Effect of Carboxyl-Group of D-Glutamic Acid or γ-Carboxy-D-glutamic Acid as N-Terminal Amino Acid of ¹¹¹In-Diethylenetriaminepentaacetic Acid-Octreotide on Accumulation of Radioactivity in Kidney

Abstract

To establish a strategy for developing ¹¹¹In-diethylenetriaminepentaacetic acid (¹¹¹In-DTPA)-octreotide, a diagnostic radiopharmaceutical agent for tumors, with reduced non-specific renal radio-accumulation, the compounds having D-glutamic acid (Glu) or γ-carboxy-D-glutamic acid (carboxy-Glu) as the N-terminal amino acid were examined for in vivo radio-distribution. Compounds carrying Glu and carboxy-Glu containing one and two negative charges, respectively, showed lower renal radio-accumulation than that carrying D-phenylalanine. It was revealed that the introduction of a negative charge reduces the renal radio-accumulation independently from the number of negative charges. The present result can be a clue for the development of ¹¹¹In-DTPA-octreotides with reduced the renal radio-accumulation.