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Background: STING is an innate immune sensor critical for the development of immunity. Tumor cells can inactivate the STING pathway to avoid immune recognition, emphasizing its importance in generating tumor-specific immunity. Broad activation of STING in advanced cancers may be required to initiate CD8+ T cell priming against unique antigenic repertoires among distinct metastases and to reverse an immune-suppressive TME. Due its ubiquitous expression, systemic delivery of untargeted STING agonists may not achieve a therapeutic index. In contrast, expression of the cytosolic DNAse 3’ repair exonuclease (TREX1) is upregulated in tumor cells in response to genomic instability, inflammatory stimuli, and DNA replication, providing an opportunity for selective activation of the STING pathway. In addition to modulating cGAS/STING signaling, interaction with DNA replication enzymes that generate immunogenic DNA waste highlight a facet of TREX1 biology that may inform clinical development of targeted inhibitors. Methods: Using a structure-based drug design strategy, we designed and optimized small-molecule inhibitors of TREX1 with drug-like physicochemical properties that were profiled in biochemical and cell-based assays. X-ray crystallography studies, thermal shift, and biochemical assays were employed to determine mechanism of action. We evaluated the in vivo profile of select compounds. Results: Inhibitors of TREX1 with < 100 µM potency were optimized into a series with nanomolar potency against purified, recombinant murine and human TREX1 protein in biochemical assays. Inhibitors had similar IC50 values against TREX1 nuclease in an intact cell-based assay. Finally, TSA results demonstrated that compound interaction required magnesium. To our knowledge, we produced the first high-resolution co-crystal structures of inhibitor-bound human TREX1. We used this to dissect mouse- and human-specific interactions, confirming MOA predicted by earlier modeling efforts. Lead compounds demonstrated good bioavailability and achieved exposures necessary for target engagement in mouse models and resulted in tumor growth inhibition when combined with sub-therapeutic doses of doxorubicin. Conclusions: We present the identification and characterization of a potential first-in-class TREX1 inhibitor with nanomolar potency against human and mouse TREX1. Treatment with TREX1 inhibitors conferred profound anti-tumor activity when combined with DNA-damaging agents. Here we demonstrate that targeting TREX1 can specifically and locally engage the STING pathway in the tumor microenvironment, enhance tumor-specific immunity, and provide therapeutic benefit. Citation Format: Valerie Chen, Brian Francica, David Hsieh, Dave Freund, Anja Holtz, Saheli Samanta, Jamie Cope, Ryan Clark, Peppi Prasit, Anne Moon, Henry Johnson, Thomas Dubensky, Dara Burdette. Generation of novel potent human TREX1 inhibitors facilitated by crystallography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1636.

We previously published on the design and synthesis of novel, potent and selective PPARα antagonists suitable for either i.p. or oral in vivo administration for the potential treatment of cancer. Described herein is SAR for a subsequent program, where we set out to identify selective and potent PPARα/δ dual antagonist molecules. Emerging literature indicates that both PPARα and PPARδ antagonism may be helpful in curbing the proliferation of certain types of cancer. This dual antagonism could also be used to study PPARs in other settings. After testing for selective and dual potency, off-target counter screening, metabolic stability, oral bioavailability and associated toxicity, compound 11, the first reported PPARα/δ dual antagonist was chosen for more advanced preclinical evaluation.

Genetic evidence from human disease and mouse genetic knock-out studies identify the Stimulator of Interferon Genes (STING) pathway as a critical innate immune sensor for the development of immunity. Tumor cells can evolve to avoid immune recognition through inactivating the STING pathway by diverse mechanisms, indicating that it is important to generating tumor-specific immunity. However, the clinical activity of STING agonists given by intratumoral (IT) administration has not compared well to preclinical studies. The scientific hypothesis supporting these first clinical studies is that localized CD8+ T cell priming would have activity against distal non-injected tumors, but findings that tumors in advanced malignancies have unique antigenic repertoires suggests that this approach may have limited activity against distal tumors. Global innate activation in metastases may therefore be necessary to prime a broadly active CD8+ T cell population targeting diverse antigens, in addition having the benefit of reversing the immune suppressive tumor microenvironment (TME). However, ubiquitous expression of STING presents a significant challenge to achieving a therapeutic index with systemic delivery of direct STING agonists. Selective activation of the STING pathway may be achieved through targeted inhibition of TREX1, a cytosolic DNA exonuclease that modulates cGAS/STING signaling. Expression of TREX1, in contrast to STING, is increased in tumor cells due to elevated levels of cytosolic DNA resulting from genetic instability, DNA repair mutation, inflammatory mediators or DNA-modifying anti-cancer therapies. These observations provide the principal scientific rationale to selectively activate the STING pathway in metastatic disease through targeted inhibition of TREX1. Utilizing published TREX1 X-ray crystal structures to guide medicinal chemistry, we discovered small molecule inhibitors of TREX1 and transformed these molecules from >100 µM leads into a series with drug-like physicochemical properties and picomolar potency against both human and mouse TREX1. We evaluated the activity of lead molecules in cell-based assays, in which TREX1 inhibition enhanced cGAS/STING signaling, and advanced molecules with desired pharmacokinetic profiles to mouse tumor studies. We observed significant anti-tumor activity in mice with CT26 tumors given a combined therapy of low dose doxorubicin to induce dsDNA breaks and increase TME TREX1 expression along with lead series TREX1 molecule inhibitors. Recognizing that TREX1 is a DNA repair enzyme, we also showed that TREX1 inhibitors were cytotoxic in DNA repair deficient human tumor cell lines, informing advancement of this new class of STING therapeutics as a clinical approach to both activate the cGAS/STING pathway to initiate immune recognition, as well as to inhibit DNA repair orthogonal to existing tumor-driver DNA repair mutations. Citation Format: Brian Francica, Dara Burdette, Ryan Clark, Jamie Cope, David Freund, Anja Holtz, Peppi Prasit, Chan Whiting, Thomas W. Dubensky. Systemic small molecule TREX1 inhibitors to selectively activate STING in the TME of metastatic disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2075.

TPS2696 Background: Prostaglandin E2 (PGE2) is a bioactive lipid that promotes cancer through diverse mechanisms including stimulating tumor proliferation, enhancing angiogenesis and suppressing immune function in the tumor microenvironment. PGE2 produced by tumor cells through upregulation of cyclooxygenase-2 (COX-2) is also a key mediator of adaptive resistance to immune checkpoint inhibitor therapy. While PGE2 signaling is important in cancer, how best to inhibit PGE2 for cancer treatment is under investigation. Inhibition of COX enzymes (e.g., with NSAIDS) has shown promise in large observational studies, but inconsistent results in prospective studies. Importantly, COX inhibition alters multiple prostanoids beyond PGE2, resulting in toxicity that limits therapeutic dosing for cancer. PGE2 signals through four receptors, EP1-4, that are variably expressed and have distinct activities. The tumor promoting and immunosuppressive activities of PGE2 predominantly arise from signaling through the EP2 and EP4 receptors, while signaling through the EP1 and EP3 receptors generally is pro-inflammatory. TPST-1495 is designed to be an oral, highly specific, antagonist of the EP2 and EP4 receptors, sparing the EP1 and EP3 receptors and the COX enzymes. Preclinical studies suggest that blocking EP2 and EP4 with TPST-1495 inhibits tumor proliferation and stimulates anti-cancer immunity better than inhibiting all 4 receptors together, the EP2 or EP4 receptors singly, or the upstream COX-2 enzyme. Methods: TPST-1495-001 is a first-in-human Phase 1 study (NCT04344795). In the Dose and Schedule Optimization Stage, the primary objectives are to characterize the safety and tolerability (including dose limiting toxicities) and determine the recommended phase 2 dose (RP2D) of TPST-1495 as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors. Additional objectives include characterization of PK, PD, and evaluation of potential biomarkers, including through paired (pre- and on-treatment) tumor biopsies. Monotherapy dose-finding employs a modified 3+3 design evaluating BID and QD TPST-1495 schedules along with continuous or intermittent (Days 1-5 every 7 days) dosing. For the pembrolizumab combination, the starting dose and schedule of TPST-1495 are determined by safety, PK and PD of monotherapy. Indication-specific Expansion Stage cohorts will evaluate TPST-1495 at the selected RP2D and schedule for both monotherapy and combination in endometrial cancer, squamous cell carcinoma of the head and neck, and microsatellite stable colorectal cancer (combination only), as well as in a biomarker-specific cohort enrolling patients with pathogenic tumor PIK3CA gene mutation. Dose and Schedule Optimization enrollment (monotherapy and combination) is ongoing at abstract submission while Expansion Stages are planned after identification of the RP2Ds. Clinical trial information: NCT04344795.

3005 Background: TPST-1120 is a first-in-class oral therapy that inhibits PPARα, a transcription factor that regulates fatty acid oxidation (FAO). TPST-1120 has diverse mechanisms of anti-tumor activity in preclinical studies, including inhibiting tumor proliferation, increasing the anti-angiogenic factor thrombospondin 1, and reducing T cell exhaustion. Methods: Subjects with advanced solid tumor malignancies received escalating doses of TPST-1120 as a single agent or in combination with nivolumab 480 mg IV every 4 weeks (combination cohort limited to RCC, cholangiocarcinoma [CCA] and HCC). Study objectives included evaluation of safety, pharmacokinetics, MTD, RP2D and anti-tumor activity as monotherapy and in combination with nivolumab. AEs were assessed per CTCAE v5 and efficacy per RECIST v1.1 Results: As of 14-Jan-2022, 35 subjects have been dosed (20 with TPST-1120 monotherapy at doses from 100 mg to 600 mg PO BID and 15 in combination with nivolumab at doses from 200 mg to 600 mg PO BID). Median prior lines of systemic therapy were 3 (2-11) in monotherapy and 2 (2-6) in combination cohorts. An MTD was not reached in monotherapy or combination, and the TPST-1120 RP2D was 600 mg PO BID for both cohorts. For TPST-1120 monotherapy, the most common treatment related AEs (TRAEs) were nausea (20%), fatigue (15%), and diarrhea (10%), all Grade 1-2. One monotherapy subject (5%) experienced a Grade 3 TRAE (hypertension). In the combination cohort the most common TRAEs related to either drug were fatigue (40%), diarrhea (27%) and nausea (20%), all Grade 1-2. Three combination subjects (19%) experienced Grade 3 TRAEs (one each arthralgia, hepatic enzyme increased, muscle spasms). A best response of stable disease was observed in 53% (10/19) of subjects treated with monotherapy. In combination, the ORR was 23% (3/13, all PRs) across all dose levels and 38% (3/8) at TPST-1120 dose levels ≥400 mg BID. These responses included 2 subjects with late-line RCC (2/2 RCC subjects enrolled, both with progression on prior anti-PD1 therapy) and one subject with heavily pre-treated CCA. At data cut off, 2 of 3 responding patients (CCA and one RCC) remained in PR and on study at 8.4 and 14 mo, respectively. Conclusions: TPST-1120 is a novel therapy designed to inhibit tumor proliferation and angiogenesis and stimulate anti-cancer immunity through inhibition of PPARα, a key regulator of FAO. The drug is well tolerated as a single agent and in combination with nivolumab. Promising objective responses have been observed in combination with nivolumab in subjects previously refractory to anti-PD-1 therapy, including 2/2 responders in late-line RCC, and a subject with heavily pretreated CCA, a tumor type generally not responsive to anti-PD-1 alone. Notably, all responders were treated at the two highest doses of TPST-1120 (ORR 38%). Updated study results including exploratory biomarkers will be presented. Clinical trial information: NCT03829436.

Tumor-specific metabolic changes can reveal new therapeutic targets. Our findings implicate a supporting role for fatty acid metabolism in chronic lymphocytic leukemia (CLL) cell survival. Peroxisome proliferator–activated receptor (PPAR)-α, a major transcriptional regulator of fatty acid oxidation, was recently shown to be upregulated in CLL. To evaluate PPARα as a potential therapeutic target, we developed a highly selective, potent small molecule antagonist of PPARα, NXT629. NXT629 inhibited agonist-induced transcription of PPARα-regulated genes, demonstrating target engagement in CLL cells. Furthermore, NXT629 induced apoptosis of CLL cells even in the presence of a protective microenvironment. To mimic the proliferative lymphoid compartment of CLL, we examined the activity of NXT629 on CLL cells that were stimulated to proliferate in vitro. NXT629 reduced the number of leukemia cells undergoing cell division. In addition, in two xenograft mouse models of CLL (one a model for nondividing and one for dividing CLL), NXT629 reduced the number of viable CLL cells in vivo. Overall, these results suggest that fatty acid metabolism promotes survival and proliferation of primary CLL cells and that inhibiting PPARα gene regulation could be a new therapeutic approach to treating CLL.

The discovery and SAR of a novel series of potent and selective PPARα antagonists are herein described. Exploration of replacements for the labile acyl sulfonamide linker led to a biaryl sulfonamide series of which compound 33 proved to be suitable for further profiling in vivo. Compound 33 demonstrated excellent potency, selectivity against other nuclear hormone receptors, and good pharmacokinetics in mouse.

Peroxisome-proliferator activated receptors (PPAR) are members of the nuclear hormone receptor superfamily which regulate gene transcription. PPARα is a key regulator of lipid homeostasis and a negative regulator of inflammation. Under conditions of metabolic stress such as fasting or glucose deprivation, PPARα is upregulated in order to control gene expression necessary for processing alternate fuel sources (e.g. fatty acid oxidation) and thereby promote maintenance of cell viability. Clinically, PPARα expression is upregulated in diseased tissues such as melanoma, chronic lymphocytic leukemia, ovarian and prostate cancer. This may allow for cellular proliferation and metastasis. Importantly, genetic knockouts of PPARα have been shown to be protected against tumor growth in a variety of syngeneic tumors models. We hypothesized that a potent and selective PPARα antagonist could represent a novel cancer therapy. Early in our discovery research, we identified NXT629 (Bravo et al., 2014). Herein we describe the pharmacology of NXT629 and demonstrate that it is a potent and selective PPARα antagonist. We identify NXT629 as a valuable tool for use in in vivo assessment of PPARα due to its good systemic exposure following intraperitoneal injection. We explore the in vivo pharmacology of NXT629 and demonstrate that it is efficacious in pharmacodynamic models that are driven by PPARα. Finally, we probe the efficacy of NXT629 in disease models where PPARα knockouts have shown to be protected. We believe that PPARα antagonists will be beneficial in diseases such as ovarian cancer and melanoma where PPARα and fatty acid oxidation may be involved.

Tumors evolve to modulate metabolism to promote their own survival and to suppress tumor-specific immunity. Hypoxic conditions in the tumor microenvironment (TME) induce fatty acid oxidation (FAO), and diverse malignancies are reliant on this metabolic pathway. Additionally, suppressive immune cell populations including M2 macrophages, myeloid-derived suppressor cells and regulatory T cells preferentially utilize FAO. Peroxisome proliferator-activated receptor alpha (PPARα) is the principal transcription factor that regulates the expression of FAO genes, and this metabolic checkpoint is critical for tumor proliferation. TPST1120 is a first-in-class selective competitive antagonist of the human PPARα. To test the hypothesis that blocking FAO with TPST-1120 confers anti-tumor efficacy, we assessed TPST-1120 in multiple syngeneic and xenograft mouse models. Blockade of PPARα with TPST-1120 mediated potent anti-tumor immune responses and significant tumor regression in syngeneic models of breast, lung, colon, pancreatic and melanoma in addition to xenograft models of CLL, AML, pancreatic and melanoma cancers as a monotherapy or in combination with chemotherapy. In pancreatic and breast cancer models, TPST-1120 augmented regression of tumor growth in combination with chemotherapy. In combination with anti-PD1, TPST-1120 treatment resulted in significant reduction of tumor growth in ovarian orthotopic (ID8) and colon (MC38) models; cured mice were completely protected against autologous tumor challenge, strongly suggesting immunological T cell memory against the primary tumor. Studies in genetic knock-out mice indicated that macrophages and antigen cross-presenting dendritic cells are required for TPST-1120 activity, mediated through thrombospondin-1(TSP-1) and stimulator of interferon genes (STING). Consistent with prior reports, inhibition of PPARα with TPST-1120 skewed macrophages in vivo toward an M1 effector phenotype. These results provide the rationale for evaluating TPST-1120 in patients with advanced malignancies. A Phase 1/1b open-label, dose-escalation and dose-expansion study of TPST-1120 as a single agent or in combination with systemic anti-cancer therapies is planned in early 2019. Citation Format: Chan C. Whiting, Nick Stock, Davorka Messmer, Traci Olafson, Derek Metzger, Amanda Enstrom, Jennifer McDevitt, David Spaner, Peppi Prasit, Dipak Panigrahy, Ginna Laport. Blockade of the PPARα metabolic checkpoint with TPST-1120 suppresses tumor growth and stimulates anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3606.

The potent 5-lipoxygenase-activating protein (FLAP) inhibitor 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxypyridin-3-yl)benzyl]-5-(5-methylpyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethylpropionic acid 11cc is described (AM803, now GSK2190915). Building upon AM103 (1) (Hutchinson et al. J. Med Chem.2009, 52, 5803-5815; Stock et al. Bioorg. Med. Chem. Lett. 2010, 20, 213-217; Stock et al. Bioorg. Med. Chem. Lett.2010, 20, 4598-4601), SAR studies centering around the pyridine moiety led to the discovery of compounds that exhibit significantly increased potency in a human whole blood assay measuring LTB(4) inhibition with longer drug preincubation times (15 min vs 5 h). Further studies identified 11cc with a potency of 2.9 nM in FLAP binding, an IC(50) of 76 nM for inhibition of LTB(4) in human blood (5 h incubation) and excellent preclinical toxicology and pharmacokinetics in rat and dog. 11cc also demonstrated an extended pharmacodynamic effect in a rodent bronchoalveolar lavage (BAL) model. This compound has successfully completed phase 1 clinical studies in healthy volunteers and is currently undergoing phase 2 trials in asthmatic patients.

The prostaglandin D(2) (PGD(2)) receptor type 2 (DP2) is a G protein-coupled receptor that has been shown to be involved in a variety of allergic diseases, including allergic rhinitis, asthma, and atopic dermatitis. In this study, we describe the preclinical pharmacological and pharmacokinetic properties of the small-molecule DP2 antagonist [2'-(3-benzyl-1-ethyl-ureidomethyl)-6-methoxy-4'-trifluoromethyl-biphenyl-3-yl]-acetic acid (AM211). We determine that AM211 has high affinity for human, mouse, rat, and guinea pig DP2 and it shows selectivity over other prostanoid receptors and enzymes. Antagonist activity of AM211 at the DP2 receptor was confirmed by inhibition of PGD(2)-stimulated guanosine 5'-O-[γ-thio]triphosphate binding to membranes expressing human DP2. A basophil activation assay and a whole-blood assay of eosinophil shape change were used to demonstrate the ability of AM211 to potently antagonize PGD(2)-stimulated functional responses in relevant human cells and in the context of a physiologically relevant environment. AM211 exhibits good oral bioavailability in rats and dogs and dose-dependently inhibits 13,14-dihydro-15-keto-PGD(2)-induced leukocytosis in a guinea pig pharmacodynamic assay. AM211 demonstrates efficacy in two animal models of allergic inflammation, including an ovalbumin-induced lung inflammation model in guinea pigs and an ovalbumin-induced mouse model of allergic rhinitis. AM211 represents a potent and selective antagonist of DP2 that may be used clinically to evaluate the role of DP2 in T helper 2-driven allergic inflammatory diseases.

Compound 21 (AM432) was identified as a potent and selective antagonist of the DP2 receptor (CRTH2). Modification of a bi-aryl core identified a series of tri-aryl antagonists of which compound 21 proved a viable clinical candidate. AM432 shows excellent potency in a human whole blood eosinophil shape change assay with prolonged incubation, a comparatively long off-rate from the DP2 receptor, excellent pharmacokinetics in dog and in vivo activity in two mouse models of inflammatory disease after oral dosing.

Prostaglandin D(2) (PGD(2)) is one of a family of biologically active lipids derived from arachidonic acid via the action of COX-1 and COX-2. PGD(2) is released from mast cells and binds primarily to two G protein-coupled receptors, namely DP1 and DP2, the latter also known as chemoattractant receptor-homologous molecule expressed on Th2 cells. DP2 is predominantly expressed on eosinophils, Th2 cells, and basophils, but it is also expressed to a lesser extent on monocytes, mast cells, and epithelial cells. Interaction of PGD(2) and its active metabolites with DP2 results in cellular chemotaxis, degranulation, up-regulation of adhesion molecules, and cytokine production. Chronic obstructive pulmonary disease (COPD) is a chronic progressive inflammatory disease characterized by elevated lung neutrophils, macrophages, and CD8+ T lymphocytes and mucus hypersecretion. Cigarette smoke contributes to the etiology of COPD and was used here as a provoking agent in a murine model of COPD. In an acute model, {2'-[(cyclopropanecarbonyl-ethyl-amino)-methyl]-6-methoxy-4'-trifluoro-methyl-biphenyl-3-yl}-acetic acid, sodium salt (AM156) and (5-{2-[(benzoyloxycarbonyl-ethyl-amino)-methyl]-4-trifluoromethyl-phenyl}-pyridin-3-yl)-acetic acid, sodium salt) (AM206), potent DP2 receptor antagonists, dose-dependently inhibited influx of neutrophils and lymphocytes to smoke-exposed airways. In a subchronic model, AM156 and AM206 inhibited neutrophil and lymphocyte trafficking to the airways. Furthermore, AM156 and AM206 treatment inhibited mucus cell metaplasia and prevented the thickening of the airway epithelial layer induced by cigarette smoke. These data suggest that DP2 receptor antagonism may represent a novel therapy for COPD or other conditions characterized by neutrophil influx, mucus hypersecretion, and airway remodeling.

The synthesis of a series of tricyclic antagonists for the prostaglandin D(2) receptor DP2 (CRTH2) is disclosed. The activities of the compounds were evaluated in a human DP2 binding assay and a human whole blood eosinophil shape change assay. Potential metabolic liabilities of the compounds were addressed through in vitro CYP studies. The lead compound was demonstrated to have efficacy in a mouse model of allergic rhinitis following oral dosing.

The purpose of this study was to characterize the alpha(4)beta(1) receptor (CD49d/CD29, very late antigen-4, VLA-4) on circulating equine leukocytes and to evaluate the intrinsic potency of an alpha(4)beta(1) receptor antagonist (Compound B) in the horse. Ultimately, these studies would allow us to determine the suitability of treating recurrent airway obstruction (RAO; heaves) affected horses by blocking the cellular recruitment of lymphocytes and neutrophils into the lung. The data demonstrates the alpha(4)beta(1) integrin is present on horse lymphocytes and neutrophils (fluorescence-assisted cell sorter, FACS) and can bind low molecular weight alpha(4)beta(1) antagonists (Compounds A and B) with high affinity. K(D) values for the binding of Compound A to non-activated alpha(4)beta(1) on isolated horse PBMCs (peripheral blood mononuclear cells) and activated neutrophils were 17 pM and 27 pM, respectively. Compound B was identified as a suitable antagonist for performing a series of in vivo experiments. Compound B was found to possess excellent potency in horse whole blood, possessing IC(50) and IC(90) values of 39 pM and 172 pM, respectively. This represents a 3.9-fold molar excess of drug over the alpha(4)beta(1) concentration in blood. Following oral administration of Compound B (5 mg/kg) to beagle dogs and rhesus monkeys, rapid and sustained alpha(4)beta(1) receptor occupancy (80%) was achieved and maintained for a period of 24 h. When Compound B was administered intravenously to the horse, by either a slow or rapid infusion at a dose of 0.3 mg/kg, receptor blockade of80% was observed out to 24 h with a concomitant leukocytosis. We believe that Compound B possesses suitable intrinsic and pharmacological properties to be evaluated clinically in horses affected by RAO.

We have prepared a series of achiral aminoacetonitriles, bearing tri-ring benzamide moieties and an aminocyclohexanecarboxylate residue at P2. This combination of binding elements resulted in sub-250 pM, reversible, selective, and orally bioavailable cathepsin K inhibitors. Lead compounds displayed single digit nanomolar inhibition in vitro (of rabbit osteoclast-mediated degradation of bovine bone). The best compound in this series, 39n (CRA-013783/L-006235), was orally bioavailable in rats, with a terminal half-life of over 3 h. 39n was dosed orally in ovariectomized rhesus monkeys once per day for 7 days. Collagen breakdown products were reduced by up to 76% dose-dependently. Plasma concentrations of 39n above the bone resorption IC50 after 24 h indicated a correlation between functional cellular and in vivo assays. Inhibition of collagen breakdown by cathepsin K inhibitors suggests this mechanism of action may be useful in osteoporosis and other indications involving bone resorption.

A water soluble choline prodrug (17) of a COX-2 selective inhibitor (16) suitable for intravenous dosing in models of cerebral ischemia has been developed. Constant infusion studies using 17 demonstrate that extrapolated brain levels of 16 may be maintained for over 24h in rats.

A novel series of nonpeptidic biaryl compounds was identified as potent and reversible inhibitors of cathepsin K. The P2-P3 amide bond of a known amino acetonitrile dipeptide 1 was replaced with a phenyl ring, thereby giving rise to this biaryl series that retained potency vs cathepsin K and showed an improved selectivity profile against other cathepsins. Structural modification within this series resulted in the identification of compound (R)-2, a potent human cathepsin K inhibitor (IC(50) = 3 nM) that is selective versus cathepsins B (IC(50) = 3950 nM), L (IC(50) = 3725 nM), and S (IC(50) = 2010 nM). In an in vitro assay involving rabbit osteoclasts and bovine bone, compound (R)-2 inhibited bone resorption with an IC(50) of 95 nM. It was shown that, unlike some peptidic nitrile inhibitors of cysteine proteases, the nitrile moiety of (R)-2 is not converted to the corresponding amide 3 by cathepsin K. This indicates that this class of nonpeptidic nitrile inhibitors is unlikely to be hydrolyzed by cysteine proteases. Furthermore, the inhibition of cathepsin K by compound (R)-2 was shown to be fully reversible and not observably time-dependent. To demonstrate the efficacy of compound (R)-2 in vivo, it was administered to ovariectomized (OVX) rhesus monkeys at 20 mg/kg, po once daily for 8 days, and a urinary marker of bone turnover, N-telopeptide of type I collagen (uNTx), was measured. During the eight-day dosing period, the mean reduction by compound (R)-2 in uNTx was 80% (p < 0.001). This demonstrates that inhibition of cathepsin K leads to an inhibition of this bone resorption marker in OVX rhesus monkeys and strongly suggests that inhibition of cathepsin K is a viable therapeutic approach for the treatment of osteoporosis.

A large-scale, chromatography-free synthesis of a potent and selective Cathepsin K inhibitor 1 is reported. The key asymmetric center was installed by addition of (R)-pantolactone to the in situ-generated ketene 4a. The final step of the convergent synthesis of 1 was completed via Suzuki coupling of aryl bromide 7a with unprotected aryl piperazine boronic acid 13. Residual palladium and iron generated in the Suzuki coupling were efficiently removed from crude 1 via a simple extractive workup using lactic acid.

Compounds containing a 1-cyanopyrrolidinyl ring were identified as potent and reversible inhibitors of cathepsins K and L. The original lead compound 1 inhibits cathepsins K and L with IC(50) values of 0. 37 and 0.45 M, respectively. Modification of compound 1 by replacement of the quinoline moiety led to the synthesis of N-(1-cyano-3-pyrrolidinyl)benzenesulfonamide (2). Compound 2 was found to be a potent inhibitor of cathepsins K and L with a K(i) value of 50 nM for cathepsin K. Replacement of the 1-cyanopyrrolidine of compound 2 by a 1-cyanoazetidine increased the potency of the inhibitor by 10-fold. This increase in potency is probably due to an enhanced chemical reactivity of the compound toward the thiolate of the active site of the enzyme. This is demonstrated when the assay is performed in the presence of glutathione at pH 7.0 which favors the formation of a GSH thiolate anion. Under these assay conditions, there is a loss of potency in the 1-cyanoazetidine series due to the formation of an inactive complex between the GSH thiolate and the 1-cyanoazetidine inhibitors. 1-Cyanopyrrolidinyl inhibitors exhibited time-dependent inhibition which allowed us to determine the association and dissociation rate constants with human cathepsin K. The kinetic data obtained showed that the increase of potency observed between different 1-cyanopyrrolidinyl inhibitors is due to an increase of k(on) values and that the association of the compound with the enzyme fits an apparent one-step mechanism. (13)C NMR experiments performed with the enzyme papain showed that compound 2 forms a covalent isothiourea ester adduct with the enzyme. As predicted by the kinetic analysis, the addition of the irreversible inhibitor E64 to the enzyme-cyanopyrrolidinyl complex totally abolished the signal of the isothiourea bond as observed by (13)C NMR, thereby demonstrating that the formation of the covalent bond with the active site cysteine residue is reversible. Finally, compound 2 inhibits bone resorption in an in vitro assay involving rabbit osteoclasts and bovine bone with an IC(50) value of 0.7 M. 1-Cyanopyrrolidine represents a new class of nonpeptidic compounds that inhibit cathepsin K and L activity and proteolysis of bone collagen.

Metabolites of the COX-2 inhibitor rofecoxib (MK-0966, Vioxx) were prepared by synthetic or biosynthetic methods. Metabolites include products of oxidation, glucuronidation, reduction and hydrolytic ring opening. Based on an in vitro whole blood assay, none of the known human metabolites of rofecoxib inhibits COX-1 nor contributes significantly to the inhibition of COX-2.

A series of [1,2,4]triazolo[3,4-f][1,6]naphthyridine allosteric dual inhibitors of Akt1 and 2 have been developed. These compounds have been shown to have potent dual Akt1 and 2 cell potency. The representative compound 13 provided potent inhibitory activity against Akt1 and 2 in vivo in a mouse model.

2-(3′,5′-Difluorophenyl)-3-(4′-methylsulfonylphenyl)cyclopent-2-enone (1) displays high selectivity and potency against COX-2. Three efficient syntheses of this diarylcyclopentenone are described. The first approach employs a Suzuki coupling reaction as the key step while the second synthesis features an intramolecular Friedel-Crafts acylation. The third, and preferred route to this compound involves a sequential malonate alkylation and acylation and ring-closure sequence.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that signals through a family of at least six G protein-coupled receptors designated LPA₁₋₆. LPA type 1 receptor (LPA₁) exhibits widespread tissue distribution and regulates a variety of physiological and pathological cellular functions. Here, we evaluated the in vitro pharmacology, pharmacokinetic, and pharmacodynamic properties of the LPA₁-selective antagonist AM095 (sodium, {4'-[3-methyl-4-((R)-1-phenyl-ethoxycarbonylamino)-isoxazol-5-yl]-biphenyl-4-yl}-acetate) and assessed the effects of AM095 in rodent models of lung and kidney fibrosis and dermal wound healing. In vitro, AM095 was a potent LPA₁ receptor antagonist because it inhibited GTPγS binding to Chinese hamster ovary (CHO) cell membranes overexpressing recombinant human or mouse LPA₁ with IC₅₀ values of 0.98 and 0.73 μM, respectively, and exhibited no LPA₁ agonism. In functional assays, AM095 inhibited LPA-driven chemotaxis of CHO cells overexpressing mouse LPA₁ (IC₅₀= 778 nM) and human A2058 melanoma cells (IC₅₀ = 233 nM). In vivo, we demonstrated that AM095: 1) had high oral bioavailability and a moderate half-life and was well tolerated at the doses tested in rats and dogs after oral and intravenous dosing, 2) dose-dependently reduced LPA-stimulated histamine release, 3) attenuated bleomycin-induced increases in collagen, protein, and inflammatory cell infiltration in bronchalveolar lavage fluid, and 4) decreased kidney fibrosis in a mouse unilateral ureteral obstruction model. Despite its antifibrotic activity, AM095 had no effect on normal wound healing after incisional and excisional wounding in rats. These data demonstrate that AM095 is an LPA₁ receptor antagonist with good oral exposure and antifibrotic activity in rodent models.

Biphenylacetic acid (5) was identified through a library screen as an inhibitor of the prostaglandin D(2) receptor DP2 (CRTH2). Optimization for potency and pharmacokinetic properties led to a series of selective CRTH2 antagonists. Compounds demonstrated potency in a human DP2 binding assay and a human whole blood eosinophil shape change assay, as well as good oral bioavailability in rat and dog, and efficacy in a mouse model of allergic rhinitis following oral dosing.

Background: Allergic conjunctivitis is characterized by itchy, watery and swollen eyes which occur in response to exposure to seasonal or environmental allergens. The early phase reaction of allergic conjunctivitis is primarily mediated by mast cell degranulation while the late phase reaction is driven by Th2 cells and eosinophils. Prostaglandin D2 (PGD2), released from mast cells, is present in allergic conjunctival tears and may elicit classical allergic responses via interaction with the high-affinity DP2 receptor (chemoattractant receptor-homologous molecule expressed on Th2 cells, CRTh2). Furthermore, antagonism of this receptor is well known to inhibit eosinophil chemotaxis, basophil activation and Th2 cytokine production. PGD2, therefore, may be involved in both early and late phase reactions in response to allergen challenge. Methods: Thus, we explored whether our novel and selective DP2 antagonist AM156 would be efficacious in animal models of allergic conjunctivitis. Furthermore, as respiratory syncytial virus (RSV) has been implicated in the pathogenesis of allergic conjunctivitis, we examined the effects of DP2 antagonism in a murine model of RSV ocular infection. Results: Utilizing a guinea pig ovalbumin model and a murine ragweed model we demonstrated that AM156 reduces redness, discharge and swelling in response to allergen challenge. These effects were equal to or greater than those of current clinical treatment options for allergic conjunctivitis including topical corticosteroids and a dual-mechanism antihistamine and decongestant. AM156 significantly reduced RSV-induced ocular inflammation and IL-4 production. Conclusion: These results suggest that a topical DP2 antagonist such as AM156 may represent a novel therapeutic for allergic conjunctivitis.

AM643 (compound 6, 3-{3-tert-butylsulfanyl-1-[4-(5-methoxy-pyrimidin-2-yl)-benzyl]-5-(5-methyl-pyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethyl-propionic acid) was identified as a potential candidate for formulation as a topical agent for the treatment of skin disorders involving leukotriene production. Dermal application of 6 using a prototypical vehicle in a murine ear arachidonic acid model showed significant reduction in the concentrations of leukotrienes in mouse skin with concomitant reduction in ear swelling.

Prostaglandin D 2 (PGD 2 ) is derived from arachidonic acid and binds with high affinity to the G protein coupled receptors prostanoid DP 1 and DP 2 . Interaction with DP 2 results in cell chemotaxis, eosinophil degranulation, eosinophil shape change, adhesion molecule upregulation and Th2 cytokine production. In allergic rhinitis and allergic asthma PGD 2 is released from mast cells in response to allergen challenge and may trigger symptoms such as sneezing, rhinorrhea, pruritus, mucus hypersecretion and pulmonary inflammation. In Japan, ramatroban, a dual prostanoid DP 2 /prostanoid TP receptor antagonist, is marketed for allergic rhinitis while selective DP 2 antagonists are currently under investigation as therapeutics for asthma and allergic rhinitis. In the studies described herein, we investigated the efficacy of AM156, a novel selective prostanoid DP 2 receptor antagonist, in murine models of allergic rhinitis and asthma. AM156 inhibited sneezing and nasal rubs in a model of allergic rhinitis. AM156 inhibited pulmonary inflammation and mucus hypersecretion induced by chronic inhalation of house dust mite. These results suggest that selective prostanoid DP 2 receptor antagonists such as AM156 may provide beneficial effects for the clinical treatment of diseases such as allergic rhinitis and asthma.

We evaluated the in vivo pharmacological properties of AM803 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxy-pyridin-3-yl)-benzyl]-5-(5-methyl-pyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethyl-propionic acid, a selective five-lipoxygenase-activating protein (FLAP) inhibitor, using rat and mouse models of acute inflammation. Oral administration of AM803 (1 mg/kg) resulted in sustained inhibition of ex vivo ionophore-challenged whole blood LTB4 biosynthesis with >90% inhibition for up to 12 h and an EC50 of approximately 7 nM. When rat lungs were challenged in vivo with calcium-ionophore, AM803 inhibited LTB4 and cysteinyl leukotriene (CysLT) production with ED50s of 0.12 mg/kg and 0.37 mg/kg, respectively. The inhibition measured 16 h following a single oral dose of 3 mg/kg was 86% and 41% for LTB4 and CysLTs, respectively. In an acute inflammation setting, AM803 dose-dependently reduced LTB4, CysLTs, plasma protein extravasation and neutrophil influx induced by peritoneal zymosan injection. Finally, AM803 increased survival time in mice exposed to a lethal intravenous injection of platelet activating factor (PAF). The magnitude of effect was similar to that of an inhibitor of five-lipoxygenase (5-LO) and LTA4 hydrolase but superior to a leukotriene CysLT1 receptor antagonist. In summary, AM803 is a novel, potent and selective FLAP inhibitor that has excellent pharmacodynamic properties in vivo and is effective in animal models of acute inflammation and in a model of lethal shock.

A series of potent 5-lipoxygenase-activating protein (FLAP) inhibitors are herein described. SAR studies focused on the discovery of novel alicyclic moieties appended to an indole core to optimize potency, physical properties and off-target activities. Subsequent SAR on the N-benzyl substituent of the indole led to the discovery of compound 39 (AM679) which showed potent inhibition of leukotrienes in human blood and in a rodent bronchoalvelolar lavage (BAL) challenge model.

The potent and selective 5-lipoxygenase-activating protein leukotriene synthesis inhibitor 3-[3-tert-butylsulfanyl-1-[4-(6-methoxy-pyridin-3-yl)-benzyl]-5-(pyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethyl-propionic acid (11j) is described. Lead optimization was designed to afford compounds with superior in vitro and in vivo inhibition of leukotriene synthesis in addition to having excellent pharmacokinetics and safety in rats and dogs. The key structural features of these new compounds are incorporation of heterocycles on the indole N-benzyl substituent and replacement of the quinoline group resulting in compounds with excellent in vitro and in vivo activities, superior pharmacokinetics, and improved physical properties. The methoxypyridine derivative 11j has an IC(50) of 4.2 nM in a 5-lipoxygenase-activating protein (FLAP) binding assay, an IC(50) of 349 nM in the human blood LTB(4) inhibition assay, and is efficacious in a murine ovalbumin model of allergen-induced asthma. Compound 11j was selected for clinical development and has successfully completed phase 1 trials in healthy volunteers.

Prior reports from our laboratories have identified the nonpeptidic inhibitor 2 as a potent and selective Cathepsin K (Cat K) inhibitor. Modelling studies suggested that the introduction of a NH linker between the P3 aryl and P2 leucinamide moieties would allow the formation of a H-bond with the Gly66 residue of Cat K, hopefully increasing potency. Aniline 4 was thus synthesized and showed improved potency over its predecessor 2 . Further modelling concluded that a 2-substituted five membered ring could more adequately place the P3 moiety of 4 into the S3 pocket of Cat K. The synthesis of the 2-substituted thiophene 5 confirmed this hypothesis by displaying a slight increase in potency against Cat K (>10-fold increase in potency vs 2 ) and a good selectivity profile against Cathepsins B, L, and S. This rationally designed inhibitor 5 also displayed increased potency in a functional bone resorption assay (10 nM) versus 2 (95 nM).

The highly potent, selective, and brain-penetrant metabotropic glutamate subtype 5 (mGlu5) receptor antagonists 3-(5-pyridin-2-yl-2H-tetrazol-2-yl)benzonitrile (47) and 3-fluoro-5-(5-pyridin-2-yl-2H-tetrazol-2-yl)benzonitrile (48) are reported. Compound 47 is active in the rat fear-potentiated startle (FPS) model of anxiety with ED(50) = 5.4 mg/kg (po) when dosed acutely. In this model the anxiolytic effects of 47 rapidly tolerate on repeated dosing.

Compounds containing a 1-cyanopyrrolidinyl ring were identified as potent and reversible inhibitors of cathepsins K and L. The original lead compound 1 inhibits cathepsins K and L with IC50 values of 0.37 and 0.45 μM, respectively. Modification of compound 1 by replacement of the quinoline moiety led to the synthesis of N-(1-cyano-3-pyrrolidinyl)benzenesulfonamide (2). Compound 2 was found to be a potent inhibitor of cathepsins K and L with a Ki value of 50 nM for cathepsin K. Replacement of the 1-cyanopyrrolidine of compound 2 by a 1-cyanoazetidine increased the potency of the inhibitor by 10-fold. This increase in potency is probably due to an enhanced chemical reactivity of the compound toward the thiolate of the active site of the enzyme. This is demonstrated when the assay is performed in the presence of glutathione at pH 7.0 which favors the formation of a GSH thiolate anion. Under these assay conditions, there is a loss of potency in the 1-cyanoazetidine series due to the formation of an inactive c...

Abstract 3879 Tumor-specific metabolic changes could serve as new therapeutic targets. While much attention has been given to the metabolism of glucose in cancer cells and intervening therapies, relatively little attention has been given to fatty acids and fatty acid β-oxidation (FAO) in promoting cancer cell survival. Here, we reveal new findings implicating fatty acid metabolism in Chronic lymphocytic leukemia (CLL) and have developed a small molecule inhibitor of this pathway as a novel therapeutic approach to treat CLL. We have found that B cells isolated from CLL patients show increased levels of b-oxidation as compared to B cells isolated from PBMCs of healthy donor controls. NXT629, a small molecule inhibitor of the FAO pathway, dose-dependently reduced b-oxidation in CLL cells but did not reduce b-oxidation in B cells isolated from healthy volunteers. A negative control compound (NXT962) that has a similar chemical structure to NXT629, but does not significantly bind to the relevant target, did not inhibit FAO. NXT629 exerted dose-dependent cytotoxicity in CLL cells (CC50=10 mM, n=5 different patient samples) whereas NXT962 was inactive. Since the cellular microenvironment can protect CLL cells from spontaneous and drug-induced apoptosis, it is pivotal to evaluate novel drugs in this context. As expected, we found that macrophages protected CLL cells from spontaneous and fludarabine-induced apoptosis in vitro. However, NXT629 significantly reduced CLL cells viablity in the co-cultures. NXT629 (at 10 mM, n=2 different patient samples) induced apoptosis in 80% of cells after 7 days of co-culture in a setting where fludarabine was inactive. Though most CLL cells in the periphery are in a resting state, CLL cells proliferate in lymphoid organs. To mimic these conditions, we examined the activity of FAO inhibition on CLL cells that were induced to proliferate in vitro. To induce proliferation, CLL cells were cultured in media containing human interleukin (IL)-4, IL-10, and allogeneic T blasts. Labeling CLL cells with carboxyfluorescein succinimidyl ester, allowed us to monitor several rounds of induced CLL-cell division via flow cytometry, and within 5 days the CLL cells had expanded 3-fold. We found that addition of NXT629 to such cultures resulted in a dose-dependent reduction in the number of leukemia cells induced to undergo cell-division (IC50=3.7 mM, n=6), whereas the negative control compound showed no activity. Furthermore, when used in combination with dexamethasone (0.3 mM), NXT629 (3 mM) showed a significant decrease in the number of viable cells (38% +/−3%) over either dexamethasone (65% +/−12%) or NXT629 (74%+/−15%) alone. The additivity of FAO inhibition and dexamethasone in vitro suggests that a combination warrants further testing and might yield improved clinical responses. Overall, these results suggest that fatty acids promote primary CLL cell survival and proliferation, and that targeting the FAO pathway could be a new therapeutic approach to treating CLL. Disclosures: Messmer: Inception Sciences: Employment, Equity Ownership. Lorrain:Inception Sciences: Employment, Equity Ownership. Bravo:Inception Sciences: Employment, Equity Ownership. Stock:Inception Sciences: Employment, Equity Ownership. Bundey:Inception Sciences: Employment, Equity Ownership. Correa:Inception Sciences: Employment, Equity Ownership. Poon:Inception Sciences: Employment, Equity Ownership. Stebbins:Inception Sciencees: Employment, Equity Ownership. Cabrera:Inception Sciences: Employment, Equity Ownership. Chen:Inception Sciences: Employment, Equity Ownership. Jacintho:Inception Sciences: Employment, Equity Ownership. Spaner:Inception Sciences: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Prasit:Inception Sciences: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Lorrain:Inception Sciences: Employment, Equity Ownership.