G3-C12 is a galectin-3 binding peptide, with Kd of 88 nM, and shows anticancer activity. G3-C12 is a galectin-3 binding peptide, with high affinity (Kd) of 88 nM, but shows no affinity for other galectin family members or to other lectins. G3-C12 bearing opolymers N-(2-hydroxypropyl)methacrylamide (HPMA) potently and selectively targets colorectal cancer (CRC) tumour cells over-expressing galectin-3 and displays superior targetability to galectin-3 compared to the galactose bearing copolymer.