Evaluation of iodovinyl antibody conjugates: comparison with a p-iodobenzoyl conjugate and direct radioiodination

Abstract

The preparations and conjugations of 2,3,5,6-tetrafluorophenyl 5-[125I/131I]iodo-4-pentenoate (7a) and 2,3,5,6-tetrafluorophenyl 3,3-dimethyl-5-[125I/131I]iodo-4-pentenoate (7b) to monoclonal antibodies are reported. Reagents 7a and 7b were prepared in high radiochemical yield by iododestannylation of their corresponding 5-tri-n-butylstannyl precursors. Radioiodinated antibody conjugates were prepared by reaction of 7a or 7b with the protein at basic pH. Evaluation of these conjugates by several in vitro procedures demonstrated that the radiolabel was attached to the antibody in a stable manner and that the conjugates maintained immunoreactivity. Comparative dual-isotope biodistribution studies of a monoclonal antibody Fab fragment conjugate of 7a and 7b with the same Fab fragment labeled with N-succinimidyl p-[131I]iodobenzoate (PIB, p-iodobenzoate, 2) or directly radioiodinated have been carried out in tumor-bearing nude mice. Coinjection of the Fab conjugate of 7a with the Fab conjugate of 2 demonstrated that the biodistributions were similar in most organs, except the neck tissue (thyroid-containing) and the stomach, which contained substantially increased levels of the 7a label. Coinjection of the Fab conjugate of 7a with the Fab fragment radioiodinated by using the chloramine-T method demonstrated that the biodistributions were remarkably similar, suggesting roughly equivalent in vivo deiodination of these labeled antibody fragments. Coinjection of the Fab conjugate of 7a with the Fab conjugate of 7b indicated that there was approximately a 2-fold reduction in the amount of in vivo deiodination of the 7b conjugate as compared to the 7a conjugate.

A humanized anti-human Fas antibody, R-125224, induces apoptosis in type I activated lymphocytes but not in type II cells

“…[ 125 I]-R-125224 was prepared using [ 125 I]p-iodobenzoate as a labeling agent (24). Tested cells (final: 1.5 3 10 6 cells ml ÿ1 ) were incubated with various concentrations of [ 125 I]labeled R-125224 and 0.2% BSA (v/v) on ice for 1 h. After incubation, the cell mixture was transferred into tubes containing mixed oils, and was centrifuged to separate the supernatants and cell pellets.…”

Radioiodine labelling of a small chemotactic peptide, utilizing two different prosthetic groups: a comparative study

“…The first step comprises the radiosyntheses of the 123 4 only referred to volatile radioiodide.) Initially, they were purified on C18 minicolumns from which the pure product was eluted with methanol.…”

“…These features would therefore most likely not be sacrificed. One of the iodovinyl compounds prepared by Hadley and Wilbur 4 was selected for this study. The methodology to prepare labelled iodovinyl peptide conjugates was investigated, and a similar methodology was applied to prepare an iodobenzoate peptide conjugate in parallel.…”

Synthesis and radioiodination of N-Boc-p-(tri-n-butylstannyl)-L-phenylalanine tetrafluorophenyl ester: Preparation of a radiolabeled phenylalanine derivative for peptide synthesis

“…Application of the TFP ester was investigated since, if successfully stannylated, a compound which could be employed directly in peptide synthesis would be obtained. The TFP "active ester" was chosen because this ester has previously been found to be quite stable under a number of conditions, yet undergoes aminolysis rapidly (41)(42)(43). Further, an example of a stannylation of a benzoic acid TFP ester had been reported (44).…”