MK-2206, an allosteric Akt inhibitor, enhances antitumor efficacy by standard chemotherapeutic agents or molecular targeted drugs in vitro and in vivo

The serine/threonine kinase Akt lies at a critical signaling node downstream of phosphatidylinositol-3-kinase and is important in promoting cell survival and inhibiting apoptosis. An Akt inhibitor may be particularly useful for cancers in which increased Akt signaling is associated with reduced sensitivity to cytotoxic agents or receptor tyrosine kinase inhibitors. We evaluated the effect of a novel allosteric Akt inhibitor, MK-2206, in combination with several anticancer agents. In vitro, MK-2206 synergistically inhibited cell proliferation of human cancer cell lines in combination with molecular targeted agents such as erlotinib (an epidermal growth factor receptor inhibitor) or lapatinib (a dual epidermal growth factor receptor/human epidermal growth factor receptor 2 inhibitor). Complementary inhibition of erlotinib-insensitive Akt phosphorylation by MK-2206 was one mechanism of synergism, and a synergistic effect was found even in erlotinib-insensitive cell lines. MK-2206 also showed synergistic responses in combination with cytotoxic agents such as topoisomerase inhibitors (doxorubicin, camptothecin), antimetabolites (gemcitabine, 5-fluorouracil), anti-microtubule agents (docetaxel), and DNA cross-linkers (carboplatin) in lung NCI-H460 or ovarian A2780 tumor cells. The synergy with docetaxel depended on the treatment sequence; a schedule of MK-2206 dosed before docetaxel was not effective. MK-2206 suppressed the Akt phosphorylation that is induced by carboplatin and gemcitabine. In vivo, MK-2206 in combination with these agents exerted significantly more potent tumor inhibitory activities than each agent in the monotherapy setting. These findings suggest that Akt inhibition may augment the efficacy of existing cancer therapeutics; thus, MK-2206 is a promising agent to treat cancer patients who receive these cytotoxic and/or molecular targeted agents.

Lung cancer cell lines harboring MET gene amplification are dependent on Met for growth and survival

Recent clinical successes of small-molecule epidermal growth factor receptor (EGFR) inhibitors in treating advanced non-small cell lung cancer (NSCLC) have raised hopes that the identification of other deregulated growth factor pathways in NSCLC will lead to new therapeutic options for NSCLC. Met, the receptor for hepatocyte growth factor, has been implicated in growth, invasion, and metastasis of many tumors including NSCLC. To assess the functional role for Met in NSCLC, we evaluated a panel of nine lung cancer cell lines for Met gene amplification, Met expression, Met pathway activation, and the sensitivity of the cell lines to short hairpin RNA (shRNA)-mediated Met knockdown. Two cell lines, EBC-1 and H1993, showed significant Met gene amplification and overexpressed Met receptors which were constitutively phosphorylated. The other seven lines did not exhibit Met amplification and expressed much lower levels of Met, which was phosphorylated only on addition of hepatocyte growth factor. We also found a strong up-regulation of tyrosine phosphorylation in beta-catenin and p120/delta-catenin in the Met-amplified EBC-1 and H1993 cell lines. ShRNA-mediated Met knockdown induced significant growth inhibition, G(1)-S arrest, and apoptosis in EBC-1 and H1993 cells, whereas it had little or no effect on the cell lines that do not have Met amplification. These results strongly suggest that Met amplification identifies a subset of NSCLC likely to respond to new molecular therapies targeting Met.

Discovery of a Novel cGAMP Competitive Ligand of the Inactive Form of STING

Drugging large protein pockets is a challenge due to the need for higher molecular weight ligands, which generally possess undesirable physicochemical properties. In this communication, we highlight a strategy leveraging small molecule active site dimers to inhibit the large symmetric binding pocket in the STING protein. By taking advantage of the 2:1 binding stoichiometry, maximal buried interaction with STING protein can be achieved while maintaining the ligand physicochemical properties necessary for oral exposure. This mode of binding requires unique considerations for potency optimization including simultaneous optimization of protein-ligand as well as ligand-ligand interactions. Successful implementation of this strategy led to the identification of 18, which exhibits good oral exposure, slow binding kinetics, and functional inhibition of STING-mediated cytokine release.

MK-2461, a novel multitargeted kinase inhibitor, preferentially inhibits the activated c-Met receptor

The receptor tyrosine kinase c-Met is an attractive target for therapeutic blockade in cancer. Here, we describe MK-2461, a novel ATP-competitive multitargeted inhibitor of activated c-Met. MK-2461 inhibited in vitro phosphorylation of a peptide substrate recognized by wild-type or oncogenic c-Met kinases (N1100Y, Y1230C, Y1230H, Y1235D, and M1250T) with IC(50) values of 0.4 to 2.5 nmol/L. In contrast, MK-2461 was several hundredfold less potent as an inhibitor of c-Met autophosphorylation at the kinase activation loop. In tumor cells, MK-2461 effectively suppressed constitutive or ligand-induced phosphorylation of the juxtamembrane domain and COOH-terminal docking site of c-Met, and its downstream signaling to the phosphoinositide 3-kinase-AKT and Ras-extracellular signal-regulated kinase pathways, without inhibiting autophosphorylation of the c-Met activation loop. BIAcore studies indicated 6-fold tighter binding to c-Met when it was phosphorylated, suggesting that MK-2461 binds preferentially to activated c-Met. MK-2461 displayed significant inhibitory activities against fibroblast growth factor receptor (FGFR), platelet-derived growth factor receptor, and other receptor tyrosine kinases. In cell culture, MK-2461 inhibited hepatocyte growth factor/c-Met-dependent mitogenesis, migration, cell scatter, and tubulogenesis. Seven of 10 MK-2461-sensitive tumor cell lines identified from a large panel harbored genomic amplification of MET or FGFR2. In a murine xenograft model of c-Met-dependent gastric cancer, a well-tolerated oral regimen of MK-2461 administered at 100 mg/kg twice daily effectively suppressed c-Met signaling and tumor growth. Similarly, MK-2461 inhibited the growth of tumors formed by s.c. injection of mouse NIH-3T3 cells expressing oncogenic c-Met mutants. Taken together, our findings support further preclinical development of MK-2461 for cancer therapy.

Discovery of a 5H-benzo[4,5]cyclohepta[1,2-b]pyridin-5-one (MK-2461) inhibitor of c-Met kinase for the treatment of cancer

c-Met is a transmembrane tyrosine kinase that mediates activation of several signaling pathways implicated in aggressive cancer phenotypes. In recent years, research into this area has highlighted c-Met as an attractive cancer drug target, triggering a number of approaches to disrupt aberrant c-Met signaling. Screening efforts identified a unique class of 5H-benzo[4,5]cyclohepta[1,2-b]pyridin-5-one kinase inhibitors, exemplified by 1. Subsequent SAR studies led to the development of 81 (MK-2461), a potent inhibitor of c-Met that was efficacious in preclinical animal models of tumor suppression. In addition, biochemical studies and X-ray analysis have revealed that this unique class of kinase inhibitors binds preferentially to the activated (phosphorylated) form of the kinase. This report details the development of 81 and provides a description of its unique biochemical properties.

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.

Suppression of E-cadherin function drives the early stages of Ras-induced squamous cell carcinoma through upregulation of FAK and Src

Advanced stages of epithelial carcinogenesis involve the loss of intercellular adhesion, but it remains unclear how proteins that regulate alterations in cell-cell and cell-matrix adhesion are deregulated to promote the early stages of cancer development. To address this, a three-dimensional human tissue model that mimics the incipient stages of Squamous Cell Carcinoma (SCC) was used to study how E-cadherin suppression promotes tumor progression in Ras-expressing human keratinocytes. We found that E-cadherin suppression triggered elevated mRNA and protein expression levels of Focal Adhesion Kinase (FAK), and increased FAK and Src activities above the level seen in Ras-expressing E-cadherin-competent keratinocytes. sh-RNA-mediated depletion of FAK and Src restored E-cadherin expression levels by increasing its stability in the membrane, and blocked tumor cell invasion in tissues. Surface transplantation of these tissues to mice resulted in reversion of the tumor phenotype to low-grade tumor islands in contrast to control tissues that manifested an aggressive, high-grade SCC. These findings suggest that the tumor-promoting effect of E-cadherin suppression, a common event in SCC development, is exacerbated by enhanced E-cadherin degradation induced by elevated FAK and Src activities. Furthermore, they imply that targeting FAK or Src in human epithelial cells with neoplastic potential may inhibit the early stages of SCC.

Lithium carbonate: Updated reproductive and developmental toxicity assessment using scientific literature and guideline compliant studies

The current publication describes most recent so far unpublished (key) guideline and GLP compliant reproductive and developmental toxicity studies of lithium carbonate in rats, including their interpretation and conclusions in terms of human hazard assessment when compared to existing literature. Particular attention was paid to the target organs and dose response of lithium ion related effects to differentiate between a primary (pharmacokinetic/pharmacodynamic) action and secondary effects as a result of systemic and target organ toxicity. In the key two-generation reproduction toxicity (OECD TG 416) study in rats, doses of 5, 15 and 45 mg/kg bw/d (0.95, 2.9 and 8.6 mg Li⁺/kg bw/d) were given by oral gavage, resulting in clear NOAELs of 15 mg/kg bw/d (2.9 mg Li⁺/kg bw/d) for systemic parental toxicity and 45 mg/kg bw/d (8.6 mg Li⁺/kg bw/d) for reproductive toxicity and fetal toxicity. Target organ changes were consistently observed in liver (cytoplasmic rarefaction) and kidney (dilated tubuli). In the key developmental toxicity (OECD TG 414) study in rats, doses given by oral gavage were 10, 30 and 90 mg/kg bw/d (1.9, 5.7 and 17.1 mg Li⁺/kg bw/d) was investigated resulting in NO(A)ELs of 30 mg/kg bw/d (5.7 mg Li⁺/kg bw/d) (maternal toxicity) and 90 mg/kg bw/d (17 mg Li⁺/kg bw/d) (fetal toxicity and teratogenicity). The highest dose of 90 mg/kg bw/day resulted in clear signs of toxicity and peak plasma concentrations at the toxic range (>1.0 mEq lithium/L). Toxic effects of lithium carbonate were not seen in the reproductive and developmental organs. No adverse effects on sperm (total motility, progressive motility and morphology of testicular and cauda epididymal sperm) were observed in the two-generation rat reproduction toxicity study. There was also no impact on fertility indices or on litter sizes in this study, nor were there any fetal effects in the two-generation reproduction toxicity and developmental toxicity study at doses causing already systemic toxicity in the dams. Secondary effects such as decreased weight (gain) and food consumption were reported in the developmental toxicity study. The absence of any reproductive/developmental findings at dose levels causing clear systemic toxicity in the test animals in these key mammalian studies, does not suggest an immediate concern for possible human reproductive or developmental toxicity effects from exposure to lithium during drug use.

A comparison of older adolescent and adult females' responses to anger-provoking situations

There has been an increase in research on anger in girls and women. However, few researchers have examined anger across different groups of females. The goal of this study was to examine the experience and expression of anger in individuals who differ by age and employee/student status. Two female populations, university students and employees, described their reactions to a hypothetical work/school-related situation. Similar factors elicited an angry emotion, but there were group differences in the responses to the anger experience. The results are interpreted from a gender schema perspective, taking the contextual influence of developmental period and employee/student role into account.

Abstract 698: MCL1 dependent cells are sensitive to the CDK inhibitor Dinaciclib

Dinaciclib is a potent inhibitor of cyclin dependent kinases (CDKs) 1, 2, 5, and 9 and is currently in Phase 3 for the treatment of refractory chronic lymphocytic leukemia (CLL). To further understand the mechanism of action, identify predictive biomarkers, and find additional cancer types which may benefit from dinaciclib, we evaluated cell viability following 24 hours treatment across a panel of ∼500 cells lines. Hematopoietic cell lines were on average 3-times more sensitive than solid tumor lines. In agreement with previous findings, mRNA expression of the anti-apoptotic family member BCL-xL or the ratio of MCL1-to-BCL-xL continue to be the best predictor of dinaciclib sensitivity in both hematopoietic and solid tumor cell lines. MCL1 appears to be an important target of dinaciclib particularly in MCL1 amplified cell lines. Dependence on MCL1 was established in a panel of 19 breast, NSCLC and SCLC cell lines by depletion of the protein by either dinaciclib treatment or MCL1 RNAi. The NSCLC line H23 was highly dependent on MCL1, as RNAi knockdown decreased viability to <20% and could be rescued by introduction of a non-targeted MCL1 expression construct. In the H23 xenograft, dinaciclib diminished MCL1 levels and induced tumor apoptosis resulting in >80% tumor regression. Cell lines which lacked pro-apoptotic proteins BAX / BAK or harbored a BAX mutation were insensitive to the inhibitor. Using apoptosis defective lines we demonstrate that 24 hours of dinaciclib treatment still impacted cell count by blocking cell cycle progression as measured by FACS. These data demonstrate that both cell cycle block and induction of apoptosis contribute to dinaciclib's mechanism of action. However, the observation that MCL1 and BCL-xL were top genes associated with sensitivity suggests that induction of apoptosis is the predominant mechanism of dinaciclib's anti-tumor effect and warrants further investigation of MCL1 amplification as a predictive biomarker in future clinical studies.

Citation Format: Harold Hatch, Robert Booher, Samanthi Perera, Thi Nguyen, Brian Dolinski, Samer Al-Assaad, Lauren Harmonay, Alwin Schuller, Minilik Angagaw, Brian Long, Xianlu Qu, Nathan Miselis, Mark Ayers, Michael Nebozhyn, Heather Hirsch, Danielle Greenawalt, Andrey Loboda, Thorseten Graef, Ellie Im, Rebecca Blanchard, Leigh Zawel, Peter Strack. MCL1 dependent cells are sensitive to the CDK inhibitor Dinaciclib. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 698. doi:10.1158/1538-7445.AM2013-698