title: [Design of radiolabeled antibody fragments for tumor-selective radioactivity localization--brush border enzyme-sensitive bond to decrease renal accumulation of radioactivity].
abstract: Nonspecific renal radioactivity localization constitutes a problem in targeted imaging and therapy with radiolabeled antibody fragments. Based on the idea that the renal radioactivity levels should be reduced if radiolabeled compounds excreted in the urine are released from antibody fragments by tubular brush border enzymes, 3'-iodohippuryl N epsilon-maleoyl-L-lysine (HML) was designed as a radioiodination reagent for antibody fragments; the glycyl-lysine sequence in HML is a substrate for a brush border enzyme and m-iodohippuric acid is released by cleavage of the linkage. In normal mice, HML-conjugated Fab demonstrated low renal radioactivity levels from early postinjection times. Directly radioiodinated Fab showed migration of radioactivity from the membrane to the lysosomal fraction of the renal cells from 10 to 30 min postinjection. On the other hand, the majority of the radioactivity was detected only in the membrane fraction after injection of HML-conjugated Fab. In tumor-bearing mice, HML-conjugated Fab showed a marked decrease in renal radioactivity localization without impairing the tumor accumulation. These findings indicate that HML is a useful reagent for reducing the renal radioactivity levels of antibody fragments.
authors.affiliation: Department of Nuclear Medicine and Diagnostic Imaging, Graduate School of Medicine, Kyoto University, 54 Shogoin, Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. tmukai@kuhp.kyoto-u.ac.jp
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mukai
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Fujioka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Arano
authors.forename: Hideo
authors.initials: H
authors.lastname: Saji
mesh_terms: D000818:Animals; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D007128:Immunoglobulin Fragments / Q000378:metabolism*; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes / Q000378:metabolism*; D007465:Iodohippuric Acid / Q000031:analogs & derivatives* / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods*; D007668:Kidney / Q000378:metabolism*; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism*; D051379:Mice; D008871:Microvilli / Q000201:enzymology*
chemical_list: C432249:3'-iodohippuryl N-maleoyl-lysine; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes; D007465:Iodohippuric Acid; D008239:Lysine