By using a robust synthetic glycopeptide library,21–24 we have established a straightforward approach to antibodies recognizing cancer-relevant glycopeptidic epitopes modified with aberrant O-glycans, namely “dynamic neoepitopes”, found in the MUC1 TRD (Fig. 2a).19,20 SN-131 (clone 1B2, IgG2a) is one of the anti-MUC1 mAbs created on the basis of this strategy that binds MUC1 TRD with Tn, T, and ST antigens attached to the immunodominant DTR motif (Fig. S1, ESI†). This evidence concerns the gene MUC1 and cancer.