Somatostatin binding compositions and methods of use thereof

A compound represented by structural formula (I)

• or a pharmaceutically acceptable salt thereof, wherein:
• CG is a chelating group, an optical dye or fluorophore, a cytotoxic agent, or an immune stimulant;
• X is OH or NH2;
• RA, RB, RC, RD, RE, RF, RG, and RH are each independently selected from hydrogen and C1-4 alkyl;
• R1 is C1-6 alkyl or phenyl, wherein said C1-6 alkyl represented by R1 is substituted with one R10;
• R10 is independently selected from phenyl and naphthyl, wherein said phenyl or naphthyl represented by R10 is optionally substituted with one or more groups selected from halogen;
• R2 is OH or
• R3 is
• R4 is C1-6 alkyl-NR4aR4b or C1-6 alkyl-NHC(═NH)NH2, wherein said C1-6 alkyl in the group represented by R4 is optionally substituted with one or more halogen or C1-3 alkyl;
• R4a is hydrogen or C1-3 alkyl and R4b is hydrogen, C1-3 alkyl, C(O)C1-3 alkyl and C(O)C1-3 haloalkyl, provided that R4a and R4b are not both hydrogen;
• R5 is C1-6 alkyl or C1-6 aralkyl, wherein the alkyl represented by R5 or the aryl portion of the aralkyl represented by R5 are independently substituted with one or more halogen, —OH, or C1-6 alkoxy.