Effectiveness of Quenchers to Reduce Radiolysis of 111In- or 177Lu-Labelled Methionine-Containing Regulatory Peptides. Maintaining Radiochemical Purity as Measured by HPLC

Abstract

An overview how to measure and to quantify radiolysis by the addition of quenchers and to maintain Radio-Chemical Purity (RCP) of vulnerable methionine-containing regulatory peptides is presented. High RCP was only achieved with a combination of quenchers. However, quantification of RCP is not standardized, and therefore comparison of radiolabelling and RCP of regulatory peptides between different HPLC-systems and between laboratories is cumbersome. Therefore we suggest a set of standardized requirements to quantify RCP by HPLC for radiolabelled DTPA- or DOTA-peptides. Moreover, a dosimetry model was developed to calculate the doses in the reaction vials during radiola-belling and storage of the radiopeptides, and to predict RCP in the presence and absence of quenchers. RCP was measured by HPLC, and a relation between radiation dose and radiolysis of RCP was established. The here described quenchers are tested individually as f(concentration) to investigate efficacy to reduce radiolysis of radiolabelled methionine-containing regulatory peptides. © 2012 Bentham Science Publishers.