Immunosuppression with belatacept-based, corticosteroid-avoiding regimens in de novo kidney transplant recipients

Secondary lymphoid tissue and costimulation-blockade resistant rejection: A nonhuman primate renal transplant study

Naïve T cell activation requires antigen presentation combined with costimulation through CD28, both of which optimally occur in secondary lymphoid tissues such as lymph nodes and the spleen. Belatacept impairs CD28 costimulation by binding its ligands, CD80 and CD86, and in doing so, impairs de novo alloimmune responses. However, in most patients belatacept is ineffective in preventing allograft rejection when used as a monotherapy, and adjuvant therapy is required for control of costimulation-blockade resistant rejection (CoBRR). In rodent models, impaired access to secondary lymphoid tissues has been demonstrated to reduce alloimmune responses to vascularized allografts. Here we show that surgical maneuvers, lymphatic ligation, and splenectomy, designed to anatomically limit access to secondary lymphoid tissues, control CoBRR and facilitate belatacept monotherapy in a nonhuman primate model of kidney transplantation without adjuvant immunotherapy. We further demonstrate that animals sustained on belatacept monotherapy progressively develop an increasingly naïve T and B cell repertoire, an effect that is accelerated by splenectomy and lost at the time of belatacept withdrawal and rejection. These pilot data inform the role of secondary lymphoid tissues on the development of CoBRR and the use of costimulation molecule-focused therapies.

The past, present, and future of costimulation blockade in organ transplantation

PURPOSE OF REVIEW

Manipulating costimulatory signals has been shown to alter T cell responses and prolong graft survival in solid organ transplantation. Our understanding of and ability to target various costimulation pathways continues to evolve.

RECENT FINDINGS

Since the approval of belatacept in kidney transplantation, many additional biologics have been developed targeting clinically relevant costimulation signaling axes including CD40-CD40L, inducible costimulator-inducible costimulator ligand (ICOS-ICOSL), and OX40-OX40L. Currently, the effects of costimulation blockade on posttransplant humoral responses, tolerance induction, and xenotransplantation are under active investigation. Here, we will discuss these pathways as well as preclinical and clinical outcomes of biologics targeting these pathways in organ transplantation.

SUMMARY

Targeting costimultion is a promising approach for not only controlling T cell but also B cell responses. Consequently, costimulation blockade shows considerable potential for improving outcomes in antibody-mediated rejection and xenotransplantation.

Alemtuzumab induction and belatacept maintenance in marginal pathology renal allografts

We performed a prospective, 12-month, single-center, nonrandomized, open-label pilot study to investigate the use of belatacept therapy combined with alemtuzumab induction in renal allografts with preexisting pathology, as these kidneys may be more susceptible to additional toxicity when exposed to calcineurin inhibitors posttransplant. Nineteen belatacept recipients were matched retrospectively to a cohort of tacrolimus recipients on the basis of preimplantation pathology. The estimated glomerular filtration rate was not significantly different between belatacept and tacrolimus recipients at either 3 or 12 months posttransplant (59 vs 45, P = 0.1 and 56 vs 48 mL/min/1.72/m² , P = 0.3). Biopsy-proven acute rejection rates at 12 months were 26% in belatacept recipients and 16% in tacrolimus recipients (P = 0.7). Graft survival at 1 year was 89% in both groups. Alemtuzumab induction combined with either calcineurin inhibitor or costimulatory blockade therapies resulted in similar acceptable one-year outcomes in kidneys with preexisting pathologic changes. Longer-term follow-up may be necessary to identify preferential strategies to improve outcomes of kidneys at a higher risk for poor function (ClinicalTrials.gov-NCT01496417).

Belatacept in Solid Organ Transplant: Review of Current Literature Across Transplant Types

Calcineurin inhibitors (CNIs) have been the backbone immunosuppressant for solid organ transplant recipients for decades. Long-term use of CNIs unfortunately is associated with multiple toxicities, with the biggest concern being CNI-induced nephrotoxicity. Belatacept is a novel agent approved for maintenance immunosuppression in renal transplant recipients. In the kidney transplant literature, it has shown promise as being an alternative agent by preserving renal function and having a minimal adverse effect profile. There are emerging studies of its use in other organ groups, particularly liver transplantation, as well as using with other alternative immunosuppressive strategies. The purpose of this review is to analyze the current literature of belatacept use in solid organ transplantation and discuss its use in current practice.

The number of FoxP3 regulatory T cells in the circulation may be a predictive biomarker for kidney transplant recipients: A multistage systematic review

BACKGROUND

The kinetics of the FoxP3 regulatory T-cell (Treg) population in kidney transplant recipients (KTR) are related to the clinical effect of immunosuppression based on mammalian Target Of Rapamycin inhibitors (mTORi) with/without belatacept (predictive biomarker).

METHODS

A multistage systematic review of published and unpublished literature is presented [registration IDs in the International Prospective Register of Systematic Reviews (PROSPERO): CRD42017057570, CRD42018085019, CRD42018084941, CRD42018085186]. A multidisciplinary supervision mechanism for contextualizing of search findings was required. The peripheral blood immune cell phenotypes encompassing all regulatory cells in KTRs were assessed in order to suggest new markers of acute rejection-associated acute allograft dysfunction (AR/AAD) events in KTRs treated with mTORi alone or combined to belatacept. Quantitative estimates and evaluation of the body of evidence are provided.

RESULTS

An increase in Tregs and other regulatory cell types in the circulation in KTRs under mTORi with/without belatacept were observed. Patients with increased Tregs presented a low frequency of AR/AAD events compared to those in which the number of Tregs remained unchanged or even diminished [Odds Ratio (OR)/95% confidence interval (95% CI)/I²/number of studies (n): 0.31/0.10-0.93/0%/6]. Nevertheless, there are too few trials to consider Tregs in the circulation as a predictive biomarker. Inadequate reporting prevents appreciating clinical relevance in such studies.

CONCLUSIONS

Despite advances, clinical qualification of potential predictive biomarkers continues to be difficult. Clinical evidence on Tregs in KTRs needs to be enlarged. Biomarkers should be able to evaluate the effect of medicines targeted to specific patient populations.

Impact of reduced exposure to calcineurin inhibitors on the development of de novo DSA: a cohort of non-immunized first kidney graft recipients between 2007 and 2014

Background

In low-immunological risk kidney transplant recipients (KTRs), reduced exposure to calcineurin inhibitor (CNI) appears particularly attractive for avoiding adverse events, but may increase the risk of developing de novo Donor Specific Antibodies (dnDSA).

Methods

CNI exposure was retrospectively analyzed in 247 non-HLA immunized first KTRs by taking into account trough levels (C0) collected during follow-up. Reduced exposure to CNI was defined as follows: C0 less than the lower limit of the international targets for ≥50% of follow-up.

Results

During a mean follow-up of 5.0 ± 2.0 years, 39 patients (15.8%) developed dnDSA (MFI ≥1000). Patients with DSA were significantly younger (46.6 ± 13.8 vs. 51.7 ± 14.0 years, p = 0.039), received more frequently poorly-matched grafts (59% with 6–8 A-B-DR-DQ HLA mismatches vs. 34.6%, p = 0.016) and had more frequently a reduced exposure to CNI (92.3% vs. 62.0%, p = 0.0002). Reduced exposure to CNI was associated with an increased risk of dnDSA (multivariable HR = 9.77, p = 0.002). Reduced exposure to CNI had no effect on patient survival, graft loss from any cause including death, or post-transplant cancer.

Conclusions

Even in a low-immunological risk population, reduced exposure to CNI is associated with increased risk of dnDSA. Benefits and risks of under-immunosuppression must be carefully evaluated before deciding on CNI minimization.

De novo belatacept in clinical vascularized composite allotransplantation

Most immunosuppressive regimens used in clinical vascularized composite allotransplantation (VCA) have been calcineurin inhibitor (CNI)-based. As such, most recipients have experienced CNI-related side effects. Costimulation blockade, specifically CD28/B7 inhibition with belatacept, has emerged as a clinical replacement for CNI-based immunosuppression in kidney transplantation. We have previously shown that belatacept can be used as a centerpiece immunosuppressant for VCA in nonhuman primates, and subsequently reported successful conversion from a CNI-based regimen to a belatacept-based regimen after clinical hand transplantation. We now report on the case of a hand transplant recipient, whom we have successfully treated with a de novo belatacept-based regimen, transitioned to a CNI-free regimen. This case demonstrates that belatacept can provide sufficient prophylaxis from rejection without chronic CNI-associated side effects, a particularly important goal in nonlifesaving solid organ transplants such as VCA.

Belatacept/CTLA4Ig: an update and critical appraisal of preclinical and clinical results

INTRODUCTION

The B7/CD28/CTLA4 signaling cascade is the most thoroughly studied costimulatory pathway and blockade with CTLA4Ig (abatacept) or its derivative belatacept has emerged as a valuable option for pharmacologic immune modulation. Several clinical studies have ultimately led to the approval of belatacept for immunosuppression in kidney transplant recipients. Areas covered: This review will discuss the immunological background of costimulation blockade and recent preclinical data and clinical results of CTLA4Ig/belatacept. Expert commentary: The development of belatacept is a major advance in clinical transplantation. However, in spite of promising results in preclinical and clinical trials, clinical use remains limited at present, in part due to increased rates of acute rejection. Recent efforts showing encouraging progress in refining such protocols might be a step toward harnessing the full potential of costimulation blockade-based immunosuppression.

mTOR inhibitors and risk of chronic antibody-mediated rejection after kidney transplantation: where are we now?

Antibody-mediated rejection (AMR) usually starts with generation of donor-specific anti-HLA antibodies (DSAs), arising from a B-cell response to antigen recognition. In vitro and preclinical data demonstrate that mammalian target of rapamycin (mTOR) inhibition attenuates the mTOR-mediated intracellular signaling pathway involved in AMR-related kidney damage. The limited available data from immunological studies in kidney transplant patients, however, have not shown such effects in vivo. In terms of clinical immunosuppression, the overriding influence on rates of de novo DSA (dnDSA) or AMR-regardless of the type of regimen-is patient adherence. To date, limited data from patients given mTOR inhibitor therapy with adequate concurrent immunosuppression, such as reduced-exposure calcineurin inhibitor (CNI) therapy, have not shown an adverse effect on the risk of dnDSA or AMR. Early switch to an mTOR inhibitor (<6-12 months post-transplant) in a CNI-free regimen, in contrast, can increase the risk of dnDSA, especially if adjunctive therapy is inadequate. Late conversion to CNI-free therapy with mTOR inhibition does not appear to affect the risk of dnDSA. More data, from prospective studies, are required to fully understand that association between use of mTOR inhibitors with different types of concomitant therapy and risk of dnDSA and AMR.

Immunosuppressive therapy for kidney transplantation in adults: a systematic review and economic model

BACKGROUND

End-stage renal disease is a long-term irreversible decline in kidney function requiring renal replacement therapy: kidney transplantation, haemodialysis or peritoneal dialysis. The preferred option is kidney transplantation, followed by immunosuppressive therapy (induction and maintenance therapy) to reduce the risk of kidney rejection and prolong graft survival.

OBJECTIVES

To review and update the evidence for the clinical effectiveness and cost-effectiveness of basiliximab (BAS) (Simulect(®), Novartis Pharmaceuticals UK Ltd) and rabbit anti-human thymocyte immunoglobulin (rATG) (Thymoglobulin(®), Sanofi) as induction therapy, and immediate-release tacrolimus (TAC) (Adoport(®), Sandoz; Capexion(®), Mylan; Modigraf(®), Astellas Pharma; Perixis(®), Accord Healthcare; Prograf(®), Astellas Pharma; Tacni(®), Teva; Vivadex(®), Dexcel Pharma), prolonged-release tacrolimus (Advagraf(®) Astellas Pharma), belatacept (BEL) (Nulojix(®), Bristol-Myers Squibb), mycophenolate mofetil (MMF) (Arzip(®), Zentiva; CellCept(®), Roche Products; Myfenax(®), Teva), mycophenolate sodium (MPS) (Myfortic(®), Novartis Pharmaceuticals UK Ltd), sirolimus (SRL) (Rapamune(®), Pfizer) and everolimus (EVL) (Certican(®), Novartis) as maintenance therapy in adult renal transplantation.

METHODS

Clinical effectiveness searches were conducted until 18 November 2014 in MEDLINE (via Ovid), EMBASE (via Ovid), Cochrane Central Register of Controlled Trials (via Wiley Online Library) and Web of Science (via ISI), Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects and Health Technology Assessment (The Cochrane Library via Wiley Online Library) and Health Management Information Consortium (via Ovid). Cost-effectiveness searches were conducted until 18 November 2014 using a costs or economic literature search filter in MEDLINE (via Ovid), EMBASE (via Ovid), NHS Economic Evaluation Database (via Wiley Online Library), Web of Science (via ISI), Health Economic Evaluations Database (via Wiley Online Library) and the American Economic Association's electronic bibliography (via EconLit, EBSCOhost). Included studies were selected according to predefined methods and criteria. A random-effects model was used to analyse clinical effectiveness data (odds ratios for binary data and mean differences for continuous data). Network meta-analyses were undertaken within a Bayesian framework. A new discrete time-state transition economic model (semi-Markov) was developed, with acute rejection, graft function (GRF) and new-onset diabetes mellitus used to extrapolate graft survival. Recipients were assumed to be in one of three health states: functioning graft, graft loss or death.

RESULTS

Eighty-nine randomised controlled trials (RCTs), of variable quality, were included. For induction therapy, no treatment appeared more effective than another in reducing graft loss or mortality. Compared with placebo/no induction, rATG and BAS appeared more effective in reducing biopsy-proven acute rejection (BPAR) and BAS appeared more effective at improving GRF. For maintenance therapy, no treatment was better for all outcomes and no treatment appeared most effective at reducing graft loss. BEL + MMF appeared more effective than TAC + MMF and SRL + MMF at reducing mortality. MMF + CSA (ciclosporin), TAC + MMF, SRL + TAC, TAC + AZA (azathioprine) and EVL + CSA appeared more effective than CSA + AZA and EVL + MPS at reducing BPAR. SRL + AZA, TAC + AZA, TAC + MMF and BEL + MMF appeared to improve GRF compared with CSA + AZA and MMF + CSA. In the base-case deterministic and probabilistic analyses, BAS, MMF and TAC were predicted to be cost-effective at £20,000 and £30,000 per quality-adjusted life-year (QALY). When comparing all regimens, only BAS + TAC + MMF was cost-effective at £20,000 and £30,000 per QALY.

LIMITATIONS

For included trials, there was substantial methodological heterogeneity, few trials reported follow-up beyond 1 year, and there were insufficient data to perform subgroup analysis. Treatment discontinuation and switching were not modelled.

FUTURE WORK

High-quality, better-reported, longer-term RCTs are needed. Ideally, these would be sufficiently powered for subgroup analysis and include health-related quality of life as an outcome.

CONCLUSION

Only a regimen of BAS induction followed by maintenance with TAC and MMF is likely to be cost-effective at £20,000-30,000 per QALY.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42014013189.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Immunosuppressive therapy for kidney transplantation in children and adolescents: systematic review and economic evaluation

BACKGROUND

End-stage renal disease is a long-term irreversible decline in kidney function requiring kidney transplantation, haemodialysis or peritoneal dialysis. The preferred option is kidney transplantation followed by induction and maintenance immunosuppressive therapy to reduce the risk of kidney rejection and prolong graft survival.

OBJECTIVES

To systematically review and update the evidence for the clinical effectiveness and cost-effectiveness of basiliximab (BAS) (Simulect,(®) Novartis Pharmaceuticals) and rabbit antihuman thymocyte immunoglobulin (Thymoglobuline,(®) Sanofi) as induction therapy and immediate-release tacrolimus [Adoport(®) (Sandoz); Capexion(®) (Mylan); Modigraf(®) (Astellas Pharma); Perixis(®) (Accord Healthcare); Prograf(®) (Astellas Pharma); Tacni(®) (Teva); Vivadex(®) (Dexcel Pharma)], prolonged-release tacrolimus (Advagraf,(®) Astellas Pharma); belatacept (BEL) (Nulojix,(®) Bristol-Myers Squibb), mycophenolate mofetil (MMF) [Arzip(®) (Zentiva), CellCept(®) (Roche Products), Myfenax(®) (Teva), generic MMF is manufactured by Accord Healthcare, Actavis, Arrow Pharmaceuticals, Dr Reddy's Laboratories, Mylan, Sandoz and Wockhardt], mycophenolate sodium, sirolimus (Rapamune,(®) Pfizer) and everolimus (Certican,(®) Novartis Pharmaceuticals) as maintenance therapy in children and adolescents undergoing renal transplantation.

DATA SOURCES

Clinical effectiveness searches were conducted to 7 January 2015 in MEDLINE (via Ovid), EMBASE (via Ovid), Cochrane Central Register of Controlled Trials (via Wiley Online Library) and Web of Science [via Institute for Scientific Information (ISI)], Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects and Health Technology Assessment (HTA) (The Cochrane Library via Wiley Online Library) and Health Management Information Consortium (via Ovid). Cost-effectiveness searches were conducted to 15 January 2015 using a costs or economic literature search filter in MEDLINE (via Ovid), EMBASE (via Ovid), NHS Economic Evaluation Databases (via Wiley Online Library), Web of Science (via ISI), Health Economic Evaluations Database (via Wiley Online Library) and EconLit (via EBSCOhost).

REVIEW METHODS

Titles and abstracts were screened according to predefined inclusion criteria, as were full texts of identified studies. Included studies were extracted and quality appraised. Data were meta-analysed when appropriate. A new discrete time state transition economic model (semi-Markov) was developed; graft function, and incidences of acute rejection and new-onset diabetes mellitus were used to extrapolate graft survival. Recipients were assumed to be in one of three health states: functioning graft, graft loss or death.

RESULTS

Three randomised controlled trials (RCTs) and four non-RCTs were included. The RCTs only evaluated BAS and tacrolimus (TAC). No statistically significant differences in key outcomes were found between BAS and placebo/no induction. Statistically significantly higher graft function (p < 0.01) and less biopsy-proven acute rejection (odds ratio 0.29, 95% confidence interval 0.15 to 0.57) was found between TAC and ciclosporin (CSA). Only one cost-effectiveness study was identified, which informed NICE guidance TA99. BAS [with TAC and azathioprine (AZA)] was predicted to be cost-effective at £20,000-30,000 per quality-adjusted life year (QALY) versus no induction (BAS was dominant). BAS (with CSA and MMF) was not predicted to be cost-effective at £20,000-30,000 per QALY versus no induction (BAS was dominated). TAC (with AZA) was predicted to be cost-effective at £20,000-30,000 per QALY versus CSA (TAC was dominant). A model based on adult evidence suggests that at a cost-effectiveness threshold of £20,000-30,000 per QALY, BAS and TAC are cost-effective in all considered combinations; MMF was also cost-effective with CSA but not TAC.

LIMITATIONS

The RCT evidence is very limited; analyses comparing all interventions need to rely on adult evidence.

CONCLUSIONS

TAC is likely to be cost-effective (vs. CSA, in combination with AZA) at £20,000-30,000 per QALY. Analysis based on one RCT found BAS to be dominant, but analysis based on another RCT found BAS to be dominated. BAS plus TAC and AZA was predicted to be cost-effective at £20,000-30,000 per QALY when all regimens were compared using extrapolated adult evidence. High-quality primary effectiveness research is needed. The UK Renal Registry could form the basis for a prospective primary study.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42014013544.

FUNDING

The National Institute for Health Research HTA programme.

Current status of costimulatory blockade in renal transplantation

PURPOSE OF REVIEW

The review will focus on the impact and current status of costimulatory blockade in renal transplantation.

RECENT FINDINGS

The mainstay of immunosuppression in kidney transplantation is calcineurin inhibitors (CNIs) which have reduced acute rejection rates but failed to improve long-term allograft survival. Their cardiometabolic side-effects and nephrotoxicity have shifted the focus of investigation to CNI-free regimens. Costimulation blockade with belatacept, a second generation, higher avidity variant of cytotoxic T-lymphocyte associated protein 4 has emerged as part of a CNI-free regimen. Belatacept has demonstrated superior glomerular filtration rate compared with CNIs, albeit with an increased risk of early and histologically severe rejection. Focus on optimizing the belatacept regimen is underway. ASKP1240, which blocks the cluster of differentiation 40 (CD40)/CD154 costimulatory pathway, has just completed a phase 2 trial with a CNI-free regimen. CFZ533, an anti-CD40, is also poised to be tested in a phase 2 trial in renal transplantation. Nonagonistic CD28 antibodies have re-emerged with two anti-CD28 candidates in preclinical development.

SUMMARY

A reliable, CNI-free regimen that maintains low acute rejection rates and improves long-term renal allograft survival has become an achievable goal with costimulation blockade. The task of clinicians and researchers is to find the optimal combinations to maintain safety and improve efficacy.

Early Conversion from Tacrolimus to Belatacept in a Highly Sensitized Renal Allograft Recipient with Calcineurin Inhibitor-Induced de novo Post-Transplant Hemolytic Uremic Syndrome

BACKGROUND

Kidney transplantation is the first-line therapy for patients with end-stage renal disease since it offers greater long-term survival and improved quality of life when compared to dialysis. The advent of calcineurin inhibitor (CNI)-based maintenance immunosuppression has led to a clinically significant decline in the rate of acute rejection and better short-term graft survival rates. However, these gains have not translated into improvement in long-term graft survival. CNI-related nephrotoxicity and metabolic side effects are thought to be partly responsible for this.

CASE PRESENTATION

Here, we report the conversion of a highly sensitized renal transplant recipient with pretransplant donor-specific antibodies from tacrolimus to belatacept within 1 week of transplantation. This substitution was necessitated by the diagnosis of CNI-induced de novo post-transplant hemolytic uremic syndrome.

CONCLUSION

Belatacept is a novel costimulation blocker that is devoid of the nephrotoxic properties of CNIs and has been shown to positively impact long-term graft survival and preserve renal allograft function in low-immunologic-risk kidney transplant recipients. Data regarding its use in patients who are broadly sensitized to human leukocyte antigens are scarce, and the increased risk of rejection associated with belatacept has been a deterrent to more widespread use of this immunosuppressive agent. This case serves as an example of a highly sensitized patient that has been successfully converted to a belatacept-based CNI-free regimen.

Belatacept Combined With Transient Calcineurin Inhibitor Therapy Prevents Rejection and Promotes Improved Long-Term Renal Allograft Function

Belatacept, a T cell costimulation blocker, demonstrated superior renal function, lower cardiovascular risk, and improved graft and patient survival in renal transplant recipients. Despite the potential benefits, adoption of belatacept has been limited in part due to concerns regarding higher rates and grades of acute rejection in clinical trials. Since July 2011, we have utilized belatacept-based immunosuppression regimens in clinical practice. In this retrospective analysis of 745 patients undergoing renal transplantation at our center, we compared patients treated with belatacept (n = 535) with a historical cohort receiving a tacrolimus-based protocol (n = 205). Patient and graft survival were equivalent for all groups. An increased rate of acute rejection was observed in an initial cohort treated with a protocol similar to the low-intensity regimen from the BENEFIT trial versus the historical tacrolimus group (50.5% vs. 20.5%). The addition of a transient course of tacrolimus reduced rejection rates to acceptable levels (16%). Treatment with belatacept was associated with superior estimated GFR (belatacept 63.8 mL/min vs. tacrolimus 46.2 mL/min at 4 years, p < 0.0001). There were no differences in serious infections including rates of cytomegalovirus or BK viremia. We describe the development of a costimulatory blockade-based strategy that ultimately allows renal transplant recipients to achieve calcineurin inhibitor-free immunosuppression.

The Role of Costimulation Blockade in Solid Organ and Islet Xenotransplantation

Pig-to-human xenotransplantation offers a potential bridge to the growing disparity between patients with end-stage organ failure and graft availability. Early studies attempting to overcome cross-species barriers demonstrated robust humoral immune responses to discordant xenoantigens. Recent advances have led to highly efficient and targeted genomic editing, drastically altering the playing field towards rapid production of less immunogenic porcine tissues and even the discussion of human xenotransplantation trials. However, as these humoral immune barriers to cross-species transplantation are overcome with advanced transgenics, cellular immunity to these novel xenografts remains an outstanding issue. Therefore, understanding and optimizing immunomodulation will be paramount for successful clinical xenotransplantation. Costimulation blockade agents have been introduced in xenotransplantation research in 2000 with anti-CD154mAb. Most recently, prolonged survival has been achieved in solid organ (kidney xenograft survival > 400 days with anti-CD154mAb, heart xenograft survival > 900 days, and liver xenograft survival 29 days with anti-CD40mAb) and islet xenotransplantation (>600 days with anti-CD154mAb) with the use of these potent experimental agents. As the development of novel genetic modifications and costimulation blocking agents converges, we review their impact thus far on preclinical xenotransplantation and the potential for future application.

Lessons Learned: Early Termination of a Randomized Trial of Calcineurin Inhibitor and Corticosteroid Avoidance Using Belatacept

The intent of this National Institutes of Health-sponsored study was to compare a belatacept-based immunosuppressive regimen with a maintenance regimen of tacrolimus and mycophenolate. Nineteen primary, Epstein-Barr virus-immune renal transplant recipients with a negative cross-match were randomized to one of three groups. All patient groups received perioperative steroids and maintenance mycophenolate mofetil. Patients in groups 1 and 2 were induced with alemtuzumab and maintained on tacrolimus or belatacept, respectively. Patients in group 3 were induced with basiliximab, received 3 mo of tacrolimus, and maintained on belatacept. There was one death with a functioning allograft due to endocarditis (group 1). There were three graft losses due to vascular thrombosis (all group 2) and one graft loss due to glomerular disease (group 1). Biopsy-proven acute cellular rejection was more frequent in the belatacept-treated groups, with 10 treated episodes in seven participants compared with one episode in group 1; however, estimated GFR was similar between groups at week 52. There were no episodes of posttransplant lymphoproliferative disorder or opportunistic infections in any group. Protocol enrollment was halted prematurely because of a high rate of serious adverse events. Such negative outcomes pose challenges to clinical investigators, who ultimately must weigh the risks and benefits in randomized trials.

A Randomized Controlled Clinical Trial Comparing Belatacept With Tacrolimus After De Novo Kidney Transplantation

BACKGROUND

Belatacept, an inhibitor of the CD28-CD80/86 costimulatory pathway, allows for calcineurin-inhibitor free immunosuppressive therapy in kidney transplantation but is associated with a higher acute rejection risk than ciclosporin. Thus far, no biomarker for belatacept-resistant rejection has been validated. In this randomized-controlled trial, acute rejection rate was compared between belatacept- and tacrolimus-treated patients and immunological biomarkers for acute rejection were investigated.

METHODS

Forty kidney transplant recipients were 1:1 randomized to belatacept or tacrolimus combined with basiliximab, mycophenolate mofetil, and prednisolone. The 1-year incidence of biopsy-proven acute rejection was monitored. Potential biomarkers, namely, CD8CD28, CD4CD57PD1, and CD8CD28 end-stage terminally differentiated memory T cells were measured pretransplantation and posttransplantation and correlated to rejection. Pharmacodynamic monitoring of belatacept was performed by measuring free CD86 on monocytes.

RESULTS

The rejection incidence was higher in belatacept-treated than tacrolimus-treated patients: 55% versus 10% (P = 0.006). All 3 graft losses, due to rejection, occurred in the belatacept group. Although 4 of 5 belatacept-treated patients with greater than 35 cells CD8CD28 end-stage terminally differentiated memory T cells/μL rejected, median pretransplant values of the biomarkers did not differ between belatacept-treated rejectors and nonrejectors. In univariable Cox regressions, the studied cell subsets were not associated with rejection-risk. CD86 molecules on circulating monocytes in belatacept-treated patients were saturated at all timepoints.

CONCLUSIONS

Belatacept-based immunosuppressive therapy resulted in higher and more severe acute rejection compared with tacrolimus-based therapy. This trial did not identify cellular biomarkers predictive of rejection. In addition, the CD28-CD80/86 costimulatory pathway appeared to be sufficiently blocked by belatacept and did not predict rejection.

Belatacept Compared With Tacrolimus for Kidney Transplantation: A Propensity Score Matched Cohort Study

BACKGROUND

Although tacrolimus is the basis of most maintenance immunosuppression regimens for kidney transplantation, concerns about toxicity have made alternative agents, such as belatacept, attractive to clinicians. However, limited data exist to directly compare outcomes with belatacept-based regimens to tacrolimus.

METHODS

We performed a propensity score matched cohort study of adult kidney transplant recipients transplanted between May 1, 2001, and December 31, 2015, using national transplant registry data to compare patient and allograft survival in patients discharged from their index hospitalization on belatacept-based versus tacrolimus-based regimens.

RESULTS

In the primary analysis, we found that belatacept was not associated with a statistically significant difference in risk of patient death (hazard ratio, 0.84; 95% confidence interval [CI], 0.61-1.15, P = 0.28) or allograft loss (hazard ratio, 0.83; 95% CI, 0.62-1.11; P = 0.20) despite an increased risk of acute rejection in the first year posttransplant (odds ratio, 3.12; 95% CI, 2.13-4.57; P < 0.001). These findings were confirmed in additional sensitivity analyses that accounted for use of belatacept in combination with tacrolimus, transplant center effects, and differing approaches to matching.

CONCLUSIONS

Belatacept appears to have similar longitudinal risk of mortality and allograft failure compared with tacrolimus-based regimens. These data are encouraging but require confirmation in prospective randomized controlled trials.

Successful Treatment of T Cell-Mediated Acute Rejection with Delayed CTLA4-Ig in Mice

Clinical observations that kidney transplant recipients receiving belatacept who experienced T cell-mediated acute rejection can be successfully treated and subsequently maintained on belatacept-based immunosuppression suggest that belatacept is able to control memory T cells. We recently reported that treatment with CTLA4-Ig from day 6 posttransplantation successfully rescues allografts from acute rejection in a BALB/c to C57BL/6 heart transplant model, in part, by abolishing B cell germinal centers and reducing alloantibody titers. Here, we show that CTLA4-Ig is additionally able to inhibit established T cell responses independently of B cells. CTLA4-Ig inhibited the in vivo cytolytic activity of donor-specific CD8⁺ T cells, and the production of IFNγ by graft-infiltrating T cells. Delayed CTLA4-Ig treatment did not reduce the numbers of graft-infiltrating T cells nor prevented the accumulation of antigen-experienced donor-specific memory T cells in the spleen. Nevertheless, delayed CTLA4-Ig treatment successfully maintained long-term graft acceptance in the majority of recipients that had experienced a rejection crisis, and enabled the acceptance of secondary BALB/c heart grafts transplanted 30 days after the first transplantation. In summary, we conclude that delayed CTLA4-Ig treatment is able to partially halt ongoing T cell-mediated acute rejection. These findings extend the functional efficacy of CTLA4-Ig therapy to effector T cells and provide an explanation for why CTLA4-Ig-based immunosuppression in the clinic successfully maintains long-term graft survival after T cell-mediated rejection.

Belatacept As an Alternative to Calcineurin Inhibitors in Patients with Solid Organ Transplants

The goal of immunosuppression in transplantation has shifted to improving long-term outcomes, reducing drug-induced toxicities while preserving the already excellent short-term outcomes. Long-term gains in solid organ transplantation have been limited at least partly due to the nephrotoxicity and metabolic side effects of calcineurin inhibitors (CNIs). The alloimmune response requires activation of the costimulatory pathway for T cell proliferation and amplification. Belatacept is a molecule that selectively blocks T cell costimulation. In June 2011, the U.S. Food and Drug Administration approved it for maintenance immunosuppression in kidney transplantation based on two open-label, randomized, phase III trials. Since its introduction, belatacept has shown promise in both short- and long-term renal transplant outcomes in several other trials. It exhibits a superior side effect profile compared to CNIs with a comparable efficacy. Across all solid organ transplants, the burden of chronic kidney disease, its associated cardiovascular morbidity, mortality, and inferior patient/allograft survival is a well-documented problem. In this review, we aim to discuss the evidence behind the use of belatacept in solid organ transplants as an effective alternative to CNIs for renal rescue in patients with acute and/or chronic kidney injury.

Belatacept after kidney transplantation in adolescents: a retrospective study

Regardless of recipient age at kidney transplantation (KTx), patients are at greatest risk for graft loss in adolescence, partly due to nonadherence to an oral immunosuppressive regimen. Belatacept, a non-nephrotoxic, first-in-class immunosuppressant that inhibits costimulation of T cells requires intravenous application only every 4 weeks, potentially leading to better adherence. However, it is only approved for use in adults. We report here the findings of the first study of belatacept in adolescents, comprising all patients in our department switched to belatacept post-KTx. Six patients (median age 15.5 years) were switched after a median of 7.5 months (range 23 days to 12 years), treatment range 3-28 months (cumulative 83 months): Three patients switched early (<3 months after KTx) had increased estimated glomerular filtration rate (GFR); one patient switched 12 years post-KTx has stable GFR; two patients were switched following rapid decline of and with markedly impaired GFR, changing slope in one patient. One patient had one acute rejection. In addition of two patients who received belatacept for other conditions, the only relevant adverse event was neutropenia (after a cumulative 109 months). Belatacept as primary immunosuppression is an option in Epstein-Barr virus-seropositive nonadherent adolescents if administered sufficiently early before deterioration of graft function.

Costimulation Blockade in Kidney Transplantation: An Update

In the setting of solid-organ transplantation, calcineurin inhibitor (CNI)-based therapy remains the cornerstone of immunosuppression. However, long-term use of CNIs is associated with some degree of nephrotoxicity. This has led to exploring the blockade of some costimulation pathways as an efficient immunosuppressive tool instead of using CNIs. The only agent already in clinical use and approved by the health authorities for kidney transplant patients is belatacept (Nulojix), a fusion protein that interferes with cytotoxic T lymphocyte-associated protein 4. Belatacept has been demonstrated to be as efficient as cyclosporine-based immunosuppression and is associated with significantly better renal function, that is, no nephrotoxicity. However, in the immediate posttransplant period, significantly more mild/moderate episodes of acute rejection have been reported, favored by the fact that cytotoxic T lymphocyte-associated protein pathway has an inhibitory effect on the alloimmune response; thereby its inhibition is detrimental in this regard. This has led to the development of antibodies that target CD28. The most advanced is FR104, it has shown promise in nonhuman primate models of autoimmune diseases and allotransplantation. In addition, research into blocking the CD40-CD154 pathway is underway. A phase II study testing ASK1240, that is, anti-CD40 antibody has been completed, and the results are pending.

Prediction, prevention, and management of delayed graft function: where are we now?

Delayed graft function (DGF) remains a major barrier to improved outcomes after kidney transplantation. High-risk transplant recipients can be identified, but no definitive prediction model exists. Novel biomarkers to predict DGF in the first hours post-transplant, such as neutrophil gelatinase-associated lipocalin (NGAL), are under investigation. Donor management to minimize the profound physiological consequences of brain death is highly complex. A hormonal resuscitation package to manage the catecholamine "storm" that follows brain death is recommended. Donor pretreatment with dopamine prior to procurement lowers the rate of DGF. Hypothermic machine perfusion may offer a significant reduction in the rate of DGF vs simple cold storage, but costs need to be evaluated. Surgically, reducing warm ischemia time may be advantageous. Research into recipient preconditioning options has so far not generated clinically helpful interventions. Diagnostic criteria for DGF vary, but requirement for dialysis and/or persistent high serum creatinine is likely to remain key to diagnosis until current work on early biomarkers has progressed further. Management centers on close monitoring of graft (non)function and physiological parameters. With so many unanswered questions, substantial reductions in the toll of DGF in the near future seem unlikely but concentrated research on many levels offers long-term promise.

Costimulatory Blockade and Use of mTOR Inhibitors: Avoiding Injury Part 2

Kidney transplantation immunosuppression relies on a calcineurin inhibitor backbone. Calcineurin inhibitors have reduced early-acute rejection rates but failed to improve long-term allograft survival. Their nephrotoxicity has shifted the focus of investigation to calcineurin inhibitor-free regimens. Costimulation blockade with belatacept, a second generation, higher avidity variant of CTLA4-Ig, has emerged as part of a calcineurin inhibitor-free regimen. Belatacept has demonstrated superior glomerular filtration rate compared with calcineurin inhibitors albeit with an increased risk of early and histologically severe rejection. Focus on optimizing the belatacept regimen to reduce the acute rejection rate while maintaining superior renal function is underway. Belatacept has also been utilized as part of a calcineurin inhibitor-free conversion strategy in stable renal transplant recipients and has demonstrated superior improvement in glomerular filtration rate with conversion vs calcineurin inhibitor continuation. Additional work is underway to better define the role of belatacept in patients on calcineurin inhibitors with allograft dysfunction not due to rejection.

Immunosuppression Minimization and Avoidance Protocols: When Less Is Not More

Kidney transplantation is well established as the best treatment option for end-stage kidney disease. It confers not only a better quality of life but also a significant survival advantage compared to dialysis. However, despite significant improvement in short-term kidney transplant graft survival over the past three decades, long-term graft survival remains suboptimal. Concerns about the possible contribution of chronic calcineurin inhibitor (CNI) nephrotoxicity to late allograft failure and other serious adverse effects of currently used immunosuppressive agents (especially corticosteroids) have led to increasing interest in developing regimens which may better preserve kidney allograft function and minimize other immunosuppression-related problems without increasing the risk of rejection. The availability of newer immunosuppressive agents has provided the opportunity to formulate such regimens. Approaches to this end include minimization, withdrawal, or avoidance of corticosteroids and CNIs. Currently, replacement of a CNI with a mammalian target of rapamycin inhibitor while continuing mycophenolate and discontinuation of corticosteroids within the first post-transplant week is being increasingly utilized. Belatacept-based, CNI-free immunosuppression is an emerging alternative approach to avoiding CNI-mediated nephrotoxicity. We also discuss the evolution, results, and pros and cons of corticosteroid- and CNI minimization protocols. Recent studies suggest that chronic alloimmune damage rather than chronic CNI nephrotoxicity is the major contributor to late kidney allograft failure. The implications of this finding for the use of CNI minimization protocols are also discussed.

A safety evaluation of belatacept for the treatment of kidney transplant

INTRODUCTION

Improving long-term survival in kidney transplantation is one of the main goals in modern immunosuppressive research. Current standard immunosuppression based in a combination of calcineurin inhibitors (CNI) and antiproliferatives, with or without steroids, has improved short-term graft survival. In the last decade, belatacept has been evaluated as a CNI free option regimen addressing better kidney transplant outcomes.

AREAS COVERED

This paper reviewed the indications, mechanisms of action, pharmacology and published trials using belatacept in different clinical situations. The main objective was to evaluate the safety of this immunosuppressive drug.

EXPERT OPINION

Kidney transplant patients receiving belatacept demonstrated improvement in renal function, less chronic allograft nephropathy, a more favorable metabolic profile and lower donor-specific antibody formation compared with cyclosporine. Based on the published data and on our personal experience, we have good expectations on belatacept use in the future. If these characteristics will translate in sustained better renal function, less chronic kidney disease-related complications and lower cardiovascular risk, improving patient and graft survival and quality of life, is still to be assessed with longer term follow-up and a larger number of exposed patients.

Belatacept for the prophylaxis of organ rejection in kidney transplant patients: an evidence-based review of its place in therapy

BACKGROUND

Belatacept is a novel immunosuppressive therapy designed to improve clinical outcomes associated with kidney transplant recipients while minimizing use of calcineurin inhibitors (CNIs).

METHODS

We searched for clinical trials related to administration of belatacept to kidney transplant patients compared to various immunosuppression regimens, as well as for studies that utilized data from belatacept trials to validate new surrogate measures. The purpose of this review is to consolidate the published evidence of belatacept's effectiveness and safety in renal transplant recipients to better elucidate its place in clinical practice.

RESULTS

Analysis of the results from the Belatacept Evaluation of Nephroprotection and Effi-cacy as First-Line Immunosuppressive Trial (BENEFIT) study, a de novo trial that compared cyclosporine (CsA)-based therapy to belatacept-based therapy in standard criteria donors, found a significant difference in mean estimated glomerular filtration rate (eGFR) of 13-15 mL/min/1.73 m(2) and 23-27 mL/min/1.73 m(2) at 1 year and 7 years, respectively. The BENEFIT-EXT study was similarly designed with the exception that it included extended criteria donors. Renal function improved significantly for the more intensive belatacept group in all years of the BENEFIT-EXT study; however, it was not significant in the less intensive group until 5 years after transplant. Belatacept regimens resulted in lower blood pressure, cholesterol levels, and incidence of new-onset diabetes after transplant compared to CsA-based regimens. Results from conversion of CNIs to belatacept therapy, dual therapy of belatacept with sirolimus, and belatacept with corticosteroid avoidance therapy are also included in this article.

CONCLUSION

The evidence reviewed in this article suggests that belatacept is an effective alternative in kidney transplant recipients. Compared to CNI-based therapy, belatacept-based therapy results in superior renal function and similar rates of allograft survival. In terms of safety, belatacept was shown to have lower incidence of hypertension, hyperlipidemia, and diabetes; however, incidence of posttransplantation lymphoproliferative disorder and the cost of belatacept may hinder use of this medication.

Cell Therapy for Prophylactic Tolerance in Immunoglobulin E-mediated Allergy

Background

Therapeutic strategies for the prophylaxis of IgE-mediated allergy remain an unmet medical need. Cell therapy is an emerging approach with high potential for preventing and treating immunological diseases.

We aimed to develop a cell-based therapy inducing permanent allergen-specific immunological tolerance for preventing IgE-mediated allergy.

Methods

Wild-type mice were treated with allergen-expressing bone marrow cells under a short course of tolerogenic immunosuppression (mTOR inhibition and costimulation blockade). Bone marrow was retrieved from a novel transgenic mouse ubiquitously expressing the major grass pollen allergen Phl p 5 as a membrane-anchored protein (BALB/c-Tg[Phlp5-GFP], here mPhl p 5). After transplantation recipients were IgE-sensitized at multiple time points with Phl p 5 and control allergen.

Results

Mice treated with mPhl p 5 bone marrow did not develop Phl p 5-specific IgE (or other isotypes) despite repeated administration of the allergen, while mounting and maintaining a strong humoral response towards the control allergen. Notably, Phl p 5-specific T cell responses and allergic airway inflammation were also completely prevented. Interestingly allergen-specific B cell tolerance was maintained independent of Treg functions indicating deletional tolerance as underlying mechanism.

Conclusion

This proof-of-concept study demonstrates that allergen-specific immunological tolerance preventing occurrence of allergy can be established through a cell-based therapy employing allergen-expressing leukocytes.

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Avoidance of IgE-mediated allergy is established by development of a tolerogenic cell-based protocol.

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Transplantation of syngeneic allergen-bearing bone marrow cells into recipients leads to tolerance towards the introduced allergen.

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Prevention of T-and B-cell responses and allergic asthma is induced by cell transfer with non-toxic pretreatment.

IgE-mediated allergy affects about 30% of the population in industrialized countries. To prevent allergy we developed a cell-based protocol with the concept to modify body's own cells to express an allergen and to reinfuse those modified cells. This concept leads to avoidance of allergic reactions after allergen contact such as specific IgE production and the development of allergic asthma. This is demonstrated in a syngeneic model in mice (i.e. autologous in human) by transplanting bone marrow cells of a unique allergen-expressing transgenic mouse into pretreated recipients.

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.

Belatacept prophylaxis against organ rejection in adult kidney-transplant recipients

End-stage renal disease is a major health problem worldwide, with kidney transplantation being the treatment of choice. Calcineurin inhibitors are still the cornerstone of immunosuppressive therapy. However, they have well-known nephrotoxic affects and increase the risk of cardiovascular disease and cancer. In contrast, belatacept is a biological immunosuppressive agent that inhibits the T-cell co-stimulation. It is approved by the US Food and Drug Administration and the European Medicine Agency for use in adult kidney-transplant recipients to prevent acute rejection. Developmental studies show that belatacept is as efficient as calcineurin inhibitors at preventing acute rejection. In addition, kidney function is better and cardiovascular risk factors are reduced in patients given belatacept. Herein, the authors review the published evidence concerning the efficacy and safety of belatacept and discuss its potential specific indications.

A Randomized 2x2 Factorial Clinical Trial of Renal Transplantation: Steroid-Free Maintenance Immunosuppression with Calcineurin Inhibitor Withdrawal after Six Months Associates with Improved Renal Function and Reduced Chronic Histopathology

INTRODUCTION

The two most significant impediments to renal allograft survival are rejection and the direct nephrotoxicity of the immunosuppressant drugs required to prevent it. Calcineurin inhibitors (CNI), a mainstay of most immunosuppression regimens, are particularly nephrotoxic. Until less toxic antirejection agents become available, the only option is to optimize our use of those at hand.

AIM

To determine whether intensive rabbit anti-thymocyte globulin (rATG) induction followed by CNI withdrawal would individually or combined improve graft function and reduce graft chronic histopathology-surrogates for graft and, therefore, patient survival. As previously reported, a single large rATG dose over 24 hours was well-tolerated and associated with better renal function, fewer infections, and improved patient survival. Here we report testing whether complete CNI discontinuation would improve renal function and decrease graft pathology.

METHODS

Between April 20, 2004 and 4-14-2009 we conducted a prospective, randomized, non-blinded renal transplantation trial of two rATG dosing protocols (single dose, 6 mg/kg vs. divided doses, 1.5 mg/kg every other day x 4; target enrollment = 180). Subsequent maintenance immunosuppression consisted of tacrolimus, a CNI, and sirolimus, a mammalian target of rapamycin inhibitor. We report here the outcome of converting patients after six months either to minimized tacrolimus/sirolimus or mycophenolate mofetil/sirolimus. Primary endpoints were graft function and chronic histopathology from protocol kidney biopsies at 12 and 24 months.

RESULTS

CNI withdrawal (on-treatment analysis) associated with better graft function (p <0.001) and lower chronic histopathology composite scores in protocol biopsies at 12 (p = 0.003) and 24 (p = 0.013) months, without affecting patient (p = 0.81) or graft (p = 0.93) survival, or rejection rate (p = 0.17).

CONCLUSION

CNI (tacrolimus) withdrawal at six months may provide a strategy for decreased nephrotoxicity and improved long-term function in steroid-free low immunological risk renal transplant patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00556933.

Does belatacept improve outcomes for kidney transplant recipients? A systematic review

BACKGROUND

Belatacept was intended to provide better outcomes for kidney transplant (KT) recipients by allowing minimization/withdrawal of calcineurin inhibitors (CNI) and steroids.

METHODS

We searched for randomized controlled trials (RCTs) in adult KT comparing belatacept with CNIs. Methodological quality was assessed. Meta-analyses were performed to calculate odds ratios (OR) and mean differences (MD).

RESULTS

Six RCTs were included. Pooled analyses found no differences for acute rejection at any time point. Renal function [Calculated glomerular filtration rate (cGFR)] was better with belatacept at 12 and 24 months (MD = 11.7 and 13.7 ml/min/1.73 m(2) ). New onset diabetes after transplantation was lower with belatacept at 12 months (OR = 0.43). Systolic and diastolic blood pressures were lower at 12 months (MD -7.2 and -3.1 mmHg) as were triglycerides at 12 and 24 months (MD = -32.9 and -41.7 mg/dl). Total and low-density lipoprotein cholesterol were lower with belatacept at 24 months (MD = -19.8 and -10.6 mg/dl). There were no differences for other outcomes.

CONCLUSION

Limited available data suggest a potential benefit for belatacept by reducing the risk of CNI toxicity, especially renal function, without evidence of increased acute rejection. There were no safety issues apart from a possible risk of post-transplant lymphoproliferative disorder in Epstein-barr virus-seronegative recipients. Further studies are required to confirm this benefit.

New directions for rabbit antithymocyte globulin (Thymoglobulin(®)) in solid organ transplants, stem cell transplants and autoimmunity

In the 30 years since the rabbit antithymocyte globulin (rATG) Thymoglobulin^® was first licensed, its use in solid organ transplantation and hematology has expanded progressively. Although the evidence base is incomplete, specific roles for rATG in organ transplant recipients using contemporary dosing strategies are now relatively well-identified. The addition of rATG induction to a standard triple or dual regimen reduces acute cellular rejection, and possibly humoral rejection. It is an appropriate first choice in patients with moderate or high immunological risk, and may be used in low-risk patients receiving a calcineurin inhibitor (CNI)-sparing regimen from time of transplant, or if early steroid withdrawal is planned. Kidney transplant patients at risk of delayed graft function may also benefit from the use of rATG to facilitate delayed CNI introduction. In hematopoietic stem cell transplantation, rATG has become an important component of conventional myeloablative conditioning regimens, following demonstration of reduced acute and chronic graft-versus-host disease. More recently, a role for rATG has also been established in reduced-intensity conditioning regimens. In autoimmunity, rATG contributes to the treatment of severe aplastic anemia, and has been incorporated in autograft projects for the management of conditions such as multiple sclerosis, Crohn’s disease, and systemic sclerosis. Finally, research is underway for the induction of tolerance exploiting the ability of rATG to induce immunosuppresive cells such as regulatory T-cells. Despite its long history, rATG remains a key component of the immunosuppressive armamentarium, and its complex immunological properties indicate that its use will expand to a wider range of disease conditions in the future.

Rapamycin and CTLA4Ig synergize to induce stable mixed chimerism without the need for CD40 blockade

The mixed chimerism approach achieves donor-specific tolerance in organ transplantation, but clinical use is inhibited by the toxicities of current bone marrow (BM) transplantation (BMT) protocols. Blocking the CD40:CD154 pathway with anti-CD154 monoclonal antibodies (mAbs) is exceptionally potent in inducing mixed chimerism, but these mAbs are clinically not available. Defining the roles of donor and recipient CD40 in a murine allogeneic BMT model, we show that CD4 or CD8 activation through an intact direct or CD4 T cell activation through the indirect pathway is sufficient to trigger BM rejection despite CTLA4Ig treatment. In the absence of CD4 T cells, CD8 T cell activation via the direct pathway, in contrast, leads to a state of split tolerance. Interruption of the CD40 signals in both the direct and indirect pathway of allorecognition or lack of recipient CD154 is required for the induction of chimerism and tolerance. We developed a novel BMT protocol that induces mixed chimerism and donor-specific tolerance to fully mismatched cardiac allografts relying on CD28 costimulation blockade and mTOR inhibition without targeting the CD40 pathway. Notably, MHC-mismatched/minor antigen-matched skin grafts survive indefinitely whereas fully mismatched grafts are rejected, suggesting that non-MHC antigens cause graft rejection and split tolerance.

Belatacept in kidney transplantation

PURPOSE OF REVIEW

Calcineurin inhibitors (CNIs) play a major role in long-term renal allograft dysfunction because of their nephrotoxic side-effects. Belatacept, a selective costimulation blockade agent, is the first biological agent approved for maintenance immunosuppression in renal transplantation.

RECENT FINDINGS

Studies have shown better preservation of glomerular filtration rate and improved metabolic end points with belatacept when compared with CNIs. More recent studies have shown that belatacept can be an effective first-line immunosuppressive agent with complete avoidance of CNIs and corticosteroids.

SUMMARY

Newer biological agents like belatacept may replace CNIs/corticosteroids in renal transplant recipients, with a benefit of better short-term and long-term renal function, better compliance, and ultimately a possible improvement in long-term renal allograft survival.

Belatacept treatment for two yr after liver transplantation is not associated with operational tolerance

Belatacept was recently evaluated in liver transplantation (LT) in a phase II multicenter trial, which was terminated prematurely. Patients were more than two yr post-LT at the time. As high rates of spontaneous tolerance after LT have been reported and as belatacept has marked immunomodulatory effects, we decided to maintain the belatacept patients enrolled at our center (n = 4) on MMF monotherapy. All belatacept patients on MMF monotherapy developed graft dysfunction consistent with acute rejection after a mean period of 10.3 (7-14) wk. Patients were therefore switched to triple therapy with CNI, MMF, and corticosteroids. Graft dysfunction resolved within 1-3 wk after switch. At the time of belatacept discontinuation, mean eGFR was 105.1 mL/min/1.73 m² (92.1-118.9) in belatacept patients compared to 58 mL/min/1.73 m² (36.1-98.2) in controls (p = 0.022). One yr after the switch to CNI therapy, eGFR had declined by 27.4 mL (19.2-39.3; p = 0.008). Thus, LT patients treated with belatacept show superior kidney function that declines upon institution of CNIs. MMF monotherapy following withdrawal of belatacept is associated with a high incidence of graft dysfunction. Belatacept has no obvious immunomodulatory effects in LT recipients that would be sufficient to allow drug withdrawal with a high rate of success.