A peptide ligand specific for MT1 -MMP comprising a polypeptide comprising two diaminopropionic acid (Dap) or N-alkyldiaminopropionic acid (N-AlkDap) residues, and a third residue selected from cysteine, Dap or N-AlkDap, separated by at least two loop sequences, and a molecular scaffold, the peptide being linked to the scaffold by covalent alkylamino linkages with the Dap or N-AlkDap residues of the polypeptide and by covalent thioether linkages with the cysteine when the third residue is cysteine, such that two polypeptide loops are formed on the molecular scaffold, wherein the peptide ligand comprises an amino acid sequence of formula (II): -A1-X1-U/O2-X3-X4-G5-A2-E6-D7-F8-Y9-X10-X11-A3- (SEQ ID NO: 1) (II) or a pharmaceutically acceptable salt thereof； wherein: A1, A2, and A3 are independently cysteine, L-2,3-diaminopropionic acid (Dap), N-beta-alkyl-L-2,3- diaminopropionic acid (N-AlkDap), or N-beta-haloalkyl-L-2,3-diaminopropionic acid (N- HAlkDap), provided that at least one of A1, A2, and A3 is Dap, N-AlkDap or N-HAlkDap； X represents any amino acid residue； U represents a polar, uncharged amino acid residue selected from N, C, Q, M, S and T； and O represents a non-polar aliphatic amino acid residue selected from G, A, I, L, P and V.
