Discovery of a fully human antibody to the proximal membrane terminus of MUC1 based on a B-cell high-throughput screening technique

Mucin 1 plays an important role in tumor signaling and is overexpressed in adenocarcinoma and the digestive system. Many antibodies have been developed against MUC1 targets. Previously developed antibodies were mainly directed against distal membrane-terminal MUC1-N, but distal membrane-terminal MUC1-N is shed during cell growth and therefore binds to antibodies developed against tandem repeat sequences and becomes ineffective. Here, we provide a simple and rapid method for preparing antibodies targeting the proximal membrane end of MUC1. Immunological target antigens were designed based on Biocytogen Renlite KO mice. With the help of B-cell high-throughput screening technology, we rapidly screened and prepared fully human antibodies with human-macaque cross-reactivity, high affinity, high specificity, and endocytosis. Using this method, we screened 40 antibodies with human-monkey cross-reactivity, which specifically recognized breast cancer cell lines with human and monkey affinities ranging from (1.04E-07-2.91E-09). Of these, the antibodies with germline genes IGHV4-59*01 and IGHV3-30*03 had nanomolar affinities, with high endocytosis effects in breast cancer cells. Ab.07 (IGHV3-30*03) coupled with monomethyl auristatin E (MMAE) showed good antitumor activity in different tumor cells. In summary, we describe a method for designing and producing excellent antibodies that can be assembled into antibody-drug conjugates and bispecific antibodies by proximal- membrane-end immunization and B-cell high-throughput screening that can rapidly generate high-quality antibodies.