Christopher J. Dinsmore

Parallel Synthesis of Ureas and Carbamates from Amines and CO2 under Mild Conditions

A mild and efficient library synthesis technique has been developed for the synthesis of ureas and carbamates from carbamic acids derived from the DBU-catalyzed reaction of amines and gaseous carbon dioxide. Carbamic acids derived from primary amines reacted with Mitsunobu reagents to generate isocyanates in situ which were condensed with primary and secondary amines to afford the desired ureas. Similarly, carbamic acids from secondary amines reacted with alcohols activated with Mitsunobu reagents to form carbamates.

Discovery of 1-[3-(1-Methyl-1H-pyrazol-4-yl)-5-oxo-5H-benzo[4,5]cyclohepta[1,2-b]pyridin-7-yl]-N-(pyridin-2-ylmethyl)methanesulfonamide (MK-8033): A Specific c-Met/Ron Dual Kinase Inhibitor with Preferential Affinity for the Activated State of c-Met

This report documents the first example of a specific inhibitor of protein kinases with preferential binding to the activated kinase conformation: 5H-benzo[4,5]cyclohepta[1,2-b]pyridin-5-one 11r (MK-8033), a dual c-Met/Ron inhibitor under investigation as a treatment for cancer. The design of 11r was based on the desire to reduce time-dependent inhibition of CYP3A4 (TDI) by members of this structural class. A novel two-step protocol for the synthesis of benzylic sulfonamides was developed to access 11r and analogues. We provide a rationale for the observed selectivity based on X-ray crystallographic evidence and discuss selectivity trends with additional examples. Importantly, 11r provides full inhibition of tumor growth in a c-Met amplified (GTL-16) subcutaneous tumor xenograft model and may have an advantage over inactive form kinase inhibitors due to equal potency against a panel of oncogenic activating mutations of c-Met in contrast to c-Met inhibitors without preferential binding to the active kinase conformation.

The discovery of tricyclic pyridone JAK2 inhibitors. Part 1: hit to lead.

This paper describes the discovery and design of a novel class of JAK2 inhibitors. Furthermore, we detail the optimization of a screening hit using ligand binding efficiency and log D. These efforts led to the identification of compound 41, which demonstrates in vivo activity in our study.

Preparation of a stable trifluoroborate salt for the synthesis of 1-aryl-2,2-difluoro-enolethers and/or 2,2-difluoro-1-aryl-ketones via palladium-mediated cross-coupling.

A bench-stable potassium trifluoroborate enol ether reagent has been prepared. This reagent is suitable for the incorporation of 2,2-difluoroenolethers into aryl and heteroaryl systems via palladium-mediated cross-coupling with suitable halide coupling partners.

Discovery of triarylethanolamine inhibitors of the Kv1.5 potassium channel.

A series of triarylethanolamine inhibitors of the Kv1.5 potassium channel have been prepared and evaluated for their effects in vitro and in vivo. The structure-activity relationship (SAR) studies described herein led to the development of potent, selective and orally active inhibitors of Kv1.5.

Evaluation of JAK3 biology in autoimmune disease using a highly selective, irreversible JAK3 inhibitor

Reversible janus associated kinase (JAK) inhibitors such as tofacitinib and decernotinib block cytokine signaling and are efficacious in treating autoimmune diseases. However, therapeutic doses are limited due to inhibition of other JAK/signal transducer and activator of transcription pathways associated with hematopoiesis, lipid biogenesis, infection, and immune responses. A selective JAK3 inhibitor may have a better therapeutic index; however, until recently, no compounds have been described that maintain JAK3 selectivity in cells, as well as against the kinome, with good physicochemical properties to test the JAK3 hypothesis in vivo. To quantify the biochemical basis for JAK isozyme selectivity, we determined that the apparent Km value for each JAK isozyme ranged from 31.8 to 2.9 μM for JAK1 and JAK3, respectively. To confirm compound activity in cells, we developed a novel enzyme complementation assay that read activity of single JAK isozymes in a cellular context. Reversible JAK3 inhibitors cannot achieve sufficient selectivity against other isozymes in the cellular context due to inherent differences in enzyme ATP Km values. Therefore, we developed irreversible JAK3 compounds that are potent and highly selective in vitro in cells and against the kinome. Compound 2, a potent inhibitor of JAK3 (0.15 nM) was 4300-fold selective for JAK3 over JAK1 in enzyme assays, 67-fold [interleukin (IL)-2 versus IL-6] or 140-fold [IL-2 versus erythropoietin or granulocyte-macrophage colony-stimulating factor (GMCSF)] selective in cellular reporter assays and >35-fold selective in human peripheral blood mononuclear cell assays (IL-7 versus IL-6 or GMCSF). In vivo, selective JAK3 inhibition was sufficient to block the development of inflammation in a rat model of rheumatoid arthritis, while sparing hematopoiesis.

Discovery of MK-1832, a Kv1.5 inhibitor with improved selectivity and pharmacokinetics.

Selective inhibition of Kv1.5, which underlies the ultra-rapid delayed rectifier current, IKur, has been pursued as a treatment for atrial fibrillation. Here we describe the discovery of MK-1832, a Kv1.5 inhibitor with improved selectivity versus the off-target current IKs, whose inhibition has been associated with ventricular proarrhythmia. MK-1832 exhibits improved selectivity for IKur over IKs (>3000-fold versus 70-fold for MK-0448), consistent with an observed larger window between atrial and ventricular effects in vivo (>1800-fold versus 210-fold for MK-0448). MK-1832 also exhibits an improved preclinical pharmacokinetic profile consistent with projected once daily dosing in humans.

The discovery of reverse tricyclic pyridone JAK2 inhibitors. Part 2: Lead optimization

This communication discusses the discovery of novel reverse tricyclic pyridones as inhibitors of Janus kinase 2 (JAK2). By using a kinase cross screening approach coupled with molecular modeling, a unique inhibitor-water interaction was discovered to impart excellent broad kinase selectivity. Improvements in intrinsic potency were achieved by utilizing a rapid library approach, while targeted structural changes to lower lipophilicity led to improved rat pharmacokinetics. This multi-pronged approach led to the identification of 31, which demonstrated encouraging rat pharmacokinetics, in vivo potency, and excellent off-target kinase selectivity.

Abstract C209: Inhibition of both c‐Met and EGFR signaling shows synergistic antitumor activity in non‐small cell lung cancer model

c‐Met and ErbB family of receptors including EGFR, ErbB‐2, ErbB‐3 and ErbB‐4 are co‐expressed in many human tumors including Non‐Small Cell Lung Cancers (NSCLC). Several reports suggest that the activation of c‐Met and ErbB family receptors is associated with poor prognosis in multiple tumors types. Recently it has been shown that activation of c‐Met is common in Erlotinib and Gefitinib‐resistant NSCLC patients. Combining c‐Met and EGFR inhibitors has been proposed as a strategy for treatment in EGFR inhibitor‐refractory lung cancers. To understand the cooperation of these pathways, we used a c‐Met activated human NSCLC cell line (EBC‐1), where EGFR signaling network is also active. In vitro treatment of EBC‐1 cells with a combination of Erlotinib and MK‐8033 (an inhibitor of c‐Met and RON kinases) resulted in greater growth inhibition relative to treatment with either agent alone. In order to validate these in vitro data, we have tested MK‐8033 and EGFR inhibitors (Erlotinib and Gefitinib) in vivo. The data suggests the effect of MK‐8033 with Gefitinib or Erlotinib on tumor growth is greater when combined as compared to monotherapy in this preclinical xenograft model. PK data suggests no drug‐drug interaction of MK‐8033 and EGFR inhibitor when administered together. Exposure of these agents was sufficient to inhibit both kinases in tumors. Our studies provide a rationale for the combination of MK‐8033 and Erlotinib or Gefitinib in EGFRi refractory patients with NSCLC. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C209.