title: Quantitative analysis of the novel depsipeptide anticancer drug Kahalalide F in human plasma by high-performance liquid chromatography under basic conditions coupled to electrospray ionization tandem mass spectrometry.
abstract: Kahalalide F (KF) is a novel cyclic depsipeptide anticancer drug, which has shown anticancer activity both in vitro and in vivo especially against human prostate cancer cell lines. To characterize the pharmacokinetics of KF during a phase I clinical trial in patients with androgen refractory prostate cancer, a method was developed and validated for the quantitative analysis of KF in human plasma using high-performance liquid chromatography (HPLC) coupled to positive electrospray ionization tandem mass spectrometry (ESI-MS/MS). Microbore reversed-phase liquid chromatography (LC) performed with mobile phases containing trifluoroacetic acid, an additive commonly used for separating peptides, resulted in substantial suppression of the signal for KF on ESI-MS/MS. An alternative approach employing a basic mobile phase provided an excellent response for KF when detected in the positive ion mode. Plasma samples were prepared for LC MS/MS by solid-phase extraction on C(18) cartridges. The LC separation was performed on a Zorbax Extend C(18) column (150 x 2.1 mm i.d., particle size 5 micro m) with acetonitrile -10 mM aqueous ammonia (85 : 15, v/v) as the mobile phase, at a flow-rate of 0.20 ml min(-1). A butyric acid analogue of KF was used as the internal standard. The lower limit of quantitation (LLQ) using a 500 micro l sample volume was 1 ng ml(-1) and the linear dynamic range extended to 1000 ng ml(-1). The inter-assay accuracy of the assay was -15.1% at the LLQ and between -2.68 and -9.05% for quality control solutions ranging in concentration from 2.24 to 715 ng ml(-1). The inter-assay precision was 9.91% or better at these concentrations. The analyte was stable in plasma under all relevant conditions evaluated and for a period of 16 h after reconstituting plasma extracts for LC analysis at ambient temperature.
authors.affiliation: Department of Pharmacy and Pharmacology, Slotervaart Hospital/The Netherlands Cancer Institute, Louwesweg 6, 1066 EC Amsterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Stokvis
authors.forename: H
authors.initials: H
authors.lastname: Rosing
authors.forename: L
authors.initials: L
authors.lastname: López-Lázaro
authors.forename: I
authors.initials: I
authors.lastname: Rodriguez
authors.forename: J M
authors.initials: JM
authors.lastname: Jimeno
authors.forename: J G
authors.initials: JG
authors.lastname: Supko
authors.forename: J H M
authors.initials: JH
authors.lastname: Schellens
authors.forename: J H
authors.initials: JH
authors.lastname: Beijnen
mesh_terms: D000970:Antineoplastic Agents / Q000097:blood* / Q000493:pharmacokinetics; D019540:Area Under Curve; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D047630:Depsipeptides; D004355:Drug Stability; D006801:Humans; D010455:Peptides / Q000097:blood* / Q000493:pharmacokinetics; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000970:Antineoplastic Agents; D047630:Depsipeptides; D010455:Peptides; C097897:kahalalide F