Disclosed are compounds represented by the following general formula (I): Cyclo-(Arg-Gly-Asp-X1-X2-X2-X4-X5) (I) wherein the variables groups X1 to X5 have the following meanings X1: Leu, Ile, Nle, Val, Tyr, Phe； X2: D-amino acid such as D-Pro, N-Me-D-Phe； X3: Pro, N-Me-amino acid such as N-Me-Lys, N-Me-Lys(Ac)； Pro-Rx3, N-Me-Lys-Rx4； X4: Gly, Ala, Ser, Thr； X5: Leu, Ala, Tyr, His, Ile, Nle, Val, Phe wherein Pro-Rx3 represents a proline residue that carries at the C-3, C-4 or C-5 carbon atom and preferably the C-4 carbon atom a functional group selected from —；NH2, —；OH, —；NH—；Ac, —；NH-hexyne, and wherein Lys-Rx4 represents a lysine residue, wherein the ω-amino nitrogen atom carries a group of the formula -L4-R4, wherein L4 is selected from the group consisting of covalent bond, —；C(O)—；, and —；C(O)—；O—；, . . . , and wherein R4 is selected from the group consisting of —；(CH2)n-C≡；CH with n=0, 1, 2, 3, 4, 5, 6, 7 or 8, or wherein the sub-sequence -X2-X3- represents a β-turn mimetic diffeωωring from the meanings above, or pharmaceutically acceptable salts, esters, solvates, polymorphs or modified forms thereof represented by the following general formula (II): (X0)n1L(X8)n2 wherein X0 represents the compound of the general formula (I) as specified above (excluding one hydrogen atom to allow bonding to the linker), L represents a linker, X8 represents the effector moiety and wherein n1 and n2 are each independently selected from the range of 1 to 5, preferably such that each of n1 and n2 represents 1, wherein n1+n2 represents the number of valencies of the linker and is preferably in the range of from 2 to 6, more preferably 2-5, with the proviso that each of n1 and n2 is at least 1, as well as uses therefore in therapy and imaging.
