P02.03 Targeting CDCP1 with single-domain antibody-based CAR T cells to treat solid tumors

Although CAR T cell therapy has shown profound success for the treatment of hematological diseases, it still poses a challenge for solid tumors. Prostate cancer is the 4th most common cancer worldwide and the most common cancer among men. Advanced and highly metastatic stages show high expression levels of the cell surface glycoprotein CDCP1 (CD318), which is associated with poor prognosis.After a successful immunization campaign and characterization of binding specificity, epitopes, and affinity, five different anti-CDCP1 single-domain antibodies (sdAbs) were selected and used as antigen-binding moieties in our second-generation Nano-CAR T cells. Through co-culture and real time killing assays we initially investigated the activation and killing potential of our Nano-CARs. Furthermore, we assessed the efficacy in vivo by establishing an adoptive Nano-CAR transfer protocol using immunocompetent C57BL/6J mice bearing human CDCP1 overexpressing MC38 mouse colon carcinoma cells.All Nano-CARs showed a specific and profound induction of TNF-α and IFN-γ when exposed to CDCP1 expressing cells in vitro; either in an overexpression system or at endogenous levels. Furthermore, all of our Nano-CARs showed a rapid and efficient killing of target cells in real-time killing assays. Upon adoptive transfer of CDCP1-Nano-CARs into tumor-bearing mice, we were able to observe a tumor growth inhibition resulting in significantly prolonged survival of treated mice. Due to our syngeneic mouse model, we were also able to investigate potential adverse immune related events mediated by on-target off tumor activity.Overall, we provide first evidence in vitro and in vivo that CDCP1-Nano-CAR T cells could be developed into a novel promising cellular therapy for solid tumors.