Patent ID: 8343458

Claim:
A composition useful for in vivo imaging of tissue containing an active cysteine protease, said composition comprising a compound according to the formula: n is an integer between 0 and 2, P 3 being absent when n=0, and there being a P 4 when n=2; R 1 and R 3 are independently selected from the group consisting of H, NH 2 , aminocarbonyl, aryl, substituted aryl, amino, lower alkyl, or cycloalkyl; P 1 , P 2 , P 3 and P 4 are independently an amino acid side chain selected from naturally occurring amino acid side chains and non-natural amino acid side chains 3, 6, 8, 23, 29, 31, 34 and 38, wherein: where P 1 , if not further bonded to a chelator or a radiolabel, is optionally bonded to a cyanine dye; and one of R 1 , R 3 , P 1 , P 2 , P 3 or P 4 is further bonded to a chelator or directly to a radiolabel, which compound specifically binds a predetermined active cysteine protease.