Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) is activated in response to a variety of endoplasmic reticulum stresses implicated in numerous disease states. Evidence that PERK is ...implicated in tumorigenesis and cancer cell survival stimulated our search for small molecule inhibitors. Through screening and lead optimization using the human PERK crystal structure, we discovered compound 38 (GSK2606414), an orally available, potent, and selective PERK inhibitor. Compound 38 inhibits PERK activation in cells and inhibits the growth of a human tumor xenograft in mice.
We recently reported the discovery of GSK2606414 (1), a selective first in class inhibitor of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), which inhibited PERK activation in cells ...and demonstrated tumor growth inhibition in a human tumor xenograft in mice. In continuation of our drug discovery program, we applied a strategy to decrease inhibitor lipophilicity as a means to improve physical properties and pharmacokinetics. This report describes our medicinal chemistry optimization culminating in the discovery of the PERK inhibitor GSK2656157 (6), which was selected for advancement to preclinical development.
The arylsulfonamide derivatives described herein were such potent inhibitors of human immunodeficiency virus type 1 (HIV-1) protease (enzyme, E) that values for the inhibition constants (K(i)) could ...not be determined by conventional steady-state kinetic techniques (i.e., the minimal enzyme concentration usable for the activity assay was much greater than the value of the dissociation constant). Consequently, two alternative methods were developed for estimation of K(i) values. The first method employed kinetic determinations of values for k(1) and k(-1), from which K(i) was determined (k(-1)/k(1)). The second method was a competitive displacement assay used to determine binding affinities of other inhibitors relative to that of GW0385. In these assays, the inhibitor of unknown affinity was used to displace (3)HGW0385 from E.(3)HGW0385. From the concentration of E.(3)HGW0385 at equilibrium, the concentrations of enzyme-bound and free inhibitors were calculated, and the ratio of the K(i) value of the unknown to that of GW0385 was determined (K(i,unknown)/K(i,GW0385)). The values of k(1) were calculated from data in which changes in the intrinsic protein fluorescence of the enzyme associated with inhibitor binding were directly or indirectly monitored. In the case of saquinavir, the fluorescence changes associated with complex formation were large enough to monitor directly. The value of k(1) for saquinavir was 62 +/- 2 microM(-1) s(-1). In the case of GW0385, the fluorescence changes associated with complex formation were too small to monitor directly. Consequently, the value of k(1) was estimated from a competition experiment in which the effect of GW0385 on the binding of E to saquinavir was determined. The value of k(1) for GW0385 was estimated from these experiments to be 137 +/- 4 microM(-1) s(-1). Because E.(3)HGW0385 was stable in the standard buffer at room temperature for greater than 33 days, the value of the first-order rate constant for dissociation of E.(3)HGW0385 (k(-1)) could be estimated from the time-course for exchange of E.(3)HGW0385 with excess unlabeled GW0385. The value of k(-1) calculated from these data was (2.1 +/- 0.1) x10(-6) s(-1) (t(1/2) = 91 h). The K(i) value of wild-type HIV-1 protease for GW0385, calculated from these values for k(1) and k(-1), was 15 +/- 1 fM. Three multidrug resistant enzymes had K(i) values for GW0385 that were less than 5 pM.
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The c-MYC oncogene transcription factor has been implicated in cell cycle regulation controlling cell growth and proliferation. It is tightly regulated in normal cells, but has been ...shown to be deregulated in cancer cells, and is thus an attractive target for oncogenic therapies. Building upon previous SAR, a series of analogues containing benzimidazole core replacements were prepared and evaluated, leading to the identification of imidazopyridazine compounds that were shown to possess equivalent or improved c-MYC HTRF pEC50 values, lipophilicity, solubility, and rat pharmacokinetics. The imidazopyridazine core was therefore determined to be superior to the original benzimidazole core and a viable alternate for continued lead optimization and medicinal chemistry campaigns.
Investigation of TRPV4 as a potential target for the treatment of pulmonary edema associated with heart failure generated a novel series of acyclic amine inhibitors displaying exceptional potency and ...PK properties. The series arose through a scaffold hopping approach, which relied on use of an internal H-bond to replace a saturated heterocyclic ring. Optimization of the lead through investigation of both aryl regions revealed approaches to increase potency through substituents believed to enhance separate intramolecular and intermolecular H-bond interactions. A proposed internal H-bond between the amine and neighboring benzenesulfonamide was stabilized by electronically modulating the benzenesulfonamide. In the aryl ether moiety, substituents para to the nitrile demonstrated an electronic effect on TRPV4 recognition. Finally, the acyclic amines inactivated CYP3A4 and this liability was addressed by modifications that sterically preclude formation of a putative metabolic intermediate complex to deliver advanced TRPV4 antagonists as leads for discovery of novel medicines.
Herein we report the discovery of pyrazolocarboxamides as novel, potent, and kinase selective inhibitors of receptor interacting protein 2 kinase (RIP2). Fragment based screening and design ...principles led to the identification of the inhibitor series, and X-ray crystallography was used to inform key structural changes. Through key substitutions about the N1 and C5 N positions on the pyrazole ring significant kinase selectivity and potency were achieved. Bridged bicyclic pyrazolocarboxamide 11 represents a selective and potent inhibitor of RIP2 and will allow for a more detailed investigation of RIP2 inhibition as a therapeutic target for autoinflammatory disorders.
Phosphoinositide-dependent protein kinase-1(PDK1) is a master regulator of the AGC family of kinases and an integral component of the PI3K/AKT/mTOR pathway. As this pathway is among the most commonly ...deregulated across all cancers, a selective inhibitor of PDK1 might have utility as an anticancer agent. Herein we describe our lead optimization of compound 1 toward highly potent and selective PDK1 inhibitors via a structure-based design strategy. The most potent and selective inhibitors demonstrated submicromolar activity as measured by inhibition of phosphorylation of PDK1 substrates as well as antiproliferative activity against a subset of AML cell lines. In addition, reduction of phosphorylation of PDK1 substrates was demonstrated in vivo in mice bearing OCl-AML2 xenografts. These observations demonstrate the utility of these molecules as tools to further delineate the biology of PDK1 and the potential pharmacological uses of a PDK1 inhibitor.
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