Potent Selective Inhibitor Research Articles

CArdiovascular Safety of Febuxostat and Allopurinol in Patients With Gout and Cardiovascular ComoRbiditiES

Comprehensive safety evaluation of new drugs for noncardiac indications is needed in the area of cardiovascular (CV) outcomes, particularly in populations with high CV risk such as gout. Febuxostat is a potent nonpurine selective inhibitor of xanthine oxidase approved for the treatment of gout. Long-term CV safety of febuxostat is being established in a randomized, allopurinol-controlled clinical study in patients with gout who have increased CV risk using an analytical approach that provides 90% power to meet a noninferiority margin of 1.3 for the hazard ratio (HR) (febuxostat relative to allopurinol). The primary CV end point for this trial is a composite of CV death, nonfatal myocardial infarction, nonfatal stroke, and unstable angina requiring urgent coronary revascularization. Approximately 7,500 men and women with gout and CV disease are being recruited and will be followed up for up to 5 years postrandomization. The statistical plan for the trial uses a design that evaluates the HR of febuxostat to allopurinol based on the primary CV composite end point when there are a maximum of 624 CV events. Interim analyses will be conducted when approximately 25%, 50%, and 75% of events have occurred. At each analysis, if the upper 1-sided confidence limit of the HR is <1.3, the study will be stopped, and the noninferiority of febuxostat relative to allopurinol with regard to CV risk will be declared. The CARES trial will define the CV safety profile of febuxostat and allopurinol in gout patients at high risk for CV events.

Splitomicin inhibits fMLP-induced superoxide anion production in human neutrophils by activate cAMP/PKA signaling inhibition of ERK pathway

Splitomicin, is a cell-permeable lactone derived from naphthol and known to be a potent selective inhibitor of Sir2 (silent information regulator 2). Previous studies have demonstrated that naphtholic compounds possess an inhibitory effect on neutrophils. Here, we present our investigation on the inhibitory effects of splitomicin in human neutrophils. The primary goal of our study was to locate a possible candidate on inflammatory reactions and to hopefully develop a novel anti-inflammatory therapy. Neutrophils were prepared following standard procedures. Neutrophils induced by either fMLP (1μM) or PMA (100nM) were observed using a flow cytometer and the intracellular production of superoxide anions was investigated at different splitomicin concentrations. The cytosolic Ca++ influx concentration was measured using a fluorescence spectrophotometer, and Mac-1 expression was detected with a flow cytometer. The MAP kinases were measured using western blotting. Our results showed that splitomicin inhibited superoxide anion production by fMLP (1μM) and NaF (20mM) in a concentration-dependent manner (37.5–450μM). Splitomicin (300 and 450μM) also suppressed fMLP-induced intracellular calcium ion mobilization and extracellular-signal regulated kinase (ERK) phosphorylation. Moreover, splitomicin could inhibit fMLP-induced Mac-1 expression and increase cAMP levels in human neutrophils. Our data demonstrated that splitomicin exhibits a noticeable inhibitory effect on superoxide anion production in human neutrophils. This negative effect was well-correlated with increased cAMP levels via PKA activity and the subsequent inhibition of ERK (p42/p44) phosphorylation to decrease superoxide anion production.

Discovery of SCH 900229, a Potent Presenilin 1 Selective γ-Secretase Inhibitor for the Treatment of Alzheimer's Disease.

An exploration of the SAR of the side chain of a novel tricyclic series of γ-secretase inhibitors led to the identification of compound (-)-16 (SCH 900229), which is a potent and PS1 selective inhibitor of γ-secretase (Aβ40 IC50 = 1.3 nM). Compound (-)-16 demonstrated excellent lowering of Aβ after oral administration in preclinical animal models and was advanced to human clinical trials for further development as a therapeutic agent for the treatment of Alzheimer's disease.

Potential Selective Inhibitors against Rv0183 of Mycobacterium tuberculosis Targeting Host Lipid Metabolism

Tuberculosis is the second leading infectious killer with 9 million new cases in 2009. Extensive use of pathogen's lipid metabolism especially in utilizing the host lipids and virulence highlights the importance of exported lipid-catabolizing enzymes. Current study aims to emphasize the importance of Rv0183, an exported monoacylglycerol lipase, involved in metabolizing the host cell membrane lipids. Sequence analysis and homology modeling shows Rv0183 is highly conserved throughout mycobacterial species even in Mycobacterium leprae and also significantly divergent from mammalian lipases. Additionally, employing virtual screening using NCI diversity set and ZINC database with criteria of molecules with higher predicted free energy of binding toward Rv0183 than human lipase, potential inhibitors have been identified for Rv0183. A tautomer of ZINC13451138, known inhibitor for HIV-1 integrase is the best hit with difference in free energy of binding of 8.72 kcal/mol. The sequence and structure analysis were helpful in identifying the ligand binding sites and molecular function of the mycobacterial specific monoacylglycerol lipase. Rv0183 represents a suitable and promising drug target and is also a step towards understanding dormancy development and reactivation, thereby addressing pathogen's drug resistance. Experimental studies on the discovered potential inhibitors in this virtual screen should further validate the therapeutic utility of Rv0183.

Abstract 4768: Design and development of selective sphingosine kinase 2 inhibitors

Abstract Sphingosine-1-phosphate (S1P) has been recently implicated to play a vital role in regulating a variety of physiological and pathological processes including proliferation, differentiation, migration, and cell survival. S1P is produced endogenously by sphingosine kinases (SKs) and the balance of the levels of S1P, its precursor sphingosine, and ceramide, referred to as the “sphingosine rheostat,” is important for normal cellular functions. To date, two isoforms of SPKs have been reported, sphingosine kinase 1 (SK1) and sphingosine kinase 2 (SK2). Many efforts have been invested to study the roles of SK1 and SK1 has been indicated in the regulation of cancer progression and development. However, much is still remain unknown for SK2 and current results of the function of SK2 are complex and controversial. This is also reflected in the development of SK inhibitors. Several potent selective SK1 inhibitors have been reported and tested as potential cancer treatment agents. However, no potent and selective SK2 inhibitors have been developed to date. Therefore, there is an urgent need to develop SK2 selective inhibitors as pharmacological tools to help unravel the roles of SK2. Recently, we discovered that a series of thiazolidine-2,4-dione analogs selectively inhibit SK2 and one lead compound was identified to inhibit SK2 with sub-µM potency but no activity to SK1 with a concentration up to 10 µM. Herein, we will report the structure activity relationship (SAR) studies of this newly identified lead SK2 inhibitor to optimize its potency and selectivity towards SK2. Furthermore, these analogs will be biologically characterized in human leukemia U937 cells. 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 4768. doi:1538-7445.AM2012-4768

Abstract 873: Combined targeting of Akt and MEK with the Akt inhibitor GDC-0068 and MEK inhibitor GDC-0973 demonstrates synergistic anti-tumor effects

Abstract Background: Akt, a serine/threonine protein kinase, and MEK, a dual specificity kinase, are key signaling nodes in the PI3K/Akt/mTOR and the Ras/Raf/MAPK pathway, respectively. Both Akt and MEK play key roles in regulating numerous cellular processes such as cell proliferation, growth, survival, protein synthesis and oncogenic transformation. Many cancer types have alterations in both of these pathways and inhibiting only one of these pathways can result in up-regulation of the other pathway. We previously reported on a potent highly selective ATP-competitive pan-Akt inhibitor, GDC-0068 as well as a potent selective inhibitor of MEK, GDC-0973 that are currently in Phase 1 clinical trials. We hypothesized that dual inhibition of both MEK and Akt pathways with the combination of these two agents would induce synergistic antitumor activity. Methods: In these studies, we evaluated the efficacy of GDC-0068 and GDC-0973 both individually and in combination on a panel of cancer cell lines. Cells were treated with either GDC-0068 or GDC-0973 or in combination at increasing concentrations and assayed after 4 days for viability. For in vivo studies, tumor cells were subcutaneously implanted in the flank of female NCR.nude mice. Once tumors reached sufficient size, mice were dosed orally for 21 days with GDC-0068, GDC-0973 or the combination of both compounds. Results: In vitro, the combination of GDC-0068 and GDC-0973 results in enhanced inhibition of cell viability compared to either single agent alone. Synergistic effects are observed in multiple cell lines; especially in cell lines that have activation of the Ras/Raf/MAPK pathway or both pathways (e.g. via the combination of PTEN loss or PI3K mutations and Ras or BRaf mutations). Combined knockdown of downstream targets of both Akt and MEK is observed at concentrations where a synergistic effect is observed, with enhanced knockdown of several converged targets. Increased cell death is also observed. These results were recapitulated in vivo in xenograft models, where the combination of GDC-0068 and GDC-0973 resulted in increased tumor growth inhibition or regression compared to either single agent alone. All combinations tested were well tolerated as assessed by animal body weights and mortalities. Conclusions: Our studies demonstrate significant combination benefit between GDC-0068 and GDC-0973 on cell viability in vitro and tumor growth in vivo. These data support the clinical development of the combination of these two compounds. 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 873. doi:1538-7445.AM2012-873

Autotaxin and Its Product Lysophosphatidic Acid Suppress Brown Adipose Differentiation and Promote Diet-Induced Obesity in Mice

Brown adipose tissue is a thermogenic organ that dissipates stored energy as heat to maintain body temperature. This process may also provide protection from development of diet-induced obesity. We report that the bioactive lipid mediator lysophosphatidic acid (LPA) markedly decreases differentiation of cultured primary brown adipocyte precursors, whereas potent selective inhibitors of the LPA-generating enzyme autotaxin (ATX) promote differentiation. Transgenic mice overexpressing ATX exhibit reduced expression of brown adipose tissue-related genes in peripheral white adipose tissue and accumulate significantly more fat than wild-type controls when fed a high-fat diet. Our results indicate that ATX and its product LPA are physiologically relevant negative regulators of brown fat adipogenesis and are consistent with a model in which a decrease in mature peripheral brown adipose tissue results in increased susceptibility to diet-induced obesity in mice.

Lapatinib for advanced or metastatic breast cancer.

Lapatinib is a potent reversible and selective inhibitor of the tyrosine kinase domains of epidermal growth factor receptor and human epidermal growth factor receptor (HER)-2 that exerts its action by competitive binding to the intracellular ATP-binding site of the receptor. It is registered for the treatment of advanced or metastatic HER-2+ breast cancer in combination with capecitabine and for hormone receptor-positive breast cancer in combination with an aromatase inhibitor. Lapatinib administered orally once daily is moderately to well tolerated, with rash and gastrointestinal adverse events as the main toxicities. In studies on the efficacy of lapatinib, direct comparisons between lapatinib and trastuzumab are lacking. Results of ongoing randomized phase III studies with lapatinib or trastuzumab in combination with taxanes as first-line agents for metastatic breast cancer as well as in the neoadjuvant and adjuvant settings are awaited.

Molecular pharmacological profile of a novel thiazolinone‐based direct and selective 5‐lipoxygenase inhibitor

The potency of many 5-lipoxygenase (5-LOX) inhibitors depends on the cellular peroxide tone and the mechanism of 5-LOX enzyme activation. Therefore, new inhibitors that act regardless of the mode of enzyme activation need to be developed. Recently, we identified a novel class of thiazolinone-based compounds as potent 5-LOX inhibitors. Here, we present the molecular pharmacological profile of (Z)-5-(4-methoxybenzylidene)-2-(p-tolyl)-5H-thiazol-4-one, compound C06. Inhibition of 5-LOX product formation was determined in intact cells [polymorphonuclear leukocytes (PMNL), rat basophilic leukaemia-1, RAW264.7] and in cell-free assays [homogenates, 100, 000×g supernatant (S100), partially purified 5-LOX] applying different stimuli for 5-LOX activation. Inhibition of peroxisome proliferator-activated receptor (PPAR), cytosolic phospholipase A(2) (cPLA(2) ), 12-LOX, 15-LOX-1 and 15-LOX-2 as well as cyclooxygenase-2 (COX-2) were measured in vitro. C06 induced non-cytotoxic, direct 5-LOX inhibition with IC(50) values about 0.66 µM (intact PMNL, PMNL homogenates) and approximately 0.3 µM (cell-free PMNL S100, partially purified 5-LOX). Action of C06 was independent of the stimulus used for 5-LOX activation and cellular redox tone and was selective for 5-LOX compared with other arachidonic acid binding proteins (PPAR, cPLA(2) , 12-LOX, 15-LOX-1, 15-LOX-2, COX-2). Experimental results suggest an allosteric binding distinct from the active site and the C2-like domain of 5-LOX. C06 was identified as a potent selective direct 5-LOX inhibitor exhibiting a novel and unique mode of action, different from other established 5-LOX inhibitors. This thiazolinone may possess potential for intervention with inflammatory and allergic diseases and certain types of cancer.

The Development of MetAP-2 Inhibitors in Cancer Treatment

Methionine aminopeptidases (MetAPs), which remove methionine residue from newly synthesized polypeptide chains, are a class of metalloproteases ubiquitously distributed in both eukaryotes and prokaryotes. MetAP-2 inhibition can induce G1 cell cycle arrest, cytostasis in tumor cells in vitro and inhibition of tumor growth in vivo. The discovery of fumagillin with potent antiangiogenic and antiproliferative activities promoted the development of fumagillin analogues as a novel class of anticancer agents. Early drug discovery efforts have focused on analogs of fumagillin, which irreversibly inhibit MetAP-2 through covalent modification of an epoxide. Several fumagillin analogs, like CKD-732, TNP-470 and PPI-2458, were found to be potent selective inhibitors of MetAP-2 (proteolytic activity) and endothelial cell proliferation. Further, they have entered in clinical trials for the treatment of different types of tumors. Recently, attention has been paid to reversible human MetAP-2 inhibitors, such as bengamides, 2-hydroxy-3-aminoamides, anthranilic acid sulfonamides and triazole analogs, which have demonstrated their potential to inhibit angiogenesis and tumor growth in vivo as well. This review article mainly discussed the development of MetAP-2 inhibitors in cancer therapy and also summarized their structure-activity relationships.

Triphenylbutanamines: Kinesin Spindle Protein Inhibitors with in Vivo Antitumor Activity

The human mitotic kinesin Eg5 represents a novel mitotic spindle target for cancer chemotherapy. We previously identified S-trityl-l-cysteine (STLC) and related analogues as selective potent inhibitors of Eg5. We herein report on the development of a series of 4,4,4-triphenylbutan-1-amine inhibitors derived from the STLC scaffold. This new generation systematically improves on potency: the most potent C-trityl analogues exhibit Kiapp ≤ 10 nM and GI50 ≈ 50 nM, comparable to results from the phase II clinical benchmark ispinesib. Crystallographic studies reveal that they adopt the same overall binding configuration as S-trityl analogues at an allosteric site formed by loop L5 of Eg5. Evaluation of their druglike properties reveals favorable profiles for future development and, in the clinical candidate ispinesib, moderate hERG and CYP inhibition. One triphenylbutanamine analogue and ispinesib possess very good bioavailability (51% and 45%, respectively), with the former showing in vivo antitumor growth activity in nude mice xenograft studies.

Inhibition of monoamine oxidase by selected C6-substituted chromone derivatives

Chromone has been reported to be a useful scaffold for the design of monoamine oxidase (MAO) inhibitors. In an attempt to discover highly potent MAO inhibitors and to contribute to the known structure–activity relationships (SAR) of MAO inhibition by chromones, in the present study, we have synthesized a series of chromone derivatives substituted at C6 with a variety of alkyloxy substituents, and evaluated the resulting compounds as inhibitors of recombinant human MAO-A and -B. The results document that the C6-substituted chromones are potent reversible MAO-B inhibitors with IC50 values in the low nM range (2–76 nM). The chromones were also found to bind reversibly to MAO-A, but with lower affinities compared to MAO-B. It may therefore be concluded that C6-substituted chromones are highly potent MAO-B selective inhibitors and promising lead compounds for the development of therapy for neurodegenerative disorders such as Parkinson’s disease. The results of this study are discussed with reference to possible binding orientations of a selected C6-substituted chromone in the active site cavities of MAO-A and -B.

Coumarin-3-carboxylic acid derivatives as potentiators and inhibitors of recombinant and native N-methyl-d-aspartate receptors

N-Methyl-d-aspartate receptors (NMDARs) are known to be involved in a range of neurological and neurodegenerative disorders and consequently the development of compounds that modulate the function of these receptors has been the subject of intense interest. We have recently reported that 6-bromocoumarin-3-carboxylic acid (UBP608) is a negative allosteric modulator with weak selectivity for GluN2A-containing NMDARs. In the present study, a series of commercially available and newly synthesized coumarin derivatives have been evaluated in a structure–activity relationship (SAR) study as modulators of recombinant NMDAR activity. The main conclusions from this SAR study were that substituents as large as iodo were accommodated at the 6-position and that 6,8-dibromo or 6,8-diiodo substitution of the coumarin ring enhanced the inhibitory activity at NMDARs. These coumarin derivatives are therefore excellent starting points for the development of more potent and GluN2 subunit selective inhibitors, which may have application in the treatment of a range of neurological disorders such as neuropathic pain, epilepsy and depression. Surprisingly, 4-methyl substitution of UBP608 to give UBP714, led to conversion of the inhibitory activity of UBP608 into potentiating activity at recombinant GluN1/GluN2 receptors. UBP714 also enhanced NMDAR mediated field EPSPs in the CA1 region of the hippocampus. UBP714 is therefore a novel template for the development of potent and subunit selective NMDAR potentiators that may have therapeutic applicability in the treatment of patients with cognitive deficits or schizophrenia.

Selective inhibition of extracellular signal-regulated kinases 1/2 blocks nerve growth factor to brain-derived neurotrophic factor signaling and suppresses the development of and reverses already established pain behavior in rats

Brain-derived neurotrophic factor (BDNF) plays a key role in the development of pathological pain. Although it is known that nerve growth factor (NGF) induces BDNF mRNA through extracellular signal-regulated kinases (ERK), whether ERK1/2 or ERK5, two closely related members of the ERK family, mediate this signal is still unclear because classical MEK inhibitors block both pathways. We studied the involvement of ERK-signaling in NGF induction of BDNF in PC12 cells, cultured dorsal root ganglia neurons, and in rats subjected to neuropathic pain models using ERK1/2- and ERK5-specific tools. Selective activation of ERK1/2 upregulated BDNF mRNA in PC12 cells, whereas selective ERK5 activation did not. AZD6244, a potent selective inhibitor of ERK1/2 activation, blocked NGF induction of BDNF mRNA in vitro suggesting that NGF induction of BDNF is mediated by ERK1/2. siRNA experiments indicated that both ERK1 or ERK2 can signal suggesting that both pathways must be blocked to prevent NGF-induced increase in BDNF mRNA. I.p. injection of AZD6244 prevented the development of pain in rats subjected to the chronic constriction injury and reversed already established pain in the spared nerve injury model. Immunohistochemical studies showed decreased phospho-ERK1/2-immunoreactivity in dorsal root ganglia and BDNF immunoreactivity in ipsilateral spinal dorsal horn in the drug-treated rats. Our results suggest the possible use of AZD6244, already in human clinical trials as an anticancer agent, for the treatment of pathological pain.

Microbial Metabolism of Rofecoxib, A Selective COX-2 Inhibitor

Microbial transformation studies of rofecoxib ( 1 ), a potent selective cyclooxygenase-2 inhibitor, using sixty microorganisms, mainly fungi and actinomycetes, have revealed that it was metabolized by three microorganisms. Using a standard two-stage screening technique, Cunninghamella echinulata var. echinulata ATCC 9244, Mucor griseocyanus ATCC 1207b, and Rhizopus oryzae ATCC 34121 showed two common more polar metabolites 2 and 3 . Moreover, it was apparent that Cunninghamella echinulata var. echinulata was the most efficient microorganism to almost completely metabolize 1 , and hence, was selected for preparative scale fermentation. These metabolites were characterized on the basis of their spectral data as 4′-hydroxyrofecoxib ( 2 ) and 3′-hydroxyrofecoxib ( 3 ).

Role of Aldo–Keto Reductase Enzymes in Mediating the Timing of Parturition

A better understanding of the mechanisms underlying parturition would provide an important step toward improving therapies for the prevention of preterm labor. Aldo–keto reductases (AKR) from the 1D, 1C, and 1B subfamilies likely contribute to determining the timing of parturition through metabolism of progesterone and prostaglandins. Placental AKR1D1 (human 5β reductase) likely contributes to the maintenance of pregnancy through the formation of 5β-dihydroprogesterone (DHP). AKR1C1, AKR1C2, and AKR1C3 catalyze the 20-ketosteroid and 3-ketosteroid reduction of progestins. They could therefore eliminate tocolytic progestins at term. Activation of the F prostanoid receptor by its ligands also plays a critical role in initiation of labor. AKR1C3 and AKR1B1 have prostaglandin (PG) F synthase activities that likely contribute to the initiation of labor. AKR1C3 converts PGH2 to PGF2α and PGD2 to 9α,11β-PGF2. AKR1B1 also reduces PGH2 to PGF2α, but does not form 9α,11β-PGF2. Consistent with the potential role for AKR1C3 in the initiation of parturition, indomethacin, which is a potent and isoform selective inhibitor of AKR1C3, has long been used for tocolysis.

CRM1/XPO1 Represents a Promising Therapeutic Target for Treatment of Chronic Lymphocytic Leukemia

Abstract 232Exportin 1 (CRM1, XPO1) is a nuclear exporter that promotes the transit of tumor suppressor proteins (TSPs) including p53, I-κB, and FOXO3A out of the nucleus, thereby preventing their activity and contributing to disrupted apoptosis and enhanced proliferation. Recently, whole-genome sequencing in patients with CLL allowed the identification of recurrent mutations in a highly conserved region of CRM1 that can potentially affects its gene function, suggesting a direct role for CRM1 in the pathogenesis of CLL (Puente XS, et al: Nature 75:101, 2011). However the role of CRM1 and the consequences of its mutation in the development of CLL have yet to be explored. CRM1 has been shown to be up-regulated in hematologic and various solid tumors, making it a highly attractive molecular target impacting multiple pro apoptotic pathways. KPT-SINEs are new, potent and irreversible small molecule selective inhibitors of nuclear export developed by Karyopharm that specifically and irreversibly bind to CRM1 and block the function of this protein. CLL is characterized by disrupted apoptosis caused both by co-dependent stromal elements and aberrant activation of several survival-promoting signaling/transcriptional pathways including PI3K/Akt, NF-kB, and p53. Because of the distinct subtypes of CLL and multiple signaling pathways dysregulated, a therapeutic agent targeting a single biological pathway is unlikely to be effective. Thus, pursuit of CRM1 inhibition as a novel strategy aimed to restore multiple death pathways is crucial and has broad implications for many types of patients. Our preliminary work demonstrated CRM1 is over-expressed in CLL cells compared to normal B cells at a protein (3 fold, p<0.005) and mRNA level (2.6 fold p=0.014). Inhibition of CRM1 by KPT-185 induced apoptosis in primary patient CLL cells in a dose and time dependent manner (EC50<500nM) while limited cytotoxicity against normal PBMC and isolated B, NK and T cells was observed (EC50 values >20 μM). Additionally, KPT-185 treatment of NK cells had no effect on their function as measured by ability of NK cells to mediate antibody dependent (ADCC) as wekk as direct cytotoxicity. The effect of KPT-185 on T function is currently under evaluation. Nuclear accumulation of FOXO3, p53 and IkB was also observed in primary CLL cells in a time dependent manner as shown by western blot and confocal microscopy. The evaluation of activated target genes is currently ongoing. Given the importance of microenvironmental stimuli on survival of CLL cells and response to therapy, we evaluated the ability of KPT-185 to induce cytotoxicity of CLL cells in the presence or absence of soluble factors such as CPG, CD40L, BAFF, TNF-α, IL-6, or IL-4, which are known to reduce the spontaneous apoptosis associated with CLL cells. KPT-185 treatment abrogated the protection induced by each of these factors suggesting that KPT-SINEs can disrupt signaling from the microenvironment that lead to in vivo CLL cell survival and potentially drug resistance. Interestingly the cytotoxic effect elicited by KPT-185 was enhanced in CPG activated cells (p=0.02). We also tested the ability of KPT-185 to kill CLL cells under coculture conditions with Hs5 stromal cell line. Coculture of CLL cells alone for 48 hours on the Hs5 stromal cell line resulted in a marked reduction of spontaneous apoptosis suggesting a strong protective effect elicited (P<0.001) by the stromal cells. Interestingly the cytotoxic effect mediated by KPT-185 was enhanced under coculture conditions (p=0.013). KPT-185 was also proven to be effective on murine TCL1+ cells (EC50<500nM) in vitro. The in vivo efficacy of this compound and other structurally related analogs is currently being assessed in an ongoing study in theTCL1 mouse model of CLL. In conclusion CRM1 represents a novel target that has not been adequately explored in CLL. KPT-SINEs are a class of promising therapeutic agents with proven selective in vitro activity in CLL cells providing the rationale for developing small molecule, drug-like CRM1 inhibitors for the treatment of this disease. Disclosures:Sandanayaka:Karyopharm Therapeutics: Employment. Shechter:Karyopharm Therapeutics: Employment. McCauley:Karyopharm Therapeutics: Employment. Shacham:Karyopharm: Equity Ownership. Kauffman:Karyopharm: Equity Ownership.

Abstract B224: Structure-based drug design of signal transducers and activator of transcription 5 inhibitors.

Abstract Signal Transducer and Activator of Transcription 5 (Stat5) protein has gained notoriety for its aberrant role in many human cancers including breast, liver, prostate, skin, head and neck. Despite the significant evidence showing Stat5's role in cancers, there has been little progress in developing small molecule inhibitors of Stat5 function. In contrast, there has been significant advancements in identifying inhibitors for the Stat3 protein. As a result, several potent and direct small molecule and oligonucleotide-based inhibitors have entered pre-clinical trials as a Stat3 therapeutic. Unfortunately, there has not been progress towards the development of potent Stat5 inhibitors. Stat5 is activated by ligand-receptor binding, which recruits Stat5 to intracellular receptor sites via their SH2 domain. Stat5 is then phosphorylated at conserved tyrosine (Y) residues Y694 and 699, which facilitates the formation of active Stat5 dimers via reciprocal pY-SH2 domain interactions. The dimers then translocate to the nucleus and induce target gene transcription. In cancer cells, Stat5 is constitutively phosphorylated leading to the aberrant expression of anti-apoptotic Stat5 target genes. In an effort to identify direct inhibitors of Stat5, we conducted an in vitro screen of a focused library of SH2 domain binding salicylic acid-containing inhibitors (∼150) against Stat5. Several potent (Ki &amp;lt; 5 μM) and Stat5 selective (&amp;gt;3-fold specificity for Stat5 cf. Stat1 and Stat3) inhibitors were identified which were then evaluated in K562 and MV-4–11 human leukemia cells which are known to harbour constitutively activated Stat5. BP-1–108 was identified as the most potent lead within these cell lines. The lead was further evaluated to show potent induction of apoptosis (IC50's ∼ 20 μM) which correlated with potent and selective suppression of Stat5 phosphorylation. In addition, it inhibited Stat5 target genes; Cyclin D1 &amp; c-myc. BP-1–108 also showed no cytotoxicity against healthy bone marrow cells at concentrations up to 160 μM. These inhibitors represent the most potent and direct inhibitors of Stat5 function reported to date. An in silico docking analysis with BP-1–108 within the Stat5b crystal structure (pdb:1Y1U) revealed a tertrapodal projection of functionality facilitating access to a number of sub pockets within the Stat5 SH2 domain. Currently we are conducting a structure-activity relationship against Stat5's SH2 domain with one projection into the hydrophobic pocket using diverse heterocycles to delineate inhibitor binding to improve the potency of our inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B224.

Erythropoietin Mediates Neurobehavioral Recovery and Neurovascular Remodeling Following Traumatic Brain Injury in Rats by Increasing Expression of Vascular Endothelial Growth Factor

Erythropoietin (EPO) improves functional recovery after traumatic brain injury (TBI). Here, we investigated the role of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) on EPO-induced therapeutic efficacy in rats after TBI. Young male Wistar rats were subjected to unilateral controlled cortical impact injury and then infused intracerebroventricularly with either a potent selective VEGFR2 inhibitor SU5416 or vehicle dimethyl sulfoxide. Animals from both groups received delayed EPO treatment (5,000 U/kg in saline) administered intraperitoneally daily at 1, 2, and 3 days post injury. TBI rats treated with saline administered intraperitoneally daily at 1, 2, and 3 days post injury served as EPO treatment controls. 5-bromo-2-deoxyuridine was administered to label dividing cells. Spatial learning and sensorimotor function were assessed using a modified Morris water maze test and modified neurological severity score, respectively. Animals were sacrificed at 4 days post injury for measurement of VEGF and VEGFR2 or 35 days post injury for evaluation of cell proliferation, angiogenesis and neurogenesis. EPO treatment promoted sensorimotor and cognitive functional recovery after TBI. EPO treatment increased brain VEGF expression and phosphorylation of VEGFR2. EPO significantly increased cell proliferation, angiogenesis and neurogenesis in the dentate gyrus after TBI. Compared to the vehicle, SU5416 infusion significantly inhibited phosphorylation of VEGFR2, cell proliferation, angiogenesis, and neurogenesis as well as abolished functional recovery in EPO-treated TBI rats. These findings indicate the VEGF/VEGFR2 activation plays an important role in EPO-mediated neurobehavioral recovery and neurovascular remodeling after TBI.

Abstract A8: Identification of novel drug targets against MMP-13 involved in breast cancer

Abstract Background: MMP-13, a zinc dependent protease highly expressed in breast cancer. Therefore, the protease has been intensively studied as a target for the inhibition of breast cancer. Recent reports suggest that selective inhibition of MMP-13 may be achieved by targeting the hemopexin (Hpx) domain of the protease, which is critical for substrate specificity. In this study the genomic DNA of MMP-13 was over expressed in MCF-7 breast cancer cell lines to check the efficacy of this drug like molecules. We also applied a cheminformatics-based drug design approach for the identification and characterization of inhibitors targeting the amino acid residues characteristic to Hpx domain of MMP-13; these inhibitors may potentially be employed in the treatment of breast cancer. Methodology/Principal Findings: Sequence-based mutual information analysis revealed five characteristic (completely conserved and unique), putative functional residues of the Hpx domain of MMP-13 (these residues hereafter are referred to as HCR-13pf). Binding of a ligand to as many of the HCR-13pf is postulated to result in an increased selective inhibition of the Hpx domain of MMP-13. Through the in silico structure-based high-throughput virtual screening (HTVS) method of Glide, against a large public library of 16908 molecules from Maybridge, PubChem and Binding, we identified 25 ligands that interact with at least one of the HCR-13pf. Assessment of cross-reactivity of the 25 ligands with MMP-1 and MMP-8, members of the collagenase family as MMP-13, returned seven lead molecules that did not bind to any one of the putative functional residues of Hpx domain of MMP-1 and any of the catalytic active site residues of MMP-1 and -8, suggesting that the ligands are not likely to interact with the functional or catalytic residues of other MMPs. Further, in silico analysis of physicochemical and pharmacokinetic parameters based on Lipinski's rule of five and ADMET (absorption, distribution, metabolism, excretion and toxicity) respectively, suggested potential utility of the compounds as drug leads. Western blot has been confirmed the over expression of MMP-13 in breast cancer cell lines. Conclusions/Significance: We have identified seven distinct drug-like molecules binding to the HCR-13pf of MMP-13 with no observable cross-reactivity to MMP-1 and MMP-8. These molecules are potential selective inhibitors of MMP-13 that can be experimentally validated and their backbone structural scaffold could serve as building blocks in designing drug-like molecules for breast cancer. The systematic cheminformatics-based drug design approach applied herein can be used for rational search of other public/commercial combinatorial libraries for more potent molecules, capable of selectively inhibiting the collagenolytic activity of MMP-13. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A8.