Jun Hirose

ASP4058, a novel agonist for sphingosine 1-phosphate receptors 1 and 5, ameliorates rodent experimental autoimmune encephalomyelitis with a favorable safety profile.

Sphingosine-1-phosphate (S1P) is a biologically active sphingolipid that acts through the members of a family of five G protein-coupled receptors (S1P1–S1P5). S1P1 is a major regulator of lymphocyte trafficking, and fingolimod, whose active metabolite fingolimod phosphate acts as a nonselective S1P receptor agonist, exerts its immunomodulatory effect, at least in part, by regulating the lymphocyte trafficking by inducing down regulation of lymphocyte S1P1. Here, we detail the pharmacological profile of 5-{5-[3-(trifluoromethyl)-4-{[(2S)-1,1,1-trifluoropropan-2-yl]oxy}phenyl]-1,2,4-oxadiazol-3-yl}-1H-benzimidazole (ASP4058), a novel next-generation S1P receptor agonist selective for S1P1 and S1P5. ASP4058 preferentially activates S1P1 and S1P5 compared with S1P2, 3, 4 in GTPγS binding assays in vitro. Oral administration of ASP4058 reduced the number of peripheral lymphocytes and inhibited the development of experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Further, ASP4058 prevented relapse of disease in a mouse model of relapsing-remitting EAE. Although these immunomodulatory effects were comparable to those of fingolimod, ASP4058 showed a wider safety margin than fingolimod for bradycardia and bronchoconstriction in rodents. These observations suggest that ASP4058 represents a new therapeutic option for treating multiple sclerosis that is safer than nonselective S1P receptor agonists such as fingolimod.

The Effect of ASP2409, a Novel CD86-Selective Variant of CTLA4-Ig, on Renal Allograft Rejection in Nonhuman Primates.

Background Blockade of CD28-mediated T cell costimulation by a modified cytotoxic T lymphocyte-associated antigen 4 (CTLA4-Ig), belatacept, is a clinically effective immunosuppressive therapy for the prevention of renal allograft rejection. Use of belatacept-based calcineurin inhibitor-free immunosuppression, however, has demonstrated an increased frequency of cellular rejection episodes and immunosuppression-related safety issues relative to conventional regimens. Furthermore, belatacept typically requires infusion for its administration chronically, which may present an inconvenience to patients. To address these issues, a novel CTLA4-Ig variant, ASP2409, with improved CD86 binding selectivity and affinity relative to belatacept was created using DNA shuffling directed evolution methods. Methods We evaluated the immunosuppressive effect of ASP2409 on in vitro alloimmune T cell responses, in vivo tetanus toxoid (TTx)-induced immunological responses and renal transplantation in cynomolgus monkeys. Results ASP2409 had 6.1-fold higher and 2.1-fold lower binding affinity to monkey CD86 and CD80 relative to belatacept, respectively. ASP2409 was 18-fold more potent in suppressing in vitro alloimmune T cell responses relative to belatacept. In a cynomolgus monkey TTx immunization model, ASP2409 inhibited anti-TTx immune responses at a 10-fold lower dose level than belatacept. In a cynomolgus monkey renal transplantation model, subcutaneous injection of 1 mg/kg ASP2409 prevented allograft rejection through complete CD86 and partial CD80 receptor occupancies and dramatically prolonged renal allograft survival in combination with tacrolimus or mycophenolate mofetil/methylprednisolone. Conclusions These results support the potential of ASP2409 as an improved CTLA4-Ig for maintenance immunosuppression in organ transplantation.

Effect of novel PKCθ selective inhibitor AS2521780 on acute rejection in rat and non-human primate models of transplantation.

Selective inhibition of protein kinase Cθ (PKCθ) may be useful in inducing T cell-specific immunosuppression with a reduced rate of side effects. To our knowledge, however, no reports have been published regarding the selective inhibition of PKCθ by small-molecule compounds in animal models of allograft rejection. Here, we investigated the effect of the newly synthesized PKCθ selective inhibitor AS2521780 in mono- and combination therapies on acute rejection in ACI-to-Lewis rat cardiac and non-human primate (NHP) renal transplantation models. In the rat cardiac transplantation model, AS2521780 significantly prolonged graft survival to 14days at 10mg/kg twice daily (b.i.d.) and to 20days at 30mg/kg b.i.d. In contrast, acute rejection occurred in all recipients in the non-treated group by Days 5 or 6 post-transplantation. Significant improvements (P<0.001) in graft survival were observed following treatment with a combination of AS2521780 at 3mg/kg b.i.d. and a suboptimal dose of tacrolimus (0.02mg/kg) or mycophenolate mofetil (15mg/kg). In the NHP renal transplantation model, AS2521780 at 3mg/kg b.i.d. and tacrolimus at 1mg/kg (suboptimal dose) significantly improved graft survival compared to tacrolimus alone (P<0.05). The present study of AS2521780 in rat cardiac and NHP renal transplantation models demonstrates the potential of PKCθ as a novel drug target for organ transplantation. As AS2521780 was well tolerated and the dose of tacrolimus or mycophenolate mofetil can be reduced when used in combination with this drug, immunosuppressive regimens containing selective inhibitors of PKCθ might have good safety profiles.

AS2553627, a novel JAK inhibitor, prevents chronic rejection in rat cardiac allografts

ABSTRACT Janus family kinases (JAKs) are essential molecules for cytokine responses and attractive targets for the treatment of transplant rejection and autoimmune diseases. Several JAK inhibitors have shown demonstrable effects on acute rejection in experimental cardiac transplant models. However, little is known about the potential benefits of JAK inhibitors on chronic rejection outcomes such as vasculopathy and fibrosis. Here, we examined the pharmacological profile of a novel JAK inhibitor, AS2553627, and explored its therapeutic potential in chronic rejection as well as acute rejection in a rat cardiac transplant model. AS2553627 potently inhibited JAK kinases but showed no inhibition of other kinases, including TCR‐associated molecules. The compound also suppressed proliferation of IL‐2 stimulated human and rat T cells. In a rat cardiac transplant model, oral administration of AS2553627 alone or co‐administration with a sub‐therapeutic dose of tacrolimus effectively prolonged cardiac allograft survival, suggesting the efficacy in treating acute rejection. To evaluate the effect on chronic rejection, recipient rats were administered a therapeutic dose of tacrolimus for 90 days. In combination with tacrolimus, AS2553627 significantly reduced cardiac allograft vasculopathy and fibrosis that tacrolimus alone did not inhibit. AS2553627 at the effective dose in rat transplantation models did not significantly reduce reticulocyte counts in peripheral whole blood after in vivo erythropoietin administration, indicating a low risk for anemia. These results suggest that AS2553627 may be a therapeutic candidate for the prevention of not only acute but also chronic rejection in cardiac transplantation.

Cell-contact-dependent activation of CD4+ T cells by adhesion molecules on synovial fibroblasts

Abstract Objective: To determine how cell–cell contact with synovial fibroblasts (SF) influence on the proliferation and cytokine production of CD4+ T cells. Methods: Naïve CD4+ T cells were cultured with SF from rheumatoid arthritis patients, stimulated by anti-CD3/28 antibody, and CD4+ T cell proliferation and IFN-γ/IL-17 production were analyzed. To study the role of adhesion molecules, cell contact was blocked by transwell plate or anti-intracellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1(VCAM-1) antibody. To study the direct role of adhesion molecules for CD4+ T cells, CD161+ or CD161- naïve CD4+ T cells were stimulated on plastic plates coated by recombinant ICAM-1 or VCAM-1, and the source of IFN-γ/IL-17 were analyzed. Results: SF enhanced naïve CD4+ T cell proliferation and IFN-γ/IL-17 production in cell-contact and in part ICAM-1-/VCAM-1-dependent manner. Plate-coated ICAM-1 and VCAM-1 enhanced naïve CD4+ T cell proliferation and IFN-γ production, while VCAM-1 efficiently promoting IL-17 production. CD161+ naïve T cells upregulating LFA-1 and VLA-4 were the major source of IFN-γ/IL-17 upon interaction with ICAM-1/VCAM-1. Conclusion: CD4+ T cells rapidly expand and secrete IFN-γ/IL-17 upon cell-contact with SF via adhesion molecules. Interfering with ICAM-1-/VCAM-1 may be beneficial for inhibiting RA synovitis.

Constitutive Activation of Integrin α9 Augments Self-Directed Hyperplastic and Proinflammatory Properties of Fibroblast-like Synoviocytes of Rheumatoid Arthritis

Despite advances in the treatment of rheumatoid arthritis (RA), currently approved medications can have significant side effects due to their direct immunosuppressive activities. Additionally, current therapies do not address residual synovial inflammation. In this study, we evaluated the role of integrin α9 and its ligand, tenascin-C (Tn-C), on the proliferative and inflammatory response of fibroblast-like synoviocytes (FLSs) from RA patients grown in three-dimensional (3D)–micromass culture. FLSs from osteoarthritis patients, when grown in the 3D-culture system, formed self-directed lining-like structures, whereas FLSs from RA tissues (RA-FLSs) developed an abnormal structure of condensed cellular accumulation reflective of the pathogenic features of RA synovial tissues. Additionally, RA-FLSs grown in 3D culture showed autonomous production of proinflammatory mediators. Predominant expression of α9 and Tn-C was observed in the condensed lining, and knockdown of these molecules abrogated the abnormal lining-like structure formation and suppressed the spontaneous expression of matrix metalloproteinases, IL-6, TNFSF11/RANKL, and cadherin-11. Disruption of α9 also inhibited expression of Tn-C, suggesting existence of a positive feedback loop in which the engagement of α9 with Tn-C self-amplifies its own signaling and promotes progression of synovial hyperplasia. Depletion of α9 also suppressed the platelet-derived growth factor–induced hyperplastic response of RA-FLSs and blunted the TNF-α–induced expression of matrix metalloproteinases and IL-6. Finally, α9-blocking Ab also suppressed the formation of the condensed cellular lining by RA-FLSs in 3D cultures in a concentration-related manner. This study demonstrates the central role of α9 in pathogenic behaviors of RA-FLSs and highlights the potential of α9-blocking agents as a nonimmunosuppressive treatment for RA-associated synovitis.

A sphingosine‐1‐phosphate receptor type 1 agonist, ASP4058, suppresses intracranial aneurysm through promoting endothelial integrity and blocking macrophage transmigration

Intracranial aneurysm (IA), common in the general public, causes lethal subarachnoid haemorrhage on rupture. It is, therefore, of utmost importance to prevent the IA from rupturing. However, there is currently no medical treatment. Recent studies suggest that IA is the result of chronic inflammation in the arterial wall caused by endothelial dysfunction and infiltrating macrophages. The sphingosine‐1‐phosphate receptor type 1 (S1P1 receptor) is present on the endothelium and promotes its barrier function. Here we have tested the potential of an S1P1 agonist, ASP4058, to prevent IA in an animal model.

An S1P1 agonist, ASP4058, suppresses intracranial aneurysm through promoting endothelial integrity and blocking macrophage transmigration.

Intracranial aneurysm (IA), common in the general public, causes lethal subarachnoid haemorrhage on rupture. It is, therefore, of utmost importance to prevent the IA from rupturing. However, there is currently no medical treatment. Recent studies suggest that IA is the result of chronic inflammation in the arterial wall caused by endothelial dysfunction and infiltrating macrophages. The sphingosine‐1‐phosphate receptor type 1 (S1P1 receptor) is present on the endothelium and promotes its barrier function. Here we have tested the potential of an S1P1 agonist, ASP4058, to prevent IA in an animal model.

Mechanism analysis of long-term graft survival by monocarboxylate transporter-1 inhibition.

Background. Monocarboxylate transporter (MCT)-1, a member of a family of molecules, transports monocarboxylates such as lactate. Inhibiting MCT-1 leads to long-term graft survival in rodent heart transplantation and induces tolerance. We evaluated an MCT-1 inhibitor, AS2495674, in a rat heart transplant model and analyzed its underlying mechanism. Methods. AS2495674 was tested on rat lymphocytes to determine its effect on lactate accumulation, proliferation, and immunoglobulin production. The effect of AS2495674 on graft survival was tested on the Brown Norway to Lewis rat strain combination with a second heart transplantation to test donor-specific suppression. Histology and ex vivo analyses were done to examine the AS2495674 effects on the immune response. Results. In vitro, AS2495674 resulted in lactate accumulation, inhibited lymphocyte proliferation, and prevented immunoglobulin production. AS2495674 induced long-term allograft survival with little evidence of chronic rejection and induced donor-specific suppression. Evaluation of the allograft and peripheral T lymphocytes from the AS2495674 group compared with that of vehicle showed (1) decreased donor-specific T lymphocyte response, (2) more forkhead box P3+ (Foxp3+) and CD45RA+ cells in the allograft, (3) higher gene expression of chemokines and chemokine receptors in the allograft, and (4) preferential inhibition of Foxp3− cells with little or no effect on Foxp3+ cells. Conclusions. AS2495674 prevents acute rejection, reduces features of chronic rejection, and induces tolerance. Our data suggest that the mechanism of AS2495674 involves generating a tolerogenic graft environment by preferentially targeting T effector cells while sparing the generation of T regulatory cells.

ASP0028 in combination with suboptimal-dose of tacrolimus in Cynomolgus monkey renal transplantation model

FTY720, a S1P-receptor modulator, has shown to be effective in several transplant and autoimmune disease models, via modulating lymphocyte homing into secondary lymphoid organs (SLOs), and thereby reducing these cells in peripheral blood. ASP0028, a newly developed S1P1/S1P5-selective agonist, presented comparable efficacy to FTY720 and wider safety margins than FTY720. In this study, we assessed the efficacy and safety of ASP0028 co-administered with suboptimal-dose of tacrolimus in the Cynomolgus monkey renal transplantation model. Seven animals in group-1 or group-2 received mono-tacrolimus 1.0mg/kg once a day (QD), or ASP0028 0.6mg/kg plus tacrolimus 1.0mg/kg QD, respectively. Eight animals in group-3 received ASP0028 1.2mg/kg plus tacrolimus 1.0mg/kg QD. The allograft median survival time (MST) in group-2 and group-3 were significantly extended to 41 and 61.5days, versus that of 28days in group-1 (p=0.036 and 0.001, respectively). ASP0028 administration remarkably reduced absolute numbers of peripheral lymphocytes, particularly subsets of CD4+/ or CD8+/naive and central memory cells, CD4+/Treg cells, and to a lesser extent on B cells, but not CD4+/ or CD8+/effector memory cells and NK cells. These data show ASP0028 combined with suboptimal-dose of tacrolimus effectively prolongs renal allograft survival in nonhuman primates (NHPs) with well tolerated safety, supporting its further investigation to optimize CNI-sparing regimens.