Abstract 1823: Preclinical efficacy and safety of CS5007, an EGFR×HER3 dual-targeting antibody-drug conjugate with a topoisomerase 1 inhibitor payload.

Abstract Background: EGFR and HER3, members of the ErbB receptor family, are key oncogenic drivers that are frequently co-overexpressed across a variety of human epithelial malignancies, Both EGFR and HER3 are clinically validated therapeutic targets for cancer therapies. Therefore, simultaneously targeting both EGFR and HER3 offers a promising strategy to overcome tumor heterogeneity and adaptive resistance commonly observed with single-target approaches. CS5007 is constructed with 1) functional EGFR 2) hydrophilic beta-glucuronide linker (our proprietary CSL20 linker) to ensure that the ADC has a mAb-like PK profile, stability and tumor selective cleavage; 3) potent, well-tolerated and clinically validated topoisomerase 1 inhibitor exatecan (Exa) conjugated to the antibody with a drug-to-antibody ratio (DAR) of 4. Methods Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1823.