Abstract LB284: CLAUDIN-1 targeting antibody ALE.C04 drives single activity and restores anti-PD1 efficacy in solid tumors

Claudin 1 (CLDN1) is a protein confined within the normal epithelial tight junctions of different tissues. Upon malignant transformation, CLDN1 is overxpressed and epitopes become exposed outside the tight junctions (non-Junctional CLDN1). ALE.C04 is a highly specific humanized monoclonal antibody that recognizes a unique CLDN1 exposed epitope in different solid tumors. Herein we show that non-Junctional CLDN1 (NJ-CLDN1) is frequently overexpressed in solid tumors. Pre-clinically, ALE.C04 drives tumor growth inhibition in different CDXs and PDX in vivo tumor models. Notably, CLDN1 expression on tumor cells positively correlates with T cell exclusion, a mechanism described to hinder the efficacy of Checkpoint inhibitors (CPIs). On this line, the overexpression of Cldn1 in mouse tumor cells promoted T-cell exclusion and resistance to anti-PD1 treatment. Importantly, ALE.C04 restored both T-cell infiltration and anti-PD1 efficacy in tumors. Mechanistically, NJ-CLDN1 interacts with different components involved in extracellular matrix remodeling, thus establishing a physical barrier that exclude immune cells from the tumor nest. ALE.C04 perturbs the interface between CLDN1+ tumor cells and the stroma, thus restoring immune cell infiltration. Our pre-clinical data showed that: i) NJ-CLDN1 is a novel and druggable target in solid tumors ii) ALE.C04 is a selective anti-CLDN1 antibody capable of driving anti-tumor activity as both single agent and in combination with anti-PD1. Citation Format: Alberto Toso, Geoffrey Teixeira, Tina Zimmermann, Stefanie Gill Gill, Daniela Schmitter, Markus Meyer, Marion Muller, Laurent Mailly, Thomas Baumert, Luigi Manenti, Roberto Iacone. CLAUDIN-1 targeting antibody ALE.C04 drives single activity and restores anti-PD1 efficacy in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB284.