title: Quantification of vorinostat and its main metabolites in plasma and intracellular vorinostat in PBMCs by liquid chromatography coupled to tandem mass spectrometry and its relation to histone deacetylase activity in human blood.
abstract: Vorinostat (suberoylanilide hydroxamic acid) is the first approved histone deacetylase (HDAC) inhibitor for the treatment of cutaneous T-cell lymphoma after progressive disease following two systemic therapies. Intracellular access of vorinostat is essential to exert its epigenetic effects. Therefore, we studied the relationship between vorinostat extracellular (plasma) and intracellular (peripheral blood mononuclear cells, PBMCs) concentration and assessed its concentration-effect relationship by HDAC activity testing. Assays were developed and validated for the low nanomolar quantification of vorinostat and two inactive metabolites in human plasma and PBMCs. For the vorinostat extraction from plasma and PBMCs solid-phase extraction and liquid-liquid extraction methods were applied. Extraction recoveries ranged from 88.6% to 114.4% for all analytes and extraction methods. Extracts were chromatographed on a Phenomenex Luna column isocratically (plasma) or by gradient (PBMCs) consisting of acidic ammonium acetate, acetonitrile, and methanol. The analytes were quantified using deuterated internal standards and positive electrospray tandem mass spectrometry (multiple reaction monitoring) with lower limits of quantification of 11.0 ng/mL (plasma) and 0.1 ng/3 × 10(6) cells (PBMCs). The calibrated ranges were linear for vorinostat in plasma 11.0-1100 (11,000) ng/mL (metabolites) and PBMCs 0.1-10.0 ng/3 × 10(6) cells with correlation coefficients >0.99, an overall accuracy varying between -6.7% and +3.8% in plasma, -8.1% and -1.5% in PBMCs, and an overall precision ranging from 3.2% to 6.1% in plasma and 0.8% to 4.0% in PBMCs (SD batch-to-batch). The application to blood samples from healthy volunteers incubated with vorinostat revealed accumulation of vorinostat in PBMCs, effective intracellular HDAC inhibition at therapeutic vorinostat concentrations and a direct vorinostat concentration dependency to HDAC inhibition.
authors.affiliation: Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, Heidelberg, Germany.
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, Heidelberg, Germany.
authors.forename: Jan-Christoph
authors.initials: JC
authors.lastname: Detering
authors.affiliation: Department of Pediatric Oncology, Hematology, Immunology and Pulmonology, University of Heidelberg, Im Neuenheimer Feld 430, Heidelberg, Germany; Clinical Cooperation Unit Pediatric Oncology (G340), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
authors.forename: Till
authors.initials: T
authors.lastname: Milde
authors.affiliation: Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, Heidelberg, Germany.
authors.forename: Walter Emil
authors.initials: WE
authors.lastname: Haefeli
authors.affiliation: Department of Pediatric Oncology, Hematology, Immunology and Pulmonology, University of Heidelberg, Im Neuenheimer Feld 430, Heidelberg, Germany; Clinical Cooperation Unit Pediatric Oncology (G340), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Witt
authors.affiliation: Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, Heidelberg, Germany. Electronic address: juergen.burhenne@med.uni-heidelberg.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Burhenne
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D056572:Histone Deacetylase Inhibitors / Q000032:analysis* / Q000097:blood* / Q000378:metabolism; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000032:analysis* / Q000097:blood* / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000737:chemistry*; D057230:Limit of Detection; D059625:Liquid-Liquid Extraction / Q000379:methods; D052616:Solid Phase Extraction / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods; D000077337:Vorinostat
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D000077337:Vorinostat; D006655:Histone Deacetylases
keywords: Histone deacetylase activity; Peripheral blood mononuclear cells; Plasma; Tandem mass spectrometry; Vorinostat