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// David K. Edwards V 1,* , David Tyler Sweeney 2,* , Hibery Ho 2 , Christopher A. Eide 2 , Angela Rofelty 2 , Anupriya Agarwal 2 , Selina Qiuying Liu 2 , Alexey V. Danilov 2 , Patrice Lee 3 , David Chantry 3 , Shannon K. McWeeney 4 , Brian J. Druker 2,5 , Jeffrey W. Tyner 1 , Stephen E. Spurgeon 2,** and Marc M. Loriaux 2,** 1 Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, OR, USA 2 Division of Hematology & Medical Oncology, Oregon Health & Science University Knight Cancer Institute, Portland, OR, USA 3 Array BioPharma, Boulder, CO, USA 4 Department of Bioinformatics and Computational Biology, Oregon Health & Science University, Portland, OR, USA 5 Howard Hughes Medical Institute, Oregon Health & Science University, Knight Cancer Institute, Portland, OR, USA * These authors have contributed equally to this work ** These authors have contributed equally to this work Correspondence to: Marc M. Loriaux, email: // Keywords : colony-stimulating factor 1 receptor; chronic lymphocytic leukemia; tumor-associated macrophages; tumor microenvironment; small-molecule inhibitors Received: September 26, 2017 Accepted: March 01, 2018 Published: May 15, 2018 Abstract In many malignancies, the tumor microenvironment includes CSF1R-expressing supportive monocyte/macrophages that promote tumor cell survival. For chronic lymphocytic leukemia (CLL), these supportive monocyte/macrophages are known as nurse-like cells (NLCs), although the potential effectiveness of selective small-molecule inhibitors of CSF1R against CLL is understudied. Here, we demonstrate the preclinical activity of two inhibitors of CSF1R, GW-2580 and ARRY-382, in primary CLL patient samples. We observed at least 25% of CLL samples showed sub-micromolar sensitivity to CSF1R inhibitors. This sensitivity was observed in samples with varying genetic and clinical backgrounds, although higher white cell count and monocyte cell percentage was associated with increased sensitivity. Depleting CD14-expressing monocytes preferentially decreased viability in samples sensitive to CSF1R inhibitors, and treating samples with CSF1R inhibitors eliminated the presence of NLCs in long-term culture conditions. These results indicate that CSF1R small-molecule inhibitors target CD14-expressing monocytes in the CLL microenvironment, thereby depriving leukemia cells of extrinsic support signals. In addition, significant synergy was observed combining CSF1R inhibitors with idelalisib or ibrutinib, two current CLL therapies that disrupt tumor cell intrinsic B-cell receptor signaling. These findings support the concept of simultaneously targeting supportive NLCs and CLL cells and demonstrate the potential clinical utility of this combination.

HER2 is a transmembrane tyrosine kinase receptor that mediates cell growth, differentiation, and survival. HER2 is overexpressed in approximately 20% of breast cancers and in subsets of gastric, colorectal, and esophageal cancers. Both antibody and small-molecule drugs that target HER2 and block its tyrosine kinase activity are effective in treating HER2-driven cancers. In this article, we describe the preclinical properties of tucatinib, an orally available, reversible HER2-targeted small-molecule tyrosine kinase inhibitor. In both biochemical and cell signaling experiments, tucatinib inhibits HER2 kinase activity with single-digit nanomolar potency and provides exceptional selectivity for HER2 compared with the related receptor tyrosine kinase EGFR, with a >1,000-fold enhancement in potency for HER2 in cell signaling assays. Tucatinib potently inhibits signal transduction downstream of HER2 and HER3 through the MAPK and PI3K/AKT pathways and is selectively cytotoxic in HER2-amplified breast cancer cell lines in vitro. In vivo, tucatinib is active in multiple HER2+ tumor models as a single agent and shows enhanced antitumor activity in combination with trastuzumab or docetaxel, resulting in improved rates of partial and complete tumor regression. These preclinical data, taken together with the phase-I tucatinib clinical trial results demonstrating preliminary safety and activity, establish the unique pharmacologic properties of tucatinib and underscore the rationale for investigating its utility in HER2+ cancers.

Glucose flux through glucokinase (GK) controls insulin release from the pancreas in response to high levels of glucose. Flux through GK is also responsible for reducing hepatic glucose output. Since many individuals with type 2 diabetes appear to have an inadequacy or defect in one or both of these processes, identifying compounds that can activate GK could provide a therapeutic benefit. Herein we report the further structure activity studies of a novel series of glucokinase activators (GKA). These studies led to the identification of pyridine 72 as a potent GKA that lowered post-prandial glucose in normal C57BL/6J mice, and after 14d dosing in ob/ob mice.

Glucose flux through glucokinase (GK) controls insulin release from the pancreas in response to high glucose concentrations. Glucose flux through GK also contributes to reducing hepatic glucose output. Because many individuals with type 2 diabetes appear to have an inadequacy or defect in one or both of these processes, compounds that can activate GK may serve as effective treatments for type 2 diabetes. Herein we report the identification and initial optimization of a novel series of allosteric glucokinase activators (GKAs). We discovered an initial thiazolylamino pyridine-based hit that was optimized using a structure-based design strategy and identified 26 as an early lead. Compound 26 demonstrated a good balance of in vitro potency and enzyme kinetic parameters and demonstrated blood glucose reductions in oral glucose tolerance tests in both C57BL/6J mice and high-fat fed Zucker diabetic fatty rats.

Tumor cells extensively utilize the pentose phosphate pathway for the synthesis of ribose. Transketolase is a key enzyme in this pathway and has been suggested as a target for inhibition in the treatment of cancer. In a pharmacodynamic study, nude mice with xenografted HCT-116 tumors were dosed with 1 ('N3'-pyridyl thiamine'; 3-(6-methyl-2-amino-pyridin-3-ylmethyl)-5-(2-hydroxy-ethyl)-4-methyl-thiazol-3-ium chloride hydrochloride), an analog of thiamine, the co-factor of transketolase. Transketolase activity was almost completely suppressed in blood, spleen, and tumor cells, but there was little effect on the activity of the other thiamine-utilizing enzymes alpha-ketoglutarate dehydrogenase or glucose-6-phosphate dehydrogenase. Synthesis and SAR of transketolase inhibitors is described.

Transketolase, a key enzyme in the pentose phosphate pathway, has been suggested as a target for inhibition in the treatment of cancer. Compound 5a ('N3'-pyridyl thiamine'; 3-(6-methyl-2-amino-pyridin-3-ylmethyl)-5-(2-hydroxy-ethyl)-4-methyl-thiazol-3-ium chloride hydrochloride), an analog of the transketolase cofactor thiamine, is a potent transketolase inhibitor but suffers from poor pharmacokinetics due to high clearance and C(max) linked toxicity. An efficient way of improving the pharmacokinetic profile of 5a is to prepare oxidized prodrugs which are slowly reduced in vivo yielding longer, sustained blood levels of the drug. The synthesis of such prodrugs and their evaluation in rodent models is reported.

A series of tetrazole amide derivatives of (+/-)-2-dodecyl-alpha-phenyl-N-(2,4,6-trimethoxyphenyl)-2H-tetrazole-5- acetamide (1) was prepared and evaluated for their ability to inhibit acyl-CoA: cholesterol O-acyltransferase (ACAT) in vitro and to lower plasma total cholesterol in vivo. For this series of compounds, our objective was to systematically replace substituents appended to the amide and tetrazole moieties of 1 with structurally diverse functionalities and assess the effect that these changes have on biological activity. The ensuing structure-activity relationship (SAR) studies identified aryl (7b) and heteroaryl (7f,g) replacements for 2,4,6-trimethoxyphenyl that potently inhibit liver microsomal and macrophage ACAT in vitro and exhibit good cholesterol lowering activity (56-66% decreases in plasma total cholesterol at 30 mg/kg), relative to 1, when compared in the acute rat model of hypercholesterolemia. Replacement of the alpha-phenyl moiety with electron-withdrawing substituents (13e-h), however, significantly reduced liver microsomal ACAT inhibitory activity (IC50 > 1 microM). This is in contrast to electron-donating substituents (13ij,m-q), which produce IC50 values ranging from 5 to 75 nM in the hepatic microsomal assay. For selected tetrazole amides (1, 7b, 13n,o), reversing the order of substituents appended to the 2- and 5-positions in the tetrazole ring (36a-d), in general, improved macrophage ACAT inhibitory activity and provided excellent cholesterol-lowering activity (ranging from 65% to 77% decreases in plasma total cholesterol at 30 mg/kg) in the acute rat screen. The most potent isomeric pair in this set of unsubstituted methylene derivatives (13n and 36a) caused adrenocortical cell degeneration in guinea pigs treated with these inhibitors. In contrast, adrenal glands taken from guinea pigs treated with the corresponding alpha-phenyl-substituted analogs (7b and 36c) were essentially unchanged compared to untreated controls. Subsequent evaluation of 7b and 36c in a rabbit bioassay showed that both compounds and/or their metabolities were present in plasma after oral dosing. Unlike 7b and 36c, compound 1 and related 2,4,6-trimethoxyanilides (13j, 30c,d) showed poor oral activity in the rabbit bioassay. Nevertheless, in cholesterol-fed rabbits, both systemically available (7b, 36c) and poorly absorbed inhibitors (1, 36d) were more effective in lowering plasma total cholesterol than the fatty acid amide CI-976.

Introduction: Monocyte/macrophage lineage cells have been reported to provide a supportive signal in a variety of neoplastic settings. Tumor-associated macrophages (TAMs) have been shown to provide microenvironmental support that maintains tumor cell viability and growth for a variety of solid tumor types, and these TAMs have been shown to depend on the receptor tyrosine kinase, CSF1R (M-CSFR). Monocyte/macrophage lineage cells have also been implicated in the microenvironment of CLL and are termed nurse-like cells in this setting. However, the role of CSF1R in CLL including potential maintenance of these nurse-like cells has not been explored. Using an ex vivo, functional screening platform applied directly to primary specimens from CLL patients, we have identified recurrent sensitivity to CSF1R inhibitors as well as decreased viability after depletion of CSF1R-expressing monocytes, thereby depriving the CLL cells of an important, microenvironmental growth/survival signal. We also have seen synergistic anti-tumor activity when combining CSF1R inhibitors with idelaisib and ibrutinib which inhibit b-cell receptor (BCR) activated pathways. Methods: We evaluated the impact on cell viability of hundreds of CLL patient specimens against panels of targeted small molecule inhibitors. These panels include two small-molecules with exquisite specificity for CSF1R (GW-2580; ARRY-382). In addition, we evaluated the impact of antibody depletion of monocytes (CD14-depletion) on ex vivo CLL cell viability as well as the effect of monocyte cell depletion on response to CSF1R inhibitors. We also evaluated the combination of GW-2580 or ARRY-382 with idelalisib (PI3kδ inhibitor) and ibrutinib (BTK inhibitor). Results: We found that 20-30% of CLL specimens showed sensitivity to inhibition of CSF1R with good concordance between GW-2580 and ARRY-382. Analysis of clinical and demographic features of these patients failed to reveal correlation of CSF1R with any prominent disease subsets. Flow cytometry analysis revealed that CSF1R was not expressed on CLL cells but only on a subpopulation of CD14-expressing monocytes. Depletion of these monocytes with CD14 antibody had little to no impact on samples not exhibiting ex vivo sensitivity to CSF1R inhibitors, however, samples showing strong sensitivity to CSF1R inhibitors were also quite sensitive to depletion of this CD14-positive monocyte population. After CD14 depletion, the remaining CLL cells showed no further sensitivity to CSF1R inhibitors. Finally, when combined with ibrutinib or idelalisib synergy was seen. Conclusions: These results show that CSF1R is a potential therapeutic target in CLL and suggest that CLL supporting monocytes (nurse-like cells) express CSF1R and depend on CSF1R for viability in a similar manner as TAMs depend on CSF1R in a variety of solid tumor settings. As such, CSF1R inhibitors may deprive CLL cells of this supportive microenvironmental signal resulting in CLL cell death. Therefore, we propose that CSF1R inhibitors, such as ARRY-382, possibly in combination with ibrutinib, idelalisib, or other approved agents, may be a promising new line of therapy to target CLL cells by impacting the tumor microenvironment. Disclosures Spurgeon: Genentech: Honoraria; Acerta Pharma: Research Funding; Bristol Meyers Squibb: Research Funding; Gilead sciences: Honoraria, Research Funding; Janssen: Research Funding; Pharmacyclics: Honoraria. Tyner:Janssen Pharmaceuticals: Research Funding; Incyte: Research Funding; Aptose Biosciences: Research Funding; Constellation Pharmaceuticals: Research Funding; Array Biopharma: Research Funding. Agarwal:CTI BioPharma: Research Funding. Lee:Array Biopharma: Employment. Chantry:Array Biopharma: Employment. Druker:Fred Hutchinson Cancer Research Center: Research Funding; Bristol-Myers Squibb: Research Funding; Henry Stewart Talks: Patents & Royalties; Millipore: Patents & Royalties; Sage Bionetworks: Research Funding; MolecularMD: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Gilead Sciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cylene Pharmaceuticals: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy; Novartis Pharmaceuticals: Research Funding; Blueprint Medicines: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Oregon Health & Science University: Patents & Royalties; CTI Biosciences: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Leukemia & Lymphoma Society: Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncotide Pharmaceuticals: Research Funding; Roche TCRC, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; McGraw Hill: Patents & Royalties; ARIAD: Research Funding; Aptose Therapeutics, Inc (formerly Lorus): Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

High-grade serous ovarian carcinoma (HGSOC) has the poorest prognosis amongst all gynecological cancers with a median survival of approximately 5 years. While most patients (pts) initially respond to therapy, few achieve long-term remission or cure; thus, new treatment strategies are needed. Paclitaxel (Pac), an agent commonly used in the treatment of HGSOC, induces the Ras/Raf/MEK/ERK pathway and resistance may be partially mediated through activation of MEK/ERK, suggesting a rationale for combining a MEK inhibitor with Pac. Binimetinib (MEK162) is an oral, potent, selective, allosteric small-molecule MEK1/2 inhibitor. The combination of binimetinib and Pac was studied in a panel of in vivo ovarian carcinoma xenograft models derived from either cell lines (A2780, SK-OV-3) or primary patient tumor resections pathologically confirmed to be HGSOC (OVC38B1, OVC604, OVC629, OVC104) and propagated solely in mice (pt-derived xenograft [PDX]). Three of these PDX models were from newly diagnosed pts, while 1 (OVC38B1) was from a pt who had relapsed following a prior response to a platinum/taxane regimen. All models were sequenced for cancer-specific genes by next-generation sequencing; no mutations were found in Ras, Raf, MEK or ERK. To evaluate single-agent and combination activity, tumor-bearing mice received 25 mg/kg Pac IP (days 1,5,9) and/or 30 mg/kg binimetinib PO (days 2-15). Single-agent binimetinib was modestly effective in 3/6 models (tumor growth inhibition [TGI] ≥ 50%), which is consistent with the lack of MAPK pathway mutations in these models. Single-agent Pac was highly effective in 3/6 models (TGI ≥ 90%) including OVC38B1 and 2 PDX models from newly diagnosed pts; the remaining models were taxane-resistant. This is consistent with expected high rates of response in the setting of newly diagnosed pts and/or prior responders. Binimetinib plus Pac had superior efficacy to either agent alone in 4/6 models including all taxane-resistant models. In 2 PDX models from newly diagnosed pts, combination activity was not improved, but Pac was highly effective as a single agent (72-82% regression) leaving little room for enhancement. Encouragingly, the combination induced tumor regressions in 2 taxane-resistant models in which no single-agent regressions were observed. In conclusion, in vivo drug sensitivity studies with binimetinib and Pac recapitulate the response expected in HGSOC based on stage, genetic background and clinical history. In models of taxane-resistant disease, combination with binimetinib had improved activity over taxane alone warranting further study of this approach in HGSOC. Citation Format: Shannon L. Winski, Karyn Bouhana, Susan Rhodes, LouAnn Cable, Deborah Anderson, Lance Williams, Brian Tunquest, Tiffany Logan, Guy Vigers, Patrice Lee. Activity of the MEK inhibitor Binimetinib (MEK162) in combination with paclitaxel in patient-derived xenograft models of high-grade serous ovarian carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 666. doi:10.1158/1538-7445.AM2015-666

Cholangiocarcinoma (CC) responds poorly to chemo- and immunotherapy and is nearly always fatal within one year. In recent years we have gained important insight into the signaling pathways that drive this cancer. These cancers are characterized by deregulated mitogen-activated protein kinase (MAPK), PI3 kinase/Akt and a dependence on the IL-6 axis of signal transduction. Importantly, we previously reported clinical responses for CC patients receiving single agent MEK inhibitors, indicating these agents have activity in this disease. We hypothesized that dual targeting of these pathways in CC using MEK162 and buparlisib would lead to potent antitumor and immunomodulatory activity, possibly circumventing resistance to single agent MEK162. In a panel of n = 7 human CC cell lines with diverse genetic profiles, constitutive phosphorylation of ERK (7/7) and Akt (2/7) was observed. Human CC cell lines displayed variable sensitivity to the growth inhibitory and pro-apoptotic effects of single agent MEK162 or buparlisib. CC cell lines with basal AKT phosphorylation (WITT, Mz-Cha-1) showed greater sensitivity to growth inhibition by buparlisib (IC50 10-20 μM), as compared to CC lines lacking pAKT (HuCCT1, HuH28, IC50 > 20μM). Immunoblot analysis confirmed decreased phosphorylated ERK (pERK) in the HuCCT1 and SNU-478 CC cell lines following treatment with MEK162. Culture supernatants from four separate human CC cell lines displayed significant reductions in IL-6, VEGF, and GM CSF in a concentration-dependent manner after treatment with MEK162. Immunomodulatory effects of MEK162 were also evident, independent of its tumor-intrinsic effects upon CC cell lines. Namely, it significantly reduced IL 6/GM-CSF driven MDSC differentiation (HLA-DRlo CD11b+ CD33+) from healthy normal donor PBMC in vitro. These observations were not due to cytotoxic activity as treatment with MEK162 for 72 hours did not reduce viability of bulk human PBMCs. Finally, to evaluate the effect of this treatment combination, in vivo studies were conducted in athymic mice bearing Mz-Cha1 or SNU-478 xenografts. Tumor bearing mice received daily oral administration of MEK162 (30 mg/kg), buparlisib (25 mg/kg), or both agents combined. Vehicle treated animals served as negative controls. Inhibition of tumor growth was observed following administration of single agent MEK162 or buparlisib as compared to control animals. This effect was further enhanced in the combination treated animals. Body weight of animals indicated this regimen was well-tolerated. Together, these data suggest that dual PI3K and MEK inhibition can target CC with varying genotypes and represents a promising therapeutic regimen with potential for direct antitumor activity and immunomodulation in CC. Citation Format: Jennifer Yang, Omar Elnaggar, Thomas Mace, Matthew Farren, Gregory Young, Patrice Lee, Kaitlin Keenan, Zheng Che, Jacob Kaufman, Denis Guttridge, David Carbone, Cynthia Timmers, Tanios Bekaii-Saab, Gregory Lesinski. Combined inhibition of MEK and PI3K elicits anti-tumor activity in human cholangiocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2656. doi:10.1158/1538-7445.AM2015-2656

The role of MEK 1,2 in cancer tumorgenesis has been clearly demonstrated preclinically, and two selective inhibitors are currently undergoing clinical evaluation to determine their role in the human disease. We have discovered 4-(4-bromo-2-fluorophenylamino)-1-methylpyridin-2(1H)-ones as a new class of ATP noncompetitive MEK inhibitors. These inhibitors exhibit excellent cellular potency and good pharmacokinetic properties and have demonstrated the ability to inhibit ERK phosphorylation in HT-29 tumors from mouse xenograft studies.

Biliary cancer (BC), or cholangiocarcinoma, is derived from the malignant transformation of epithelial cells in the bile ducts. The disease usually presents at advanced stages and is almost uniformly deadly. Current therapeutic regimens have limited efficacy for treatment of BC, thus the need for developing novel and effective targeted strategies is a priority. This malignancy is characterized by deregulated PI3 kinase/Akt signaling, upregulated mitogen-activated protein kinase (MAPK) pathway and an autocrine IL-6/STAT3 signal transduction feedback loop, which can also drive immunosuppression. A recent report showed clinical responses for BC patients receiving the MEK inhibitor AZD244, which promoted more extensive pre-clinical studies to validate the effect of MEK inhibition and importance of this pathway in BC. In the present study, MEK162, a MEK inhibitor, was used to assess the growth inhibitory, pro-apoptotic, and immunomodulatory effects in BC. In vitro studies in a panel of human BC cell lines (HuCCT1, HuH28, MzCha1) revealed that MEK162 significantly inhibited cell growth and induced apoptosis in a concentration-dependent manner in all three cell lines. Immunoblot data confirmed decreased phosphorylated ERK (pERK) in the HuCCT1 BC cell line following a 24 hour treatment with MEK162. MEK inhibition was also associated with clinically-relevant immunomodulatory effects. First, culture supernatants from human BC cells displayed significant reductions in IL-6 protein by ELISA after treatment with MEK162 at varying concentrations. Second, MEK162 inhibited in vitro generation of human myeloid derived suppressor cells from peripheral blood mononuclear cells cultured with IL-6 and GM-CSF. Finally, in vivo studies in athymic mice bearing HuCCT1 xenografts showed that daily oral administration of MEK162 (30 mg/kg in 1% (w/v) carboxymethylcellulose, 0.5% (v/v) Tween 80) was well-tolerated and resulted in significant growth inhibition as compared to vehicle-treated controls (p < 0.0001). Immunohistochemical analysis of tumor xenografts revealed significant decreases in both Ki67 and pERK staining in the MEK162-treated mice as compared to controls (p = 0.0163 and 0.0132,respectively). Together, these data suggest that MEK inhibition represents a promising therapeutic approach with potential for direct antitumor activity and immunomodulation in BC. Citation Format: Jennifer Yang, Thomas A. Mace, Gergory S. Young, Patrice A. Lee, Kaitlin E. Keenan, Zheng Che, Tonios Bekaii-saab, Gregory B. Lesinski. MEK162, an allosteric MEK inhibitor promotes apoptosis and in vivo antitumor activity against human biliary cancer cell lines. [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 934. doi:10.1158/1538-7445.AM2013-934

The Trk family of genes, which includes trkA/NTRK1, trkB/NTRK2 and trkC/NTRK3, encode the tyrosine kinase receptors for the neurotrophin family of nerve growth factors. Deregulated kinase activity of trk family members is associated with human cancer. Oncogenic translocations involving trkC kinase domain have been identified in AML, salivary gland carcinoma, adult secretory breast cancer, congenital fibrosarcoma, and pediatric nephroma. Oncogenic trkA translocations have been reported in papillary thyroid and colorectal cancers. We have identified orally bioavailable, potent and selective ATP-competitive inhibitors of the trk family of receptor tyrosine kinases and are developing these for the treatment of Trk-driven cancers. AR523 is a pan-Trk inhibitor which demonstrates similar activity against TrkA, TrkB and TrkC receptors in a cell based assay (IC50 ∼10 nM). In a screen at 1 µM against a panel of 230 kinases, AR523 inhibited only three additional kinases more than 50% (TNK2, Bmx and Txk). In cell culture AR523 was found to exhibit selective anti-proliferative activity toward the cell line KM12, which harbors the oncogenic TPM-TrkA translocation, while exhibiting no activity toward HT29, a cell line with no trk gene rearrangements. Studies in mice engrafted with KM12 tumors revealed significant anti-tumor and pharmacodynamic activity of AR523. Administration of a single oral dose of AR523 reduced tyrosine phosphorylation of TrkA by nearly 80% at twelve hours after dosing. Parallel analysis of Akt and Erk revealed reduced phosphorylation of these downstream effectors. Administration of 100 mg AR523 daily for two weeks to mice with KM12 xenografts produced mean tumor growth inhibition of 86% and a mean of 42% tumor regression. AR523 exhibits dose dependent inhibition of tumor growth at 10 and 30 mg/kg in KM12 xenografts with 54 and 72% TGI respectively. AR523 was well-tolerated, causing no weight loss or deaths compared with vehicle control. Increasingly Trk mutations have been shown to be activating and the use of Trk inhibitors may provide a new therapeutic strategy for targeted treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1798. doi:1538-7445.AM2012-1798

The RAS/RAF/MEK/ERK and PI3K signaling pathways are known to play key roles in cell growth, proliferation and survival. Targeted agents against factors in these pathways have been shown to provide therapeutic benefit in the treatment of cancer. However, there exists a considerable degree of cross-talk between these pathways such that when one pathway is inhibited the other is upregulated to sustain growth and survival signaling. Therefore, it would be expected that the concomitant use of targeted agents against both of these pathways would overcome the negative effects of this crosstalk, and enhance the ability of these agents to block cancer cell growth. We sought to understand whether or not the combination of the MEK inhibitor ARRY-438162 and the TORC1 inhibitor Everolimus would combine to enhance cell killing compared to the activity of the single agents. It has been established that in the majority of cancers, constituents of one or both of these pathways are mutated conferring constitutive activation to the pathway. Thus, we investigated whether key common mutations in either of these pathways conferred particular sensitivity or resistance to the combination. The growth inhibitory activities of ARRY-438162 and Everolimus were assessed alone and in combination in 26 different cell lines from a variety of human cancers with documented mutations in the KRAS, PTEN, PI3K and BRAF genes. In this regard, we report the identification of key genotypes that are associated with antagonistic, additive, and synergistic responses to the combination. In particular, treatment of the NCI-H460 NSCLC line [KRASG12D/PIK3CA] was only modestly responsive to either ARRY-162 or Everolimus as single agents (10% and 20% growth inhibition, respectively). However, the combination significantly inhibited the growth of this line, a result that was confirmed as synergistic by Bliss analysis. In order to validate the relevance of our in vitro data, an in vivo study was performed using NCI-H460 xenografts in nude mice. Everolimus alone showed no tumor growth inhibition while ARRY-438162 at doses of 30, 100 and 300 mg/kg, BID produced dose-related modest tumor growth inhibition (up to ∼50%). Combining the agents produced enhanced activity at all dose levels of ARRY-438162 without altering the exposure of either agent. Finally, in addition to growth inhibition, the biochemical effects of the single agent and the combination treatment on S6 protein, Erk, Akt, and various apoptosis regulator proteins were assessed as well as their effects on apoptosis and autophagy. ARRY-438162 having demonstrated significant tumor growth inhibitory activity in numerous pre-clinical models and acceptable preclinical and clinical safety profiles has advanced into Phase 1 clinical development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3855.

MAPK kinase pathway-activation is implicated in uncontrolled cell proliferation and tumor growth in numerous tumor types. Targeting MEK may inhibit cancer cell signaling mediated by a wide variety of signals, making MEK an attractive target for the treatment of cancer. Recent data suggests that some cancers are resistant/refractory to MEK inhibitors due to activation of alternate pathways that optimal efficacy may require inhibition of additional pathways. We report activity of the MEK inhibitor, ARRY-162, in combination with inhibitors of mTOR and the ErbB receptor family, as well as standard-of-care chemotherapeutics in various tumor xenograft models. ARRY-162 is a novel, potent and selective allosteric MEK inhibitor that has entered clinical development for the treatment of cancer. In vivo, ARRY-162 is efficacious in numerous tumor xenograft models that harbor b-Raf or Ras mutations. ARRY-162 activity, alone and in combination with, an mTOR inhibitor (ARR-mTOR-1) was evaluated in A549 (KRas mutant) and in NCI-H460 (KRas mutant and constitutively active PI3K) models. In A549, both ARRY-162 and ARR-mTOR-1, as single agents, produced significant tumor growth inhibition (TGI; 71 and 82%, respectively). Enhanced inhibition (89% TGI) and regressions were seen when these agents were given in combination. In NCI-H460, ARRY-162 alone was inactive while ARR-mTOR-1 showed moderate activity (64 %TGI). Combination of these treatments enhanced TGI and produced significant tumor growth delay confirming recent reports that mTor pathway activation confers resistance to MEK inhibitors. The LoVo CRC model (KRas mut and pEGFR overexpression) has demonstrated resistance to EGFR-targeted therapies (i.e., cetuximab). In LoVo xenografts, ARRY-162 produced modest TGI (50%) as did ARRY-543, a pan-ErbB KI (57% TGI), with no tumor regressions in either single agent group. Combination treatment produced 83% TGI with 3 partial responses (>50% tumor regression). Thus, combining ARRY-162 with agents that inhibit signaling through the ErbB pathway produced additive efficacy and significant regressions. Lastly, the activity of ARRY-162 in combination with gemcitabine or paclitaxel was determined. ARRY-162 alone produced 40 and 79% TGI while gemcitabine or paclitaxel alone achieved 16% and 43% TGI in MiaPaCa or COLO 205 xenografts, respectively. When dosed as combinations in either model, TGI was enhanced and regressions were achieved. Thus, ARRY-162 has demonstrated significant single agent activity as well as promising additivity with anti-cancer agents. The added activity in these wide-ranging models with many different chemotherapeutics suggests a large versatility may be expected when this drug is used in combination in the clinic. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2514.