It is the objective of the present invention to provide a gastrin analogue which show high uptake in CCK-2 receptor positive tumours by simultaneously very low accumulation in the kidneys. This objective is achieved according to the present invention by a mini-gastrin analogue PP-F11 having the formula: PP-F11-X-DGlu-DGlu-DGlu-DGlu-DGlu-DGlu-Ala-Tyr-Gly-Trp-Y-Asp-Phe-NH 2 , wherein Y stands for an amino acid replacing methionine and X stands for a chemical group attached to the peptide for the purpose of diagnostic and/or therapeutic intervention at CCK-2 receptor relevant diseases. In particular, very suitable compounds with respect to a high tumour to kidney ratio are mini-gastrin analogues with six D-glutamic acids or six glutamines. These compounds still possess a methionine which can be oxidised easily which is a disadvantage for clinical application under GMP due to the forms which may occur. Therefore, the elimination of the methionine leads to a lower affinity to oxidation which in general favours the tumour-kidney-ratio. In a preferred embodiment of the present invention, the methionine is replaced by norleucine. This so-called PP-F11N mini gastrin exhibits currently the best tumour-kidney-ratio and is therefore the most promising candidate for clinical applications.
