Replacement of mycophenolate mofetil with a JAK inhibitor, AS2553627, in combination with low-dose tacrolimus, for renal allograft rejection in non-human primates

JAK Inhibitors in Solid Organ Transplantation

Janus kinase (JAK) inhibitors are a novel group of immunosuppressive drugs approved to treat certain rheumatic and allergic disorders; however, their efficacy in the regulation of alloimmune responses after solid organ transplantation has not yet been elucidated. In the present review, we have summarized the results of in vitro, in vivo, experimental, and clinical trial studies about the efficacy and safety of JAK inhibitors in improving allograft survival in solid organ transplantations, including kidney, heart, lung, and liver transplants. Moreover, reports on administering JAK inhibitors to steroid-resistant patients with graft versus host disease (GvHD) after solid organ transplantation have been reviewed. Overall findings are suggestive of a beneficial role for JAK inhibitors in organ transplantation: for example, they have been shown to improve allograft function, reduce the rate and score of acute rejection, downregulate the expression of proinflammatory cytokines and adhesion molecules, and decrease oxidative stress. However, the adverse effects of these drugs, in particular bone marrow suppression and infection, remain an obstacle.

Impacts of dosing and drug withdrawal period on tacrolimus-based triple therapy in a non-human primate renal transplantation model

Non-human primate (NHP) renal transplantation models are widely used vivo models for researching new immunosuppressive therapies including allograft tolerance strategies. To enroll animals into a tolerance study, an immunosuppressive regimen that efficiently establishes stable renal function in NHPs is needed. Here, we assessed the effect of triple therapy comprising 2.0 mg/kg tacrolimus, mycophenolate mofetil and a steroid and its success rate for achieving stable renal function. In addition, to predict the pathophysiological consequences of withdrawing immunosuppressants, an indispensable process after induction of tolerance, we also assessed changes in the stable renal state maintained by triple therapy after drug withdrawal. Six cynomolgus monkeys were used. The median survival time was >176 days over the dosing period and 45 days after drug withdrawal. The triple therapy successfully induced stable graft function without calcineurin inhibitor nephrotoxicity in three of six recipients, although adopting trough-dependent tacrolimus dose adjustment rather than a preset dose regimen could improve on the present strategy. Further, drug withdrawal led to deterioration of renal function, de novo donor specific antibody production and increased the memory/naïve T cell ratio within two weeks post drug withdrawal. We expect that these findings contribute to establish one of the choices for animal model for evaluating future tolerance therapy for renal transplantation.

SARS-CoV-2 infection in immunocompromised patients: humoral versus cell-mediated immunity

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic placed unprecedented pressure on various healthcare systems, including departments that use immunotherapies such as chimeric antigen receptor (CAR) T-cell therapy and immunosuppression therapy in organ transplantation units. The true impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on immunocompromised CAR T-cell therapy recipients and kidney transplant recipients (KTRs) has not yet been established.

CASE PRESENTATION

In this report, we compare two patients with severe COVID-19 pneumonia in either the humoral or cell-mediated immunodeficient states. The first patient was a man in his early 30s who was diagnosed with refractory multiple myeloma. He received fully humanized, anti-B-cell maturation antigen, CAR T-cell therapy before 4 months and achieved strict complete remission. He was infected with SARS-CoV-2 starting on January 26, 2019 and gradually progressed to severe pneumonia. Throughout the clinical progression of the disease, SARS-CoV-2 could not be cleared due to his humoral immunodeficient state. During this period of his severe COVID-19 pneumonia, elevated cytotoxic T-cells were observed in this patient's peripheral blood while elevated plasma levels of interleukin (IL)-2R, IL-6, tumor necrosis factor α, and ferritin were observed in his cytokine profiles. This patient eventually progressed into acute respiratory distress syndrome and recieved non-invasive ventilatory support. He failed to generate specific SARS-CoV-2 antibodies and died of respiratory failure on day 33 (d33). The second patient was a 52-year-old kidney transplant recipient (KTR) who took ciclosporin after renal transplantation for more than 7 years. He confirmed SARS-CoV-2 infection on January 20, 2019 and gradually progressed into severe pneumonia on d16 with a slightly elevated B-cell percentage and normal T-lymphocyte subsets. Viral clearance occurred together with the generation of specific anti-immunoglobulin G-SARS-CoV-2 antibodies after 2 weeks of treatment. He was symptom-free and discharged from the hospital on d42.

CONCLUSION

We report a CAR T-cell therapy recipient diagnosed with COVID-19 for the first time. His virus clearance failure and life-threating cytokine storm during SARS-CoV-2 infection suggested that any decision to proceed CAR T-cell therapy during COVID-19 pandemics will require extensive discussion of potential risks and benefits. Immunosuppressant treatment based on ciclosporin could be relatively safe for KTRs diagnosed with COVID-19.

TRIAL REGISTRATION NUMBER

ChiCTR-OPN-1800018137.

The PI3Kδ selective inhibitor AS2541019 suppresses donor-specific antibody production in rat cardiac and non-human primate renal allotransplant models

Long-term graft survival after organ transplantation is difficult to achieve because of the development of chronic rejection. One cause of chronic rejection arises from antibody-mediated rejection (AMR), which is dependent on the production of donor-specific antibodies (DSA). Current immunosuppression in organ transplantation is effective in preventing acute T cell-mediated rejection, but the risk of DSA production and graft loss due to AMR remains unchanged. Phosphatidylinositol-3-kinase p110δ (PI3Kδ), a member of the family of PI3K lipid kinases, is a key mediator of B cell activation, proliferation and antibody production. AS2541019 is a novel PI3Kδ selective inhibitor that prevents antibody production by inhibiting B cell immunity. The purpose of this study was to evaluate the inhibitory effect of AS2541019 on DSA production in preclinical rodent and non-human primate allotransplant models. Concomitant administration of AS2541019 with tacrolimus and mycophenolate mofetil (MMF) inhibited de novo DSA production in an ACI-to-Lewis rat cardiac allotransplant model. To predict the efficacy of AS2541019 in clinical practice, we evaluated its effects in cynomolgus monkeys. AS2541019 inhibited B cell proliferation and major histocompatibility complex (MHC) class II expression on B cells in cynomolgus monkeys. Oral administration of AS2541019 inhibited MHC class II expression on peripheral B cells and anti-tetanus toxoid antibody production. In cynomolgus monkey renal allotransplant model, concomitant administration of AS2541019 with tacrolimus and MMF significantly inhibited de novo DSA production. Together, our findings indicate that the PI3Kδ selective inhibitor AS2541019 is a potential candidate for preventing AMR development by inhibiting DSA production.