M1231, a joint venture between Merck and Sutro Biopharma, is a bsADC targeting EGFR and mucin 1 (MUC1), which are highly co-expressed in cancers such as NSCLC, esophageal squamous cell carcinoma, HNSCC, TNBC, and ovarian cancer [140]. Here, MUC1 is linked to esophageal squamous cell carcinoma.