Novel WRN Helicase Inhibitors Selectively Target Microsatellite Unstable Cancer Cells.

Microsatellite-unstable (MSI) cancers require WRN helicase to resolve replication stress due to expanded DNA (TA)n-dinucleotide repeats. WRN is a promising synthetic lethal target for MSI tumours, and WRN inhibitors are in development. Here, we used CRISPR-Cas9 base editing to map WRN residues critical for MSI cells, validating the helicase domain as the primary drug target. Fragment-based screening led to the development of potent and highly selective WRN helicase covalent inhibitors. These compounds selectively suppressed MSI model growth In vitro and In vivo by mimicking WRN loss, inducing DNA double-strand breaks at expanded TA-repeats and DNA damage. Assessment of biomarkers in preclinical models linked TA-repeat expansions and mismatch repair (MMR) alterations to compound activity. Efficacy was confirmed in immunotherapy-resistant organoids and patient-derived xenograft (PDX) models. The discovery of potent, selective covalent WRN inhibitors provides proof of concept for synthetic-lethal targeting of WRN in MSI cancer and tools to dissect WRN biology.

Model-Based Virtual PK/PD Exploration and Machine Learning Approach to Define PK Drivers in Early Drug Discovery.

While poor translatability of preclinical efficacy models can be responsible for clinical phase II failures, misdefinition of the optimal PK properties required to achieve therapeutic efficacy can also be a contributing factor. In the present work, the pharmacological dependency of PK end points in driving efficacy is demonstrated for six common pharmacological processes via model-based analysis. The analysis shows that the response is driven by multiple pharmacology-specific PK end points that change with how the response is defined. Moreover, the results demonstrate that the most important chemical structural features influencing response are specific to both target and downstream pharmacology, meaning the design and screening criteria must be defined uniquely for each target and corresponding pharmacology. The model-based virtual exploration of PK/PD relationships presented in this work offers one approach to identify target pharmacology-specific PK drivers and the associated potency-ADME space early in discovery to increase the probability of success and, ultimately, clinical attrition.

Applications of Model-Based Target Pharmacology Assessment in Defining Drug Design and DMPK Strategies: GSK Experiences.

Many critical decisions faced in early discovery require a thorough understanding of the dynamic behavior of pharmacological pathways following target engagement. From fundamental decisions on the optimal target to pursue and the ultimate drug product profile (combination of modality, potency, and compound properties) expected to elicit the desired clinical outcome to tactical program decisions such as what chemical series to pursue, what chemical properties require optimization, and what compounds to synthesize and progress, all demand detailed consideration of pharmacodynamics. Model-based target pharmacology assessment (mTPA) is a computational approach centered around large-scale virtual exploration of pharmacokinetic and pharmacodynamic models built early in discovery to guide these decisions. The present work summarizes several examples (use cases) from programs at GlaxoSmithKline that demonstrate the utility of mTPA throughout the drug discovery lifecycle.

Overcoming the Pregnane X Receptor Liability: Rational Design to Eliminate PXR-Mediated CYP Induction.

The pregnane X receptor (PXR) regulates expression of proteins responsible for all three phases required for the detoxification mechanism, which include CYP450 enzymes, phase II enzymes, and multidrug efflux pumps. Therefore, PXR is a prominent receptor that is responsible for xenobiotic excretion and drug-drug interactions. Pyrimidinone 1 is an antagonist of the calcium sensing receptor (CaSR) and a strong activator of PXR. Repeat oral administration revealed diminished exposures over time, which prohibited further progression. A medicinal chemistry campaign was initiated to understand and abolish activation of PXR in order to increase systemic exposures. Rational structure-activity relationship investigations utilizing cocrystal structures and a de novo pharmacophore model resulted in compounds devoid of PXR activation. These studies culminated in the first orally active CaSR antagonist 8 suitable for progression. Cocrystallography, the pharmacophore model employed, and additional observations reported herein supported rational elimination of PXR activation and have applicability across diverse chemical classes to help erase PXR-driven drug-drug interactions.

Correction to Identification of Quinoline-Based RIP2 Kinase Inhibitors with an Improved Therapeutic Index to the hERG Ion Channel.

[This corrects the article DOI: 10.1021/acsmedchemlett.8b00344.].

Understanding Pharmacokinetic Disconnect in Preclinical Species for 4-Aminoquinolines: Consequences of Low Permeability and High P-glycoprotein Efflux Ratio on Rat and Dog Oral Pharmacokinetics.

Receptor Interacting Protein 2 (RIP2) kinase inhibitors have been reported for therapeutic opportunities in inflammatory bowel diseases such as Ulcerative Colitis and Crohn's disease. During lead optimization, team identified 4-aminoquinoline series and several compounds from this series were investigated in rat and dog pharmacokinetic studies. While compounds such as GSKA and GSKB demonstrated acceptable pharmacokinetics in rat and dog, further progression of these compounds was halted due to adverse findings in advanced safety studies. Structurally similar analogues incorporating polarity at C-7 position of 4-aminoquinoline resulted in identification of GSKC - GSKF. Interestingly, following oral administration to rat at similar low dose, GSKC - GSKF demonstrated significantly low systemic drug exposure compared to GSKA and GSKB (3-17-fold difference). However, in dog, dose normalized oral systemic exposure for GSKC - GSKF was comparable to GSKA and GSKB (within 2-fold). A series of studies were conducted to understand the disconnect which highlighted that an intrinsic reduction in permeability and high P-glycoprotein (P-gp) efflux ratio for C-7 substituted analogues were driving pharmacokinetic disconnect between rat and dog. Oral absorption was minimally impacted in dog by P-gp mediated efflux compared to rat because the leakier gastrointestinal tract in dog likely overcomes this effect.

Enteric RET inhibition attenuates gastrointestinal secretion and motility via cholinergic signaling in rat colonic mucosal preparations.

BACKGROUND: The expression of RET in the developing enteric nervous system (ENS) suggests that RET may contribute to adult intestinal function. ENS cholinergic nerves play a critical role in the control of colonic function through the release of acetylcholine (ACh). In the current study, we hypothesized that a RET-mediated mechanism may regulate colonic ion transport and motility through modulation of cholinergic nerves. METHODS: The effect of RET inhibition on active ion transport was assessed electrophysiologically in rat colonic tissue mounted in Ussing chambers via measurements of short circuit current (Isc) upon electrical field stimulation (EFS) or pharmacologically with cholinergic agonists utilizing a gastrointestinal (GI)-restricted RET inhibitor. We assessed the effect of the RET inhibitor on propulsive motility via quantification of fecal pellet output (FPO) induced by the acetylcholinesterase inhibitor neostigmine. KEY RESULTS: We found that enteric ganglia co-expressed RET and choline acetyltransferase (ChAT) transcripts. In vitro, the RET kinase inhibitor GSK3179106 attenuated the mean increase in Isc induced by either EFS or carbachol but not bethanechol. In vivo, GSK3179106 significantly reduced the prokinetic effect of neostigmine. CONCLUSION AND INFERENCES: Our findings provide evidence that RET-mediated mechanisms regulate colonic function by maintaining cholinergic neuronal function and enabling ACh-evoked chloride secretion and motility. We suggest that modulating the cholinergic control of the colon via a RET inhibitor may represent a novel target for the treatment of intestinal disorders associated with increased secretion and accelerated GI transit such as irritable bowel syndrome with diarrhea (IBS-D).

Exploring the Potential of RET Kinase Inhibition for Irritable Bowel Syndrome: A Preclinical Investigation in Rodent Models of Colonic Hypersensitivity.

Abdominal pain represents a significant complaint in patients with irritable bowel syndrome (IBS). While the etiology of IBS is incompletely understood, prior exposure to gastrointestinal inflammation or psychologic stress is frequently associated with the development of symptoms. Inflammation or stress-induced expression of growth factors or cytokines may contribute to the pathophysiology of IBS. Here, we aimed to investigate the therapeutic potential of inhibiting the receptor of glial cell line-derived neurotrophic factor, rearranged during transfection (RET), in experimental models of inflammation and stress-induced visceral hypersensitivity resembling IBS sequelae. In RET-cyan fluorescent protein [(CFP) RetCFP/+] mice, thoracic and lumbosacral dorsal root ganglia were shown to express RET, which colocalized with calcitonin gene-related peptide. To understand the role of RET in visceral nociception, we employed GSK3179106 as a potent, selective, and gut-restricted RET kinase inhibitor. Colonic hyperalgesia, quantified as exaggerated visceromotor response to graded pressures (0-60 mm Hg) of isobaric colorectal distension (CRD), was produced in multiple rat models induced 1) by colonic irritation, 2) following acute colonic inflammation, 3) by adulthood stress, and 4) by early life stress. In all the rat models, RET inhibition with GSK3179106 attenuated the number of abdominal contractions induced by CRD. Our findings identify a role for RET in visceral nociception. Inhibition of RET kinase with a potent, selective, and gut-restricted small molecule may represent a novel therapeutic strategy for the treatment of IBS through the attenuation of post-inflammatory and stress-induced visceral hypersensitivity.

Identification of Quinoline-Based RIP2 Kinase Inhibitors with an Improved Therapeutic Index to the hERG Ion Channel.

RIP2 kinase was recently identified as a therapeutic target for a variety of autoimmune diseases. We have reported previously a selective 4-aminoquinoline-based RIP2 inhibitor GSK583 and demonstrated its effectiveness in blocking downstream NOD2 signaling in cellular models, rodent in vivo models, and human ex vivo disease models. While this tool compound was valuable in validating the biological pathway, it suffered from activity at the hERG ion channel and a poor PK/PD profile thereby limiting progression of this analog. Herein, we detail our efforts to improve both this off-target liability as well as the PK/PD profile of this series of inhibitors through modulation of lipophilicity and strengthening hinge binding ability. These efforts have led to inhibitor 7, which possesses high binding affinity for the ATP pocket of RIP2 (IC50 = 1 nM) and inhibition of downstream cytokine production in human whole blood (IC50 = 10 nM) with reduced hERG activity (14 µM).

TLR2 agonism reverses chemotherapy-induced neutropenia in Macaca fascicularis.

Neutropenia is a common consequence of radiation and chemotherapy in cancer patients. The resulting immunocompromised patients become highly susceptible to potentially life-threatening infections. Granulocyte colony-stimulating factor (G-CSF) is known to stimulate neutrophil production and is widely used as a treatment of chemotherapy-induced neutropenia. A small-molecule G-CSF secretagogue without a requirement for refrigerated supply chain would offer a more convenient and cost-effective treatment of chemotherapy-induced neutropenia. Bacterial lipopeptides activate innate immune responses through Toll-like receptor 2 (TLR2) and induce the release of cytokines, including G-CSF, from macrophages, monocytes, and endothelial. Pam2CSK4 is a synthetic lipopeptide that effectively mimics bacterial lipoproteins known to activate TLR2 receptor signaling through the TLR2/6 heterodimer. Substrate-based drug design led to the discovery of GSK3277329, which stimulated the release of G-CSF in activated THP-1 cells, peripheral blood mononuclear cells, and human umbilical vein endothelial cells. When administered subcutaneously to cynomolgus monkeys (Macaca fascicularis), GSK3277329 caused systemic elevation of G-CSF and interleukin-6 (IL-6), but not IL-1ß or tumor necrosis factor α, indicating a selective cytokine-stimulation profile. Repeat daily injections of GSK3277329 in healthy monkeys also raised circulating neutrophils above the normal range over a 1-week treatment period. More importantly, repeated daily injections of GSK3277329 over a 2-week period restored neutrophil loss in monkeys given chemotherapy treatment (cyclophosphamide, Cytoxan). These data demonstrate preclinical in vivo proof of concept that TLR2 agonism can drive both G-CSF induction and subsequent neutrophil elevation in the cynomolgus monkey and could be a therapeutic strategy for the treatment of chemotherapy-induced neutropenia.

RIP3 induces apoptosis independent of pronecrotic kinase activity.

Receptor-interacting protein kinase 3 (RIP3 or RIPK3) has emerged as a central player in necroptosis and a potential target to control inflammatory disease. Here, three selective small-molecule compounds are shown to inhibit RIP3 kinase-dependent necroptosis, although their therapeutic value is undermined by a surprising, concentration-dependent induction of apoptosis. These compounds interact with RIP3 to activate caspase 8 (Casp8) via RHIM-driven recruitment of RIP1 (RIPK1) to assemble a Casp8-FADD-cFLIP complex completely independent of pronecrotic kinase activities and MLKL. RIP3 kinase-dead D161N mutant induces spontaneous apoptosis independent of compound, whereas D161G, D143N, and K51A mutants, like wild-type, only trigger apoptosis when compound is present. Accordingly, RIP3-K51A mutant mice (Rip3(K51A/K51A)) are viable and fertile, in stark contrast to the perinatal lethality of Rip3(D161N/D161N) mice. RIP3 therefore holds both necroptosis and apoptosis in balance through a Ripoptosome-like platform. This work highlights a common mechanism unveiling RHIM-driven apoptosis by therapeutic or genetic perturbation of RIP3.

Titanium(IV) isopropoxide mediated synthesis of pyrimidin-4-ones.

A novel, one-step method for the synthesis of tri- and tetrasubstituted pyrimidin-4-ones is reported. This method involves a titanium(IV)-mediated cyclization involving two sequential condensations of primary and beta-ketoamides. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted pyrimidin-4-one scaffolds. The high functional group compatibility allows for substantial diversification in the products generated from this transformation.

Intermolecular enolate heterocoupling: scope, mechanism, and application.

This full account presents the background on, discovery of, and extensive insight that has been gained into the oxidative intermolecular coupling of two different carbonyl species. Optimization of this process has culminated in reliable and scalable protocols for the union of amides, imides, ketones, and oxindoles using soluble copper(II) or iron(III) salts as oxidants. Extensive mechanistic studies point to a metal-chelated single-electron-transfer process in the case of copper(II), while iron(III)-based couplings appear to proceed through a non-templated heterodimerization. This work presents the most in-depth findings on the mechanism of oxidative enolate coupling to date. The scope of oxidative enolate heterocoupling is extensive (40 examples) and has been shown to be efficient even on a large scale (gram-scale or greater). Finally, the method has been applied to the total synthesis of the unsymmetrical lignan lactone (-)-bursehernin and a medicinally important 2,3-disubstituted succinate derivative.