Renal Metabolism of 3'-Iodohippuryl N-Maleoyl-L-lysine (HML)-Conjugated Fab Fragments
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- 作者：Yasushi Fujioka ; Yasushi Arano ; Masahiro Ono ; Tomoya Uehara ; Kazuma Ogawa ; Shinji Namba ; Tsuneo Saga ; Yuji Nakamoto ; Takahiro Mukai ; Junji Konishi ; and Hideo Saji
- 刊名：Bioconjugate Chemistry
- 出版年：2001
- 出版时间：March 2001
- 年：2001
- 卷：12
- 期：2
- 页码：178 - 185
- 全文大小：113K
- 年卷期：v.12,no.2(March 2001)
- ISSN：1520-4812
文摘
Renal localization of radiolabeled antibody fragments constitutes a problem in targeted imaging andradiotherapy. Recently, we reported use of a novel radioiodination reagent, 3'-[131I]iodohippuryl N
-maleoyl-L-lysine (HML), that liberates m-iodohippuric acid before antibody fragments are incorporatedinto renal cells. In mice, HML-conjugated Fab demonstrated low renal radioactivity levels from earlypostinjection times. In this study, renal metabolism of HML-conjugated Fab fragments prepared bydifferent thiolation chemistries and by direct radioiodination were investigated to determine themechanisms responsible for the low renal radioactivity levels. Fab fragments were thiolated by2-iminothiolane modification or by reduction of disulfide bonds in the Fab fragments, followed byconjugation with radioiodinated HML to prepare [131I]HML-IT-Fab and [125I]HML-Fab, respectively.In biodistribution studies in mice, both [131I]HML-IT-Fab and [125I]HML-Fab demonstrated significantlylower renal radioactivity levels than those of [125I]Fab. In subcellular distribution studies, [125I]Fabshowed migration of radioactivity from the membrane to the lysosomal fraction of the renal cells from10 to 30 min postinjection. On the other hand, the majority of the radioactivity was detected only inthe membrane fraction at the same time points after injection of both [131I]HML-IT-Fab and [125I]HML-Fab. In metabolic studies, while [125I]Fab remained intact at 10 min postinjection, both HML-conjugated Fab fragments generated m-iodohippuric acid as a radiometabolite at the same postinjectiontime. [131I]HML-IT-Fab registered two radiometabolites (intact [131I]HML-IT-Fab and m-iodohippuricacid), whereas additional radiometabolites were observed with [125I]HML-Fab. This suggested thatmetabolism of both HML-conjugated Fab fragments would occur in the membrane fractions of therenal cells. The findings of this study reinforced our previous hypothesis that radiochemical design ofantibody fragments that liberate radiometabolites that are excreted into the urine by the action ofbrush border enzymes would constitute a useful strategy to reduce renal radioactivity levels fromearly postinjection times.
-maleoyl-L-lysine (HML), that liberates m-iodohippuric acid before antibody fragments are incorporatedinto renal cells. In mice, HML-conjugated Fab demonstrated low renal radioactivity levels from earlypostinjection times. In this study, renal metabolism of HML-conjugated Fab fragments prepared bydifferent thiolation chemistries and by direct radioiodination were investigated to determine themechanisms responsible for the low renal radioactivity levels. Fab fragments were thiolated by2-iminothiolane modification or by reduction of disulfide bonds in the Fab fragments, followed byconjugation with radioiodinated HML to prepare [131I]HML-IT-Fab and [125I]HML-Fab, respectively.In biodistribution studies in mice, both [131I]HML-IT-Fab and [125I]HML-Fab demonstrated significantlylower renal radioactivity levels than those of [125I]Fab. In subcellular distribution studies, [125I]Fabshowed migration of radioactivity from the membrane to the lysosomal fraction of the renal cells from10 to 30 min postinjection. On the other hand, the majority of the radioactivity was detected only inthe membrane fraction at the same time points after injection of both [131I]HML-IT-Fab and [125I]HML-Fab. In metabolic studies, while [125I]Fab remained intact at 10 min postinjection, both HML-conjugated Fab fragments generated m-iodohippuric acid as a radiometabolite at the same postinjectiontime. [131I]HML-IT-Fab registered two radiometabolites (intact [131I]HML-IT-Fab and m-iodohippuricacid), whereas additional radiometabolites were observed with [125I]HML-Fab. This suggested thatmetabolism of both HML-conjugated Fab fragments would occur in the membrane fractions of therenal cells. The findings of this study reinforced our previous hypothesis that radiochemical design ofantibody fragments that liberate radiometabolites that are excreted into the urine by the action ofbrush border enzymes would constitute a useful strategy to reduce renal radioactivity levels fromearly postinjection times.