Immunoassay of taxol using anti-taxol antibody and radiolabeled taxol

Taxol (Paclitaxel), an antineoplastic agent, has been used for treatment of ovarian and breast cancer. Prompt analysis of taxol concentration in the human serum is beneficial to maintain an appropriate taxol concentration in blood, which will enhance therapeutic effect of the drug. This study was aimed to establish a radioimmunoassay system for monitoring the taxol level in blood during cancer treatment. Hemisuccinyltaxol (HT) was synthesized by esterification of taxol with succinic anhydride. Tyraminehemisuccinyltaxol (THT) was synthesized by amide bond formation of the hemisuccinyltaxol with tyramine in the presence of isobutylchloroformate. The synthesized THT was purified by HPLC, Tyraminehemisuccinyltaxol was dissolved in 80% acetonitrile solution, which was stored at 4 .deg. C or 37 .deg. C for 7 days. The stability of tyraminehemisuccinyltaxol was monitored during the storage period. Tyramine-hemisuccinyltaxol was labeled with 125I (3.7 x 107 Bq) by Chloramine-T. The radiolabeled product, (125I)iodo-tyraminehemiscuccinyltasol, was allowed to stand at 4 .deg. C or 37 .deg. C for up to 7 days to estimate its stability. The radiochemical purity of (125I) iodotyramine-hemisuccinyltaxol was determined by HPLC. In other hand, the titer of taxol monoclonal antibody (3G5A7) was determined by radioimmunoassay using (125I) iodotyramine-hemisuccinyltaxol as a radiolabeled antigen. A standard dose response curve was plotted by taxolcompetitive radioimmunoassay. Hemisuccinyltaxol was synthesized with 79.9% yield. Tyraminehemisuccinyltaxol was synthesized with 19.5% yield and purified by HPLC. the chemical purity of Tyraminehemisuccinyltaxol was maintained at 96.5% and 97.5% after 7 days storage at 4 .deg. C and 37.deg. C respectively. The radiochemical purity of (125I) iodotyramine-hemisuccinyltaxol was diminished to 88.1% and 86.2% after 7 days storage at 4 .deg. C and 37. deg.C, respectively. The antibody titer against taxol was 1/256 and the plotted standard dose-response curve could be useful to monitor the taxol concentration in patient's blood during taxol treatment. Tyraminehemisccinyltaxol was stable for 7 days and (125I) iodotyraminehemisuccinyltaxol was stable for at least 3 days. The taxol-competitive radioimmunoassay established in this study can be used to monitor the taxol concnetration in human serum