Back
Peptide linkers lead to modification of liver metabolism and improved tumor targeting of copper-67-labeled antibody fragments.
Journal article

Peptide linkers lead to modification of liver metabolism and improved tumor targeting of copper-67-labeled antibody fragments.

  • 2002-01-16
Published in:
  • Cancer biotherapy & radiopharmaceuticals. - 2001
Animals
Antibodies, Neoplasm
Chromatography, High Pressure Liquid
Colonic Neoplasms
Copper Radioisotopes
Electrophoresis, Polyacrylamide Gel
Female
Humans
Immunoconjugates
Immunoglobulin Fab Fragments
Isotope Labeling
Liver
Mice
Mice, Nude
Oligopeptides
Radioimmunotherapy
Transplantation, Heterologous
English In order to determine if tumor/nontarget tissue ratios of 67Cu-labeled antibody fragments can be improved, modifying the DO3A copper chelate with tripeptide linkers was investigated. The peptide-linked chelates 1,4,7,10-tetraazacyclodecane-N,N',N",N"'-tetraacetate (DOTA)-triglycyl-L-p-isothiocyanato-phenylalanine (DOTA-R1-NCS), DOTA-glycyl-phenylalanyl-glycyl-L-p-isothiocyanato-phenylalanine (DOTA-R2-NCS), DOTA-glycyl-prolyl-glycyl-L-p-isothiocyanato-phenylalanine (DOTA-R3-NCS) and DOTA-glycyl-L-p-isothiocyanato-phenylalanine (DOTA-R4-NCS) were synthesized and coupled to F(ab')2 fragments of anti-colon carcinoma mAb35. In vitro, the 67Cu-labeled antibody fragments were fully immunoreactive and stable in human serum. In vivo in nude mice bearing human colon carcinoma xenografts the conjugates R1 and R3 showed improved tumor uptake and lower levels of radioactivity in the liver compared with the other conjugates. Biodistributions of the DOTA-R2-F(ab')2 showed at early time points after injection higher levels of radioactivity in the liver, lower levels of activity persisting in the blood and lower accumulation of activity in the tumor. When liver homogenates were analyzed 30 min post injection by SDS-PAGE or FPLC gel chromatography, it was found that radioactivity was released more slowly from the triglycine (R1)-F(ab')2 than from the immunoconjugates with the R2 or the R4 linker. The main radioactive metabolites were protein bands at 66 kD, 31 kD and low molecular weight fragments. The results show that the rate of cleavage of the copper complex from F(ab')2 fragments in vivo can be influenced by the amino acid sequence close to the complex, with significant consequences on biodistributions.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/113307
Statistics
Document views: 21 File downloads: