SQ-33600

A specific and sensitive radioimmunoassay (RIA) for the measurement of SQ 33,600 in biological fluids has been developed. The assay utilizes a SQ 33,600 polyclonal antibody, [125I]iodohistamine-SQ 33,600 radiolabel, and standards in serum. Satisfactory zero binding and sensitivity were obtained after an overnight incubation at 4 degrees C. Separation of the antibody-bound and free radiolabel was achieved by employing polyethylene glycol-goat anti-rabbit gamma-globulin (PEG-GARG) separant. A quantitative recovery in serum and urine of the exogenous analyte was obtained at all concentrations of SQ 33,600 tested. Intra-assay coefficients of variation (CVs) were 6.19 and 5.57% for the low and high controls, respectively. Interassay CVs were 6.64 and 6.06% for the low and medium controls, respectively. Results from the parallelism studies were acceptable for both serum and urine samples. Comparison of results from samples which were assayed by RIA and high-performance liquid chromatography (HPLC) demonstrated a significant correlation (r = 0.994; HPLC = 1.09 RIA + 57.98; n = 45). The present RIA has been successfully used to assay clinical specimens from pharmacokinetic studies.

A method for the determination of SQ 33,600 in human serum is presented. This compound, which contains both carboxylic and phosphinic acid functional groups, is an HMG CoA reductase inhibitor currently under clinical investigation at the Bristol-Myers Squibb Pharmaceutical Research Institute. Human serum extracts prepared using solid-phase techniques were analyzed by combining high-performance liquid chromatography and atmospheric pressure ionization mass spectrometry. Under the conditions of the analysis, SQ 33,600 and its fluorinated analog, SQ 33,547, used as the internal standard, existed as anions in solution and could be sampled directly using the ionspray technique. The method utilized a simple isocratic mobile-phase system. No sample derivatization was required for these polar molecules. The retention time of the analytes was 3.5 min with a total analysis time of 5 min. The limit of detection was 0.5 ng ml-1 serum with a minimum quantifiable limit of 2.0 ng ml-1. The method was linear to at least 400 ng ml-1.