Synthesis and characterization of rhenium and technetium-99m tricarbonyl complexes bearing the 4-[3-bromophenyl]quinazoline moiety as a biomarker for EGFR-TK imaging.
Aiming at the development of technetium-99m ((99m)Tc) complexes for early detection and staging of EGFR positive tumors, the tyrosine kinase inhibitor 6-amino-4-[(3-bromophenyl)amino]quinazoline was derivatized with pyridine-2-carboxaldehyde to generate the imine 6-(pyridine-2-methylimine)-4-[(3-bromophenyl)amino]quinazoline suitable for reacting with the fac-[(99m)Tc(CO)(3)](+) core as an N,N bidentate ligand. The labelling was performed in high yield (>90%) by ligand exchange reaction using fac-[(99m)Tc(OH(2))(3)(CO)(3)](+) as precursor. The (99m)Tc complex was characterized by comparative HPLC analysis using the analogous rhenium (Re) complex as reference. The Re complex was prepared by ligand exchange reaction using the fac-[ReBr(3)(CO)(3)](2-) as precursor and was fully characterized by NMR and IR spectroscopies and elemental analysis. In vitro studies indicate that both the ligand and its Re complex inhibit the EGFR autophosphorylation (IC(50): 17+/-3.7 and 114+/-23 nM respectively) in intact A431 cells, bind the receptor in a reversible mode, and inhibit A431 cell growth (IC(50): 5.2+/-1.1 and 2.0+/-0.98 microM respectively). Biodistribution of the (99m)Tc complex in healthy animals showed a rather fast blood and soft tissue clearance between 1 and 15 min p.i. with excretion occurring mainly via the hepatobiliary system.