Differential inhibitory effect of L‐lysine on renal accumulation of 67Cu‐labelled F(ab′)2 fragments in mice

The basic amino acid L‐lysine was administered to mice in an attempt to circumvent unwanted renal accumulation of 67Cu‐labelled F(ab′)2 fragments derived from the anti‐NCAM IgG1, SEN7 and anti‐CEA IgG1 monoclonal antibody (MAb)35. In control experiments, significant renal uptake of both 67Cu‐labelled F(ab′)2 fragments was observed, radiolabel being primarily localised to proximal tubules in the renal cortex. Following optimised L‐lysine dosing protocols, renal uptake of 67Cu‐MAb35 F(ab′)2 was inhibited by up to 42%. Surprisingly, little inhibition (