The histamine H4 receptor mediates inflammation and Th17 responses in preclinical models of arthritis.

OBJECTIVE: The histamine H4 receptor (H4R) has been shown to drive inflammatory responses in models of asthma, colitis and dermatitis, and in these models it appears to affect both innate and adaptive immune responses. In this study, we used both H4R-deficient mice and a specific H4R antagonist, JNJ 28307474, to investigate the involvement of the H4R in mouse arthritis models. METHODS: H4R-deficient mice and wild-type mice administered the H4R antagonist were studied in models of collagen antibody-induced arthritis (CAIA) and collagen-induced arthritis (CIA). The impact on Th17 cells was assessed by restimulation of inguinal lymphocytes in the disease or immunisation models and with in vitro stimulation of whole blood. RESULTS: Both H4R-deficient mice and mice treated with the H4R antagonist exhibited reduced arthritis disease severity in both CAIA and CIA models. This was evident from the reduction in disease score and in joint histology. In the CIA model, treatment with the H4R antagonist reduced the number of interleukin (IL)-17 positive cells in the lymph node and the total production of IL-17. Th17 cell development in vivo was reduced in H4R-deficient mice or in mice treated with an H4R antagonist. Finally, treatment of both mouse and human blood with an H4R antagonist reduced the production of IL-17 when cells were stimulated in vitro. CONCLUSIONS: These results implicate the H4R in disease progression in arthritis and in the production of IL-17 from Th17 cells. This work supports future clinical exploration of H4R antagonists for the treatment of rheumatoid arthritis.

Mast cell mediators cause early allergic bronchoconstriction in guinea-pigs in vivo: a model of relevance to asthma.

One feature of allergic asthma, the EAR (early allergic reaction), is not present in the commonly used mouse models. We therefore investigated the mediators involved in EAR in a guinea-pig in vivo model of allergic airway inflammation. Animals were sensitized using a single OVA (ovalbumin)/alum injection and challenged with aerosolized OVA on day 14. On day 15, airway resistance was assessed after challenge with OVA or MCh (methacholine) using the forced oscillation technique, and lung tissue was prepared for histology. The contribution of mast cell mediators was investigated using inhibitors of the main mast cell mediators [histamine (pyrilamine) and CysLTs (cysteinyl-leukotrienes) (montelukast) and prostanoids (indomethacin)]. OVA-sensitized and challenged animals demonstrated AHR (airway hyper-responsiveness) to MCh, and lung tissue eosinophilic inflammation. Antigen challenge induced a strong EAR in the sensitized animals. Treatment with a single compound, or indomethacin together with pyrilamine or montelukast, did not reduce the antigen-induced airway resistance. In contrast, dual treatment with pyrilamine together with montelukast, or triple inhibitor treatment, attenuated approximately 70% of the EAR. We conclude that, as in humans, the guinea-pig allergic inflammation model exhibits both EAR and AHR, supporting its suitability for in vivo identification of mast cell mediators that contribute to the development of asthma. Moreover, the known mast cell mediators histamine and leukotrienes were major contributors of the EAR. The data also lend further support to the concept that combination therapy with selective inhibitors of key mediators could improve asthma management.

Antagonism of the histamine H4 receptor reduces LPS-induced TNF production in vivo.

OBJECTIVE: Antagonism of the histamine H4 receptor (H4R) has been shown to be anti-inflammatory in a number of preclinical disease models, however the exact mechanisms behind this are still being uncovered. In vitro, the receptor interacts with TLR and impacts inflammatory mediator production from a number of different cell types. Here it is shown that this interaction also occurs in vivo. MATERIALS AND METHODS: Wild-type and H4R deficient BALB/c mice received an i.p. injection of LPS in PBS in conjunction with p.o. JNJ 7777120 or JNJ 28307474 (H4R antagonists). Two hours later blood was collected and TNF was measured. RESULTS: Two different H4R antagonists inhibited LPS-induced TNF production in mice and this production was also reduced in H4R-deficient mice. The TNF mRNA analysis showed that the major source of the cytokine was the liver and not blood, and that the H4R antagonist only reduced the expression levels in the liver. Depletion or inactivation of macrophages reduced the TNF levels and eliminated the H4R sensitivity. Treatment with an H4R antagonist also reduced LPS-induced liver injury and blocked LPS-enhanced lung inflammation in mice. CONCLUSION: The data support an interaction between H4R and TLR activation in vivo that can drive inflammatory responses.

Identification of benzofuran central cores for the inhibition of leukotriene A(4) hydrolase.

Leukotrienes (LT's) are known to play a physiological role in inflammatory immune response. Leukotriene A(4) hydrolase (LTA(4)H) is a cystolic enzyme that stereospecifically catalyzes the transformation of LTA(4) to LTB(4). LTB(4) is a known pro-inflammatory mediator. This paper describes the identification and synthesis of substituted benzofurans as LTH(4)H inhibitors. The benzofuran series demonstrated reduced mouse and human whole blood LTB(4) levels in vitro and led to the identification one analog for advanced profiling. Benzofuran 28 showed dose responsive target engagement and provides a useful tool to explore a LTA(4)H inhibitor for the treatment of inflammatory diseases, such as asthma and inflammatory bowel disease (IBD).

Azabenzthiazole inhibitors of leukotriene A4 hydrolase.

Previously, benzthiazole containing LTA(4)H inhibitors were discovered that were potent (1-3), but were associated with the potential for a hERG liability. Utilizing medicinal chemistry first principles (e.g., introducing rigidity, lowering cLogD) a new benzthiazole series was designed, congeners of 1-3, which led to compounds 7a, 7c, 12a-d which exhibited LTA(4)H IC(50)=3-6 nM and hERG Dofetilide Binding IC(50)=8.9-> >10 µM.

Histamine H4 receptor antagonism diminishes existing airway inflammation and dysfunction via modulation of Th2 cytokines.

BACKGROUND: Airway remodeling and dysfunction are characteristic features of asthma thought to be caused by aberrant production of Th2 cytokines. Histamine H4 receptor (H4R) perturbation has previously been shown to modify acute inflammation and Th2 cytokine production in a murine model of asthma. We examined the ability of H4R antagonists to therapeutically modify the effects of Th2 cytokine production such as goblet cell hyperplasia (GCH), and collagen deposition in a sub-chronic model of asthma. In addition, effects on Th2 mediated lung dysfunction were also determined. METHODS: Mice were sensitized to ovalbumin (OVA) followed by repeated airway challenge with OVA. After inflammation was established mice were dosed with the H4R antagonist, JNJ 7777120, or anti-IL-13 antibody for comparison. Airway hyperreactivity (AHR) was measured, lungs lavaged and tissues collected for analysis. RESULTS: Therapeutic H4R antagonism inhibited T cell infiltration in to the lung and decreased Th2 cytokines IL-13 and IL-5. IL-13 dependent remodeling parameters such as GCH and lung collagen were reduced. Intervention with H4R antagonist also improved measures of central and peripheral airway dysfunction. CONCLUSIONS: These data demonstrate that therapeutic H4R antagonism can significantly ameliorate allergen induced, Th2 cytokine driven pathologies such as lung remodeling and airway dysfunction. The ability of H4R antagonists to affect these key manifestations of asthma suggests their potential as novel human therapeutics.

Leukotriene A(4) hydrolase inhibition attenuates allergic airway inflammation and hyperresponsiveness.

RATIONALE: Allergic asthma is characterized by reversible airway obstruction, lung inflammation, and airway hyperresponsiveness (AHR). Previous studies using leukotriene B(4) (LTB(4)) receptor 1-deficient mice and adoptive transfer experiments have suggested that LTB(4) plays a role in lung inflammation and AHR. OBJECTIVES: In this study, we used a leukotriene A(4) hydrolase (LTA(4)H) inhibitor as a pharmacological tool to directly examine the role of LTB(4) in a mast cell-dependent murine model of allergic airway inflammation. METHODS: We used the forced oscillation technique to test the effects of an LTA(4)H inhibitor dosed during the challenge phase on AHR. Lung tissue and lavage were collected for analysis. MEASUREMENTS AND MAIN RESULTS: Treatment with an LTA(4)H inhibitor improved multiple parameters encompassing AHR and lung function. Significant decreases in inflammatory leukocytes, cytokines, and mucin were observed in the lung lumen. Serum levels of antigen-specific IgE and IgG1 were also decreased. Labeled antigen uptake by lung dendritic cells and subsequent trafficking to draining lymph nodes and the lung were decreased on LTA(4)H inhibitor treatment. Provocatively, inhibition of LTA(4)H increased lipoxin A(4) levels in lung lavage fluid. CONCLUSIONS: These data suggest that LTB(4) plays a key role in driving lung inflammation and AHR. Mechanistically, we provide evidence that inhibition of LTA(4)H, affects recruitment of both CD4(+) and CD8(+) T cells, as well as trafficking of dendritic cells to draining lymph nodes, and may beneficially modulate other pro- and antiinflammatory eicosanoids in the lung. Inhibition of LTA(4)H is thus a potential therapeutic strategy that could modulate key aspects of asthma.

Identification of a potent, selective, and orally active leukotriene a4 hydrolase inhibitor with anti-inflammatory activity.

LTA 4H is a ubiquitously distributed 69 kDa zinc-containing cytosolic enzyme with both hydrolase and aminopeptidase activity. As a hydrolase, LTA 4H stereospecifically catalyzes the transformation of the unstable epoxide LTA 4 to the diol LTB 4, a potent chemoattractant and activator of neutrophils and a chemoattractant of eosinophils, macrophages, mast cells, and T cells. Inhibiting the formation of LTB 4 is expected to be beneficial in the treatment of inflammatory diseases such as inflammatory bowel disease (IBD), asthma, and atherosclerosis. We developed a pharmacophore model using a known inhibitor manually docked into the active site of LTA 4H to identify a subset of compounds for screening. From this work we identified a series of benzoxazole, benzthiazole, and benzimidazole inhibitors. SAR studies resulted in the identification of several potent inhibitors with an appropriate cross-reactivity profile and excellent PK/PD properties. Our efforts focused on further profiling JNJ 27265732, which showed encouraging efficacy in a disease model relevant to IBD.

A novel B-RAF inhibitor blocks interleukin-8 (IL-8) synthesis in human melanoma xenografts, revealing IL-8 as a potential pharmacodynamic biomarker.

B-RAF mutations have been identified in the majority of melanoma and a large fraction of colorectal and papillary thyroid carcinoma. Drug discovery efforts targeting mutated B-RAF have yielded several interesting molecules, and currently, three compounds are undergoing clinical evaluation. Inhibition of B-RAF in animal models leads to a slowing of tumor growth and, in some cases, tumor reduction. Described within is a novel series of diaryl imidazoles with potent, single-digit nanomolar, anti-B-RAF activity. One compound from this series has been detailed here and has been shown to block B-RAF(V600E)-dependent extracellular signal-regulated kinase 1/2 phosphorylation in SK-MEL-28 melanoma cells as well as soft agar colony formation and proliferation. Importantly, interleukin-8 (IL-8) was identified by quantitative real-time PCR and ELISA as a product of the elevated mitogen-activated protein kinase signaling in these cells. Plasma concentrations of IL-8 in mice bearing melanoma xenografts were significantly reduced following exposure to B-RAF inhibitors. Taken together, these data suggest that IL-8 could serve as a tractable clinical biomarker.

Anti-inflammatory activity of a potent, selective leukotriene A4 hydrolase inhibitor in comparison with the 5-lipoxygenase inhibitor zileuton.

Leukotriene A(4) hydrolase (LTA(4)H) catalyzes production of the proinflammatory lipid mediator, leukotriene (LT) B(4), which is implicated in a number of inflammatory diseases. We have identified a potent and selective inhibitor of both the epoxide hydrolase and aminopeptidase activities of recombinant human LTA(4)H (IC(50), approximately 10 nM). In a murine model of arachidonic acid-induced ear inflammation, the LTA(4)H inhibitor, JNJ-26993135 (1-[4-(benzothiazol-2-yloxy)-benzyl]-piperidine-4-carboxylic acid), dose-dependently inhibited ex vivo LTB(4) production in blood, in parallel with dose-dependent inhibition of neutrophil influx (ED(50), 1-3 mg/kg) and ear edema. In murine whole blood and in zymosan-induced peritonitis, JNJ-26993135 selectively inhibited LTB(4) production, without affecting cysteinyl leukotriene production, while maintaining or increasing production of the anti-inflammatory mediator, lipoxin (LX) A(4). The 5-lipoxygenase (5-LO) inhibitor zileuton showed inhibition of LTB(4), LTC(4), and LXA(4) production. Although zileuton inhibited LTB(4) production in the peritonitis model more effectively than the LTA(4)H inhibitor, the influx of neutrophils into the peritoneum after 1 and 2 h was significantly higher in zileuton- versus JNJ-26993135-treated animals. This difference may have been mediated by the increased LXA(4) levels in the presence of the LTA(4)H inhibitor. The selective inhibition of LTB(4) production by JNJ-26993135, while increasing levels of the anti-inflammatory mediator, LXA(4), may translate to superior therapeutic efficacy versus 5-LO or 5-LO-activating protein inhibitors in LTB(4)-mediated inflammatory diseases.

The histamine H4 receptor mediates allergic airway inflammation by regulating the activation of CD4+ T cells.

Histamine is an important inflammatory mediator that is released in airways during an asthmatic response. However, current antihistamine drugs are not effective in controlling the disease. The discovery of the histamine H4 receptor (H4R) prompted us to reinvestigate the role of histamine in pulmonary allergic responses. H4R-deficient mice and mice treated with H4R antagonists exhibited decreased allergic lung inflammation, with decreases in infiltrating lung eosinophils and lymphocytes and decreases in Th2 responses. Ex vivo restimulation of T cells showed decreases in IL-4, IL-5, IL-13, IL-6, and IL-17 levels, suggesting that T cell functions were disrupted. In vitro studies indicated that blockade of the H4R on dendritic cells leads to decreases in cytokine and chemokine production and limits their ability to induce Th2 responses in T cells. This work suggests that the H4R can modulate allergic responses via its influence on T cell activation. The study expands the known influences of histamine on the immune system and highlights the therapeutic potential of H4R antagonists in allergic conditions.

Maternal and fetal distribution of a phosphorothioate oligonucleotide in rats after intravenous infusion.

BACKGROUND: Fetal uptake of an antisense oligonucleotide was evaluated after intravenous (i.v.) dosing of ISIS 2105, a 20-base phosphorothioate oligonucleotide, in timed-pregnant Sprague-Dawley rats. METHODS: To maximize the potential for fetal exposure, ISIS 2105 was administered as a 3-hr infusion at 6.6 mg/kg/hr with a total dose of 20 mg/kg, or as a continuous 7-day infusion at 0.35 mg/kg/hr with a total dose of 59 mg/kg. This dosing regime is higher than a patient would be expected to receive in the clinical use of oligonucleotides. Infusions were delivered through a jugular vein cannula by syringe pump on gestation day (GD) 19 (3-hr exposure) or by osmotic pumps implanted subcutaneously (s.c.) starting on GD 12 (7-day exposures). RESULTS: After a 3-hr infusion, maternal and fetal plasma concentrations of ISIS 2105 were >100 microg/ml and <0.07 microg/ml, respectively with a maternal fetal ratio of >1,000. Maternal regions of the placenta had twice the oligonucleotide concentration compared to fetal regions of the placenta (6 microg/g vs. 3 microg/g). After this acute exposure the concentrations in fetal kidney and liver were approximately 140- and 500-fold less than the maternal kidney and liver respectively. After 7-day infusion maternal plasma concentrations were 0.82 microg/ml and fetal concentrations were <0.22 microg/ml. By capillary gel electrophoresis (CGE) only the fetal liver consistently had quantifiable oligonucleotide concentrations (range=1.01-4.95 microg/g) compared to a mean concentration of 50.11+/-1.71 microg/g in the maternal liver a maternal to fetal ratio of approximately 10:50 after 7 days of infusion. CONCLUSIONS: There was a low level of transfer from dam to fetus, consistent with a slow equilibrium but the permeability of placenta to this 6 kDa polyanionic compound seemed to be limited even at supraclinical doses.

A potent and selective histamine H4 receptor antagonist with anti-inflammatory properties.

Histamine mediates its physiological function through binding to four known histamine receptors. Here, we describe the first selective antagonist of the histamine H4 receptor, the newest member of the histamine receptor family, and provide evidence that such antagonists have anti-inflammatory activity in vivo. 1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine (JNJ 7777120) has a K(i) of 4.5 nM versus the human receptor and a pA(2) of 8.1. It is equipotent against the human, mouse, and rat receptors. It exhibits at least 1000-fold selectivity over H1, H2, or H3 receptors and has no cross-reactivity against 50 other targets. This compound has an oral bioavailability of approximately 30% in rats and 100% in dogs, with a half-life of approximately 3 h in both species. JNJ 7777120 blocks histamine-induced chemotaxis and calcium influx in mouse bone marrow-derived mast cells. In addition, it can block the histamine-induced migration of tracheal mast cells from the connective tissue toward the epithelium in mice. JNJ 7777120 significantly blocks neutrophil infiltration in a mouse zymosan-induced peritonitis model. This model is reported to be mast cell-dependent, which suggests that the compound effect may be mediated by mast cells. These results indicate that the histamine H4 receptor plays a role in the inflammatory process. Selective H4 receptor antagonists like JNJ 7777120 may have the potential to be useful in treating inflammation in humans.

Identification of a potent and selective noncovalent cathepsin S inhibitor.

Cathepsin S is considered crucial for normal presentation of major histocompatibility complex (MHC) class II-restricted antigens by antigen presenting cells to CD4+ T cells. It is a key enzyme for the degradation of the class II-associated invariant chain, a process that is required for effective antigen loading of class II molecules. Here, we report a selective, orally available, high-affinity cathepsin S inhibitor, 1-[3-[4-(6-Chloro-2,3-dihydro-3-methyl-2-oxo-1H-benzimidazol-1-yl)-1-piperidinyl]propyl]-4,5,6,7-tetrahydro-5-(methylsulfonyl)-3-[4-(trifluoromethyl)phenyl]-1H-pyrazolo[4,3-c]pyridine. (JNJ 10329670), that represents a novel class of immunosuppressive compounds. JNJ 10329670 is a highly potent (Ki of approximately 30 nM), nonpeptidic, noncovalent inhibitor of human cathepsin S, but it is much less active against the mouse, dog, monkey, and bovine enzymes. The compound is inactive against other proteases, including the closely related cathepsins L, F, and K. This selectivity makes JNJ 10329670 an excellent tool for exploring the role of cathepsin S in human systems. Treatment of human B cell lines and primary human dendritic cells with JNJ 10329670 resulted in the accumulation of the p10 fragment of the invariant chain (IC50 of approximately 1 microM). In contrast, inhibition of invariant chain proteolysis was much less effective in a human monocytic cell line, suggesting that other enzymes may degrade the invariant chain in this cell type. JNJ 10329670 was shown to block the proteolysis of the invariant chain in vivo by using immunocompromised mice injected with human peripheral blood mononuclear cells (PBMCs). Furthermore, this inhibitor blocks the presentation of tetanus toxoid and giant ragweed by human PBMCs. The properties of JNJ 10329670 make it a candidate for immunosuppressive therapy of allergies and autoimmune diseases.