Short-chain peptide-dye conjugates as contrast media for optical diagnosis

A peptide-polymethine-dye conjugate compound of formula (I):

• A1—(X)m—A2 I
• in which
• X stands for an α-, β- or γ-amino acid with D- or L-configuration, and
• m stands for a number from 5 to 30, whereby the resulting amino acid sequence or peptide, (X)m, is optionally cyclized in a straight-chain nature or via a disulfide bridge between two cysteines or homocysteines or amidically between the N- and C-terminus, and (X)m is an amino acid sequence of the vaso-active intestinal peptide (VIP), somatostatin or neurotensin and wherein any amino acid in the (X)m peptide may be interchanged with other natural or unnatural amino acids so long as the functional characteristics of the peptide-polymethine-dye conjugate remain unchanged.
• A1 is a hydrogen atom, an acetyl radical or an alkyl radical with 1 to 10 C-atoms, which is optionally substituted with 1 to 3 carboxy groups and/or 1 to 6 hydroxy groups, or a poly(oxyethylene) radical with 2 to 30 —CH2CH2O units, or a dye molecule selected from polymethine dyes which have at least one absorption maximum in the range of 380 to 1200 nm,
• A2 is a hydroxy group, an amino group or a dye molecule selected from polymethine dyes which have at least one absorption maximum in the range of 380 to 1200 nm,
• under the condition that at least one of radicals A1 or A2 is a dye molecule selected from polymethine dyes which have at least one absorption maximum in the range of 380 to 1200 nm,
• whereby for the case that A1 and/or A2 is a dye molecule selected from polymethine dyes which have at least one absorption maximum in the range of 380 to 1200 nm, A1 is linked to an N-terminal amino group of amino acid sequence (X)m, and A2 is linked to an amino group of the amino acid lysine or to a hydroxy group of the amino acid serine in any position within the amino acid sequence (X)m;
• or a physiologically compatible salt thereof and wherein the polymethine dye is useable as a synthesis component in the solid-phase synthetic production of the conjugates and thus is stable under such conditions.