Search

Background Janus kinase (JAK) inhibitors are thought to be promising candidates to aid renal transplantation. However, the effectiveness of JAK inhibitors against features of chronic rejection, including interstitial fibrosis/tubular atrophy (IF/TA) and glomerulosclerosis, has not been elucidated. Here, we investigated the effect of AS2553627, a novel JAK inhibitor, on the development of chronic rejection in rat renal transplantation. Methods Lewis (LEW) to Brown Norway (BN) rat renal transplantation was performed. Tacrolimus (TAC) at 0.1 mg/kg was administered intramuscularly once a day for 10 consecutive days starting on the day of transplantation (days 0 to 9) to prevent initial acute rejection. After discontinuation of TAC treatment from days 10 to 28, AS2553627 (1 and 10 mg/kg) was orally administered with TAC. At 13 weeks after renal transplantation, grafts were harvested for histopathological and mRNA analysis. Creatinine and donor-specific antibodies were measured from plasma samples. Urinary protein and kidney injury markers were also evaluated. Results AS2553627 in combination with TAC exhibited low plasma creatinine and a marked decrease in urinary protein and kidney injury markers, such as tissue inhibitor of metalloproteinase-1 and kidney injury molecule-1. At 13 weeks, histopathological analysis revealed that AS2553627 treatment inhibited glomerulosclerosis and IF/TA. In addition, upregulation of cell surface markers, fibrosis/epithelial–mesenchymal transition and inflammation-related genes were reduced by the combination of AS2553672 and TAC, particularly CD8 and IL-6 mRNAs, indicating that AS2553627 prevented cell infiltration and inflammation in renal allografts. Conclusions These results indicate the therapeutic potential of JAK inhibitors in chronic rejection progression, and suggest that AS2553627 is a promising agent to improve long-term graft survival after renal transplantation.

Donor-specific antibodies (DSA) are a major risk factor for antibody-mediated rejection (ABMR) in solid organ transplantation, and ABMR remains a medical challenge. Therefore, effective anti-ABMR therapies are needed to improve overall graft survival. Cathepsin S (Cat S) is an essential protease for antigen peptide loading onto lysosomal/endosomal major histocompatibility complex (MHC) class II molecules to promote antigen presentation. Cat S deficiency produces immuno-deficient phenotypes including a suppressed humoral immune response, and Cat S inhibition reportedly prevents autoimmunity. However, little is known about the effects of Cat S inhibitors on organ transplantation, especially ABMR. Here, we report the pharmacological profile of novel Cat S inhibitors, AS2761325 and AS2863995, and explore their preventive potential on DSA production and acute rejection in a mouse cardiac transplantation model. Cat S inhibitors potently inhibited upregulation of antigen peptide loading MHC class II expression on the surface of splenic B cells and suppressed ovalbumin-induced T cell-dependent antibody production in mice. In a mouse cardiac transplantation model, oral administration of AS2761325 monotherapy inhibited DSA production without affecting graft survival. When combined with a suboptimal dose of tacrolimus, AS2761325 significantly prolonged graft survival. The more potent Cat S inhibitor AS2863995 also prolonged graft survival and almost completely suppressed DSA production. These results suggest that Cat S inhibitors may be promising ABMR prophylaxis drug candidates. Combination therapy comprising a Cat S inhibitor and calcineurin inhibitors may be a more effective immunosuppressive maintenance therapy for controlling both cell-mediated and antibody-mediated rejection.

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.

Inosine 5'-monophosphate (IMP) dehydrogenase is a critical target in solid organ transplantation. To this end, the development of mycophenolate mofetil (MMF) represents a major advance in transplant medicine. Here, we investigated the in vitro and in vivo pharmacological effects of a novel IMP dehydrogenase inhibitor, AS2643361, in several immunological and non-immunological models. The in vitro inhibitory activity of AS2643361 on immune cell and endothelial cell proliferation and on antibody production from lipopolysaccharide-stimulated B cells, was significantly more potent than that of mycophenolic acid, the active form of MMF, despite the similar potency of these compounds on IMP dehydrogenase. In a rat heterotopic cardiac transplant model, monotherapy using orally administered AS2643361 at 10 or 20mg/kg/day prolonged the median graft survival time from 6 to 16 and 19days, respectively. In dinitrophenol-lipopolysaccharide stimulated rats, oral administration of AS2643361 at 2.5, 5 or 10mg/kg/day resulted in suppression of antibody production. In vivo antibody production against alloantigen was also suppressed by AS2643361 treatment at 5 or 10mg/kg/day. Furthermore, treatment with AS2543361 effectively inhibited balloon injury induced-intimal thickening, which is a major cause of late allograft loss. Overall, the in vivo activity of AS2643361 was over two-fold more potent than that of MMF. In addition, gastrointestinal toxicity, considered a dose-limiting factor for MMF, was reduced with AS2643361 treatment. These results suggest AS2643361 has higher potency and less toxicity than MMF, making it a potential candidate for treatment of acute and chronic rejection in transplant medicine.