Biotransformation and Rearrangement of Laromustine.
This review highlights the recent research into the biotransformations and rearrangement of the sulfonylhydrazine-alkylating agent laromustine. Incubation of [(14)C]laromustine with rat, dog, monkey, and human liver microsomes produced eight radioactive components (C-1 to C-8). There was little difference in the metabolite profile among the species examined, partly because NADPH was not required for the formation of most components, which instead involved decomposition and/or hydrolysis. The exception was C-7, a hydroxylated metabolite, largely formed by CYP2B6 and CYP3A4/5. Liquid chromatography-multistage mass spectrometry (LC-MS(n)) studies determined that collision-induced dissociation, and not biotransformation or enzyme catalysis, produced the unique mass spectral rearrangement. Accurate mass measurements performed with a Fourier-transform ion cyclotron resonance mass spectrometer (FTICR-MS) significantly aided determination of the elemental compositions of the fragments and in the case of laromustine revealed the possibility of rearrangement. Further, collision-induced dissociation produced the loss of nitrogen (N2) and methylsulfonyl and methyl isocyanate moieties. The rearrangement, metabolite/decomposition products, and conjugation reactions were analyzed utilizing hydrogen-deuterium exchange, exact mass, (13)C-labeled laromustine, nuclear magnetic resonance spectroscopy (NMR), and LC-MS(n) experiments to assist with the assignments of these fragments and possible mechanistic rearrangement. Such techniques produced valuable insights into these functions: 1) Cytochrome P450 is involved in C-7 formation but plays little or no role in the conversion of [(14)C]laromustine to C-1 through C-6 and C-8; 2) the relative abundance of individual degradation/metabolite products was not species-dependent; and 3) laromustine produces several reactive intermediates that may produce the toxicities seen in the clinical trials.
Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut (A.-E.F.N., A.V.W.); Department of Chemistry, University of Connecticut, Storrs, Connecticut (A.-E.F.N.); Metastagen, Inc., Wilmington, Delaware (I.K.) ala.nassar@yale.edu.
Alaa-Eldin F
AE
Nassar
Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut (A.-E.F.N., A.V.W.); Department of Chemistry, University of Connecticut, Storrs, Connecticut (A.-E.F.N.); Metastagen, Inc., Wilmington, Delaware (I.K.).
Adam V
AV
Wisnewski
Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut (A.-E.F.N., A.V.W.); Department of Chemistry, University of Connecticut, Storrs, Connecticut (A.-E.F.N.); Metastagen, Inc., Wilmington, Delaware (I.K.).
Ivan
I
King
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D001711:Biotransformation; D065702:Cytochrome P-450 CYP2B6 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D004285:Dogs; D000882:Haplorhini; D006801:Humans; D006834:Hydrazines / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D006900:Hydroxylation; D008862:Microsomes, Liver / Q000201:enzymology*; D015394:Molecular Structure; D051381:Rats; D013379:Substrate Specificity; D013449:Sulfonamides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity
D018906:Antineoplastic Agents, Alkylating; D006834:Hydrazines; D013449:Sulfonamides; C483604:laromustine; C585599:CYP2B6 protein, human; C510164:CYP3A5 protein, human; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human