Methods for radiolabelling GRPR antagonists and their kits

The present invention relates to methods for radiolabelling GRPR antagonists such as NeoB, and their kits. In particular, the invention to a method for labeling a gastrin-releasing peptide receptor (GRPR) antagonist with a radioactive isotope, preferably 6 8 Ga, 67Ga or 64Cu, said 5 method comprising the steps of: i. providing a first vial comprising said GRPR antagonist in dried form, ii. adding a solution of said radioactive isotope into said first vial, thereby obtaining a solution of said GRPR antagonist with said radioactive isotope, iii. mixing the solution obtained in ii. with at least a buffering agent and 10 incubating it for a sufficient period of time for obtaining said GRPR antagonist labeled with said radioactive isotope, and, iv. optionally, adjusting the pH of the solution.