Allosteric AKT Inhibitor Research Articles

Abstract A53: Akt inhibitior MK2206 combination to neoadjuvant radiotherapy: Improving the rectal cancer treatment

Abstract Resistance to therapy is the major obstacle to a favorable outcome in cancer treatment. Neoadjuvant chemoradiotherapy (nCRT) can lead to complete tumor regression in a significant proportion of patients with rectal cancer (up to 40%). The possibility of avoiding radical surgery and its associated functional consequences for those who present complete response has become increasingly attractive, but approximately 60% of patients have only partial or no tumor remission after nCRT. In order to identify molecular mechanisms determining poor response to nCRT and to uncover optimized treatment strategies, we have conducted global gene expression analysis followed by pathway enrichment analysis in pretreatment biopsies from patients showing complete or poor clinical response to nCRT. We show that mitochondrial oxidative phosphorylation and phosphatidylinositol signaling pathways are consistently altered in rectal tumors comparatively. Both pathways have already been associated with resistance to radiation and chemotherapy in solid tumors and appear to converge on the activation of the Akt pathway in nonresponding tumors. To further address the role of Akt activation in response to nCRT, we evaluated by immunohistochemistry, Akt activation in an independent set of pretreatment biopsies from rectal cancer patients and observed not only high pAkt levels in those presenting poor response to nCRT but also that nuclear pAkt can also discriminate resistant tumors. We also evaluated the combination of an allosteric Akt-inhibitor MK2206 to chemoradiation in a radioresistant colorectal cancer cell line SW480 either in vitro and in vivo and observed an improvement of 50% of tumoricidal effect. Altogether, our results indicate that activation of the Akt pathway is a key event affecting response to nCRT and that combining chemoradiotherapy and Akt inhibitors such as MK2206 may significantly improve response rates to neoadjuvant therapy in rectal cancer. Citation Format: Fernanda C. Koyama, Camila M. Lopes Ramos, Jennifer M. Fernandes, Fernanda C. Ledesma, Venancio A F Alves, Fernanda C. Vailati, Angelita Habr-Gama, Rodrigo O. Perez, Anamaria A. Camargo. Akt inhibitior MK2206 combination to neoadjuvant radiotherapy: Improving the rectal cancer treatment [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A53.

The allosteric AKT inhibitor, MK2206, decreases tumor growth and invasion in patient derived xenografts of endometrial cancer

ABSTRACTThe purpose of this study was to test the effect of MK2206, an allosteric inhibitor of AKT, on the growth and invasion of patient-derived xenografts (PDX) of endometrial cancer. Three PDX lines, USC1 (uterine serous), EEC2 (endometrioid grade 2) and EEC4 (endometrioid grade 3) of endometrial cancer were grafted under the renal capsule of NSG mice. After 2 weeks of tumor growth the mice were treated with vehicle or 120mg/kg MK2206 twice a week for 3 weeks. Growth of all 3 PDX lines of different type and grade was significantly inhibited in response to MK2206 compared with vehicle control. Histological analysis revealed invasion and spread of EEC2 and EEC4 tumors were significantly decreased with MK2206 treatment. Immunohistochemical analysis showed a decrease in Ki67 in EEC2 upon MK2206 treatment, while USC1 and EEC4 tumors did not show differences in Ki67 levels. PR levels were evident in EEC2 which dramatically increased upon MK2206 treatment. In vitro analysis of EEC4 and AN3CA cells showed a dose-dependent decrease in p(Ser473)-AKT and p(Thr308)-AKT with MK2206. Invasion of EEC4 and AN3CA cells also significantly decreased after 36h and 72h of MK2206 treatment. PDX tumors provide an appropriate model for the testing of compounds that incorporates the heterogeneous nature of endometrial cancer. Further studies to determine efficacy of MK2206 alone or in combination with other compounds can also identify predictors of response to these pathway inhibitors.

Role of reactive oxygen species in hypoxia-induced non-small cell lung cancer migration

Objective: To explore reactive oxygen species (ROS) generation and its role on A549 cell migration under hypoxic condition. Methods: Human non-small cell lung cancer (NSCLC) cell line A549 was incubated in a hypoxic environment (1%O(2), hypoxia group) or in a normoxic environment (21%O(2), normoxia group). The generation of ROS was measured by flow cytometry. The cell motility of A549 cells was detected by Transwell assay. The protein levels of protein kinase B (AKT), p38 mitogen-activated protein kinase (p38) were determined by Western blot analysis. Results: After 16 h hypoxic treatment, the migration of A549 cells in hypoxia group was significantly more than that of normoxia group [(85±10) vs (56±7) per lower magnification, P<0.001]. Besides, the generation of ROS was in a time-depended manner in hypoxia group. The ROS level was increased with the prolonged hypoxia time. It was significantly higher at 24 h than that in normoxia group [(273±4)% vs (102±6)%, P<0.001]. The migrated cells in hypoxia group co-treated with 2 mmol/L NAC for 16 h were less than that with hypoxic treatment alone [(47±13) vs (105±14) per lower magnification, P=0.011]. Meanwhile, the phosphorylation of AKT and p38 increased after 12 h hypoxic treatment in hypoxia group, however, 2 mmol/L NAC co-treatment attenuated this effect. Furthermore, inhibition of phosphorylated AKT with 0.1 μmol/L allosteric AKT inhibitor (MK-2206) in hypoxia group for 16 h reversed the hypoxia-induced A549 cell migration. The migrated cells in hypoxia+ MK-2206 group were significantly less than that in hypoxia group [(155±21) vs (249±32) per lower magnification, P<0.001]. Conclusions: Hypoxia increases the generation of ROS in A549, resulting from oxidative stress under hypoxia. The increased ROS level promotes cell motility through the activation of AKT.

Efficacy of AKT Inhibitor ARQ 092 Compared with Sorafenib in a Cirrhotic Rat Model with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second most common cause of cancer-related mortality worldwide. The AKT pathway has been found activated in 50% of HCC cases, making it a promising target. Therefore, we assess efficacy of the allosteric AKT inhibitor ARQ 092 compared with untreated control and standard treatment, sorafenib, in vitro and in vivo ARQ 092 blocked phosphorylation of AKT in vitro and strongly inhibited cell growth with significantly higher potency than sorafenib. Similarly, apoptosis and cell migration were strongly reduced by ARQ 092 in vitro To mimic human advanced HCC, we used a diethylnitrosamine-induced cirrhotic rat model with fully developed HCC. MRI analyses showed that ARQ 092 significantly reduced overall tumor size. Furthermore, number of tumors was decreased by ARQ 092, which was associated with increased apoptosis and decreased proliferation. Tumor contrast enhancement was significantly decreased in the ARQ 092 group. Moreover, on tumor tissue sections, we observed a vascular normalization and a significant decrease in fibrosis in the surrounding liver of animals treated with ARQ 092. Finally, pAKT/AKT levels in ARQ 092-treated tumors were reduced, followed by downregulation of actors of AKT downstream signaling pathway: pmTOR, pPRAS40, pPLCγ1, and pS6K1. In conclusion, we demonstrated that ARQ 092 blocks AKT phosphorylation in vitro and in vivo In the HCC-rat model, ARQ 092 was well tolerated, showed antifibrotic effect, and had stronger antitumor effect than sorafenib. Our results confirm the importance of targeting AKT in HCC. Mol Cancer Ther; 16(10); 2157-65. ©2017 AACR.

Activation of phosphatidylinositol 3-kinase/AKT/snail signaling pathway contributes to epithelial-mesenchymal transition-induced multi-drug resistance to sorafenib in hepatocellular carcinoma cells.

Sorafenib, an orally available kinase inhibitor, is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), and it exerts potent inhibitory activity against epithelial–mesenchymal transition (EMT) and multidrug resistance (MDR) by inhibiting mitogen-activated protein kinase (MAPK) signaling in HCC. However, after long-term exposure to sorafenib, HCC cells exhibit EMT and resistance to sorafenib. The activation of AKT by sorafenib is thought to be responsible for the development of these characteristics. The present study aims to examine the underlying mechanism and seek potential strategies to reverse this resistance and the progression to EMT. Sorafenib-resistant cells showed increased metastatic and invasive ability, with a higher expression of P-glycoprotein (P-gp), compared with the parental cells. This phenomenon was at least partially due to EMT and the appearance of MDR in sorafenib-resistant HCC cells. Moreover, MDR was a downstream molecular event of EMT. Silencing Snail with siRNA blocked EMT and partially reversed the MDR, thereby markedly abolishing invasion and metastasis in sorafenib-resistant HCC cells, but silencing of MDR1 had no effect on the EMT phenotype. Additionally, HCC parental cells that were stably transfected with pCDNA3.1-Snail exhibited EMT and MDR. Two sorafenib-resistant HCC cell lines, established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to MK-2206, a novel allosteric AKT inhibitor. Thus, the combination of sorafenib and MK-2206 led to significant reversion of the EMT phenotype and P-gp-mediated MDR by downregulating phosphorylated AKT. These findings underscore the significance of EMT, MDR and enhanced PI3K/AKT signaling in sorafenib-resistant HCC cells.

Identification of 4-phenylquinolin-2(1H)-one as a specific allosteric inhibitor of Akt

Akt plays a major role in tumorigenesis and the development of specific Akt inhibitors as effective cancer therapeutics has been challenging. Here, we report the identification of a highly specific allosteric inhibitor of Akt through a FRET-based high-throughput screening, and characterization of its inhibitory mechanism. Out of 373,868 compounds screened, 4-phenylquinolin-2(1H)-one specifically decreased Akt phosphorylation at both T308 and S473, and inhibited Akt kinase activity (IC50 = 6 µM) and downstream signaling. 4-Phenylquinolin-2(1H)-one did not alter the activity of upstream kinases including PI3K, PDK1, and mTORC2 as well as closely related kinases that affect cell proliferation and survival such as SGK1, PKA, PKC, or ERK1/2. This compound inhibited the proliferation of cancer cells but displayed less toxicity compared to inhibitors of PI3K or mTOR. Kinase profiling efforts revealed that 4-phenylquinolin-2(1H)-one does not bind to the kinase active site of over 380 human kinases including Akt. However, 4-phenylquinolin-2(1H)-one interacted with the PH domain of Akt, apparently inducing a conformation that hinders S473 and T308 phosphorylation by mTORC2 and PDK1. In conclusion, we demonstrate that 4-phenylquinolin-2(1H)-one is an exquisitely selective Akt inhibitor with a distinctive molecular mechanism, and a promising lead compound for further optimization toward the development of novel cancer therapeutics.

Inhibition of AKT1 signaling promotes invasion and metastasis of non-small cell lung cancer cells with K-RAS or EGFR mutations

Accumulating evidence supports a role of the PI3K-AKT pathway in the regulation of cell motility, invasion and metastasis. AKT activation is known to promote metastasis, however under certain circumstances, it also shows an inhibitory activity on metastatic processes, and the cause of such conflicting results is largely unclear. Here we found that AKT1 is an important regulator of metastasis and down-regulation of its activity is associated with increased metastatic potential of A549 cells. Inhibition of AKT1 enhanced migration and invasion in KRAS- or EGFR-mutant non-small cell lung cancer (NSCLC) cells. The allosteric AKT inhibitor MK-2206 promoted metastasis of KRAS-mutated A549 cells in vivo. We next identified that the phosphorylation of Myristoylated alanine-rich C-kinase substrate (MARCKS) and LAMC2 protein level were increased with AKT1 inhibition, and MARCKS or LAMC2 knockdown abrogated migration and invasion induced by AKT1 inhibition. This study unravels an anti-metastatic role of AKT1 in the NSCLC cells with KRAS or EGFR mutations, and establishes an AKT1-MARCKS-LAMC2 feedback loop in this regulation.

Suppression of angiogenesis and tumour progression by combretastatin and derivatives

The search for small molecule inhibitors has gained prominence with the recognition of their inherent advantage for cancer therapy. Combretastatin is a naturally occurring small stilbenoid. By virtue of the ability to bind to tubulin combretastatin and its derivatives promote depolymerisation of microtubules as well as inhibit tubulin polymerisation. This suppresses cell proliferation signalling and induces apoptosis. Combretastatins activate mitotic checkpoints that lead to mitotic catastrophe and apoptosis. They subvert the signalling systems which stimulate invasion, activate EMT (epithelial mesenchyme transition) and promote tumour progression. Allied with the ability to suppress angiogenesis these compounds have been viewed as potential inhibitors of metastasis.The notion of merging RTK (receptor tyrosine kinase) inhibition with suppression of invasion and possible inhibition of EMT has contributed to the credibility of combretastatins as anti-cancer agents. Invaluable are their attributes of inhibiting tumour growth and induction of apoptosis and necrosis by reducing blood supply to the tumour. Aside from these biological effects, this commentary also discusses the issues of the targeting of combretastatins to the tumour vasculature and effective delivery of the drugs encapsulated in nanospheres. Notwithstanding the perceived benefits, one can see a compelling need to understand the effects of combretastatin on the actin cytoskeletal dynamics and the disruption of microtubule polymerisation, and whether it is more efficient a tumour inhibitor than the conventional drugs that target microtubule dynamics. Combinations of combretastatins with other vascular disrupting agents have been attempted. It is essential to establish the perceived inhibition of EMT beyond reasonable doubt. This might justify using the combretastatins with allosteric EMT and Akt inhibitors as additional choices for pre-clinical/clinical studies.

Abstract 2856: Measuring tumor metabolism in cancer spheroids and biopsies

Abstract Introductory Sentence Real-time metabolic flux can be measured non-invasively using hyperpolarized magnetic resonance spectroscopy in cancer spheroids as well as tumor biopsies. Experimental Procedures LnCAP cells were resuspended in a 1:1 mixture of Matrigel:alginate (1x105 cells/ml) and grown in a porous hollow fiber (A/G Technology Corporation, NY). [1-13C] pyruvate was polarized in a SpinLab (General Electric, NY) before dissolving with appropriate buffers. NMR studies were performed on a 1 Tesla Magritek Spectrometer (Magritek, CA). HP spectra were acquired (10o degree flip angle with repetition time of 4s for 25 scans in total). Cell tracking used the manual tracking function in ImageJ. Xenograft biopsies were obtained from LnCAP tumors using a 2mm punch. Data Summary LnCAP cells seeded sparsely enable cancer spheroid formation remain viable as assessed by Live/DEAD fluorescent staining. Histological sectioning revealed spheroids of approximately 200 µm in diameter. Direct deposition of these threads into a 5mm NMR tube allows measurement of metabolic flux using hyperpolarized [1-13C] pyruvate resulting in the formation of [1-13C] lactate. To modulate metabolism, we used an allosteric AKT inhibitor, MK2206. This drug resulted in relocalization of AKT from the plasma membrane as well as a reduction in cell motility from 0.72 ± 0.04 to 0.46 ± 0.03 μm/s (n=5, p&amp;lt;0.05). Administration of hyperpolarized pyruvate resulted in approximately 30% of lactate production 24 hr after treatment. Histological staining of spheroids after treatment revealed sustained decrease of AKT phosphorylation after treatment. These measurements are in good accordance with measurements of lactate secretion in the same cells grown under standard conditions, with MK2206 resulting in loss of AKT Ser473 phosphorylation as early as 2 hr post-treatment, followed by a decrease in lactate secretion in the media from 5.16 ± 0.2 to 1.35 ± 0.05 mM/106 cells (n=3, p&amp;gt;0.05) 24 hr after treatment. To ensure that these methods are applicable clinical settings, LnCAP xenograft biopsies (~60mg) were deposited directly into an NMR tube to measure hyperpolarized [1-13C] pyruvate metabolism. Line-width of the pyruvate peak was measured to be 1.72 ± 0.19 Hz (n=3) in the first spectra, demonstrating good homogeneity of the magnetic field and conversion to lactate was observed. Future experiments will focus on measuring the metabolism of patient-derived xenografts and effects of treatment response. Conclusions Metabolic measurements using hyperpolarized pyruvate can be performed on cancer spheroids as well as biopsies, allowing quantification of metabolism to complement on-going clinical trials utilizing hyperpolarized MR imaging. Citation Format: Sui Seng Tee. Measuring tumor metabolism in cancer spheroids and biopsies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2856. doi:10.1158/1538-7445.AM2017-2856

In vivo efficacy of the AKT inhibitor ARQ 092 in Noonan Syndrome with multiple lentigines-associated hypertrophic cardiomyopathy.

Noonan Syndrome with Multiple Lentigines (NSML, formerly LEOPARD syndrome) is an autosomal dominant "RASopathy" disorder manifesting in congenital heart disease. Most cases of NSML are caused by catalytically inactivating mutations in the protein tyrosine phosphatase (PTP), non-receptor type 11 (PTPN11), encoding the SH2 domain-containing PTP-2 (SHP2) protein. We previously generated knock-in mice harboring the PTPN11 mutation Y279C, one of the most common NSML alleles; these now-termed SHP2Y279C/+ mice recapitulate the human disorder and develop hypertrophic cardiomyopathy (HCM) by 12 weeks of age. Functionally, heart and/or cardiomyocyte lysates from SHP2Y279C/+ mice exhibit increased basal and agonist-induced AKT and mTOR activities. Here, we sought to determine whether we could reverse the hypertrophy in SHP2Y279C/+ mice using ARQ 092, an oral and selective allosteric AKT inhibitor currently in clinical trials for patients with PI3K/AKT-driven tumors or Proteus syndrome. We obtained echocardiographs of SHP2Y279C/+ and wildtype (SHP2+/+) littermates, either in the presence or absence of ARQ 092 at 12, 14, and 16 weeks of age. While SHP2Y279C/+ mice developed significant left ventricular hypertrophy by 12 weeks, as indicated by decreased chamber dimension and increased posterior wall thickness, treatment of SHP2Y279C/+ mice with ARQ 092 normalized the hypertrophy in as early as 2 weeks following treatment, with hearts comparable in size to those in wildtype (SHP2+/+) mice. In addition, we observed an increase in fractional shortening (FS%) in SHP2Y279C/+ mice, an effect of increased compensatory hypertrophy, which was not apparent in SHP2Y279C/+ mice treated with ARQ 092, suggesting functional improvement of HCM upon treatment with the AKT inhibitor. Finally, we found that ARQ 092 specifically inhibited AKT activity, as well as its downstream effectors, PRAS and S6RP in NSML mice. Taken together, these data suggest ARQ 092 may be a promising novel therapy for treatment of hypertrophy in NSML patients.

Characterization of the tumor immune microenvironment (TIM) with multiplex immunohistochemistry (mIHC) in patients with breast cancer following treatment with MK-2206.

e12109 Background: The PAM (PI3K/Akt/mTOR) signaling pathway has been implicated in the oncogenesis of multiple solid malignancies, including breast cancer (BC). Our aim is to characterize the TIM in a series of patients with operable stage I-III BC treated with MK-2206, an allosteric Akt inhibitor within a presurgical trial. In NCT01319539 , patients received 2 doses of MK-2206 with first dose at day -9 and second at day -2 from surgery. Methods: mIHC was performed using immune biomarkers (DAPI, CD3, CD8, CD4, FOXP3, CD68, Pancytokeratin) on full section (4uM) tissue slides from core biopsy specimens and postsurgical specimens of 10 patients - 5 treated with MK-2206, 5 paired controls. Images were taken using Vectra, a novel pathology workstation and analyzed using inForm software to perform cell classification and phenotyping. T- tests were used to compare biomarker changes before and after MK-2206. Results: Our preliminary analysis demonstrates that patients treated with MK-2206 exhibited an increase in median cytotoxic T-cells (CD3CD8+) density, as compared to the control population , which was statistically significant (87% vs.0.2%, p &lt; 0.05). We did not identify a change in macrophage (CD68) or T helper/T reg (CD4/CD4FOXP3+) density following MK-2206 treatment in this small cohort. We are currently expanding our myeloid panel as well as performing additional tissue analysis to validate our findings. As data is exploratory no correction was made for multiple comparisons. Conclusions: Tumor infiltrating lymphocytes (TILs) are both prognostic of overall survival as well as predictive of response to neoadjuvant chemotherapy in BC. At present, there are currently both FDA approved therapies, as well as agents in clinical development that exert antineoplastic activity through the PAM pathway. Investigations that endeavour to understand the impact of these therapies on the tumor immune microenvironment may lead to both an increased understanding of the bioactivity of these agents and potentially identify aspects of the immune response which can be exploited in future therapeutics.

MK2206 enhances the cytocidal effects of bufalin in multiple myeloma by inhibiting the AKT/mTOR pathway

Despite the development of promising cancer therapeutic drugs, multiple myeloma (MM) remains an incurable disease. Bufalin is a bufanolide steroid compound of the traditional Chinese medicine Chan Su that was previously shown to exert growth suppression effects on myeloma cell lines. Previous studies conducted by our group demonstrated that bufalin activated the AKT/mTOR pathway in myeloma cells, which is considered an essential pathway to disease progression and is related to drug resistance in MM. In view of the significant role of AKT in MM, the allosteric AKT inhibitor MK2206 was selected in order to enhance the antitumor effects of bufalin in different MM cell lines (NCI-H929, U266, LP-1 and RPMI8226). The data indicated that MK2206 enhanced the cytotoxicity of bufalin in MM cells, via the suppression of cellular proliferation and the induction of apoptosis, as demonstrated by cleavage of apoptosis-related proteins. This effect was further noted in the presence of exogenous interleukin-6 and/or following the co-culture of MM cells with bone marrow stromal cells (BMSC). This process was associated with the inhibition of the AKT/mTOR pathway. The combination of bufalin with MK2206 reduced the secretion of IL-6 in U266 cells. The combined treatment exhibited similar anti-MM effects in bortezomib-resistant cell lines (NCI-H929R, U266R). In addition to the in vitro cell line models, the synergistic effect was noted in primary MM cells and in MM xenografts of BALB-c and NOD-SCID mice. In conclusion, the data suggested that MK2206 significantly enhanced the cytocidal effects of bufalin in MM cells, regardless of the sensitivity to bortezomib, via the inhibition of the AKT/mTOR pathway. The study provided the basis of a promising treatment approach for MM.

Curcuminoid EF24 enhances the anti-tumour activity of Akt inhibitor MK-2206 through ROS-mediated endoplasmic reticulum stress and mitochondrial dysfunction in gastric cancer.

Gastric cancer is one of the leading causes of morbidity and mortality worldwide. Akt is an anti-apoptotic kinase that plays a dynamic role in cell survival and is implicated in the pathogenesis of gastric cancer. MK-2206, the first allosteric inhibitor of Akt, is in clinical trials for a number of cancers. Although preclinical studies showed promise, clinical trials reported it had no effect when given alone at tolerated doses. The aim of our study was to delineate the effects of MK-2206 on gastric cancer cells and explore the ability of combination treatments to enhance the anti-tumour activity of MK-2206. SGC-7901, BGC-823 cells and immunodeficient mice were chosen as a model to study the treatment effects. Changes in cell viability, apoptosis and ROS, endoplasmic reticulum stress and mitochondrial dysfunction in the cells were analysed by MTT assays, ROS imaging and FACSCalibur, electron microscopy, JC-1 staining and western blotting. MK-2206 induced apoptotic cell death through the generation of ROS. We utilized ROS production to target gastric cancer cells by combining MK-2206 and an ROS inducer EF24. Our in vitro and in vivo xenograft studies showed that combined treatment with MK-2206 and EF24 synergistically induced apoptosis in gastric cancer cells and caused cell cycle arrest. These activities were mediated through ROS generation and the induction of endoplasmic reticulum stress and mitochondrial dysfunction. Targeting ROS generation by using a combination of an Akt inhibitor and EF24 could have potential as a therapy for gastric cancer.

A randomized phase 2 study of MK-2206 versus everolimus in refractory renal cell carcinoma

Activation of the phosphoinisitide-3 kinase (PI3K) pathway through mutation and constitutive upregulation has been described in renal cell carcinoma (RCC), making it an attractive target for therapeutic intervention. We performed a randomized phase II study in vascular endothelial growth factor (VEGF) therapy refractory patients to determine whether MK-2206, an allosteric inhibitor of AKT, was more efficacious than the mammalian target of rapamycin inhibitor everolimus. A total of 43 patients were randomized in a 2:1 distribution, with 29 patients assigned to the MK-2206 arm and 14 to the everolimus arm. Progression-free survival (PFS) was the primary endpoint. The trial was closed at the first futility analysis with an observed PFS of 3.68 months in the MK-2206 arm and 5.98 months in the everolimus arm. Dichotomous response rate profiles were seen in the MK-2206 arm with one complete response and three partial responses in the MK-2206 arm versus none in the everolimus arm. On the other hand, progressive disease was best response in 44.8% of MK2206 versus 14.3% of everolimus-treated patients. MK-2206 induced significantly more rash and pruritis than everolimus, and dose reduction occurred in 37.9% of MK-2206 versus 21.4% of everolimus-treated patients. Genomic analysis revealed that 57.1% of the patients in the PD group had either deleterious TP53 mutations or ATM mutations or deletions. In contrast, none of the patients in the non-PD group had TP53 or ATM defects. No predictive marker for response was observed in this small dataset. Dichotomous outcomes are observed when VEGF therapy refractory patients are treated with MK-2206, and MK-2206 does not demonstrate superiority to everolimus. Additionally, mutations in DNA repair genes are associated with early disease progression, indicating that dysregulation of DNA repair is associated with a more aggressive tumor phenotype in RCC.

The allosteric AKT inhibitor MK2206 shows a synergistic interaction with chemotherapy and radiotherapy in glioblastoma spheroid cultures

BackgroundGlioblastoma multiforme (GBM) is the most common, invasive and deadly primary type of malignant brain tumor. The Phosphatidylinositol-3-Kinase/AKT (PI3K/AKT) pathway is highly active in GBM and has been associated with increased survival and resistance to therapy. The aim of this study is to investigate the effects of AKT inhibition in combination with the current standard of care which consists of irradiation and temozolomide (TMZ) on human malignant glioma cells growing adherent and as multicellular spheroids in vitro.MethodsThe effects of the allosteric inhibitor MK2206 combined with irradiation and TMZ were assessed on glioma cells growing adherent and as multicellular 3D spheroids. The interaction was studied on proliferation, clonogenic cell survival, cell invasion, −migration and on expression of key proteins in the PI3K-AKT pathway by western blot.ResultsA differential effect was found at low- (1 μM) and high dose (10 μM) MK2206. At 1 μM, the inhibitor reduced phosphorylation of Thr308 and Ser473 residues of AKT in both adherent cells and spheroids. Low dose MK2206 delayed spheroid growth and sensitized spheroids to both irradiation and TMZ in a synergistic way (Combination index <0.35). In contrast, neither low nor high dose MK2206 did enhance therapy sensitivity in adherent growing cells. Effective inhibition of invasion and migration was observed only at higher doses of MK2206 (>5 μM).ConclusionsThe data show that a 3D spheroid model show different sensitivity to irradiation when combined with AKT inhibition. Thereby we show that MK2206 has potential synergistic efficacy to the current standard of care for glioma patients.

Combined Targeting of mTOR and Akt Using Rapamycin and MK-2206 in The Treatment of Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC), caused by loss-of-function mutations in the TSC1 or TSC2 genes, is an autosomal dominant disease characterized by benign tumor formation in multiple organs. Hyperactivation of mammalian target of rapamycin (mTOR) is the primary alteration underlying TSC tumor. Thus, rapamycin, as an mTOR specific inhibitor, has been assumed as a potential drug for the treatment of TSC. However, its application in TSC patients has been limited due to side effects. By analyzing Tsc1- or Tsc2-null mouse embryonic fibroblasts (MEFs), we found that loss of TSC1 or TSC2 led to a decreased sensitivity to MK-2206, a novel allosteric Akt inhibitor. Ectopic expression of a constitutively activated Akt (myristoylated Akt-1, myrAkt-1) sensitized Tsc2-null and Tsc1-null MEFs to MK-2206. Furthermore, MK-2206 increased the cytotoxicity of rapamycin in Tsc1-/-or Tsc2-/- MEFs. Moreover, the benefit of the combinatorial treatment was also demonstrated in a TSC xenograft mouse model. We conclude that the combination of rapamycin and MK-2206 may be utilized as a new therapeutic regimen for TSC.

Specific Inhibition of AKT with ARQ 092, an Orally-Available Selective AKT Inhibitor, Attenuates Acute Vaso-Occlusive Events in Sickle Cell Disease

▪Previous studies have identified the Ser/Thr protein kinase, AKT, as a therapeutic target for thromboinflammatory diseases. Recently, we have shown that the basal levels of AKT phosphorylation were significantly increased in neutrophils and platelets isolated from sickle cell disease (SCD) patients compared with those cells from healthy donors and that specific inhibition of AKT2 impaired neutrophil-endothelial cell and neutrophil-platelet interactions in venules of Berkeley (SCD) mice (Li et al. J Clin Invest 2014; Barazia et al. Blood 2015). Although our results suggest that AKT2 inhibition may be a novel therapy to treat a vaso-occlusive crisis in SCD patients, no AKT2 specific inhibitor is available in clinic. Using ARQ 092, an orally-available, allosteric AKT inhibitor that is currently in Phase I clinical trials in oncology indications and AKT-driven overgrowth disease, Proteus syndrome, here we report that specific inhibition of AKT attenuates the adhesive function of neutrophils and platelets from sickle cell disease (SCD) patients in vitro and heterotypic cell-cell interactions in the Berkeley mouse model of SCD in vivo. Studies using neutrophils and platelets isolated from SCD patients revealed that treatment with 50-500 nM ARQ 092 significantly blocks αMβ2 integrin function in neutrophils and reduces P-selectin exposure and glycoprotein Ib/IX/V-mediated agglutination in platelets. Consistently, treatment of isolated platelets and neutrophils with ARQ 092 inhibited heterotypic cell-cell aggregation under shear conditions. Using in vivo real-time fluorescence intravital microscopy, we demonstrated that short-term oral administration of ARQ 092 (100 mg/kg body weight) or hydroxyurea (HU, 250 mg/kg body weight), a main therapy for the treatment of SCD, diminishes neutrophil-endothelial cell and neutrophil-platelet interactions in venules of Berkeley mice challenged with TNF-α to induce a vaso-occlusive crisis. Co-administration of HU and ARQ 092 further reduced the adhesive function of neutrophils in venules and neutrophil transmigration into alveoli, inhibited the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) in the cremaster vessel wall, and improved survival in these mice. Ex vivo studies in Berkeley mice suggested that co-administration of HU and ARQ 092 efficiently blocks neutrophil and platelet activation and reactive oxygen species generation. The synergistic effects of both inhibitors resulted from increased NO production by HU and specific inhibition of AKT by ARQ 092. Our results provide important evidence that ARQ 092 has potential as a novel drug to be developed to prevent or treat the acute vaso-occlusive complications in SCD patients. DisclosuresAbbadessa:ArQule, Inc: Employment. Yu:ArQule, Inc: Employment. Schwartz:ArQule, Inc: Employment.

Upregulation of AKT3 Confers Resistance to the AKT Inhibitor MK2206 in Breast Cancer.

Acquired resistance to molecular targeted therapy represents a major challenge for the effective treatment of cancer. Hyperactivation of the PI3K/AKT pathway is frequently observed in virtually all human malignancies, and numerous PI3K and AKT inhibitors are currently under clinical evaluation. However, mechanisms of acquired resistance to AKT inhibitors have yet to be described. Here, we use a breast cancer preclinical model to identify resistance mechanisms to a small molecule allosteric AKT inhibitor, MK2206. Using a step-wise and chronic high-dose exposure, breast cancer cell lines harboring oncogenic PI3K resistant to MK2206 were established. Using this model, we reveal that AKT3 expression is markedly upregulated in AKT inhibitor-resistant cells. Induction of AKT3 is regulated epigenetically by the bromodomain and extra terminal domain proteins. Importantly, knockdown of AKT3, but not AKT1 or AKT2, in resistant cells restores sensitivity to MK2206. AKT inhibitor-resistant cells also display an epithelial to mesenchymal transition phenotype as assessed by alterations in the levels of E-Cadherin, N-Cadherin, and vimentin, as well as enhanced invasiveness of tumor spheroids. Notably, the invasive morphology of resistant spheroids is diminished upon AKT3 depletion. We also show that resistance to MK2206 is reversible because upon drug removal resistant cells regain sensitivity to AKT inhibition, accompanied by reexpression of epithelial markers and reduction of AKT3 expression, implying that epigenetic reprogramming contributes to acquisition of resistance. These findings provide a rationale for developing therapeutics targeting AKT3 to circumvent acquired resistance in breast cancer. Mol Cancer Ther; 15(8); 1964-74. ©2016 AACR.

Abstract 2868: Mechanisms of transcriptional regulation of FOXO3 by cofactors upon PI3K/AKT/mTOR inhibition

Abstract The PI3K/AKT/mTOR pathway is frequently deregulated in breast cancer. Specific inhibition of its key signaling nodes results in cell death and tumor growth arrest, but also in activation of feedback loops that ultimately limit therapeutic activity. The subcellular localization and activity of Forkhead box O3 (FOXO3) transcription factor is heavily regulated by the PI3K pathway. Phosphorylation of FOXO3 by AKT inhibits its transcriptional functions leading to cell survival and growth. Although our understanding of the transcription function of FOXO3 downstream of the PI3K pathway has increased significantly in recent years, it is still unclear how FOXO3 acts in concert with other cofactors of the transcription machinery. We conjectured that inhibition of the PI3K/AKT/mTOR signaling by specific agents targeting the pathway at different nodes leads to unique FOXO3-mediated transcriptional programs unveiling a complex network of regulation. We therefore sought to identify proteins that differentially co-immunoprecipitate with FOXO3 upon PI3K, AKT or mTOR blockade. To target the pathway at different levels, we used BYL719, a PI3Kα inhibitor; MK2206, an allosteric AKT inhibitor; and RAD001, an allosteric mTORC1 inhibitor. Upon treatment, we immunopreciptated endogenous FOXO3 and searched for FOXO3 interactors by mass spectrometry analysis. In parallel RNA samples from each treatment were analyzed using gene expression microarrays. Gene expression analyses revealed that each specific compound originated distinct transcriptional signatures. Accordingly, mass spectrometry analysis revealed novel FOXO3 co-interactors engaging in different transcriptional complexes at each treatment conditions. We identified some of these proteins as CUL1, the core component of the SCF (SKP1-CUL1-F-BOX protein) E3 ubiquitin-protein ligase complex, the cyclin-dependent kinase 5 (CDK5), the upstream binding transcription factor (UBTF), and the core component of RNA polymerase I POLR1C (polymerase RNA I polypeptide C). We performed coimmunoprecipitation analyses to confirm that these cofactors are bona fide FOXO3-interacting proteins. We then analyzed the effects of overexpressing these proteins on FOXO3 transcriptional activity. Luciferase assays demonstrated an increase in FOXO3 transcriptional activity when CUL1, UBTF, CDK5 or POLR1C were overexpressed. The overexpression of cofactors also induced the expression of FOXO3 target genes such as TRAIL or IRS2. Furthermore, overexpression of these co-interactors enhanced the binding of FOXO3 to its target gene promoters. We are now engaged in both elucidating how these cofactors can modulate the transcriptional activity of FOXO3 upon PI3K/AKT/mTOR inhibition and understanding the therapeutic implications of these FOXO3-containing complexes. Citation Format: Vasilis Hristidis, James Cownie, Ana Bosch, Joanne Soong, Pau Castel, Maurizio Scaltriti, Baselga José. Mechanisms of transcriptional regulation of FOXO3 by cofactors upon PI3K/AKT/mTOR inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2868.

Abstract 374: In vitro and in vivo anti-tumor activity of ARQ 751, a potent and selective AKT inhibitor

Abstract Dysregulation of the PI3K-AKT signaling pathway is associated with a number of cancers. AKT can be activated through activated receptor tyrosine kinases, gain-of-function mutations of PIK3CA, PTEN deficiency, and AKT amplification or activating mutations such as AKT1-E17K. We present here the preclinical characterization of ARQ 751, which has distinct physico-chemical properties compared to our first generation inhibitor, ARQ 092. ARQ 751 has IC50 values of 0.55 nM, 0.81 nM and 1.31 nM for AKT1, 2 and 3, respectively, and does not inhibit any other kinase (out of the 245 tested) by greater than 50% at 5 μM, nor does it inhibit AKT lacking the PH domain. ARQ 751 strongly binds to wild-type AKT1 and mutant AKT1-E17K with Kd of 1.2 nM and 8.6 nM, respectively, and suppresses pAKT(S473) in 293T cells transiently transfected with AKT1-E17K. Additionally, membrane translocation of both wild-type and AKT1-E17K is inhibited in NIH 3T3 cells transiently transfected with wild-type AKT1 or mutant AKT1-E17K. Tests on 240 cancer cell lines (Oncopanel) showed the best antiproliferative effects on esophageal (100%, 3/3), breast (87.5%, 14/16), and head and neck cancer cells (67%, 4/6), with GI50 values GI50 &amp;lt; 1 μM. Cancer cell lines with PIK3CA/PIK3R1 mutations (73%; 33/45) are more sensitive to ARQ 751 (GI50&amp;lt;1μM) compared to wild-type (42%, 74/175). Interestingly, among PIK3CA/PIK3R1 wild type cell lines, the PTEN mutant (55%, 11/20) exhibited a similar sensitivity to PTEN wild-type cell lines (48%, 95/197). Of 17 tested breast cancer cell lines, all 8 with PIK3CA mutations are sensitive to ARQ 751. An in vivo efficacy study in AN3CA endometrial cancer xenograft model shows that ARQ 751 inhibits tumor growth (by up to 92% at the well tolerated continuous daily dose of 120 mg/kg) in a dose-dependent manner. Additionally, ARQ 751 exerted dose-dependent anti-tumor activity (by up to 98% at the 5 days on, 2 days off dose of 75mg/kg) in an AKT1-E17K mutant endometrial patient-derived xenograft (PDX) model. ARQ 751 causes significant pathway inhibition in vitro (at the concentrations of 3 nM on pAKT[S473] and 70 nM on pPRAS40 [T246]) and in vivo (on both pAKT[S473] and pPRAS40[T246] after 6 hours of dosing as low as 10 mg/kg) using AN3CA models. Pharmacokinetic data from repeat doses of ARQ 751 show a plasma half-life of 4 to 5 hours and no tissue accumulation. In conclusion, ARQ 751 is a potent and selective allosteric AKT inhibitor. PIK3CA/PIK3R1 and AKT mutations but not PTEN may predict ARQ 751 sensitivity. Our analysis suggests that endometrial, breast, esophageal, and head and neck cancers may represent viable indications for ARQ 751. Both PIK3CA/PIK3R1 and AKT1 mutations could be predictive biomarkers for patient selection, regardless of tumor type. Citation Format: Yi Yu, Ronald E. Savage, Sudharshan Eathiraj, Terence Hall, Brian Schwartz, Giovanni Abbadessa. In vitro and in vivo anti-tumor activity of ARQ 751, a potent and selective AKT inhibitor. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 374.