99m
Tc-EDDA-HYNIC-D-Phe 1 ,Tyr 3 ]-Octreotide ( 99m Tc-EDDA/HYNIC-TOC) is a promising new radiopharmaceutical with the potential to replace [ 111 In-DTPA-D-Phe 1 ]-Octreotide ( 111 In-DTPA-OCT) as the radiopharmaceutical for somatostatin receptor scintigraphy due to the advantage of improved image quality, lower radiation dose for the patient, and daily availability. Here we describe the development of a freeze-dried kit formulation based on the Tricine/EDDA exchange labeling approach for the preparation of this radiopharmaceutical in a clinical setting. Three parameters were of major importance to achieve a suitable formulation with a radiochemical purity (RCP) >90%: addition of bulking agent, the pH of the freeze-drying solution, and the content of stannous chloride. The final formulation consisted of 20 mg Tricine, 10 mg EDDA, 50 mg Mannitol, 20 mg SnCl 2 ร 2H 2 O, and 20 mg [HYNIC-D-Phe 1 , Tyr 3 ]-Octreotide (HYNIC-TOC). Radiolabeling was performed by addition of 0.2 M Na 2 HPO 4 to adjust the pH to 6-7, followed by 0.5-2 GBq 99m Tc sodium pertechnetate, in a total volume of 2 mL and incubation for 10 min in a boiling water bath. Mean RCP values of 10 batches showed values >90% over a storage period of up to 1 year, a high stability up to 24 h of the final preparation, and retained biological activity. The developed kit formulation forms the basis for further clinical evaluation of this promising new radiopharmaceutical. ร 2004