DEVELOPMENT OF 2 RADIOIMMUNOASSAYS TO DETECT PACLITAXEL IN SERA AND IN CEREBROSPINAL, ASCITIC, AND PLEURAL FLUIDS

BACKGROUND. Paclitaxel is an antimitotic agent isolated from the Pacif ic yew tree, It has demonstrated antitumor activity in several cancers and is the first of a new class of antineoplastic agents containing a taxane ring system. Its levels in serum and urine have been measured previously by high performance liquid chromatography (HPLC). In this s tudy, the authors developed two competitive radioimmunoassay methods t o determine whether they could reliably be used to measure levels of p aclitaxel in sera and in cerebrospinal, ascitic, and pleural fluids. M ETHODS. A monoclonal antibody prepared against paclitaxel was employed in an immunoradiometric assay (IRMA), in which I-125-labeled antibody nas used, and in a more conventional tritiated radioimmunoassay (RIA) ,in which H-3-paclitaxel was used. RESULTS. Both radioimmunoassays det ected levels of paclitaxel in sera that were comparable to those obser ved with HPLC. However, the IRMA was tile most sensitive. Only the IRM A was able to detect low levels of paclitaxel in cerebrospinal fluid a fter paclitaxel infusion and in sera 3 weeks after infusion. Both the IRMA and RIA methods were able to detect paclitaxel in ascitic and ple ural fluids. CONCLUSIONS. Monitoring paclitaxel levels reliably in ser a and other bodily fluids is possible with these radioimmunoassays and may be of value in predicting and preventing toxicity and optimizing paclitaxel treatments. (C) 1997 American Cancer Society.