HER3 and MUC1 are co-expressed in a variety of solid tumors, including those with the high mortalities, making them excellent bsAb targets. DM002 bsAb is a novel fully human bispecific antibody targeting HER3xMUC1, generated by the RenLite® common light chain antibody platform, cross-reactive with human and monkey HER3 and the MUC1 juxtamembrane domain. DM002 bsAb demonstrated higher endocytosis activity compared with its parental antibodies and HER3 and MUC-1 benchmark antibodies. DM002 bsADCs displayed potent inhibition of tumor growth of HER3 and MUC1 double positive CDX and PDX tumor. BLD1102 is our novel DNA topoisomerase I inhibitor-based linker payload system. DM002-BLD1102 bsADC potently inhibited growth of PDX models that were resistant to benchmark ADCs. DM002 is a first in class (FIC) bsADC with promising potential targeting a variety of HER3 and MUC-1-positive cancers.