The First-In-Class Anti-AXLxCD3ε Pronectin™-Based Bispecific T-Cell Engager Is Active in Preclinical Models of Human Soft Tissue and Bone Sarcomas

Sarcomas are heterogeneous malignancies with limited therapeutic options and a poor prognosis. We developed an innovative immunotherapeutic agent, a first-in-class Pronectin (TM) -based Bispecific T-Cell Engager (pAXLxCD3e), for the targeting of AXL, a TAM family tyrosine kinase receptor highly expressed in sarcomas. AXL expression was first analyzed by flow cytometry, qRT-PCR, and Western blot on a panel of sarcoma cell lines. The T-cell-mediated pAXLxCD3e cytotoxicity against sarcoma cells was investigated by flow cytometry, luminescence assay, and fluorescent microscopy imaging. The activation and degranulation of T cells induced by pAXLxCD3e were evaluated by flow cytometry. The antitumor activity induced by pAXLxCD3e in combination with trabectedin was also investigated. In vivo activity studies of pAXLxCD3e were performed in immunocompromised mice (NSG), engrafted with human sarcoma cells and reconstituted with human peripheral blood mononuclear cells from healthy donors. Most sarcoma cells showed high expression of AXL. pAXLxCD3e triggered T-lymphocyte activation and induced dose-dependent T-cell-mediated cytotoxicity. The combination of pAXLxCD3e with trabectedin increased cytotoxicity. pAXLxCD3e inhibited the in vivo growth of human sarcoma xenografts, increasing the survival of treated mice. Our data demonstrate the antitumor efficacy of pAXLxCD3e against sarcoma cells, providing a translational framework for the clinical development of pAXLxCD3e in the treatment of human sarcomas, aggressive and still-incurable malignancies.