Disclosed is a prostate-specific membrane antigen (PSMA)-binding polypeptide comprising a humanized PSMA-binding domain wherein the PSMA binding domain comprises (i) an immunoglobulin light chain variable region comprising LCDR1, LCDR2, and LCDR3, and (ii) an immunoglobulin heavy chain variable region comprising HCDR1, HCDR2, and HCDR3, wherein the LCDR1, LCDR2 and LCDR3 has the amino acid sequences KSISKY, SGS and QQHIEYPWT, respectively, and the HCDR1, HCDR2, and HCDR3 has the amino acid sequences SGYTFTDYYMH, YFNPYNDYTR and CARSDGYYDAMDYW, respectively. Also disclosed is the use of a dimeric PSMA-binding protein comprising two polypeptide chains of the above-described PSMA-binding protein in the manufacture of a medicament for the treatment of a disorder in a subject characterised by overexpression of prostate-specific membrane antigen (PSMA).
