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: Dana M Clausen, Jianxia Guo, Robert A Parise, Jan H Beumer, Merrill J Egorin, John S Lazo, Edward V Prochownik, Julie L Eiseman
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 335 Issue 3 Pg. 715-27 (Dec 2010) ISSN: 1521-0103 [Electronic] United States
• PMID: 20801893 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• 10074-G5
• 5-(4-ethylbenzylidene)-2-thioxothiazolidin-4-one
• Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
• Blood Proteins
• Glucuronates
• MAX protein, human
• MYC protein, human
• Oxadiazoles
• Proto-Oncogene Proteins c-myc
• Thiazoles
• Doxorubicin
• Glucuronidase

Topics

• Animal Structures (metabolism)
• Animals
• Basic Helix-Loop-Helix Leucine Zipper Transcription Factors (antagonists & inhibitors, metabolism)
• Blood Proteins (metabolism)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Doxorubicin (therapeutic use)
• Feces (chemistry)
• Female
• Glucuronates (metabolism)
• Glucuronidase (metabolism)
• HL-60 Cells
• Humans
• Inhibitory Concentration 50
• Liver (metabolism)
• Mice
• Mice, SCID
• Neoplasms (metabolism, pathology)
• Oxadiazoles (metabolism, pharmacokinetics, pharmacology, therapeutic use, toxicity)
• Plasma (metabolism)
• Protein Binding (drug effects)
• Protein Multimerization (drug effects)
• Proto-Oncogene Proteins c-myc (antagonists & inhibitors, metabolism)
• Tandem Mass Spectrometry
• Thiazoles (pharmacology)
• Treatment Outcome
• Urine (chemistry)
• Xenograft Model Antitumor Assays