cell surface protein over-expressed in a number of cancer types. Several antibody- and cellular-based MSLN targeting agents have been tested in clinical trials where their therapeutic efficacy has been moderate at best. Previous studies using antibody and CAR-T strategies have shown the importance of particular MSLN epitopes for optimal therapeutic response, while other studies have found certain MSLN-positive tumors can produce proteins that can bind to subsets of IgG1-type antibodies and suppress their immune-effector activities. In an attempt to develop an improved anti-MSLN targeting agent, we engineered a humanized divalent anti-MSLN/anti-CD3ε bispecific antibody that avoids suppressive factors, can target a MSLN epitope proximal to the tumor cell surface and is capable of effectively binding, activating and redirecting T-cells to the surface of MSLN-positive tumor cells. NAV-003 has shown significantly improved tumor cell killing against lines producing immunosuppressive proteins in vitro and in vivo. Moreover, NAV-003 demonstrated good tolerability in mice and efficacy against patient-derived mesothelioma xenografts co-engrafted with human peripheral blood mononuclear cells. Together these data support the potential for NAV-003 clinical development and human proof-of-concept studies in patients with MSLN-expressing cancers. This article is protected by copyright. All rights reserved.