Metastatic or locally advanced penile cancer (PeCa) has limited systemic treatment options and a 5-year survival rate of ~10% in metastatic disease. Using the in vitro and ex vivo models we preclinically assessed CC-3, a B7-H3xCD3 bispecific antibody (bsAb) currently in a Phase I basket trial (NCT05999396).
Primary PeCa cells were isolated from surgical specimens and characterized for surface antigen expression by flow cytometry (n = 4). B7-H3 expression was additionally evaluated in primary penile cancer tissues by immunohistochemistry (n = 10). The functional activity of the bsAb CC-3 was assessed in co-culture assays with PBMC, analyzing cytotoxicity, cytokine release, and T cell activation.
Immunohistochemistry of tumors from ten PeCa patients revealed strong and consistent B7-H3 (CD276) expression, with a mean H-score of 200, in tumor cells and tumor-associated vasculature, potentially enhancing T cell influx upon targeting. In vitro and ex vivo co-cultures of primary PeCa cells with peripheral blood mononuclear cells from healthy donors and PeCa patients showed that CC-3 robustly activated CD4⁺ and CD8⁺ T cells, as defined by upregulation of CD69 and CD25, with donor-dependent kinetics. CC-3 also induced potent tumor cell lysis and T cell proliferation across all patient-derived tumor samples, whereas the isotype control had no effect, confirming target-restricted activity.
These results demonstrate the strong immunostimulatory capacity of CC-3 and validate B7-H3 as a relevant target for T cell-based immunotherapy in PeCa. Our findings support the ongoing inclusion of PeCa patients in the clinical CC-3 trial and encourage further development of B7-H3-directed strategies for this rare, understudied malignancy.
ImmunoTargets and therapy. 2026 May 01*** epublish ***
Aleksander Kielbik, Veronika Bahlinger, Christian M Schürch, Maria Luisa Barcena, Olesya Vakhrusheva, Anita Thomas, Igor Tsaur, Jonas S Heitmann, Helmut R Salih, Ilona Hagelstein
Clinical Collaboration Unit Translational Immunology, Department of Internal Medicine, University Hospital Tuebingen, Tuebingen, Germany., Cluster of Excellence iFIT (EXC 2180) "Image-Guided and Functionally Instructed Tumor Therapies", University of Tuebingen, Tuebingen, Germany., Department of Urology, University Hospital Tuebingen, Tuebingen, Germany., Department of Urology and Pediatric Urology, University Medical Center Mainz, Mainz, Germany.