A sensitive bioassay for measuring blood levels of 12-O-tetradecanoylphorbol-13-acetate (TPA) in patients: preliminary pharmacokinetic studies.
Oncol Res 2003;
13:169-74. [PMID:
12549626]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
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.
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