Preparation of Re-188-RC-160 somatostatin analog: A peptide for local/regional radiotherapy

Conditions are described for the preparation of Re-188-RC-160, a radiolabeled synthetic peptide derived from an analogue of somatostatin, using a lyophilized labeling kit containing RC-160 (200 mu g) and stannous tartrate to which is added carrier-free Re-188 (beta, E(max), 2.12 MeV; gamma, 155 keV, 10%; T-1/2 = 16.7 h). The kits have been radiolabeled with > 2960 MBq (80 mCi) with a high labeling efficiency and no need for subsequent purification. Radiolabeling results in one major peak when analyzed by reverse-phase (RP) HPLC. Presumptive radiolysis was detected at 2.5 h post-labeling; however, a convenient method is described for stabilizing the kits against radiolysis by the post-labeling addition of ascorbic acid. (C) 1997 Elsevier Science Ltd.