title: Development of methods for the bioanalysis of RRx-001 and metabolites.
abstract: BACKGROUND
  Bioanalytical methods were required to study the novel anticancer drug, RRx-001 preclinically and for clinical pharmacokinetic analysis; however, RRx-001 quickly and completely disappeared on intravenous administration in preclinical species.
  
  
  RESULTS
  Quantification of RRx-001 directly or by derivatization was unsuccessful. On exposure to whole blood, RRx-001 formed the glutathione (GSH) adduct very rapidly, suggesting this metabolite as the bioanalyte. However, rapid enzymatic degradation in the blood matrix of RRx-001-GSH posed significant technical problems. Herein, we describe a novel and broadly applicable solution to stabilize GSH conjugates in blood samples by inhibiting the degrading enzyme. Liquid chromatography-tandem mass spectrometry methods for analysis of RRx-001-GSH in rat, dog and human plasma were developed and successfully validated to good laboratory practice standards.
  
  
  CONCLUSIONS
  Extensive breakdown of RRx-001-GSH was effectively stopped by addition of the enzyme inhibitor, acivicin. The developed liquid chromatography-tandem mass spectrometry assay for RRx-001-GSH was validated for use in preclinical toxicology studies and the Phase I first-in-human clinical trial.
authors.affiliation: RadioRx Inc., 800 W El Camino Real, Suite 180, Mountain View, CA  94040, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Scicinski
authors.forename: Bryan
authors.initials: B
authors.lastname: Oronsky
authors.forename: Vance
authors.initials: V
authors.lastname: Cooper
authors.forename: Michael
authors.initials: M
authors.lastname: Taylor
authors.forename: Mike
authors.initials: M
authors.lastname: Alexander
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hadar
authors.forename: Rebecca
authors.initials: R
authors.lastname: Cosford
authors.forename: Thomas
authors.initials: T
authors.lastname: Fleischmann
authors.forename: William L
authors.initials: WL
authors.lastname: Fitch
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism* / Q000493:pharmacokinetics; D001384:Azetidines / Q000378:metabolism* / Q000493:pharmacokinetics; D002138:Calibration; D002853:Chromatography, Liquid; D004285:Dogs; D006801:Humans; D009574:Nitro Compounds / Q000378:metabolism* / Q000493:pharmacokinetics; D051381:Rats; D053719:Tandem Mass Spectrometry
chemical_list: D000970:Antineoplastic Agents; D001384:Azetidines; D009574:Nitro Compounds; C577469:RRx-001