N-Succinimidyl 3-[131I]Iodo-4-phosphonomethylbenzoate ([131I]SIPMB), a Negatively Charged Substituent-Bearing Acylation Agent for the Radioiodination of Peptides and mAbs
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- 作者：Sriram Shankar ; Ganesan Vaidyanathan ; Donna Affleck ; Phillip C. Welsh ; and Michael R. Zalutsky
- 刊名：Bioconjugate Chemistry
- 出版年：2003
- 出版时间：March 2003
- 年：2003
- 卷：14
- 期：2
- 页码：331 - 341
- 全文大小：131K
- 年卷期：v.14,no.2(March 2003)
- ISSN：1520-4812
文摘
An important criterion in design of acylation agents for the radioiodination of internalizing monoclonalantibodies (mAbs) is to maximize the retention of radioiodine in the tumor following mAb intracellularprocessing. We have previously shown that labeling methods that generate positively chargedcatabolites have enhanced tumor retention. Herein we have extended this strategy to investigate thepotential utility of labeling internalizing mAbs with an acylation agent that yielded labeled catabolitesthat would be negatively charged at lysosomal pH. The negatively charged acylation agent,N-succinimidyl 3-[131I]iodo-4-phosphonomethylbenzoate ([131I]SIPMB), was prepared from its tinprecursor, N-succinimidyl 4-di-tert-butylphosphonomethyl-3-trimethylstannylbenzoate (tBu-SPMTB),in 40% radiochemical yield. The free acid, 3-[131I]iodo-4-phosphonomethylbenzoic acid ([131I]IPMBA),was also prepared from the corresponding precursor, 4-di-tert-butylphosphonomethyl-3-trimethylstannylbenzoic acid (tBu-PMTBA), in 80% radiochemical yield. The rapidly internalizing mAb L8A4was conjugated to [131I]SIPMB in 25-40% yield with preservation of its immunoreactivity. Internalization and processing in the U87
EGFR glioma cell line was studied in a paired label format withL8A4 labeled with 125I using the Iodogen method. Retention of initially bound radioactivity in thesecells at 24 h from [131I]SIPMB-labeled mAb was approximately 6-fold higher than that for directlylabeled mAb. Catabolite analysis demonstrated that this difference reflected an order of magnitudehigher retention of low molecular weight species in these cells. The [131I]SIPMB-L8A4 conjugate wasintact over the first 2 h; thereafter, lysine-[131I]SIPMB was the predominant catabolite. In contrast,L8A4 labeled using Iodogen rapidly gave rise to mono-[125I]iodotyrosine within 2 h, which then clearedrapidly from the cells. These results suggest that SIPMB could be a potent candidate for labelinginternalizing mAbs and warrant further study.
EGFR glioma cell line was studied in a paired label format withL8A4 labeled with 125I using the Iodogen method. Retention of initially bound radioactivity in thesecells at 24 h from [131I]SIPMB-labeled mAb was approximately 6-fold higher than that for directlylabeled mAb. Catabolite analysis demonstrated that this difference reflected an order of magnitudehigher retention of low molecular weight species in these cells. The [131I]SIPMB-L8A4 conjugate wasintact over the first 2 h; thereafter, lysine-[131I]SIPMB was the predominant catabolite. In contrast,L8A4 labeled using Iodogen rapidly gave rise to mono-[125I]iodotyrosine within 2 h, which then clearedrapidly from the cells. These results suggest that SIPMB could be a potent candidate for labelinginternalizing mAbs and warrant further study.