title: In vitro cytotoxicity and in vivo efficacy, pharmacokinetics, and metabolism of 10074-G5, a novel small-molecule inhibitor of c-Myc/Max dimerization.
abstract: The c-Myc oncoprotein is overexpressed in many tumors and is essential for maintaining the proliferation of transformed cells. To function as a transcription factor, c-Myc must dimerize with Max via the basic helix-loop-helix leucine zipper protein (bHLH-ZIP) domains in each protein. The small molecule 7-nitro-N-(2-phenylphenyl)-2,1,3-benzoxadiazol-4-amine (10074-G5) binds to and distorts the bHLH-ZIP domain of c-Myc, thereby inhibiting c-Myc/Max heterodimer formation and inhibiting its transcriptional activity. We report in vitro cytotoxicity and in vivo efficacy, pharmacodynamics, pharmacokinetics, and metabolism of 10074-G5 in human xenograft-bearing mice. In vitro, 10074-G5 inhibited the growth of Daudi Burkitt's lymphoma cells and disrupted c-Myc/Max dimerization. 10074-G5 had no effect on the growth of Daudi xenografts in C.B-17 SCID mice that were treated with 20 mg/kg 10074-G5 intravenously for 5 consecutive days. Inhibition of c-Myc/Max dimerization in Daudi xenografts was not seen 2 or 24 h after treatment. Concentrations of 10074-G5 in various matrices were determined by high-performance liquid chromatography-UV, and metabolites of 10074-G5 were identified by liquid chromatography/tandem mass spectrometry. The plasma half-life of 10074-G5 in mice treated with 20 mg/kg i.v. was 37 min, and peak plasma concentration was 58 μM, which was 10-fold higher than peak tumor concentration. The lack of antitumor activity probably was caused by the rapid metabolism of 10074-G5 to inactive metabolites, resulting in tumor concentrations of 10074-G5 insufficient to inhibit c-Myc/Max dimerization. Our identification of 10074-G5 metabolites in mice will help design new, more metabolically stable small-molecule inhibitors of c-Myc.
authors.affiliation: Molecular Therapeutics/Drug Discovery Program, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Dana M
authors.initials: DM
authors.lastname: Clausen
authors.forename: Jianxia
authors.initials: J
authors.lastname: Guo
authors.forename: Robert A
authors.initials: RA
authors.lastname: Parise
authors.forename: Jan H
authors.initials: JH
authors.lastname: Beumer
authors.forename: Merrill J
authors.initials: MJ
authors.lastname: Egorin
authors.forename: John S
authors.initials: JS
authors.lastname: Lazo
authors.forename: Edward V
authors.initials: EV
authors.lastname: Prochownik
authors.forename: Julie L
authors.initials: JL
authors.lastname: Eiseman
mesh_terms: D000825:Animal Structures / Q000378:metabolism; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000627:therapeutic use; D005243:Feces / Q000737:chemistry; D005260:Female; D005965:Glucuronates / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008099:Liver / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D010069:Oxadiazoles / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D010949:Plasma / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects*; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D013844:Thiazoles / Q000494:pharmacology; D016896:Treatment Outcome; D014556:Urine / Q000737:chemistry; D023041:Xenograft Model Antitumor Assays
chemical_list: C534883:10074-G5; C524814:5-(4-ethylbenzylidene)-2-thioxothiazolidin-4-one; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001798:Blood Proteins; D005965:Glucuronates; C499330:MAX protein, human; C489427:MYC protein, human; D010069:Oxadiazoles; D016271:Proto-Oncogene Proteins c-myc; D013844:Thiazoles; D004317:Doxorubicin; D005966:Glucuronidase
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