title: Quantitative determination of mithramycin in human plasma by a novel, sensitive ultra-HPLC-MS/MS method for clinical pharmacokinetic application.
abstract: Mithramycin is a neoplastic antibiotic synthesized by various Streptomyces bacteria. It is under investigation as a chemotherapeutic treatment for a wide variety of cancers. Ongoing and forthcoming clinical trials will require pharmacokinetic analysis of mithramycin in humans, both to see if target concentrations are achieved and to optimize dosing and correlate outcomes (response/toxicity) with pharmacokinetics. Two published methods for mithramycin quantitation exist, but both are immunoassays that lack current bioanalytical standards of selectivity and sensitivity. To provide an upgraded and more widely applicable assay, a UPLC-MS/MS method for quantitation of mithramycin in human plasma was developed. Solid-phase extraction allowed for excellent recoveries (>90%) necessary for high throughput analyses on sensitive instrumentation. However, a ∼55% reduction in analyte signal was observed as a result of plasma matrix effects. Mithramycin and the internal standard chromomycin were separated on a Waters Acquity BEH C18 column (2.1×50 mm, 1.7 μm) and detected using electrospray ionization operated in the negative mode at mass transitions m/z 1083.5→268.9 and 1181.5→269.0, respectively, on an AB Sciex QTrap 5500. The assay range was 0.5-500 ng/mL and proved to be linear (r(2)>0.996), accurate (≤10% deviation), and precise (CV<15%). Mithramycin was stable in plasma at room temperature for 24 h, as well as through three freeze-thaw cycles. This method was subsequently used to quantitate mithramycin plasma concentrations from patients enrolled on two clinical trials at the NCI.
authors.affiliation: Clinical Pharmacology Program, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Roth
authors.affiliation: Clinical Pharmacology Program, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Cody J
authors.initials: CJ
authors.lastname: Peer
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Widemann
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Cole
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Rachel
authors.initials: R
authors.lastname: Ershler
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Bethesda, MD, United States.
authors.forename: Lee
authors.initials: L
authors.lastname: Helman
authors.affiliation: Thoracic Oncology Branch, National Cancer Institute, Bethesda, MD, United States.
authors.forename: David
authors.initials: D
authors.lastname: Schrump
authors.affiliation: Clinical Pharmacology Program, National Cancer Institute, Bethesda, MD, United States. Electronic address: figgw@helix.nih.gov.
authors.forename: William D
authors.initials: WD
authors.lastname: Figg
mesh_terms: D001798:Blood Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D016014:Linear Models; D008926:Plicamycin / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D052616:Solid Phase Extraction; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D001798:Blood Proteins; D008926:Plicamycin
keywords: Mithramycin; Tandem mass spectrometry; Ultra-HPLC