Joseph L. Woolley

Pharmacokinetics and Hematological Effects of the PEGylated Thrombopoietin Peptide Mimetic GW395058 in Rats and Monkeys After Intravenous or Subcutaneous Administration

GW395058, a potent PEGylated peptide human thrombopoietin receptor (HuTPOr) agonist in vitro, is being evaluated for the treatment of thrombocytopenia. GW395058 shares no sequence homology with TPO. In this report the pharmacokinetics and hematological effects of GW395058 in rats and monkeys are described. Doses eliciting thrombocytosis in rodents (2 or 10 μg/kg s.c.) produced insufficient plasma concentration data for pharmacokinetic parameter estimate calculations. At higher i.v. doses in rats (500, 1,000 or 2,000 μg/kg) serum t½ (half‐life) values were >20 h, and the area under the concentration time curve increased proportionally with dose. In cynomolgus monkeys GW395058 plasma t½ values ranged from 37 to 68 h after s.c. or i.v. dosing, and similar values were observed in rhesus monkeys following s.c. dosing. Rat platelet counts increased following 2 (1.6‐fold) or 10 μg/kg (fourfold) s.c. doses. Cynomolgus and rhesus monkey platelet counts did not change significantly at comparable s.c. doses, but did increase slightly (

High-performance liquid chromatographic assay for the simultaneous measurement of trimethoprim and sulfamethoxazole in plasma or urine.

Procedures for the simultaneous determination of trimethoprim (TMP) and sulfamethoxazole (SMX) in plasma or urine are reported. The drugs are extracted from plasma or urine by a single solid-phase extraction and quantitated by high-performance liquid chromatography. Both drugs are analyzed in the same chromatographic run. Intra- and interassay variability are <10% for both compounds, and the recovery and precision of TMP measurement are unaffected by concurrent SMX concentrations. Limits of quantitation for TMP and SMX in plasma were 0.02 and 0.21 μg/ml, respectively. In urine, the limit of quantitation for both drugs was 1.0 μg/ml. Metabolites of TMP and SMX did not interfere with the assay. Pharmacokinetic parameters from volunteers given two formulations of co-trimoxazole in a crossover comparison study are reported.

High-performance liquid chromatographic assay for the measurement of atovaquone in plasma

A rapid and efficient isocratic high-performance liquid chromatographic assay for the measurement of atovaquone in plasma has been developed and validated. The drug was extracted from plasma with organic solvents, assayed on a C1 column with a mobile phase of methanol-0.1% acetic acid (70:30, v/v), and detected by ultraviolet absorbance at 254 nm. Recovery of atovaquone from plasma was greater than 85%. Intra- and inter-assay variability were less than 8%, and the average accuracy of the assay (expressed as % bias) ranged from -7.4 to + 2.2%. The upper and lower limits of quantitation were 100 and 0.25 microgram/ml, respectively. Measurement of atovaquone in spiked plasma control samples during routine runs of clinical trial samples confirmed the reliability of the assay.

Effects of Aerosolized Synthetic Surfactant, Atovaquone, and the Combination of These on Murine Pneumocystis carinii Pneumonia

An immunosuppressed rat model was used to determine the pharmacokinetics of aerosolized atovaquone (administered with and without a synthetic surfactant) and to evaluate the efficacy of inhaled atovaquone in the prevention and treatment of Pneumocystis carinii pneumonia (PCP). After a single dose by aerosol, mean peak concentrations of atovaquone averaged 52 microg/mL in plasma and 31 microg/g in lungs of rats infected with P. carinii. When atovaquone was combined with surfactant, mean peak concentrations of 94 microg/mL in plasma and 51 microg/g in lung were achieved. Aerosolized synthetic surfactant alone significantly increased survival of rats with PCP and, when combined with atovaquone, increased plasma and lung concentrations of the drug and eradication of the organism.

A phase I clinical and pharmacological study of weekly intravenous infusions of piritrexim (BW301U)

Thirty-eight patients with advanced resistant cancers were enrolled on this study of piritrexim (PTX; BW 301U) administered intravenously weekly for 4 weeks. Of 50 courses of treatment begun, 39 evaluable 4-week courses of the drug were completed by this group of patients. Dosages ranged from 44 to 530 mg/m2/week. One patient at each dosage level received an initial weekly dose of PTX in oral form accompanied by pharmacokinetic blood sampling after the oral dose and also after a subsequent intravenous dose. Toxicities included mild nausea and vomiting, and moderate to severe peripheral vein phlebitis. Anemia and thrombocytopenia were the dominant hematological toxicities. One patient with pulmonary metastases from malignant fibrous histiocytoma experienced a 12-week partial response to PTX treatment at a dosage of 400 mg/m2/week. Pharmacokinetic analysis of plasma for PTX concentrations was accomplished utilizing a competitive protein binding assay. The estimated total body clearance ranged from 136 to 173 ml/min/1.73 m2. Mean terminal half-life after intravenous administration was 5.61 +/- 2.38 h (S.D.), and after oral administration was 5.72 +/- 2.04 h. Mean systemic bioavailability after oral administration was 75 +/- 56%.

The pharmacokinetics of 1954U89, 1,3-diamino-7-(1-ethylpropyl)-8-methyl-7H-pyrrolo-(3,2-f)quinazoline, in dogs and rats after intravenous and oral administration

1954U89, 1, 3‐diamino‐7‐(1‐ethylpropyl)‐8‐methyl‐7H‐pyrrolo‐(3, 2‐f  )quinazoline, is a potent, lipid‐soluble inhibitor of dihydrofolate reductase. The pharmacokinetics and bioavailability of 1954U89 were examined in male beagle dogs and male CD rats. Dogs received single intravenous (2·5 mg kg−1) and oral (5·0 mg kg−1) doses of 1954U89 with and without successive administration of calcium leucovorin. Single intravenous (5·0 mg kg−1) and oral (10 mg kg−1) doses of [1,3‐14C2]1954U89 were administered to rats. Plasma concentrations of total radiocarbon were determined by scintillation counting, and intact 1954U89 was measured by HPLC. The mean plasma half‐life was 3·2 ± 0·62 and 4·2 ± 0·68 h after intravenous and oral administration, respectively, to dogs. The pooled plasma half‐life after intravenous administration to rats averaged 1·2 h; a reliable plasma half‐life value after oral administration could not be determined. Mean total‐body clearance was 2·4 ± 0·39 and 4·5 ± 1·1 L h−1 kg−1 after intravenous and oral administration, respectively, to dogs, and averaged 12 and 77 L h−1 kg−1 after intravenous and oral administration, respectively, to rats. Neither clearance nor bioavailability of 1954U89 in dogs was affected significantly by administration of calcium leucovorin. Absolute bioavailability was 54 ± 12% in dogs and 16% in rats.

High Performance Liquid Chromatographic Assay with Fluorescence Detection for the Analysis of 1954U89, 1,3-Diamino-7-(1-ethylpropyl)-8-methyl-7H-pyrrolo-(3,2-f)-quinazoline, in Plasma

Abstract 1954U89, 1,3-diamino -7 - (1-ethylpropyl) -8- methyl-7H-pyrrolo(3,2-f)-quinazoline, is a potent, lipid-soluble inhibitor of dihydrofolate reductase that is under preclinical evaluation as an anticancer agent. A rapid and selective high performance liquid chromatographic assay with fluorescence detection was developed for the quantitation of 1954U89 in rat and dog plasma. The compound was removed from plasma by solid phase extraction, and the extracts were chromatographed on a Hypersil C1 column (4.6 mm × 15 cm) under isocratic conditions. The HPLC mobile phase consisted of methanol and 0.02 M ammonium acetate buffer (pH = 4.5) delivered in a ratio of 70:30 and at a flow rate of 1.0 mL/min. The compound was quantitated by fluorescence detection with excitation and emission wavelengths set at 335 and 460 nm, respectively. The quantitation range of the assay was 0.01 to 2.0 μg/mL. The intra- and interassay precision of the method were approximately 4 and 6%, respectively, in rats, and approximately ...