In the present study, we show that cathepsin S is on the surface of tumour cells and that this localization can be exploited with a fully human IgG1 version of Fsn0503 (Fsn0503h) to induce ADCC, demonstrating the clinical potential of the engineered cathepsin S specific human antibody Fsn0503h. The gene discussed is CTSS; the disease is neoplasm.