Sotrastaurin in calcineurin inhibitor-free regimen using everolimus in de novo kidney transplant recipients

Long-Term Outcome after Early Mammalian Target of Rapamycin Inhibitor-Based Immunosuppression in Kidney Transplant Recipients

Background: The use of mammalian target of rapamycin inhibitors (mTORis) in kidney transplantation increases the risk of donor-specific human leukocyte antigen (HLA) antibody formation and rejection. Here, we investigated the long-term consequences of early mTORi treatment compared to calcineurin inhibitor (CNI) treatment. Methods: In this retrospective single-center analysis, key outcome parameters were compared between patients participating in randomized controlled immunosuppression trials between 1998 and 2011, with complete follow-up until 2018. The outcomes of eligible patients on a CNI-based regimen (n = 384) were compared with those of patients randomized to a CNI-free mTORi-based regimen (n = 81) and 76 patients randomized to a combination of CNI and mTORi treatments. All data were analyzed according to the intention-to-treat (ITT) principle. Results: Deviation from randomized immunosuppression for clinical reasons occurred significantly more often and much earlier in both mTORi-containing regimens than in the CNI treatment. Overall patient survival, graft survival, and death-censored graft survival did not differ between the treatment groups. Donor-specific HLA antibody formation and BPARs were significantly more common in both mTORi regimens than in the CNI-based immunosuppression. Conclusions: The tolerability and efficacy of the mTORi treatment in kidney graft recipients are inferior to those of CNI-based immunosuppression, while the long-term patient and graft survival rates were similar.

Regulatory T-cell therapy approaches

Regulatory T cells (Tregs) have enormous therapeutic potential to treat a variety of immunopathologies characterized by aberrant immune activation. Adoptive transfer of ex vivo expanded autologous Tregs continues to progress through mid- to late-phase clinical trials in several disease spaces and has generated promising preliminary safety and efficacy signals to date. However, the practicalities of this strategy outside of the clinical trial setting remain challenging. Here, we review the current landscape of regulatory T-cell therapy, considering emergent approaches and technologies presenting novel ways to engage Tregs, and reflect on the progress necessary to deliver their therapeutic potential to patients.

New immunosuppressive agents in transplantation

Immunosuppressive agents have enabled the development of allogenic transplantation during the last 40 years, allowing considerable improvement in graft survival. However, several issues remain such as the nephrotoxicity of calcineurin inhibitors, the cornerstone of immunosuppressive regimens and/or the higher risk of opportunistic infections and cancers. Most immunosuppressive agents target T cell activation and may not be efficient enough to prevent allo-immunization in the long term. Finally, antibody mediated rejection due to donor specific antibodies strongly affects allograft survival. Many drugs have been tested in the last decades, but very few have come to clinical use. The most recent one is CTLA4-Ig (belatacept), a costimulation blockade molecule that targets the second signal of T cell activation and is associated with a better long term kidney function than calcineurin inhibitors, despite an increased risk of acute cellular rejection. The research of new maintenance long-term immunosuppressive agents focuses on costimulation blockade. Agents inhibiting CD40-CD40 ligand interaction may enable a good control of both T cells and B cells responses. Anti-CD28 antibodies may promote regulatory T cells. Agents targeting this costimulation pathways are currently evaluated in clinical trials. Immunosuppressive agents for ABMR treatment are scarce since anti-CD20 agent rituximab and proteasome inhibitor bortezomib have failed to demonstrate an interest in ABMR. New drugs focusing on antibodies removal (imlifidase), B cell and plasmablasts (anti-IL-6/IL-6R, anti-CD38…) and complement inhibition are in the pipeline, with the challenge of their evaluation in such a heterogeneous pathology.

Activators and Inhibitors of Protein Kinase C (PKC): Their Applications in Clinical Trials

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinase, is classed into three subfamilies based on their structural and activation characteristics: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or non-classic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). PKC inhibitors and activators are used to understand PKC-mediated intracellular signaling pathways and for the diagnosis and treatment of various PKC-associated diseases, such as cancers, neurological diseases, cardiovascular diseases, and infections. Many clinical trials of PKC inhibitors in cancers showed no significant clinical benefits, meaning that there is a limitation to design a cancer therapeutic strategy targeting PKC alone. This review will focus on the activators and inhibitors of PKC and their applications in clinical trials.

Transplantation and immunosuppression: a review of novel transplant-related immunosuppressant drugs

Immunosuppressive drugs used in the transplantation period are generally defined as induction and maintenance therapy. The use of immunosuppressants, which are particularly useful and have fewer side effects, decreased both mortality and morbidity. Many drugs such as steroids, calcineurin inhibitors (cyclosporine-A, tacrolimus), antimetabolites (mycophenolate mofetil, azathioprine), and mTOR inhibitors (sirolimus, everolimus) are used as immunosuppressive agents. Although immunosuppressant drugs cause many side effects such as hypertension, infection, and hyperlipidemia, they are the agents that should be used to prevent organ rejection. This shows the importance of individualized drug use. The optimal immunosuppressive therapy post-transplant is not established. Therefore, discovering less toxic but more potent new agents is of great importance, and new experimental and clinical studies are needed in this regard.Our review discussed the mechanism of immunosuppressants, new agents' discovery, and current therapeutic protocols in the transplantation.

Costimulation Blockade in Kidney Transplant Recipients

Costimulation between T cells and antigen-presenting cells is essential for the regulation of an effective alloimmune response and is not targeted with the conventional immunosuppressive therapy after kidney transplantation. Costimulation blockade therapy with biologicals allows precise targeting of the immune response but without non-immune adverse events. Multiple costimulation blockade approaches have been developed that inhibit the alloimmune response in kidney transplant recipients with varying degrees of success. Belatacept, an immunosuppressive drug that selectively targets the CD28-CD80/CD86 pathway, is the only costimulation blockade therapy that is currently approved for kidney transplant recipients. In the last decade, belatacept therapy has been shown to be a promising therapy in subgroups of kidney transplant recipients; however, the widespread use of belatacept has been tempered by an increased risk of acute kidney transplant rejection. The purpose of this review is to provide an overview of the costimulation blockade therapies that are currently in use or being developed for kidney transplant indications.

Novel Targets of Immunosuppression in Transplantation

It is increasingly recognized that calcineurin inhibitors (CNI) such as cyclosporine and tacrolimus are not ideal immunosuppressive agents. Side effects, including increased rates of infection, hypertension, and malignancy, can be severe. Thus, in the past decade, there has been much focus on the development of novel therapeutic agents and strategies designed to replace or minimize CNI exposure in transplant patients. This article reviews potential novel targets in T cells, alloantibody-producing B cells, plasma cells, and complement in transplantation.

Simulated annealing molecular dynamics and ligand-receptor contacts analysis for pharmacophore modeling

AIM

Ligand-based pharmacophore modeling requires long list of inhibitors, while pharmacophores based on single ligand-receptor crystallographic structure can be too restricted or promiscuous.

METHODOLOGY

This prompted us to combine simulated annealing molecular dynamics (SAMD) with ligand-receptor contacts analysis as means to construct pharmacophore model(s) from single ligand-receptor complex. Ligand-receptor contacts that survive numerous heating-cooling SAMD cycles are considered critical and are used to guide pharmacophore development.

RESULTS

This methodology was implemented to develop pharmacophores for acetylcholinesterase and protein kinase C-θ. The resulting models were validated by receiver-operating characteristic analysis and in vitro bioassay. Assay identified four new protein kinase C-θ inhibitors among captured hits, two of which exhibited nanomolar potencies.

CONCLUSION

The results illustrate the ability of the new method to extract valid pharmacophores from single ligand-protein complex.

Limitations of the interpretation and extrapolation of clinical trial data in kidney transplant recipients

OBJECTIVE

The risks and benefits of the participation of kidney transplant recipients in randomized clinical trials (RCTs) investigating new immunosuppressive therapies are unknown.

DESIGN AND SETTING

We included patients from 12 prospective phase II/III RCTs randomized to the experimental (G1, n=319) or standard-of-care internal control group (G2, n=118). We constructed two additional external control groups with (G3, n=319) or without (G4, n=319) matching inclusion/exclusion criteria based on transplant date. The primary outcome analysis was the composite clinical efficacy failure, defined as biopsy-proven acute rejection (BPAR), graft loss, death, or loss to follow-up 12 months after kidney transplantation.

RESULTS

Survival free of composite clinical efficacy failure was higher among participants in RCT, without difference between experimental or standard-of-care therapy (80∙3 vs 78∙0 vs 69∙9 vs 66∙1%, P<.001), respectively. Patient (98.1 vs 99.2 vs 96.9 vs 91.8 P<.001) and graft (94.0 vs 98.3 vs 90.9 vs 82.4) survivals were also higher in G1 compared to G4, but no differences in survival free of BPAR were observed (85.3 vs 78.8 vs 82.8 vs 81.2 P>.05), respectively.

CONCLUSION

These findings suggested that new treatments investigated in kidney transplant recipients are not associated with detectable harm compared to standard of care.

Emerging drugs for prevention of T-cell mediated rejection in liver and kidney transplantation

INTRODUCTION

Acute and chronic graft rejection continues to be an important problem after solid organ transplantation. With the introduction of potent immunosuppressive agents such as calcineurin inhibitors, the risk of rejection has been significantly reduced. However, the adverse effects of life-long immunosuppression remain a concern, and there exist a fine balance between over-immunosuppression and risk of rejection. Areas covered: In this review, the current standard of care in immunosuppressive therapy, including the use of steroids, calcineurin inhibitors, mycophenolate prodrugs and mammalian target of rapamycin inhibitors, will be discussed. Newer immunosuppressive agents showing promising early data after liver and kidney transplantation will also be explored. Expert Opinion: Currently, calcineurin inhibitors continue to be a vital component of immunosuppressive therapy after solid organ transplantation. Although minimization and avoidance strategies have been developed, the ultimate goal of inducing tolerance remains elusive. Newer emerging agents should have potent and specific immunosuppressive activity, with minimal associated side effects. An individualized approach should be adopted to tailor immunosuppression according to the different needs of recipients.

The use of kinase inhibitors in solid organ transplantation

INTRODUCTION

Despite the efficacy of current immunosuppression regimes used in solid organ transplantation, graft dysfunction, graft lost and antibody-mediated rejection continue to be problematic. As a result, clear attraction in exploiting key potential targets controlled by kinase phosphorylation has led to a number of studies exploring the use of these drugs in transplantation. Aim In this review, we consider the role of tyrosine kinase as a target in transplantation and summarize the relevant studies on kinase inhibitors that have been reported to date.

METHODS

Narrative review of literature from inception to December 2016, using OVID interface searching EMBASE and MEDLINE databases. All studies related to kinase based immunosuppression were examined for clinical relevance with no exclusion criteria. Key ideas were extracted and referenced.

CONCLUSION

The higher incidence of infections when using kinase inhibitors is an important consideration, however the number and range inhibitors and their clinical indications are likely to expand, but their exact role in transplantation is yet to be determined.

Inhibition of JAK3 and PKC via Immunosuppressive Drugs Tofacitinib and Sotrastaurin Inhibits Proliferation of Human B Lymphocytes In Vitro

BACKGROUND

Antibody-mediated response in solid organ transplantation is critical for graft dysfunction and loss. The use of immunosuppressive agents partially inhibits the B-lymphocyte response leading to a risk of acute and chronic antibody-mediated rejection. This study evaluated the impact of JAK3 and PKC inhibitors tofacitinib (Tofa) and sotrastaurin (STN), respectively, on B-cell proliferation, apoptosis, and activation in vitro.

METHODS

Human B cells isolated from peripheral blood of healthy volunteers were cocultured with CD40 ligand-transfected fibroblasts as feeder cells in the presence of interleukin (IL) 2, IL-10, and IL-21. The cocultures were treated with immunosuppressants Tofa, STN, and rapamycin (as a control), to analyze the proliferation and apoptosis of B cells by means of Cyquant and flow cytometry, respectively. CD27 and IgG staining were applied to evaluate whether treatments modified the activation of B cells.

RESULTS

Tofa and STN were able to inhibit B-cell proliferation to the same extent as rapamycin, without inducing cell apoptosis. After 6 days in coculture with feeder cells, all B cells showed CD27 memory B-cell phenotype. None of the immunosuppressive treatments modified the proportion between class-switched and non-class-switched memory B cells observed in nontreated cultures. The high predominance of CD27⁺CD24⁺ phenotype was not modified by any immunosuppressive treatment.

CONCLUSIONS

Our results show that Tofa and STN can suppress B-cell antibody responses to an extent similar to rapamycin, in vitro; therefore these compounds may be a useful therapy against antibody-mediated rejection in transplantation.

Protein kinase C theta is required for efficient induction of IL-10-secreting T cells

Secretion of interleukin-10 (IL-10) by CD4+ T cells is an essential immunoregulatory mechanism. The work presented here assesses the role of the signaling molecule protein kinase C theta (PKCθ) in the induction of IL-10 expression in CD4+ T cells. Using wildtype and PKCθ-deficient Tg4 T cell receptor transgenic mice, we implemented a well-described protocol of repeated doses of myelin basic protein (MBP)Ac1-9[4Y] antigen to induce Tr1-like IL-10+ T cells. We find that PKCθ is required for the efficient induction of IL-10 following antigen administration. Both serum concentrations of IL-10 and the proportion of IL-10+ T cells were reduced in PKCθ-deficient mice relative to wildtype mice following [4Y] treatment. We further characterized the T cells of [4Y] treated PKCθ-deficient Tg4 mice and found reduced expression of the transcription factors cMaf, Nfil3 and FoxP3 and the surface receptors PD-1 and Tim3, all of which have been associated with the differentiation or function of IL-10+ T cells. Finally, we demonstrated that, unlike [4Y] treated wildtype Tg4 T cells, cells from PKCθ-deficient mice were unable to suppress the priming of naïve T cells in vitro and in vivo. In summary, we present data demonstrating a role for PKCθ in the induction of suppressive, IL-10-secreting T cells induced in TCR-transgenic mice following chronic antigen administration. This should be considered when contemplating PKCθ as a suitable drug target for inducing immune suppression and graft tolerance.

Impact of regulatory assessment on clinical studies in Brazil

INTRODUCTION

Despite the recent expansion of clinical studies allocated to Brazil, the delay of local regulatory deadlines directly impacts their completion.

OBJECTIVE

This article examines the allocation process of clinical studies to Brazil in comparison with other countries, as well as the financial impact of studies not completed due to interruption caused by the delay in the regulatory process.

METHOD

The allocation processes of studies were compared in nine countries with similar stages of economic development and countries in Latin America using the websites http://data.worldbank.org/data-catalog/GDP-rankings-table and http://worldpopulationreview.com and clinicaltrials.gov, comprising 185 countries. The 46 studies sponsored by the pharmaceutical industry underwent an analysis of the regulatory review process.

RESULTS

46 studies sponsored by the industry and submitted in the country between June 2007 and June 2013 were analyzed; 18 (39%) were discontinued due to the delay in obtaining the necessary approvals. For the approved studies, patient recruitment began an average of 11 months after the other countries. It is estimated that 530 Brazilians patients did not have the opportunity to participate in these studies. Financial losses were to the order of 14.6 million dollars for the country, including patient, medication and supplies costs, and expenses.

CONCLUSION

Brazil has enormous potential for the realization of clinical studies. Researchers, associations of disabled people and patients with chronic diseases, sponsors and the authorities must work together to develop an approval process that is efficient, predictable and, most of all, transparent. The current regulatory environment must and can be improved and optimized in order to result in tangible benefits for patients, society and the country's scientific development.

Efficacy and Safety of Elective Conversion From Sotrastaurin (STN) to Tacrolimus (TAC) or Mycophenolate (MPS) in Stable Kidney Transplant Recipients

BACKGROUND

This study aimed to evaluate the efficacy and safety outcomes of conversion strategies in stable kidney transplant recipients after premature termination of the sotrastaurin (STN) development program.

METHODS

This is an exploratory and prospective study, including 38 stable renal transplant recipients. Tacrolimus (TAC) group [STN → mycophenolate sodium (MPS)] consisted of 9 patients receiving TAC, STN, and prednisone that were converted from STN to MPS. Everolimus (EVR) group (STN → TAC) consisted of 29 patients receiving EVR, STN, and prednisone that were converted from STN to TAC.

RESULTS

In TAC (STN → MPS) group, dose-adjusted TAC concentrations decreased from baseline to first week (2.3 ± 1.1 versus 1.5 ± 1.0 ng·mL·mg, P < 0.05). Two patients experienced a first acute rejection episode. Conversion to MPS was associated with a higher incidence of adverse events. In EVR (STN → TAC) group, dose-adjusted EVR concentrations decreased from baseline to first week (3.6 ± 2.3 ng·mL·mg versus 1.9 ± 0.8 ng·mL·mg, P < 0.01). The proportion of patients with donor-specific antibodies was lower in TAC (STN → MPS) (11%) compared to EVR (STN → TAC) (31%) before conversion. Conversion from STN to TAC was associated with a reduction in estimated glomerular filtration rate (69.6 ± 16.9 versus 61.0 ± 18.8 mL·min·1.73 m, P < 0.01) and a decreased proportion of patients with donor-specific antibodies (31% versus 14%) at 12 months.

CONCLUSIONS

Conversion from TAC/STN to TAC/MPS or from EVR/STN to TAC/EVR was associated with significant pharmacokinetic changes in both TAC and EVR whole-blood trough concentrations due to known drug-to-drug interaction, which were associated with changes in efficacy and safety.

Reviewing 15 years of experience with sirolimus

Here, we review 15 years of clinical use of sirolimus in our transplant center, in context with the developing immunosuppressive strategies use worldwide. The majority of studies were conducted in de novo kidney transplant recipients, using sirolimus (SRL) in combination with calcineurin inhibitors (CNIs). We also explored steroid (ST) or CNI-sparing therapies, including CNI minimization, elimination, or conversion strategies in combination with mycophenolate (MMF/MPS). Pooled long-term outcomes were comparable with those obtained with CNI and antimetabolite combination. Surprisingly, there are still several areas that need further investigation to improve the risk/benefit profile of SRL in kidney transplantation, including pharmacokinetic/pharmacodynamic drug-to-drug interaction with cyclosporine (CsA) or tacrolimus (TAC), mechanisms of SRL-associated adverse reactions and combinations with other drugs such as belatacept and once-daily TAC, possibly leading to improved long-term adherence. These studies, along with others investigating the benefits of SRL associated lower viral infections and malignancies, are essential as we do not expect the introduction of new immunosuppressive drugs in the near future.

Protein kinase C inhibitor sotrastaurin in de novo liver transplant recipients: a randomized phase II trial

Efficacy and safety of protein kinase C inhibitor sotrastaurin (STN) with tacrolimus (TAC) was assessed in a 24-month, multicenter, phase II study in de novo liver transplant recipients. A total of 204 patients were randomized (1:1:1:1) to STN 200 mg b.i.d. + standard-exposure TAC (n = 50) or reduced-exposure TAC (n = 52), STN 300 mg b.i.d. + reduced-exposure TAC (n = 50), or mycophenolate mofetil (MMF) 1 g b.i.d. + standard-exposure TAC (control, n = 52); all with steroids. Owing to premature study termination, treatment comparisons were only conducted for Month 6. At Month 6, composite efficacy failure rates (treated biopsy-proven acute rejection episodes of Banff grade ≥1, graft loss, or death) were 25.0%, 16.5%, 20.9% and 15.9% for STN 200 mg + standard TAC, STN 200 mg + reduced TAC, STN 300 mg + reduced TAC and control groups, respectively. Median estimated glomerular filtration rates were 84.0, 83.3, 81.1 and 75.3 mL/min/1.73 m(2), respectively. Gastrointestinal events (constipation, diarrhea, and nausea), infection, and tachycardia were more frequent in STN groups. More patients in STN groups experienced serious adverse events compared with the control group (62.3-70.8% vs. 51.9%). STN-based regimens were associated with a higher efficacy failure rate and higher incidence of adverse events with no significant difference in renal function between the groups.

What's new in clinical solid organ transplantation by 2013

Innovative and exciting advances in the clinical science in solid organ transplantation continuously realize as the results of studies, clinical trials, international conferences, consensus conferences, new technologies and discoveries. This review will address to the full spectrum of news in transplantation, that verified by 2013. The key areas covered are the transplantation activity, with particular regards to the donors, the news for solid organs such as kidney, pancreas, liver, heart and lung, the news in immunosuppressive therapies, the news in the field of tolerance and some of the main complications following transplantation as infections and cancers. The period of time covered by the study starts from the international meetings held in 2012, whose results were published in 2013, up to the 2013 meetings, conferences and consensus published in the first months of 2014. In particular for every organ, the trends in numbers and survival have been reviewed as well as the most relevant problems such as organ preservation, ischemia reperfusion injuries, and rejections with particular regards to the antibody mediated rejection that involves all solid organs. The new drugs and strategies applied in organ transplantation have been divided into new way of using old drugs or strategies and drugs new not yet on the market, but on phase Ito III of clinical studies and trials.

Targeting protein kinase C in sarcoma

Protein kinase C (PKC) is a family of serine/threonine tyrosine kinases that regulate many cellular processes including division, proliferation, survival, anoikis and polarity. PKC is abundant in many human cancers and aberrant PKC signalling has been demonstrated in cancer models. On this basis, PKC has become an attractive target for small molecule inhibition within oncology drug development programmes. Sarcoma is a heterogeneous group of mesenchymal malignancies. Due to their relative insensitivity to conventional chemotherapies and the increasing recognition of the driving molecular events of sarcomagenesis, sarcoma provides an excellent platform to test novel therapeutics. In this review we provide a structure-function overview of the PKC family, the rationale for targeting these kinases in sarcoma and the state of play with regard to PKC inhibition in the clinic.

Rotterdam: main port for organ transplantation research in the Netherlands

This overview describes the full spectrum of current pre-clinical and clinical kidney-, liver-, heart- and lung transplantation research performed in Erasmus MC - University Medical Centre in Rotterdam, The Netherlands. An update is provided on the development of a large living donor kidney transplantation program and on optimization of kidney allocation, including the implementation of a domino kidney-donation program. Our current research efforts to optimize immunosuppressive regimens and find novel targets for immunosuppressive therapy, our recent studies on prevention of ischemia-reperfusion-induced graft injury, our newest findings on stimulation of tissue regeneration, our novel approaches to prevent rejection and viral infection, and our latest insights in the regulation of allograft rejection, are summarized.

The protein kinase C inhibitor sotrastaurin allows regulatory T cell function

The novel immunosuppressant sotrastaurin is a selective inhibitor of protein kinase C isoforms that are critical in signalling pathways downstream of the T cell receptor. Sotrastaurin inhibits nuclear factor (NF)-κB, which directly promotes the transcription of forkhead box protein 3 (FoxP3), the key regulator for the development and function of regulatory T cells (Tregs). Our center participated in a randomized trial comparing sotrastaurin (n = 14) and the calcineurin inhibitor Neoral (n = 7) in renal transplant recipients. We conducted ex vivo mixed lymphocyte reaction (MLR) and flow cytometry studies on these patient samples, as well as in vitro studies on samples of blood bank volunteers (n = 38). Treg numbers remained stable after transplantation and correlated with higher trough levels of sotrastaurin (r = 0·68, P = 0·03). A dose-dependent effect of sotrastaurin on alloresponsiveness was observed: the half maximal inhibitory concentration (IC50 ) to inhibit alloactivated T cell proliferation was 45 ng/ml (90 nM). In contrast, Treg function was not affected by sotrastaurin: in the presence of in vitro-added sotrastaurin (50 ng/ml) Tregs suppressed the proliferation of alloactivated T effector cells at a 1:5 ratio by 35 versus 47% in the absence of the drug (P = 0·33). Signal transducer and activator of transcription 5 (STAT)-5 phosphorylation in Tregs remained intact after incubation with sotrastaurin. This potent Treg function was also found in cells of patients treated with sotrastaurin: Tregs inhibited the anti-donor response in MLR by 67% at month 6, which was comparable to pretransplantation (82%). Sotrastaurin is a potent inhibitor of alloreactivity in vitro, while it did not affect Treg function in patients after kidney transplantation.

Beyond calcineurin inhibitors: emerging agents in kidney transplantation

PURPOSE OF REVIEW

Despite their effectiveness, calcineurin inhibitors (CNIs) represent a major obstacle in the improvement of long-term graft survival in transplantation. The identification of new agents to implement CNI-free regimens is the focus of current transplant research. The purpose of this review is to summarize the novel immunosuppressive agents, including details about their mechanisms of action, stages of development, potential benefits and challenges.

RECENT FINDINGS

Targeting costimulation with belatacept is now an option for controlling the alloimmune response and has proved to be more effective in preserving long-term allograft function than CNIs despite an increased rate of acute rejection in some studies. mTOR inhibitors are also promising with their remarkable antineoplastic properties, though frequent side-effects may limit their broader use. Other agents under development include JAK inhibitors, CD40 blockade and leukocyte adhesion blockers, with unique potential benefits and side-effects in transplantation.

SUMMARY

Novel immunosuppressive agents are now available for use in CNI-free regimens in solid organ transplantation. Timing of initiation as well as long-term efficacy and safety are questions that remain to be answered in future clinical trials.

Novel immunosuppressive agents in kidney transplantation

Excellent outcomes have been achieved in the field of renal transplantation. A significant reduction in acute rejection has been attained at many renal transplant centers using contemporary immunosuppressive, consisting of an induction agent, a calcineurin inhibitor, an antiproliferative agent plus or minus a corticosteroid. Despite improvements with these regimens, chronic allograft injury and adverse events still persist. The perfect immunosuppressive regimen would limit or eliminate calcineurin inhibitors and/or corticosteroid toxicity while providing enhanced allograft outcomes. Potential improvements to the calcineurin inhibitor class include a prolonged release tacrolimus formulation and voclosporin, a cyclosporine analog. Belatacept has shown promise as an agent to replace calcineurin inhibitors. A novel, fully-human anti-CD40 monoclonal antibody, ASKP1240, is currently enrolling patients in phase 2 trials with calcineurin minimization and avoidance regimens. Another future goal of transplant immunosuppression is effective and safe treatment of allograft rejection. Novel treatments for antibody mediated rejection include bortezomib and eculizumab. Several investigational agents are no longer being pursed in transplantation including the induction agents, efalizumab and alefacept, and maintenance agents, sotrastaurin and tofacitinib. The purpose of this review is to consolidate the published evidence of the effectiveness and safety of investigational immunosuppressive agents in renal transplant recipients.