Targeting ITGB4 with a topoisomerase I ADC: Preclinical antitumor activity in colorectal and head and neck cancers

Integrin beta 4 (ITGB4) was identified as a promising tumor-specific antigen through the GNOCLE™ platform, a drug discovery engine that leverages real-world clinical data. ITGB4 is highly expressed in various solid tumors, including head & neck, colorectal, and esophageal cancers, but shows minimal expression in matched normal tissues, as confirmed through immunohistochemistry analysis, supporting a favorable therapeutic window. In cancer progression, ITGB4 promotes epithelial detachment, migration, and invasion. Its high expression is linked to resistance to chemo and targeted therapies and correlates with poor prognosis and aggressive tumor behavior. Based on its tumor-specific profile and functional relevance, ITGB4 was selected as an attractive target for antibody-drug conjugate (ADC) development. Here, we report the preclinical activity and safety of GENA-120, an ITGB4-targeting ADC composed of a humanized anti-ITGB4 antibody (GENA-120B17), a cleavable hydrophilic linker (LinkerE) designed to minimize retro-Michael elimination, and the topoisomerase I inhibitor payload exatecan. GENA-120B17 demonstrated high binding affinity to ITGB4, as well as efficient internalization into ITGB4-expressing cancer cells. Because ITGB4 exclusively dimerizes with integrin alpha6 to form alpha6beta4 and interacts with its extracellular ligand, the binding and functional role of GENA-120B17 were further investigated in the context of alpha6beta4-ligand interactions. Off-target screening confirmed high specificity to the primary target, with no detectable binding to irrelevant targets. GENA-120 was readily internalized into ITGB4-positive cancer cell lines and showed efficient lysosomal trafficking. In cellular assays, GENA-120 exhibited potent, target-dependent cytotoxic activity against multiple cancer cell lines. GENA-120 also demonstrated strong bystander activity in co-culture systems of ITGB4-positive and negative cancer cells. In addition, treatment with GENA-120 significantly increased ATP and HMGB1 release from ITGB4-positive cancer cells, indicating the induction of immunogenic cell death. In in vivo studies, GENA-120 demonstrated potent antitumor activity in ITGB4-positive cell-derived colorectal and head & neck cancer xenograft models (COLO205, LS174T, and FaDu). GENA-120 exhibited high stability in mouse, cynomolgus monkey, and human serum, as well as a favorable pharmacokinetic profile in mice. It was well tolerated in mice at single doses up to 140 mg/kg, with no maximum tolerated dose reached and no dose-limiting toxicities observed. These robust preclinical data, demonstrating strong efficacy, favorable pharmacokinetics, excellent cross-species serum stability, and a promising safety profile, support the continued development of GENA-120 as a therapeutic candidate for ITGB4-expressing solid tumors, including colorectal and head & neck cancers.