The potent and selective RIPK2 inhibitor BI 706039 improves intestinal inflammation in the TRUC mouse model of inflammatory bowel disease.

Mouse and human data implicate the NOD1 and NOD2 sensors of the intestinal microbiome and the associated signal transduction via the receptor interacting protein kinase 2 (RIPK2) as a potential key signaling node for the development of inflammatory bowel disease (IBD) and an attractive target for pharmacological intervention. The TRUC mouse model of IBD was strongly indicated for evaluating RIPK2 antagonism for its effect on intestinal inflammation based on previous knockout studies with NOD1, NOD2, and RIPK2. We identified and profiled the BI 706039 molecule as a potent and specific functional inhibitor of both human and mouse RIPK2 and with favorable pharmacokinetic properties. We dosed BI 706039 in the spontaneous TRUC mouse model from age 28 to 56 days. Oral, daily administration of BI 706039 caused dose-responsive and significant improvement in colonic histopathological inflammation, colon weight, and terminal levels of protein-normalized fecal lipocalin (all P values <0.001). These observations correlated with dose responsively increasing systemic levels of the BI 706039 compound, splenic molecular target engagement of RIPK2, and modulation of inflammatory genes in the colon. This demonstrates that a relatively low oral dose of a potent and selective RIPK2 inhibitor can modulate signaling in the intestinal immune system and significantly improve disease associated intestinal inflammation.NEW & NOTEWORTHY The RIPK2 kinase at the apex of microbiome immunosensing is an attractive target for pharmacological intervention. A low oral dose of a RIPK2 inhibitor leads to significantly improved intestinal inflammation in the murine TRUC model of colitis. A selective and potent inhibitor of the RIPK2 kinase may represent a new class of therapeutics that target microbiome-driven signaling for the treatment of IBD.

Circulating monocytes are reduced by sphingosine-1-phosphate receptor modulators independently of S1P3.

Sphingosine-1-phosphate (S1P) receptors are critical for lymphocyte egress from secondary lymphoid organs, and S1P receptor modulators suppress lymphocyte circulation. However, the role of S1P receptors on monocytes is less clear. To elucidate this, we systematically evaluated monocytes in rats and mice, both in naive and inflammatory conditions, with S1P receptor modulators FTY720 and BAF312. We demonstrate that S1P receptor modulators reduce circulating monocytes in a similar time course as lymphocytes. Furthermore, total monocyte numbers were increased in the spleen and bone marrow, suggesting that S1P receptor modulation restricts egress from hematopoietic organs. Monocytes treated ex vivo with FTY720 had reduced CD40 expression and TNF-α production, suggesting a direct effect on monocyte activation. Similar reductions in protein expression and cytokine production were also found in vivo. Suppression of experimental autoimmune encephalomyelitis in mice and rats by FTY720 correlated with reduced numbers of lymphocytes and monocytes. These effects on monocytes were independent of S1P3, as treatment with BAF312, a S1P1,4,5 modulator, led to similar results. These data reveal a novel role for S1P receptors on monocytes and offer additional insights on the mechanism of action of S1P receptor modulators in disease.

G protein-coupled bile acid receptor 1 stimulation mediates arterial vasodilation through a K(Ca)1.1 (BK(Ca))-dependent mechanism.

Bile acids (BAs) and BA receptors, including G protein-coupled bile acid receptor 1 (GPBAR1), represent novel targets for the treatment of metabolic and inflammatory disorders. However, BAs elicit myriad effects on cardiovascular function, although this has not been specifically ascribed to GPBAR1. This study was designed to test whether stimulation of GPBAR1 elicits effects on cardiovascular function that are mechanism based that can be identified in acute ex vivo and in vivo cardiovascular models, to delineate whether effects were due to pathways known to be modulated by BAs, and to establish whether a therapeutic window between in vivo cardiovascular liabilities and on-target efficacy could be defined. The results demonstrated that the infusion of three structurally diverse and selective GPBAR1 agonists produced marked reductions in vascular tone and blood pressure in dog, but not in rat, as well as reflex tachycardia and a positive inotropic response, effects that manifested in an enhanced cardiac output. Changes in cardiovascular function were unrelated to modulation of the levothyroxine/thyroxine axis and were nitric oxide independent. A direct effect on vascular tone was confirmed in dog isolated vascular rings, whereby concentration-dependent decreases in tension that were tightly correlated with reductions in vascular tone observed in vivo and were blocked by iberiotoxin. Compound concentrations in which cardiovascular effects occurred, both ex vivo and in vivo, could not be separated from those necessary for modulation of GPBAR1-mediated efficacy, resulting in project termination. These results are the first to clearly demonstrate direct and potent peripheral arterial vasodilation due to GPBAR1 stimulation in vivo through activation of large conductance Ca(2+) activated potassium channel K(Ca)1.1.

Piperazinyl-oxadiazoles as selective sphingosine-1-phosphate receptor agonists.

The discovery of a new series of selective S1P1 agonists is described. This series of piperazinyl-oxadiazole derivatives was rapidly optimized starting from high-throughput screening hit 1 to afford potent and selective lead compound 10d. Further SAR studies showed that 10d was converted to the active phosphate metabolite 29 in vivo. Oral administration of compound 10d to rats was shown to induce lymphopenia at 3 mg/kg.

Mechanisms and regulation of IL-22-mediated intestinal epithelial homeostasis and repair.

AIMS: Ulcerative colitis and Crohn's disease, collectively known as inflammatory bowel disease (IBD), are chronic inflammatory disorders of the intestine for which key elements in disease initiation and perpetuation are defects in epithelial barrier integrity. Achieving mucosal healing is essential to ameliorate disease outcome and so new therapies leading to epithelial homeostasis and repair are under investigation. This study was designed to determine the mechanisms by which IL-22 regulates intestinal epithelial cell function. MAIN METHODS: Human intestinal organoids and resections, as well as mice were used to evaluate the effect of IL-22 on stem cell expansion, proliferation and expression of mucus components. IL-22 effect on barrier function was assessed in polarized T-84 cell monolayers. Butyrate co-treatments and organoid co-cultures with immune cells were performed to monitor the impact of microbial-derived metabolites and inflammatory environments on IL-22 responses. KEY FINDINGS: IL-22 led to epithelial stem cell expansion, proliferation, barrier dysfunction and anti-microbial peptide production in human and mouse models evaluated. IL-22 also altered the mucus layer by inducing an increase in membrane mucus but a decrease in secreted mucus and goblet cell content. IL-22 had the same effect on anti-microbial peptides and membrane mucus in both healthy and IBD human samples. In contrast, this IL-22-associated epithelial phenotype was different when treatments were performed in presence of butyrate and organoids co-cultured with immune cells. SIGNIFICANCE: Our data indicate that IL-22 promotes epithelial regeneration, innate defense and membrane mucus production, strongly supporting the potential clinical utility of IL-22 as a mucosal healing therapy in IBD.

Optimized Culture Conditions for Improved Growth and Functional Differentiation of Mouse and Human Colon Organoids.

Background & Aims: Diligent side-by-side comparisons of how different methodologies affect growth efficiency and quality of intestinal colonoids have not been performed leaving a gap in our current knowledge. Here, we summarize our efforts to optimize culture conditions for improved growth and functional differentiation of mouse and human colon organoids. Methods: Mouse and human colon organoids were grown in four different media. Media-dependent long-term growth was measured by quantifying surviving organoids via imaging and a cell viability readout over five passages. The impact of diverse media on differentiation was assessed by quantifying the number of epithelial cell types using markers for enterocytes, stem cells, Goblet cells, and enteroendocrine cells by qPCR and histology upon removal of growth factors. Results: In contrast to Wnt3a-conditioned media, media supplemented with recombinant Wnt3a alone did not support long-term survival of human or mouse colon organoids. Mechanistically, this observation can be attributed to the fact that recombinant Wnt3a did not support stem cell survival or proliferation as demonstrated by decreased LGR5 and Ki67 expression. When monitoring expression of markers for epithelial cell types, the highest level of organoid differentiation was observed after combined removal of Wnt3a, Noggin, and R-spondin from Wnta3a-conditioned media cultures. Conclusion: Our study defined Wnt3a-containing conditioned media as optimal for growth and survival of human and mouse organoids. Furthermore, we established that the combined removal of Wnt3a, Noggin, and R-spondin results in optimal differentiation. This study provides a step forward in optimizing conditions for intestinal organoid growth to improve standardization and reproducibility of this model platform.

Assay optimization: a statistical design of experiments approach.

With the transition from manual to robotic HTS in the last several years, assay optimization has become a significant bottleneck. Recent advances in robotic liquid handling have made it feasible to reduce assay optimization timelines with the application of statistically designed experiments. When implemented, they can efficiently optimize assays by rapidly identifying significant factors, complex interactions, and nonlinear responses. This article focuses on the use of statistically designed experiments in assay optimization.

Development of a high-throughput assay to measure histidine decarboxylase activity.

Histamine is a well-known mediator of allergic, inflammatory, and neurological responses. More recent studies suggest a role for histamine and its receptors in a wide range of biological processes, including T-cell maturation and bone remodeling. Histamine serum levels are regulated mainly by the activity of the histamine-synthesizing enzyme histidine decarboxylase (HDC). Despite the importance of this enzyme in many physiological processes, very few potent HDC inhibitors have been identified. HDC assays suitable for high-throughput screening have not been reported. The authors describe the development of a fluorescence polarization assay to measure HDC enzymatic activity. They used a fluorescein-histamine probe that binds with high affinity to an antihistamine antibody for detection. Importantly, they show that probe binding is fully competed by histamine, but no competition by the HDC substrate histidine was observed. The automated assay was performed in a total volume of 60 muL, had an assay window of 80 to 100 mP, and had a Z' factor of 0.6 to 0.7. This assay provides new tools to study HDC activity and pharmacological modulation of histamine levels.

No differences observed among multiple clinical S1P1 receptor agonists (functional antagonists) in S1P1 receptor down-regulation and degradation.

Sphingosine-1-phosphate (S1P) is a bioactive metabolite with pleiotropic effects on multiple cellular processes in health and disease. Responses elicited by S1P are a result of binding to five specific G-protein-coupled receptors. We have developed multiple assays to systematically study the downstream signaling of these receptors, including early events such as direct receptor activation (GTPγS) as well as more distal events such as S1P1 receptor degradation. Employing such assays, we have characterized and compared multiple S1P1 agonists that are in clinical development including FTY720, BAF312, CS-0777, and other molecules from the S1P1 patent literature. Our parallel assessment has allowed us to compare their potency against S1P1, their selectivity against the four other S1P receptors, as well as species cross-reactivity. We note that all of the compounds studied signal in an identical manner through S1P1, leading to receptor degradation.

A GPBAR1 (TGR5) small molecule agonist shows specific inhibitory effects on myeloid cell activation in vitro and reduces experimental autoimmune encephalitis (EAE) in vivo.

GPBAR1 is a G protein-coupled receptor that is activated by certain bile acids and plays an important role in the regulation of bile acid synthesis, lipid metabolism, and energy homeostasis. Recent evidence suggests that GPBAR1 may also have important effects in reducing the inflammatory response through its expression on monocytes and macrophages. To further understand the role of GPBAR1 in inflammation, we generated a novel, selective, proprietary GPBAR1 agonist and tested its effectiveness at reducing monocyte and macrophage activation in vitro and in vivo. We have used this agonist, together with previously described agonists to study agonism of GPBAR1, and shown that they can all induce cAMP and reduce TLR activation-induced cytokine production in human monocytes and monocyte-derived macrophages in vitro. Additionally, through the usage of RNA sequencing (RNA-Seq), we identified a select set of genes that are regulated by GPBAR1 agonism during LPS activation. To further define the in vivo role of GPBAR1 in inflammation, we assessed GPBAR1 expression and found high levels on circulating mouse monocytes. Agonism of GPBAR1 reduced LPS-induced cytokine production in mouse monocytes ex vivo and serum cytokine levels in vivo. Agonism of GPBAR1 also had profound effects in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis, where monocytes play an important role. Mice treated with the GPBAR1 agonist exhibited a significant reduction in the EAE clinical score which correlated with reduced monocyte and microglial activation and reduced trafficking of monocytes and T cells into the CNS. These data confirm the importance of GPBAR1 in controlling monocyte and macrophage activation in vivo and support the rationale for selective agonists of GPBAR1 in the treatment of inflammatory diseases.

The clinically-tested S1P receptor agonists, FTY720 and BAF312, demonstrate subtype-specific bradycardia (S1P1) and hypertension (S1P3) in rat.

Sphingosine-1-phospate (S1P) and S1P receptor agonists elicit mechanism-based effects on cardiovascular function in vivo. Indeed, FTY720 (non-selective S1P(X) receptor agonist) produces modest hypertension in patients (2-3 mmHg in 1-yr trial) as well as acute bradycardia independent of changes in blood pressure. However, the precise receptor subtypes responsible is controversial, likely dependent upon the cardiovascular response in question (e.g. bradycardia, hypertension), and perhaps even species-dependent since functional differences in rodent, rabbit, and human have been suggested. Thus, we characterized the S1P receptor subtype specificity for each compound in vitro and, in vivo, the cardiovascular effects of FTY720 and the more selective S1P1,5 agonist, BAF312, were tested during acute i.v. infusion in anesthetized rats and after oral administration for 10 days in telemetry-instrumented conscious rats. Acute i.v. infusion of FTY720 (0.1, 0.3, 1.0 mg/kg/20 min) or BAF312 (0.5, 1.5, 5.0 mg/kg/20 min) elicited acute bradycardia in anesthetized rats demonstrating an S1P1 mediated mechanism-of-action. However, while FTY720 (0.5, 1.5, 5.0 mg/kg/d) elicited dose-dependent hypertension after multiple days of oral administration in rat at clinically relevant plasma concentrations (24-hr mean blood pressure = 8.4, 12.8, 16.2 mmHg above baseline vs. 3 mmHg in vehicle controls), BAF312 (0.3, 3.0, 30.0 mg/kg/d) had no significant effect on blood pressure at any dose tested suggesting that hypertension produced by FTY720 is mediated S1P3 receptors. In summary, in vitro selectivity results in combination with studies performed in anesthetized and conscious rats administered two clinically tested S1P agonists, FTY720 or BAF312, suggest that S1P1 receptors mediate bradycardia while hypertension is mediated by S1P3 receptor activation.

The discovery of carboline analogs as potent MAPKAP-K2 inhibitors.

The discovery of a series of potent, carboline-based MK2 inhibitors is described. These compounds inhibit MK2 with IC50s as low as 10 nM, as measured in a DELFIA assay. An X-ray crystal structure reveals that they bind in a region near the p-loop and the hinge region of MK2a.