Discovery of the c-Jun N-Terminal Kinase Inhibitor

As a result of emerging biological data suggesting that within the c-Jun N-terminal kinase (JNK) family, JNK1 and not JNK2 or JNK3 may be primarily responsible for fibrosis pathology, we sought to identify JNK inhibitors with an increased JNK1 bias relative to our previous clinical compound tanzisertib (CC-930). This manuscript reports the synthesis and structure-activity relationship (SAR) studies for a novel series of JNK inhibitors demonstrating an increased JNK1 bias. SAR optimization on a series of 2,4-dialkylamino-pyrimidine-5-carboxamides resulted in the identification of compounds possessing low nanomolar JNK inhibitory potency, overall kinome selectivity, and the ability to inhibit cellular phosphorylation of the direct JNK substrate c-Jun. Optimization of physicochemical properties in this series resulted in compounds that demonstrated excellent systemic exposure following oral dosing, enabling in vivo efficacy studies and the selection of a candidate for clinical development, CC-90001, which is currently in clinical trials (Phase II) in patients with idiopathic pulmonary fibrosis (NCT03142191).

Discovery of the Selective Protein Kinase C-θ Kinase Inhibitor, CC-90005

The PKC-θ isoform of protein kinase C is selectively expressed in T lymphocytes and plays an important role in the T cell antigen receptor (TCR)-triggered activation of mature T cells, T cell proliferation, and the subsequent release of cytokines such as interleukin-2 (IL-2). Herein, we report the synthesis and structure-activity relationship (SAR) of a novel series of PKC-θ inhibitors. Through a combination of structure-guided design and exploratory SAR, suitable replacements for the basic C4 amine of the original lead (3) were identified. Property-guided design enabled the identification of appropriately substituted C2 groups to afford potent analogs with metabolic stability and permeability to support in vivo testing. With exquisite general kinase selectivity, cellular inhibition of T cell activation as assessed by IL-2 expression, a favorable safety profile, and demonstrated in vivo efficacy in models of acute and chronic T cell activation with oral dosing, CC-90005 (57) was selected for clinical development.

Optimization of a Series of Triazole Containing Mammalian Target of Rapamycin (mTOR) Kinase Inhibitors and the Discovery of CC-115

We report here the synthesis and structure-activity relationship (SAR) of a novel series of triazole containing mammalian target of rapamycin (mTOR) kinase inhibitors. SAR studies examining the potency, selectivity, and PK parameters for a series of triazole containing 4,6- or 1,7-disubstituted-3,4-dihydropyrazino[2,3-b]pyrazine-2(1H)-ones resulted in the identification of triazole containing mTOR kinase inhibitors with improved PK properties. Potent compounds from this series were found to block both mTORC1(pS6) and mTORC2(pAktS473) signaling in PC-3 cancer cells, in vitro and in vivo. When assessed in efficacy models, analogs exhibited dose-dependent efficacy in tumor xenograft models. This work resulted in the selection of CC-115 for clinical development.

CC-223, a Potent and Selective Inhibitor of mTOR Kinase: In Vitro and In Vivo Characterization

mTOR is a serine/threonine kinase that regulates cell growth, metabolism, proliferation, and survival. mTOR complex-1 (mTORC1) and mTOR complex-2 (mTORC2) are critical mediators of the PI3K-AKT pathway, which is frequently mutated in many cancers, leading to hyperactivation of mTOR signaling. Although rapamycin analogues, allosteric inhibitors that target only the mTORC1 complex, have shown some clinical activity, it is hypothesized that mTOR kinase inhibitors, blocking both mTORC1 and mTORC2 signaling, will have expanded therapeutic potential. Here, we describe the preclinical characterization of CC-223. CC-223 is a potent, selective, and orally bioavailable inhibitor of mTOR kinase, demonstrating inhibition of mTORC1 (pS6RP and p4EBP1) and mTORC2 [pAKT(S473)] in cellular systems. Growth inhibitory activity was demonstrated in hematologic and solid tumor cell lines. mTOR kinase inhibition in cells, by CC-223, resulted in more complete inhibition of the mTOR pathway biomarkers and improved antiproliferative activity as compared with rapamycin. Growth inhibitory activity and apoptosis was demonstrated in a panel of hematologic cancer cell lines. Correlative analysis revealed that IRF4 expression level associates with resistance, whereas mTOR pathway activation seems to associate with sensitivity. Treatment with CC-223 afforded in vivo tumor biomarker inhibition in tumor-bearing mice, after a single oral dose. CC-223 exhibited dose-dependent tumor growth inhibition in multiple solid tumor xenografts. Significant inhibition of mTOR pathway markers pS6RP and pAKT in CC-223-treated tumors suggests that the observed antitumor activity of CC-223 was mediated through inhibition of both mTORC1 and mTORC2. CC-223 is currently in phase I clinical trials.

Characterization and kinetic mechanism of catalytic domain of human vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR2 TK), a key enzyme in angiogenesis

Vascular endothelial growth factor (VEGF) is a dimeric protein which induces formation of new blood vessels (angiogenesis) through binding to VEGF-receptor-2 tyrosine kinase (VEGFR2 TK) or KDR (kinase insert domain-containing receptor) on the surface of endothelial cells. Angiogenesis has been shown to be essential for malignancy of tumors; therefore, VEGFR2 TK is a potential therapeutic target for the treatment of cancer. Sequence homology studies indicate that VEGFR2 TK contains three domains: extracellular (ligand-binding domain), transmembrane, and intracellular (catalytic domain). In this work, the catalytic domain of VEGFR2 TK was cloned and expressed in a soluble active form using a baculovirus expression system. In the absence of ligand, the enzyme is shown to catalyze its autophosphorylation in a time-dependent and enzyme-concentration-dependent manner, consistent with a trans mechanism for this reaction. Mass spectrometry analysis revealed incorporation of 5.5 +/- 0.5 mol of phosphate/mole of enzyme (monomer). In addition, the enzyme was shown to catalyze phosphorylation of a synthetic peptide, poly(E4Y). Using poly(E4Y) as substrate, the kinetic constants of both native and phosphorylated enzyme were determined. Enzyme phosphorylation increased catalytic efficiency of the enzyme by at least an order of magnitude. Furthermore, the enzyme was shown to catalyze the reverse reaction using phospho-poly(E4Y) as substrate. Cd2+ was found to be an inhibitor of the enzyme. Kinetic studies revealed that inhibition by Cd2+ was competitive with respect to Mg2+ and noncompetitive with respect to MgATP. These results indicate that Cd2+ competes for a second metal-binding site. Therefore, the reaction catalyzed by this enzyme was treated as a terreactant system. The kinetic mechanism of VEGFR2 TK was elucidated through the use of steady-state kinetic studies. According to these studies, the enzyme binds Mg2+ and MgATP in a random fashion followed by ordered addition of the peptide substrate. The release of product is also ordered, with MgADP being released last. The order of substrate binding was confirmed by using AMP-PCP, a dead-end inhibitor.