ABSTRACT
Targeting the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway represents a promising anticancer strategy. Recently, we have reported a novel class of potent and selective non-ATP-competitive MEK1/2 inhibitors with a unique structure and mechanism of action. RO5068760 is a representative of this class showing significant efficacy in a broad spectrum of tumors with aberrant mitogen-activated protein kinase pathway activation. To understand the relationship between systemic exposures and target (MEK1/2) inhibition as well as tumor growth inhibition, the current study presents a detailed in vivo characterization of efficacy, pharmacokinetics, and pharmacodynamics of RO5068760 in multiple xenograft tumor models. For inhibition of MEK1/2 as measured by the phosphorylated ERK levels, the estimated EC(50)s in plasma were 1.36 micromol/L (880 ng/mL) and 3.35 micromol/L (2168 ng/mL) in LOX melanoma and HT-29 colorectal cancer models, respectively. A similar EC(50) (1.41 micromol/L or 915 ng/mL) was observed in monkey peripheral blood lymphocytes. To achieve tumor growth inhibition (>or=90%), an average plasma drug concentration of 0.65 or 5.23 micromol/L was required in B-RafV600E or K-Ras mutant tumor models, respectively, which were remarkably similar to the IC(90) values (0.64 or 4.1 micromol/L) determined in vitro for cellular growth inhibition. With equivalent in vivo systemic exposures, RO5068760 showed superior efficacy in tumors harboring B-RafV600E mutation. The plasma concentration time profiles indicate that constant p-ERK suppression (>50%) may not be required for optimal efficacy, especially in highly responsive tumors. This study may facilitate future clinical trial design in using biochemical markers for early proof of mechanism and in selecting the right patients and optimal dose regimen.
Subject(s)
Imidazolidines/pharmacology , Imidazolidines/pharmacokinetics , MAP Kinase Kinase 1/antagonists & inhibitors , MAP Kinase Kinase 2/antagonists & inhibitors , Phenylbutyrates/pharmacology , Phenylbutyrates/pharmacokinetics , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/pharmacokinetics , Xenograft Model Antitumor Assays , Animals , Cell Line, Tumor , Drug Screening Assays, Antitumor , Humans , Imidazolidines/blood , Imidazolidines/chemistry , Macaca fascicularis , Mice , Mice, Nude , Phenylbutyrates/blood , Phenylbutyrates/chemistry , Protein Kinase Inhibitors/blood , Protein Kinase Inhibitors/chemistryABSTRACT
The mitogen-activated protein kinase (MAPK) signal transduction pathway plays a central role in regulating tumor cell growth, survival, differentiation, and angiogenesis. The key components of the Ras/Raf/MEK/ERK signal module are frequently altered in human cancers. Targeting this pathway represents a promising anticancer strategy. Small molecule inhibitors targeting MEK1/2 have shown promise in the clinic; however, ultimate clinical proof-of-concept remains elusive. Here, we report a potent and highly selective non-ATP-competitive MEK1/2 inhibitor, RO4927350, with a novel chemical structure and unique mechanism of action. It selectively blocks the MAPK pathway signaling both in vitro and in vivo, which results in significant antitumor efficacy in a broad spectrum of tumor models. Compared with previously reported MEK inhibitors, RO4927350 inhibits not only ERK1/2 but also MEK1/2 phosphorylation. In cancer cells, high basal levels of phospho-MEK1/2 rather than phospho-ERK1/2 seem to correlate with greater sensitivity to RO4927350. Furthermore, RO4927350 prevents a feedback increase in MEK phosphorylation, which has been observed with other MEK inhibitors. We show that B-Raf rather than C-Raf plays a critical role in the feedback regulation. The unique MAPK signaling blockade mediated by RO4927350 in cancer may reduce the risk of developing drug resistance. Thus, RO4927350 represents a novel therapeutic modality in cancers with aberrant MAPK pathway activation.
Subject(s)
Antineoplastic Agents/pharmacology , Imidazoles/pharmacology , MAP Kinase Kinase 1/antagonists & inhibitors , MAP Kinase Kinase 2/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Thiazoles/pharmacology , Animals , Cell Line , Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Humans , MAP Kinase Kinase 1/metabolism , MAP Kinase Kinase 2/metabolism , MAP Kinase Signaling System/drug effects , Macaca fascicularis , Mice , PhosphorylationABSTRACT
New modifications on the C-8 4-aminobenzyl unit of the previously reported 3-alkyl-1,8-dibenzylxanthine inhibitors of cPEPCK are presented. The most active compound reported here is the 5-chloro-1,3-dimethyl-1H-pyrazole-4-sulfonic acid amide derivative 2 with an IC(50) of 0.29+/-0.08 microM. An X-ray analysis of a heteroaromatic sulfonamide is presented showing a new pi-pi interaction.
Subject(s)
Cytosol/enzymology , Enzyme Inhibitors/pharmacology , Phosphoenolpyruvate Carboxykinase (GTP)/antagonists & inhibitors , Xanthines/pharmacology , Enzyme Inhibitors/chemistry , Humans , Models, Molecular , Xanthines/chemistryABSTRACT
A systematic structure-activity relationship investigation of the lead compound 1 resulted the identification of several N-[(substituted alkyl)cycloalkanoyl]-4-[((2,6-dichlorophenyl)carbonyl)amino]-L-phenylalanine derivatives as potent VCAM/VLA-4 antagonists. The data are consistent with a model of these compounds in which these alkanoylphenylalanines reside in a compact gauche (-) bioactive conformation.
