title: Characterization of the metabolism of benzaldehyde dimethane sulfonate (NSC 281612, DMS612).
abstract: BACKGROUND
  Benzaldehyde dimethane sulfonate (BEN, DMS612, NSC281612) is a bifunctional alkylating agent currently in clinical trials. We previously characterized the degradation products of BEN in plasma and blood. The conversion of BEN to its carboxylic acid analogue (BA) in whole blood, but not plasma, suggests that an enzyme in RBCs may be responsible for this conversion. BEN conversion to BA was observed in renal carcinoma cells and appeared to correlate with IC₅₀. To better understand the pharmacology of BEN, we aimed to evaluate the metabolism and enzymes potentially responsible for the conversion of BEN to BA.
  
  
  METHODS
  Human red blood cells (RBC) were used to characterize kinetics and susceptibility to enzyme-specific inhibitors. Recombinant enzymes were used to confirm metabolism of BEN to BA. Analytes were quantitated with established LC-MS/MS methods.
  
  
  RESULTS
  Average apparent Vmax and Km were 68 ng/mL min(-1) [10% RBC](-1) and 373 ng/mL, respectively. The conversion of BEN to BA in RBC was not inhibited by carbon monoxide, nitrogen gas, or menadione, an inhibitor of aldehyde oxidase. The conversion was inhibited by disulfiram, an inhibitor of ALDH. Of available ALDH isoforms ALDH1A1, ALDH3A1, ALDH2, and ALDH5A1, only ALDH1A1 converted BEN to BA.
  
  
  CONCLUSIONS
  The activating conversion of BEN to BA is mediated not by CYP450 enzymes or aldehyde oxidase, but by ALDH1A1. This enzyme, a potential stem cell marker, may be a candidate biomarker for clinical activity of BEN.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Hillman Research Pavilion, Room G27E, 5117 Centre Avenue, Pittsburgh, PA, 15213-1863, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Parise
authors.forename: Julie L
authors.initials: JL
authors.lastname: Eiseman
authors.forename: Dana M
authors.initials: DM
authors.lastname: Clausen
authors.forename: Kimberly P
authors.initials: KP
authors.lastname: Kicielinski
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Hershberger
authors.forename: Merrill J
authors.initials: MJ
authors.lastname: Egorin
authors.forename: Jan H
authors.initials: JH
authors.lastname: Beumer
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000097:blood*; D001547:Benzaldehydes / Q000097:blood*; D002292:Carcinoma, Renal Cell / Q000097:blood* / Q000201:enzymology; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007680:Kidney Neoplasms / Q000097:blood*
chemical_list: D018906:Antineoplastic Agents, Alkylating; D001547:Benzaldehydes; C492379:NSC281612