A sensitive bioassay for measuring blood levels of 12-O-tetradecanoylphorbol-13-acetate (TPA) in patients: preliminary pharmacokinetic studies.
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.
Cui
Xiao Xing
XX
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.
Chang
Richard L
RL
Zheng
Xi
X
Woodward
Donald
D
Strair
Roger
R
Conney
Allan H
AH
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*
D013755:Tetradecanoylphorbol Acetate