Immunosuppressive effect of ASP2408, a novel CD86-selective variant of CTLA4-Ig, in rats and cynomolgus monkeys.

The CTLA4-Ig fusion proteins abatacept and belatacept inhibit CD28-mediated T cell activation by binding CD80 (B7-1) and CD86 (B7-2) costimulatory ligands and are clinically proven immunosuppressants used for rheumatoid arthritis and renal transplantation, respectively. Abatacept and belatacept preferentially bind CD80, yet CD86 has been implicated as the dominant ligand for CD28-mediated costimulation of T cells. We investigated the immunosuppressive effects of ASP2408, a novel CTLA4-Ig with CD86 selectivity and high potency created by directed evolution methods. Here we evaluated the effect of ASP2408 in vitro using cynomolgus monkey and rat T cell proliferation assays and in vivo using cynomolgus monkey tetanus toxoid (TTx) immunization and a rat rheumatoid arthritis model. ASP2408 was 290-fold and 21-fold more potent in suppressing in vitro monkey T cell proliferation than abatacept and belatacept, respectively. ASP2408 inhibited anti-TTx immunological reactions in cynomolgus monkey at a 10-fold lower dose level than belatacept, through complete CD86 and partial CD80 receptor occupancies, and also suppressed inflammation in the rat collagen-induced arthritis model. Overall, improved immunosuppressive potency of ASP2408 relative to abatacept and belatacept correlated well with improved CD86 binding affinity. These results may support the advantage of preferential enhancement of CD86 binding affinity to inhibit T cell-mediated immune response and improved dosing convenience in humans relative to abatacept or belatacept.

Inhibition of c-Rel DNA binding is critical for the anti-inflammatory effects of novel PIKfyve inhibitor.

Aberrant production of proinflammatory cytokines is linked to many autoimmune diseases, and their inhibition by small molecule compounds is considered beneficial. Here, we performed phenotypic screening in IFNγ/LPS-activated RAW264.7, mouse macrophage cells, and discovered AS2677131 and AS2795440 as novel and potent inhibitors of IL-12p40, a subunit of IL-23. Interestingly, these compounds exhibited unique pharmacological activities in their inhibition of the production of IL-12p40, IL-6 and IL-1ß but not TNFα in activated macrophages or dendritic cells, and expression of IgM-induced MHC class II on B cells. To reveal these mechanisms, we synthesized two different activity probes which were structurally related to the AS compounds, and identified probe-specific binding proteins, including PIKfyve, a Class III PI kinase. The AS compounds inhibited PIKfyve activity and mimicked the properties of PIKfyve-deficient cells, eventually validating PIKfyve as target molecule. Regarding mechanism, AS2677131 regulated DNA binding activity of c-Rel on IL-12p40 and IL-1ß promoter. As expected, a PIKfyve inhibitor prevented the development of arthritis in rats. Taken together, our findings of the novel and potent PIKfyve inhibitors AS2677131 and AS2795440 reveal the critical role of PIKfyve in proinflammatory cytokine production and B cell activation, and may indicate a potential new therapeutic option for treatment of inflammatory diseases.

Anti-inflammatory effect and selectivity profile of AS1940477, a novel and potent p38 mitogen-activated protein kinase inhibitor.

Given the key role p38 mitogen-activated protein kinase (MAPK) plays in inflammatory responses through the production of cytokines and inflammatory mediators, its inhibition is considered a promising therapeutic strategy for chronic inflammatory diseases such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. Here, we evaluated the anti-inflammatory effect and selectivity profile of the novel p38 MAPK inhibitor AS1940477. AS1940477 inhibited the enzymatic activity of recombinant p38α and ß isoforms but showed no effect against other 100 protein kinases including p38γ and δ isoforms. We also confirmed the selectivity of AS1940477 in the intracellular signaling pathway. In human peripheral blood mononuclear cells, AS1940477 inhibited lipopolysaccharide (LPS)- or phytohemagglutinin A (PHA)-induced production of proinflammatory cytokines, including TNFα, IL-1ß, and IL-6 at low concentrations (LPS/TNFα, IC(50)=0.45n M; PHA/TNFα, IC(50)=0.40 nM). In addition, equivalent concentrations of AS1940477 that inhibited cytokine production also inhibited TNFα- and IL-1 ß-induced production of IL-6, PGE(2), and MMP-3 in human synovial stromal cells. AS1940477 was also found to potently inhibit TNF production in whole blood (IC(50)=12 nM) and effectively inhibited TNFα production induced by systemically administered LPS in rats at less than 0.1mg/kg (ED(50)=0.053 mg/kg) with an anti-inflammatory effect lasting for 20h after oral administration. Overall, this study demonstrated that AS1940477 is a novel and potent p38 MAPK inhibitor and may be useful as a promising anti-inflammatory agent for treating inflammatory disorders.

Identification, synthesis, and biological evaluation of 6-[(6R)-2-(4-fluorophenyl)-6-(hydroxymethyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-3-yl]-2-(2-methylphenyl)pyridazin-3(2H)-one (AS1940477), a potent p38 MAP kinase inhibitor.

Several p38 MAPK inhibitors have been shown to effectively block the production of cytokines such as IL-1ß, TNFα, and IL-6. Inhibitors of p38 MAP kinase therefore have significant therapeutic potential for the treatment of autoimmune disease. Compound 2a was identified as a potent TNFα production inhibitor in vitro but suffered from poor oral bioavailability. Structural modification of 2a led to the discovery of tetrahydropyrazolopyrimidine derivatives, exemplified by compound 3, with an improved pharmacokinetic profile. We found that blocking metabolism at the methyl group of the amine and constructing the tetrahydropyrimidine core were important to obtaining compounds with good biological profiles and oral bioavailability. Pursuing the structure-activity relationships of this series led to the discovery of AS1940477 (3f), with excellent cellular activity and a favorable pharmacokinetic profile. This compound represents a highly potent inhibitor of p38 MAP kinase with regard to in vivo activity in an adjuvant-induced arthritis model.

Insulin-like growth factor-I prevents lethal acute liver failure induced by D-galactosamine and lipopolysaccharide in rats.

The aim of this study was to evaluate the effect of insulin-like growth factor-I (IGF-I) on lethality and liver function in experimental acute liver failure. Intravenous co-administration of D-galactosamine (GalN) and lipopolysaccharide (LPS) to rats induced high mortality and marked increases in aspartate aminotransferase, alanine aminotransferase and total bilirubin, associated with hypoglycemia. One-hour pre-treatment with IGF-I significantly prevented lethality and blood parameter changes in rats. Histological examination also showed that massive hepatocellular hemorrhagic necrosis and inflammatory cell infiltration around peri-central veins in the liver, as well as shrinkage of cytoplasm and nuclear condensation, were induced by GalN plus LPS injection, but these all were improved by pre-treatment with IGF-I. Overall, this study showed that IGF-I treatment resulted in effective prevention of lethal acute liver failure in rats induced by GalN plus LPS, suggesting a therapeutic potential for IGF-I in the prevention of acute liver failure.

CD4(+)CD25(+) regulatory T cells can mediate suppressor function in the absence of transforming growth factor beta1 production and responsiveness.

CD4(+)CD25(+) regulatory T cells inhibit organ-specific autoimmune diseases induced by CD4(+)CD25(-) T cells and are potent suppressors of T cell activation in vitro. Their mechanism of suppression remains unknown, but most in vitro studies suggest that it is cell contact-dependent and cytokine independent. The role of TGF-beta1 in CD4(+)CD25(+) suppressor function remains unclear. While most studies have failed to reverse suppression with anti-transforming growth factor (TGF)-beta1 in vitro, one recent study has reported that CD4(+)CD25(+) T cells express cell surface TGF-beta1 and that suppression can be completely abrogated by high concentrations of anti-TGF-beta suggesting that cell-associated TGF-beta1 was the primary effector of CD4(+)CD25(+)-mediated suppression. Here, we have reevaluated the role of TGF-beta1 in CD4(+)CD25(+)-mediated suppression. Neutralization of TGF-beta1 with either monoclonal antibody (mAb) or soluble TGF-betaRII-Fc did not reverse in vitro suppression mediated by resting or activated CD4(+)CD25(+) T cells. Responder T cells from Smad3(-/-) or dominant-negative TGF-beta type RII transgenic (DNRIITg) mice, that are both unresponsive to TGF-beta1-induced growth arrest, were as susceptible to CD4(+)CD25(+)-mediated suppression as T cells from wild-type mice. Furthermore, CD4(+)CD25(+) T cells from neonatal TGF-beta1(-/-) mice were as suppressive as CD4(+)CD25(+) from TGF-beta1(+/+) mice. Collectively, these results demonstrate that CD4(+)CD25(+) suppressor function can occur independently of TGF-beta1.