title: A sensitive bioassay for measuring blood levels of 12-O-tetradecanoylphorbol-13-acetate (TPA) in patients: preliminary pharmacokinetic studies.
abstract: 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a potent stimulator of differentiation in myelocytic leukemia cells, and it has been shown to have activity in patients with acute myelocytic leukemia. Because attempts to develop a suitable mass spectrometry assay for TPA were unsuccessful (because of the lack of sufficient sensitivity), we developed a novel and highly sensitive blood level bioassay for TPA that measures ethyl acetate-extractable differentiating activity in blood. Differentiating activity in ethyl acetate extracts of blood was measured in HL-60 cells by measuring the formation of adherent cells. The sensitivity of the assay was approximately 0.1 ng TPA/ml blood. The assay for TPA has a high degree of specificity and does not measure deesterifed potential metabolites (phorbol, phorbol-13-acetate, or phorbol-12-myristate), and the presence of GM-CSF, G-CSF, interferon-alpha, or interferon-gamma does not interfere with the assay. Blood levels of TPA as measured by the bioassay immediately after an IV infusion of TPA (0.125 mg/m2; approximately 0.25 mg per patient) and 1 and 3 h later were 1.75 +/- 0.55, 0.93 +/- 0.54, and 0.69 +/- 0.42 ng/ml, respectively (mean +/- SD from eight infusions in five patients). Terminal half-lives were determined in a few patients where TPA blood levels were measured at multiple time intervals after the TPA infusion. In these patients, the terminal half-life was 11.1 +/- 3.9 h (from five infusions in four patients). To the best of our knowledge, this is the first analytical method for the measurement of TPA.
authors.affiliation: Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8020, USA.
authors.forename: Xiao Xing
authors.initials: XX
authors.lastname: Cui
authors.forename: Richard L
authors.initials: RL
authors.lastname: Chang
authors.forename: Xi
authors.initials: X
authors.lastname: Zheng
authors.forename: Donald
authors.initials: D
authors.lastname: Woodward
authors.forename: Roger
authors.initials: R
authors.lastname: Strair
authors.forename: Allan H
authors.initials: AH
authors.lastname: Conney
mesh_terms: D001681:Biological Assay / Q000379:methods*; D002448:Cell Adhesion / Q000187:drug effects; D004355:Drug Stability; D018922:HL-60 Cells / Q000187:drug effects; D006207:Half-Life; D006801:Humans; D007262:Infusions, Intravenous; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy; D012680:Sensitivity and Specificity; D013755:Tetradecanoylphorbol Acetate / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*
chemical_list: D013755:Tetradecanoylphorbol Acetate