An easy-to-use imaging tool and radiopharmaceutical agent derived from CCK4 for internal radiotherapy: Synthesis and assessment of an original biovector

S-EOE-MAG3-β-alanine-CCK4 vector (S-EOE-MAG3-β-alanine: S-(1-ethoxyethyl) mercaptoacetyltriglycyl -β-alanine and CCK4: Trp-Met-Asp-Phe-NH2) was obtained by successive condensations of activated amino acids on resin with high chemical purity. This biovector was complexed at high dilution scale with 99mTc as well as at ponderable level with 185/187Re and 99Tc. In particular, this biovector was efficiently labelled with 99mTc (yield>95%) in one step under pH 7–8 and 45 °C conditions and then injected, In vivo, for biodistribution and targeting of pancreatic adenocarcinoma tumoral grafts (AR4-J). 99mTc-MAG3-β-alanine-CCK4 exhibits remarkable biological properties related to its low background noise resulting from the fast blood clearance (tissular distribution half-life ≈10 min, elimination half-life ≈ 20 min), low hepatic uptake (0.03% injected dose/g of tissue 2 h after injection) and good affinity for the CCKB receptors (IC50=8×10−8 M) expressed by tumoral cells.