A novel bispecific antibody-drug conjugate (ADC), BCG016, targeting both 5T4 and MUC1-C antigens, was developed for solid tumors. It showed extensive activity in various tumor cell lines and enhanced internalization compared to parental antibodies. In preclinical studies, BCG016 demonstrated superior anti-tumor efficacy in a patient-derived lung cancer model compared to benchmark ADCs, indicating its potential as a novel therapeutic for tumors co-expressing 5T4 and MUC1.