L1CAMxCD3 bispecific antibodies exert potent anti-tumor effects in preclinical pancreatic cancer models with representation of the complex tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressive tumor microenvironment (TME) with pancreatic myofibroblasts (PMF) and macrophages being two prominent cell populations essentially impairing tumor responses to (immuno)therapies. L1 cell adhesion molecule (L1CAM) is upregulated in PDAC cells in primary and metastatic tissues and associated with tumor progression and therapy resistance. Using L1CAM as tumor-associated antigen, two bispecific antibodies (bsAB) targeting L1CAM and CD3 were developed in the IgG-(L)-ScFv format and their anti-tumorigenic activity was investigated in different preclinical PDAC models. In 2D models, both L1-bsAB exerted L1CAM-specific anti-PDAC cell activity when co-cultured with activated CD8+ T cells. Strong anti-PDAC cell effects along with elevated release of T cell effector molecules were also observed upon co-culture with peripheral blood mononuclear cells (PMBC) from healthy donors and PDAC patients. Of note, both L1-bsAB were also effective in 3D PDAC cell spheroids and neither impaired by PMF nor macrophages. Finally, application of L1-bsAB on organotypic tissue slice cultures from PDAC tissues comprising the entire complex TME also induced PDAC cell apoptosis and release of T cell effector molecules. Overall, our results highlight relevant anti-PDAC cell activity of L1-bsAB in immunosuppressive contexts supporting their potential as immunotherapeutic strategy for PDAC.