title: Biodistribution study of 188Re-labeled trisuccin-HuCC49 and trisuccin-HuCC49deltaCh2 conjugates in athymic nude mice bearing intraperitoneal colon cancer xenografts.
abstract: The trihydroxamate bifunctional chelating agent (BCA), trisuccin, has been shown to be a potential ligand for radiolabeling of monoclonal antibodies (MAbs) with rhenium radioisotopes, through an indirect postconjugation approach. The use of this trihydroxamate BCA made it possible to prepare stable BCA-MAb conjugates in pure form that could be radiolabeled with carrier-free 188Re. The anti-TAG-72 murine MAb, CC49, and its humanized derivatives are promising agents in the treatment of a number of malignancies with the CH2 domain-deleted MAb (HuCC49deltaCH2), which is of particular interest due to its rapid blood clearance. The biodistribution of 188Re-labeled conjugates of trisuccin with both humanized CC49 (HuCC49) and HuCC49deltaCH2 in athymic nude mice implanted i.p. with LS174T human colon carcinoma was studied. Trisuccin-MAb conjugates were synthesized at different BCA:MAb ratios by the 6-oxoheptanoic acid method using trisuccin hydrazide. The conjugates were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy for the number of incorporated trisuccin molecules. The conjugates were radiolabeled with carrier-free, generator-produced 188Re and purified by gel filtration on Sephadex G-25. Labeling yields and homogeneity of the labeled conjugates were analyzed by high-pressure liquid chromatography and instant TLC. Athymic nude mice were injected i.p. with LS174T human colon carcinoma cells, 7 days prior to injection of the labeled antibodies. 188Re-labeled MAbs were injected i.p., and the mice were sacrificed 24 h postinjection. Matrix-assisted laser desorption/ionization time-of-flight analyses showed stable incorporation of trisuccin into each MAb, with the measured ligand:MAb values positively correlating with the theoretical ratios. Labeling of the conjugates with 188Re proceeded with high yields, producing homogeneous 188Re-MAbs with good stabilities as shown by instant TLC and biodistribution analyses. Biodistribution of the radiolabeled MAbs at 24 h after injection showed median tumor uptake values of 23.5%ID/g and 17.6%ID/g for the 188Re-HuCC49deltaCH2 and 188Re-HuCC49, respectively. The blood clearance of the domain-deleted MAb was faster than that of the intact antibody. The blood values at 24 h after injection were 0.7%ID/g for 188Re-HuCC49deltaCH2 and 3.2%ID/g for 188Re-HuCC49. The results indicate that trisuccin is a promising agent for postconjugation labeling of antibodies with 188Re. Additionally, these results illustrate the potential of 188Re-HuCC49deltaCH2 in radioimmunodiagnosis and radioimmunotherapy of cancer.
authors.affiliation: Department of Radiation Oncology, University of Alabama at Birmingham, 35294, USA. safavy@uab.edu
authors.forename: A
authors.initials: A
authors.lastname: Safavy
authors.forename: M B
authors.initials: MB
authors.lastname: Khazaeli
authors.forename: K
authors.initials: K
authors.lastname: Safavy
authors.forename: M S
authors.initials: MS
authors.lastname: Mayo
authors.forename: D J
authors.initials: DJ
authors.lastname: Buchsbaum
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics* / Q000627:therapeutic use; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000532:radiotherapy; D006801:Humans; D006877:Hydroxamic Acids / Q000493:pharmacokinetics* / Q000627:therapeutic use; D007553:Isotope Labeling; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D016499:Radioimmunotherapy; D011868:Radioisotopes / Q000493:pharmacokinetics*; D012211:Rhenium / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013386:Succinates / Q000493:pharmacokinetics* / Q000627:therapeutic use; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
chemical_list: D000911:Antibodies, Monoclonal; D006877:Hydroxamic Acids; D011868:Radioisotopes; D013386:Succinates; C082055:trisuccin; D012211:Rhenium