Co-stimulatory blockade with belatacept in kidney transplantation

Trichosanthes kirilowii lectin alleviates diabetic nephropathy by inhibiting the LOX1/NF-κB/caspase-9 signaling pathway

Trichosanthes kirilowii lectin (TKL) has been reported to exert hypoglycemic effects in alloxan-induced diabetic mice. However, there is no evidence showing that it helps to prevent diabetic nephropathy (DN). We used a high glucose (HG)-induced HK-2 cell model and a streptozocin (STZ)-induced Wistar rat model to investigate the effects of TKL on DN, as well as the mechanisms for those effects. Our results showed that TKL significantly increased the viability of HG-treated HK-2 cells and inhibited cell apoptosis. In vivo experiments demonstrated that TKL attenuated STZ-induced histopathological damage and the inflammatory response in rat kidney tissues. Pre-treatment of HK-2 cells or STZ-treated rats with polyinosinic acid (Poly IC), an inhibitor of lectin-like oxLDL receptor 1 (LOX1), blocked the protective effect of TKL against HG- or STZ-induced damage to kidney tissue, indicating that TKL might exert its effect via LOX1-mediated endocytosis. Additional results suggested that TKL inhibits the phosphorylation of IκB kinase β (IKKβ) and the nuclear factor-κB (NF-κB) inhibitor protein (IκBα), and thereby reduces the nuclear translocation of NF-κB (p65). ChIP assay data indicated that TKL markedly inhibits the binding of p65 to the CASP9 gene in HG-treated HK-2 cells, subsequently suppressing transcription of the CASP9 gene. In the dual-luciferase reporter assay, TKL significantly inhibited luciferase activity in cells co-transfected with p65 and a wild-type capase-9 construct instead of mutated caspase-9 constructs.

Taken together, our results show that TKL helps to protect against DN by inhibiting the LOX1/NF-κB/caspase-9 signaling pathway, suggesting TKL as a promising agent for treating DN.

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.

Mechanistic Insight and Management of Diabetic Nephropathy: Recent Progress and Future Perspective

Diabetic nephropathy (DN) is the most serious microvascular complication of diabetes and the largest single cause of end-stage renal disease (ESRD) in many developed countries. DN is also associated with an increased cardiovascular mortality. It occurs as a result of interaction between both genetic and environmental factors. Hyperglycemia, hypertension, and genetic predisposition are the major risk factors. However, the exact mechanisms of DN are unclear. Despite the benefits derived from strict control of glucose and blood pressure, as well as inhibition of renin-angiotensin-aldosterone system, many patients continue to enter into ESRD. Thus, there is urgent need for improving mechanistic understanding of DN and then developing new and effective therapeutic approaches to delay the progression of DN. This review focuses on recent progress and future perspective about mechanistic insight and management of DN. Some preclinical relevant studies are highlighted and new perspectives of traditional Chinese medicine (TCM) for delaying DN progression are discussed in detail. These findings strengthen the therapeutic rationale for TCM in the treatment of DN and also provide new insights into the development of novel drugs for the prevention of DN. However, feasibility and safety of these therapeutic approaches and the clinical applicability of TCM in human DN need to be further investigated.

Pharmacokinetics, Pharmacodynamics, Safety, and Tolerability of ASP2408, a Potent Selective T-Cell Costimulation Modulator After Single and Multiple Ascending Doses in Healthy Volunteers and RA Patients

ASP2408 is a next-generation anti-cytotoxic T lymphocyte antigen-4 fusion protein engineered for improved CD86 binding affinity as a treatment for rheumatoid arthritis (RA). In 72 healthy subjects (n = 6/treatment), ASP2408 was administered as single ascending doses intravenously at 0.003 to 10.0 mg/kg or subcutaneously at 0.3 to 3.0 mg/kg. It showed decreased clearance and prolonged half-life with increasing doses, consistent with target-mediated disposition. The apparent bioavailability was 36.3%-56.7% across single subcutaneous doses. Sixteen RA patients (n = 8/treatment) on stable methotrexate received 3 × 3.0 mg/kg subcutaneously every 4 weeks or every 2 weeks. Similar to single-dose treatment, ASP2408 concentrations peaked 2 to 3 days postdose, with a median t1/2 of approximately 8 days. Using CD86 receptor occupancy (RO) as a mechanistic biomarker, ASP2408 demonstrated dose-dependent binding to its target. ASP2408 3.0 mg/kg subcutaneously every 4 weeks and every 2 weeks led to a mean %CD86 RO ≥ 74.7% and ≥ 81.5%, respectively, within each dosing interval. ASP2408 was well tolerated across studies with no evidence of dose-limiting toxicity or clinically significant changes in clinical laboratory test results, vital signs, or 12-lead electrocardiograms. ASP2408 elicited antidrug antibodies in the majority of patients, but with no clinical sequelae.

The podocyte as a direct target for treatment of glomerular disease?

The Centers for Disease Control and Prevention estimates more than 10% of adults in the United States, over 20 million Americans, have chronic kidney disease (CKD). A failure to maintain the glomerular filtration barrier directly contributes to the onset of CKD. The visceral epithelial cells, podocytes, are integral to the maintenance of this renal filtration barrier. Direct podocyte injury contributes to the onset and progression of glomerular diseases such as minimal change disease (MCD), focal segmental glomerular sclerosis (FSGS), diabetic nephropathy, and HIV-associated nephropathy (HIVAN). Since podocytes are terminally differentiated with minimal capacity to self-replicate, they are extremely sensitive to cellular injury. In the past two decades, our understanding of the mechanism(s) by which podocyte injury occurs has greatly expanded. With this newfound knowledge, therapeutic strategies have shifted to identifying targets directed specifically at the podocyte. Although the systemic effects of these agents are important, their direct effect on the podocyte proves to be essential in ameliorating glomerular disease. In this review, we highlight the mechanisms by which these agents directly target the podocyte independent of its systemic effects.

Nonimmunologic targets of immunosuppressive agents in podocytes

Proteinuria is a characteristic finding in glomerular diseases and is closely associated with renal outcomes. In addition, therapeutic interventions that reduce proteinuria improve renal prognosis. Accumulating evidence has demonstrated that podocytes act as key modulators of glomerular injury and proteinuria. The podocyte, or glomerular visceral epithelial cell, is a highly specialized and differentiated cell that forms interdigitated foot processes with neighboring podocytes, which are bridged together by an extracellular structure known as the "slit diaphragm" (SD). The SD acts as a size- and charge-selective barrier to plasma protein. Derangement of SD structure or loss of SD-associated protein results in podocyte injury and proteinuria. During the past decades, several immune-modulating agents have been used for the treatment of glomerular diseases and for the reduction of proteinuria. Interestingly, recent studies have demonstrated that immunosuppressive agents can have a direct effect on the SD-associated proteins and stabilize actin cytoskeleton in podocyte and have therefore introduced the concept of nonimmunologic mechanism of renoprotection by immunomodulators. This review focuses on the evidence that immuno-modulating agents directly target podocytes.