The peptides of formula (I) R1&mdash(X)K&mdashP&mdashY, where: R1 is the group attached to the N-terminal of the first amino acid of the sequence P, optionally via the ligand X, and is selected from H, CH3C(&boxHO)&mdash, and maleimide X is a biradical selected from &mdashNH&mdash(CH2)r&mdashC(&boxHO)&mdash, &mdashC(&boxHO)&mdash(CH2)r&mdashC(&boxHO)&mdash, &mdashS(CH2)r&mdash, &mdashS&mdash(CH2)r&mdashC(&boxHO)&mdash, &mdashO&mdash(CH2)r&mdash, &mdashS&mdashCH2&mdashCH(NH2)&mdashC(&boxHO)&mdash, &mdashO&mdash(CH2)r&mdashC(&boxHO)&mdash, &mdash(CH2)r&mdashC(&boxHO)&mdash, &mdashNH&mdashO&mdashCH2&mdashC(&boxHO)&mdashNH&mdash(CH2)r&mdashCH(NH2)&mdashC(&boxHO)&mdash, &mdash(CH2)r&mdashC(&boxHO)&mdashNH&mdash(CH2)r&mdashCH(NH2)&mdashC(&boxHO)&mdash, and &mdashNH&mdash(CH2)r&mdashCH(NHC(&boxHO)CH2NH2)&mdashC(&boxHO)&mdash r is 1-5 P is a biradical of an amino acid sequence comprising the sequence D-Pro-D-Trp-D-Val-D-Pro-D-Ser-D-Trp-D-Met-D-Pro-D-Pro-D-Arg-D-His-D-Thr (SEQ ID NO: 1) Y is the group attached to the C-terminal of the last amino acid of the sequence P, and is selected from &mdashNH2, &mdashOH, &mdashOR2 and &mdashNHR2 R2 is a radical selected from (C1-C6)-alkyl and (CH2)2&mdashNH&mdashC(&boxHO)&mdashCH2&mdashO&mdashNH2 k is 0-2 m is 0-1 with the proviso that when the biradical X is &mdashC(&boxHO)(CH2)rC(&boxHO)&mdash, then R1 is H when the N of the amino acid of the sequence P to which is attached the biradical X is a biradical &mdashNH&mdash, then m is 1, and when is a biradical &mdashN&mdash, then m is 0 and when R1 is maleimide then the biradical X is &mdashC(&boxHO)&mdash(CH2)r&mdashC(&boxHO)&mdash, &mdashCH(NH2)&mdashC(&boxHO)&mdash, &mdash(CH2)r&mdashC(&boxHO)&mdash, and &mdash(CH2)r&mdashC(&boxHO)&mdashNH&mdash(CH2)r&mdashCH(NH2)&mdashC(&boxHO)&mdash. The peptides are useful as shuttles through the blood brain barrier (BBB). The constructions BBB-shuttle-cargo, being the cargo of a biologically active substance or for use in a diagnostic method, are
