Discovery of 3-(3-(4-(1-Aminocyclobutyl)phenyl)-5-phenyl-3H-imidazo[4,5-b]pyridin-2-yl)pyridin-2-amine (ARQ 092): An Orally Bioavailable, Selective, and Potent Allosteric AKT Inhibitor.

The work in this paper describes the optimization of the 3-(3-phenyl-3H-imidazo[4,5-b]pyridin-2-yl)pyridin-2-amine chemical series as potent, selective allosteric inhibitors of AKT kinases, leading to the discovery of ARQ 092 (21a). The cocrystal structure of compound 21a bound to full-length AKT1 confirmed the allosteric mode of inhibition of this chemical class and the role of the cyclobutylamine moiety. Compound 21a demonstrated high enzymatic potency against AKT1, AKT2, and AKT3, as well as potent cellular inhibition of AKT activation and the phosphorylation of the downstream target PRAS40.

Discovery and optimization of a series of 3-(3-phenyl-3H-imidazo[4,5-b]pyridin-2-yl)pyridin-2-amines: orally bioavailable, selective, and potent ATP-independent Akt inhibitors.

This paper describes the implementation of a biochemical and biophysical screening strategy to identify and optimize small molecule Akt1 inhibitors that act through a mechanism distinct from that observed for kinase domain ATP-competitive inhibitors. With the aid of an unphosphorylated Akt1 cocrystal structure of 12j solved at 2.25 Å, it was possible to confirm that as a consequence of binding these novel inhibitors, the ATP binding cleft contained a number of hydrophobic residues that occlude ATP binding as expected.

A novel mode of protein kinase inhibition exploiting hydrophobic motifs of autoinhibited kinases: discovery of ATP-independent inhibitors of fibroblast growth factor receptor.

Protein kinase inhibitors with enhanced selectivity can be designed by optimizing binding interactions with less conserved inactive conformations because such inhibitors will be less likely to compete with ATP for binding and therefore may be less impacted by high intracellular concentrations of ATP. Analysis of the ATP-binding cleft in a number of inactive protein kinases, particularly in the autoinhibited conformation, led to the identification of a previously undisclosed non-polar region in this cleft. This ATP-incompatible hydrophobic region is distinct from the previously characterized hydrophobic allosteric back pocket, as well as the main pocket.

Discovery of a novel mode of protein kinase inhibition characterized by the mechanism of inhibition of human mesenchymal-epithelial transition factor (c-Met) protein autophosphorylation by ARQ 197.

A number of human malignancies exhibit sustained stimulation, mutation, or gene amplification of the receptor tyrosine kinase human mesenchymal-epithelial transition factor (c-Met). ARQ 197 is a clinically advanced, selective, orally bioavailable, and well tolerated c-Met inhibitor, currently in Phase 3 clinical testing in non-small cell lung cancer patients. Herein, we describe the molecular and structural basis by which ARQ 197 selectively targets c-Met.

In vitro metabolism of beta-lapachone (ARQ 501) in mammalian hepatocytes and cultured human cells.

ARQ 501 (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione, beta-lapachone) is an anticancer agent, currently in multiple phase II clinical trials as monotherapy and in combination with other cytotoxic drugs. This study focuses on in vitro metabolism in cryopreserved hepatocytes from mice, rats, dogs and humans using [(14)C]-labeled ARQ 501. Metabolite profiles were characterized using liquid chromatography/mass spectrometry combined with an accurate radioactivity counter.

Synthetic methods for the preparation of ARQ 501 (beta-Lapachone) human blood metabolites.

ARQ 501 (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b] pyran-5,6-dione), a synthetic version of beta-Lapachone, is a promising anti-cancer agent currently in multiple Phase II clinical trials. Promising anti-cancer activity was observed in Phase I and Phase II trials. Metabolism by red blood cells of drugs is an understudied area of research and the metabolites arising from oxidative ring opening (M2 and M3), decarbonylation/ring contraction (M5), and decarbonylation/oxidation (M4 and M6) of ARQ 501 offer a unique opportunity to provide insight into these metabolic processes.

Identification of the in vitro metabolites of 3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; beta-lapachone) in whole blood.

3,4-Dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione (ARQ 501; beta-lapachone) showed promising anticancer activity in phase I clinical trials as monotherapy and in combination with cytotoxic drugs. ARQ 501 is currently in multiple phase II clinical trials. In vitro incubation in fresh whole blood at 37 degrees C revealed that ARQ 501 is stable in plasma but disappears rapidly in whole blood.

Insight into the reactive form of the anticancer agent iproplatin.

The reaction of iproplatin with reduced glutathione at different mole ratios yielded cis-di(isopropylamine)chloro-glutathionatoplatinum(II), not the expected cis-dichloro- species, indicating a mode of action of this anticancer agent that is different from that of cis-diamminedichloroplatinum(II).

Unwinding of DNA polymerases by the antitumor drug, cis-diamminedichloroplatinum(II).

The helix-turn-helix motifs of the DNA binding domains of human polymerase-alpha and polymerase-kappa are dramatically perturbed upon binding to cisplatin with concomitant release of zinc.

HPLC determination of binding of cisplatin to DNA in the presence of biological thiols: implications of dominant platinum-thiol binding to its anticancer action.

Purpose: The purpose of this work is to evaluate the extent of the binding of cisplatin (cis-diamminedichloroplatinum(II)) to DNA in the presence and absence of biological thiols, glutathione, and cysteine, and to test the hypothesis whether the platinum-thiol complexes can serve as a drug reservoir for subsequent binding to DNA.

Methods: Reactions of cisplatin (50 microM to 1.0 mM) with calf thymus DNA (870 microM to 6.