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.

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.

Histamine H4 receptor antagonists are superior to traditional antihistamines in the attenuation of experimental pruritus.

BACKGROUND: Histamine is a potent mediator of itch in humans, yet histamine H(1) receptor antagonists have been shown to be of limited use in the treatment of certain chronic pruritic diseases. The histamine H(4) receptor is a recently described histamine receptor, expressed on hematopoietic cells, linked to the pathology of allergy and asthma. OBJECTIVE: The contribution of the novel histamine H(4) receptor to histaminergic and allergic pruritus was investigated. RESULTS: Histamine and a selective histamine H(4) receptor agonist caused scratching responses in mice, which were almost completely attenuated in histamine H(4) receptor knockout mice or by pretreatment with the selective histamine H(4) receptor antagonist, JNJ 7777120. Pruritus induced by allergic mechanisms was also potently inhibited with histamine H(4) receptor antagonist treatment or in histamine H(4) receptor knockout mice. In all cases, the inhibitory effect of histamine H(4) receptor antagonist was greater than those observed with histamine H(1) receptor antagonists. The histamine H(4) receptor-mediated pruritus was shown to be independent of mast cells or other hematopoietic cells and may result from actions on peripheral neurons. CONCLUSION: These results demonstrate that the histamine H(4) receptor is involved in pruritic responses in mice to a greater extent than the histamine H(1) receptor. CLINICAL IMPLICATIONS: Histamine H(4) receptor antagonists may have therapeutic utility for treating chronic pruritic diseases in humans where histamine H(1) receptor antagonists are not effective.

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.

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.