N-succinimidyl 3-[At-211]astato-4-guanidinomethylbenzoate: an acylation agent for labeling internalizing antibodies with alpha-particle emitting At-21
ABSTRACT The objective of this study was to develop a method for labeling internalizing monoclonal antibodies (mAbs) such as those reactive to the anti-epidermal growth factor receptor variant III (EGFRvIII) with the alpha-particle emitting radionuclide (211)At. Based on previous work utilizing the guanidine-containing acylation agent, N-succinimidyl 4-guanidinomethyl-3-[(131)I]iodobenzoate ([(131)I]SGMIB), we have now investigated the potential utility of its astato analogue for labeling the anti-EGFRvIII mAb L8A4. N-succinimidyl 3-[(211)At]astato-4-guanidinomethylbenzoate ([(211)At]SAGMB) in its Boc-protected form was prepared from a tin precursor in 61.7 +/- 13.1% radiochemical yield, in situ deprotected to [(211)At]SAGMB, which was coupled to L8A4 in 36.1 +/- 1.9% yield. Paired-label internalization assays demonstrated that tumor cell retention of radioactivity for L8A4 labeled using [(211)At]SAGMB was almost identical to L8A4 labeled using [(131)I]SGMIB, and 3-4-fold higher than for mAb radioiodinated using Iodogen. Paired-label biodistribution of L8A4 labeled using [(211)At]SAGMB and [(131)I]SGMIB in athymic mice hosting U87MGdeltaEGFR xenografts resulted in identical uptake of both (211)At and (131)I in tumor tissues over 24 h. Although higher levels of (211)At compared with (131)I were sometimes seen in tissues known to sequester free astatide, these (211)At/(131)I uptake ratios were considerably lower than those seen with other labeling methods. These results suggest that [(211)At]SAGMB may be a useful acylation agent for labeling internalizing mAbs with (211)At.
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ABSTRACT: In this work a new coupling reagent, N-[2-(maleimido)ethyl]-3-(trimethylstannyl)benzamide, for radiohalogenation has been synthesized and characterized. The reagent is intended to either be attached to reduced disulfide bridges of proteins (making the halogenation site-specific) or to free terminal cysteine groups on peptides. The new reagent was also shown to be easily halogenated with inactive bromine and iodine as well as (125)I and (211)At, indicating potential use within targeted radiotherapy. Copyright © 2014 Elsevier Ltd. All rights reserved.Applied Radiation and Isotopes 11/2014; 96C:1-5. DOI:10.1016/j.apradiso.2014.11.007 · 1.06 Impact Factor
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ABSTRACT: Introduction The clinical development of radioimmunotherapy with astatine-211 is limited by the lack of a stable radiolabeling method for antibody fragments. An astatinated N-heterocyclic carbene (NHC) Rhodium complex was assessed for the improvement of radiolabeling methodologies with astatine. Methods Wet harvested astatine-211 in diisopropyl ether was used. Astatine was first reduced with cysteine then was reacted with a chlorinated Rh-NHC precursor to allow the formation of the astatinated analogue. Reaction conditions have been optimized. Astatine and iodine reactivity were also compared. Serum stability of the astatinated complex has been evaluated. Results Quantitative formation of astatide was observed when cysteine amounts higher than 46.2 nmol/μl of astatine solution were added. Nucleophilic substitution kinetics showed that high radiolabeling yields were obtained within 15 min at 60 °C (88%) or within 5 min at 100 ° C (95%). Chromatographic characteristics of this new astatinated compound have been correlated with the cold iodinated analog ones. The radioiodinated complex was also synthesized from the same precursor (5 min. at 100 °C, up to 85%) using [125I]NaI as a radiotracer. In vitro stability of the astatinated complex was controlled after 15 h. incubation in human serum at 4 °C and 37 °C. No degradation was observed, indicating the good chemical and enzymatic stability. Conclusion The astatinated complex was obtained in good yield and exhibits good chemical and enzymatic stability. These preliminary results demonstrate the interest of this new radiolabeling methodology and further functionalizations should open new possibilities in astatine chemistry. Advances in Knowledge and Implications for patient Care Although there are many steps and pitfalls before clinical use for a new prosthetic group from the family of NHC complexes, this work may open a new path for astatine-211 targeting.Nuclear Medicine and Biology 01/2013; DOI:10.1016/j.nucmedbio.2013.12.004 · 2.41 Impact Factor
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ABSTRACT: With 2,3,5,6-tetrafluorophenyl 3-(nodo-carboranyl) propionate (TCP) as a new potential bi-functional linker, bovine serum albumin (BSA) was conjugated with 211At, and the conjugated model protein (211At-TCP-BSA) was preliminarily evaluated in vitro and in vivo by comparison with 211At-SAB-BSA and 211At-SAPC-BSA, which conjugated with 211At via aryl derivatives ATE (N-succinimidyl-3-(tri-n-butylstannyl) benzoate) or SPC (N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate). The radiolabeled intermediate 211At-TCP was coupled to BSA in yields ranging from 35 to 45% with radiochemical purity of more than 98%. The conjugated 211At-TCP-BSA exhibited considerable stability in vitro in 0.1 mol/L PBS (pH 7.6) at room temperature (RT), similar to 211At-SAPC-BSA and 211At-SAB-BSA. Biodistribution of the 211At conjugated protein was investigated in NIH strain mice by I.V injection. The results showed that 211At-TCP-BSA was constantly stable in vivo as well as in vitro, but more stable than 211At-SAPC-BSA and 211At-SAB-BSA. These results implied that radioastatinated carboranes based on B–At bonds are higher stability than radioastatinated aryl derivatives based on C–At to in vivo deastatination. In other word, TCP should be a promising bi-functional linker for 211At conjugation of proteins or antibodies.Journal of Radioanalytical and Nuclear Chemistry 04/2010; 288(1). DOI:10.1007/s10967-010-0872-2 · 1.42 Impact Factor