A phase III study of belatacept-based immunosuppression regimens versus cyclosporine in renal transplant recipients (BENEFIT study)

Integrin antagonists prevent costimulatory blockade-resistant transplant rejection by CD8(+) memory T cells

The success of belatacept in late-stage clinical trials inaugurates the arrival of a new class of immunosuppressants based on costimulatory blockade, an immunosuppression strategy that disrupts essential signals required for alloreactive T-cell activation. Despite having improved renal function, kidney transplant recipients treated with belatacept experienced increased rates of acute rejection. This finding has renewed focus on costimulatory blockade-resistant rejection and specifically the role of alloreactive memory T cells in mediating this resistance. To study the mechanisms of costimulatory blockade-resistant rejection and enhance the clinical efficacy of costimulatory blockade, we developed an experimental transplant system that models a donor-specific memory CD8(+) T-cell response. After confirming that graft-specific memory T cells mediate costimulatory blockade-resistant rejection, we characterized the role of integrins in this rejection. The resistance of memory T cells to costimulatory blockade was abrogated when costimulatory blockade was coupled with either anti-VLA-4 or anti-LFA-1. Mechanistic studies revealed that in the presence of costimulatory blockade, anti-VLA-4 impaired T-cell trafficking to the graft but not memory T-cell recall effector function, whereas anti-LFA-1 attenuated both trafficking and memory recall effector function. As antagonists against these integrins are clinically approved, these findings may have significant translational potential for future clinical transplant trials.

Transplantation in 2011: New agents, new ideas and new hope

The past year was marked by several excellent studies that represent important therapeutic advances in kidney transplantation or that further our understanding of the genetic basis of chronic allograft dysfunction, clinical tolerance and outcomes of kidney transplantation.

Belatacept: from rational design to clinical application

Gradually improved immunosuppression has contributed significantly to the progress achieved in transplantation medicine so far. Nevertheless, current drug regimens are associated with late graft loss--in particular as a result of immunologic damage or drug toxicity--and substantial morbidity. Recently, the costimulation blocker belatacept (marketed under the name Nulojix®) has been approved for immunosuppression in renal transplantation. Belatacept (a mutated version of CTLA4Ig) is a fusion protein rationally designed to block CD28, a critical activating receptor on T cells, by binding and saturating its ligands B7-1 and B7-2. In phase II and III trials, belatacept was compared with cyclosporine (in combination with basiliximab, MMF, and steroids). Advantages observed with belatacept include superior graft function, preservation of renal structure and improved cardiovascular risk profile. Concerns associated with belatacept are a higher frequency of cellular rejection episodes and more post-transplant lymphoproliferative disorder (PTLD) cases especially in EBV seronegative patients, who should be excluded from belatacept-based regimens. Thus, after almost three decades of calcineurin inhibitors as mainstay of immunosuppression, belatacept offers a potential alternative. In this article, we will provide an overview of belatacept's preclinical development and will discuss the available evidence from clinical trials.

The PROMISE study: a phase 2b multicenter study of voclosporin (ISA247) versus tacrolimus in de novo kidney transplantation

Voclosporin (VCS, ISA247) is a novel calcineurin inhibitor being developed for organ transplantation. PROMISE was a 6-month, multicenter, randomized, open-label study of three ascending concentration-controlled groups of VCS (low, medium and high) compared to tacrolimus (TAC) in 334 low-risk renal transplant recipients. The primary endpoint was demonstration of noninferiority of biopsy proven acute rejection (BPAR) rates. Secondary objectives included renal function, new onset diabetes after transplantation (NODAT), hypertension, hyperlipidemia and pharmacokinetic-pharmacodynamic evaluation. The incidence of BPAR in the VCS groups (10.7%, 9.1% and 2.3%, respectively) was noninferior to TAC (5.8%). The incidence of NODAT for VCS was 1.6%, 5.7% and 17.7% versus 16.4% in TAC (low-dose VCS, p = 0.03). Nankivell estimated glomerular filtration rate was respectively: 71, 72, 68 and 69 mL/min, statistically lower in the high-dose group, p = 0.049. The incidence of hypertension and adverse events was not different between the VCS groups and TAC. VCS demonstrated an excellent correlation between trough and area under the curve (r(2) = 0.97) and no difference in mycophenolic acid exposure compared to TAC. This 6-month study shows VCS to be as efficacious as TAC in preventing acute rejection with similar renal function in the low- and medium-exposure groups, and potentially associated with a reduced incidence of NODAT.

Recent advances in immunosuppressive therapy for prevention of renal allograft rejection

PURPOSE OF REVIEW

Current immunosuppressive therapies are highly successful at regulating acute allograft rejection and inducing long-term transplanted kidney survival; however, currently available medications are associated with generalized immune suppression and drug toxicities, including nephrotoxicity. In recent years, advances in immunosuppression that target specific pathways involved in immune activation have been developed.

RECENT FINDINGS

In particular, promising medications are currently under evaluation that target ischemia-reperfusion injury as well as the cellular and humoral branches of the adaptive immune response. Targets of T-cell-mediated activation include antibodies and fusion proteins interfering with LFA-1/ICAM-1, CD2/LFA-3, CD40/CD154, and CD28/B7.1 and B7.2 interactions. Intracellular targets involved in T- and B-cell activation pathways are being evaluated, including protein kinase C inhibitors, Janus-associated kinase (JAK) inhibitors, and proteasome inhibitors. Several new medications demonstrate promise in inhibiting donor-directed humoral immunity by targeting B-cell-activating factor (BAFF) and complement activation pathways.

SUMMARY

The present review evaluates the recent clinical advances in immunosuppressive therapies for kidney transplantation. Publications regarding advances in immunosuppressive therapies over the past year were evaluated in the context of the specific immune pathways involved in allograft rejection.

Immunosuppressive protocols and immunological challenges related to hand transplantation

There are many immunological challenges related to hand transplantation. Curbing the immune system's ability to effectively mount an immune response against the graft is the goal. As the various components of the immune response are defined and their mechanisms of action delineated, more specific immunosuppressive agents and protocols have been developed. Complications related to immunosuppression in hand transplant recipients are similar to incidences among solid organ recipients. With longer follow-up, the increased cardiovascular risk factors or the development of a neoplasm will likely cause mortality. Standardizing immunosuppression in hand transplantation with the long-term goal of minimization is critically needed.

Hot-topic debate on kidney function: renal-sparing approaches are beneficial

1. Renal function is frequently compromised in candidates for transplantation with advanced cirrhosis. These patients frequently have chronic and irreversible kidney changes at the time of transplantation. 2. The accumulated incidence of chronic renal failure is high in liver transplant recipients. Chronic renal failure has a deleterious impact on the outcome. 3. Calcineurin inhibitor (CNI)-based immunosuppression is highly effective at preventing rejection. However, CNI nephrotoxicity has a central role in the occurrence of chronic renal failure. 4. Renal function impairment frequently occurs within the first year after transplantation. Once renal function is significantly impaired [glomerular filtration rate (GFR) < 60 mL/minute/1.73 m(2) ], any intervention is unlikely to result in a return to normal renal function. Early interventions are needed to prevent chronic and irreversible kidney injury. 5. De novo CNI minimization has been proven to be effective at reducing the rate of impaired renal function after transplantation. The reduction in the CNI doses should be offset by the addition of mycophenolate mofetil or enteric-coated mycophenolate sodium. 6. Delayed CNI minimization in patients with established renal insufficiency may result in a significant improvement in the GFR, even though the increase in the GFR after minimization is generally modest. 7. Mammalian target of rapamycin (mTOR) inhibitors are considered nonnephrotoxic immunosuppressive agents. They may be an option for improving renal function in liver transplant recipients. However, not all patients with renal dysfunction benefit from a switch to mTOR inhibitors. In addition, the benefits in terms of renal function should be balanced against specific side effects. 8. New immunosuppressive agents without intrinsic nephrotoxicity are currently under development for solid organ transplantation. These agents could help to reduce the burden of impaired renal function in transplantation in the near future.

Future prospects in immunosuppression for liver transplantation

1. Our increasing understanding of signaling pathways and cellular interactions in transplant immunobiology and the availability of novel immunosuppressive agents have facilitated targeted strategies. 2. The driving forces behind the development of new immunosuppressive regimens are the long-term complications of current immunosuppressive regimens (particularly renal dysfunction and metabolic disturbances). 3. By regulatory mandate, the requirement for the primary endpoint to be a composite of death, graft loss, and rejection remains intact; however, current and future clinical trials could incorporate key secondary endpoints that address renal and metabolic derangements.

Hot-topic debate on kidney function: renal-sparing approaches are ineffective

1. Both acute kidney injury and chronic renal disease are common in patients undergoing liver transplantation. The etiologies are mixed. 2. The incidence of chronic renal failure after liver transplantation is unacceptable, and it has a significant impact on long-term outcomes after liver transplantation. 3. The role of calcineurin inhibitors (CNIs) in the development of posttransplant chronic renal failure is likely overrated. 4. The use of CNIs in the early posttransplant period is currently essential. 5. Whether new agents will be able to provide effective immunosuppression as primary immunosuppressives remains to be proven.

Belatacept-versus cyclosporine-based immunosuppression in renal transplant recipients with pre-existing diabetes

BACKGROUND AND OBJECTIVES

Renal transplant recipients with pre-existing diabetes (PD) have reduced graft survival and increased risk of mortality and ischemic heart disease compared with nondiabetic transplant recipients. To assess the effect of belatacept in this high-risk group, we evaluated outcomes of the subpopulation with PD from previously published BENEFIT and BENEFIT-EXT trials.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A post hoc analysis evaluated pooled data from BENEFIT (living donors or standard criteria donors) and BENEFIT-EXT (extended criteria donors). Patients were randomized to receive cyclosporine or a more intensive (MI) or less intensive (LI) belatacept regimen.

RESULTS

Of 1209 intent-to-treat patients, 336 had PD. At 12 months, the belatacept LI arm demonstrated a numerically higher rate of patients surviving with a functioning graft (90.4% MI [103 of 114], 92.8% LI [90 of 97], and 80.8% cyclosporine [101 of 125]), and fewer serious adverse events than cyclosporine or MI patients. Three cases of posttransplant lymphoproliferative disorder were reported in LI patients, one involving the central nervous system. Higher rates (% [95% confidence interval]: 22.8% MI [15.1 to 30.5]; 20.6% LI [12.6 to 28.7]; 14.4% cyclosporine (8.2 to 20.6]) and grades of acute rejection were observed with belatacept. Measured GFR (ml/min per 1.73 m(2), 59.8 MI; 62.5 LI; 45.4 cyclosporine), and cardiovascular risk profile were better for belatacept versus cyclosporine.

CONCLUSIONS

In post hoc analysis of patients with PD, patient/graft survival and renal function at 12 months were numerically higher with belatacept versus cyclosporine, but not statistically significant. Further study is necessary to confirm the benefits belatacept may provide in these patients.

Quantitative analysis predicts the relative therapeutic efficacy of different forms of CTLA4Ig

Modulating the activities of costimulatory molecules controlling immune responses holds considerable promise for immunotherapy. CTLA4Ig (abatacept), a soluble version of the T cell-expressed membrane receptor CTLA-4, is approved for the treatment of rheumatoid arthritis. Like natural CTLA-4 molecules, CTLA4Ig ligates B7-1 and B7-2 on antigen presenting cells, preventing CD28-mediated costimulation of T cells. However, CTLA4Ig can also prevent ligation of CTLA-4, potentially blocking vital inhibitory signals, thereby augmenting immunity. There have been no quantitative analyses of the likely effects of CTLA4Ig on costimulatory interactions at the immunological synapse. We present a mathematical model, based on rigorous biophysical and expression data, for simulating the effects of abatacept and a mutated derivative, LEA29Y, on the synaptic interactions of CD28 and CTLA-4. The simulations reveal an unexpectedly large window within which CD28, but not CTLA-4, ligation is blocked by CTLA4Ig, perhaps explaining the efficacy of abatacept at the recommended therapeutic dose (10mg/kg) and its relative safety. However, the simulations suggest that the present dosing regimen is close to the maximum theoretically safe dose. The simulations also show that, within the therapeutic window, LEA29Y enhances the interaction of CTLA-4 with the more potent of its two native ligands, B7-1. They also suggest that CTLA-4 ligation by B7-1 could, in principle, be enhanced by further decreasing the off-rate of CTLA4Ig for binding to B7-2. Our findings therefore offer molecular explanations for why LEA29Y might prove to be more effective than abatacept in a clinical setting, and suggest ways in which its therapeutic efficacy could be further optimised.

LFA-1 blockade induces effector and regulatory T-cell enrichment in lymph nodes and synergizes with CTLA-4Ig to inhibit effector function

Despite encouraging results using lymphocyte function antigen-1 (LFA-1) blockade to inhibit BM and solid organ transplantation rejection in nonhuman primates and humans, the precise mechanisms underlying its therapeutic potential are still poorly understood. Using a fully allogeneic murine transplantation model, we assessed the relative distribution of total lymphocyte subsets in untreated versus anti-LFA-1-treated animals. Our results demonstrated a striking loss of naive T cells from peripheral lymph nodes, a concomitant gain in blood after LFA-1 blockade, and a shift in phenotype of the cells remaining in the node to a CD62LloCD44hi profile. We determined that this change was due to a specific enrichment of activated, graft-specific effectors in the peripheral lymph nodes of anti-LFA-1-treated mice compared with untreated controls, and not to a direct effect of anti-LFA-1 on CD62L expression. LFA-1 blockade also resulted in a dramatic increase in the frequency of CD4+ FoxP3+ regulatory T cells in graft-draining nodes. Our results suggest that the differential impact of LFA-1 blockade on the distribution of naive versus effector and regulatory T cells may underlie its ability to inhibit alloreactive T-cell responses after transplantation.

Immunosuppression: does one regimen fit all?

There has been considerable interest in the individualization of immunosuppressive regimens in an attempt to avoid side effects and improve long-term outcomes. Most available studies have addressed steroid and calcineurin inhibitor minimization in an attempt to prevent the development of chronic allograft dysfunction and cardiovascular mortality. Herein, we evaluate the available evidence for incorporation of these novel strategies in standard clinical care of kidney transplant recipients. Protocol biopsies, pharmacogenetics, and other assays have been developed to guide tailoring of immunosuppression; however, although promising results have been obtained, trials showing their ability to improve long-term outcome are lacking and urgently needed.

Meta-analysis of calcineurin-inhibitor-sparing regimens in kidney transplantation

Calcineurin-inhibitor-sparing strategies in kidney transplantation may spare patients the adverse effects of these drugs, but the efficacy of these strategies is unknown. Here, we conduct a meta-analysis to assess outcomes associated with reducing calcineurin inhibitor exposure from the time of transplantation. We search Medline, Embase, and Cochrane Register of Controlled Trials for randomized controlled trials published between 1966 and 2010 that compared de novo calcineurin-inhibitor-sparing regimens to calcineurin-inhibitor-based regimens. In this analysis, we include 56 studies comprising data from 11337 renal transplant recipients. Use of the contemporary agents belatacept or tofacitinib, in combination with mycophenolate, decreased the odds of overall graft failure (OR 0.61; 95% CI 0.39-0.96; P = 0.03). Similarly, minimization of calcineurin inhibitors in combination with various induction and adjunctive agents reduces the odds of graft failure (OR 0.73; 95% CI 0.58-0.92; P = 0.009). Conversely, the use of inhibitors of mammalian target of rapamycin (mTOR), in combination with mycophenolate, increases the odds of graft failure (OR 1.43; 95% CI 1.08-1.90; P = 0.01). Calcineurin-inhibitor-sparing strategies are associated with less delayed graft function (OR 0.89; 95% CI 0.80-0.98; P = 0.02), improved graft function, and less new-onset diabetes. The more contemporary protocols did not seem to increase rates of acute rejection. In conclusion, this meta-analysis suggests that reducing exposure to calcineurin inhibitors immediately after kidney transplantation may improve clinical outcomes.

Immunobiology of transplantation: impact on targets for large and small molecules

Organ transplantation is the preferred method of treatment for many forms of end-stage organ failure. However, immunosuppressive drugs that are used to avoid rejection can result in numerous undesirable effects (infection, malignancy, hypertension, diabetes, and accelerated arteriosclerosis). Moreover, they are not effective at preventing chronic rejection resulting in late graft loss. This review summarizes the fundamental concepts underlying the rejection of solid-organ allografts with the aim of highlighting potential new targets for therapeutics. Future improvement will depend on new therapeutic moieties, including biologics, to target various pathways of both the innate and adaptive arms of immunity. Results from some of the most recent clinical trials in transplantation and emerging new therapies are also discussed.

Challenges and opportunities in targeting the costimulation pathway in solid organ transplantation

Signaling through the costimulatory pathway is critical in the regulation of T cell activation. Abatacept, a selective costimulatory antagonist FDA approved for the treatment of moderate to severe rheumatoid arthritis, binds to CD80 and CD86 on antigen presenting cells, blocking the interaction with CD28 on T cells. Belatacept, a second generation CTLA4-Ig with 2 amino acid substitutions, has shown considerable promise in clinical transplantation as part of a maintenance immunosuppression regimen. This review will summarize the role of costimulation in T cell activation, detail the development of costimulation antagonists and highlight the pertinent clinical trials completed and ongoing utilizing belatacept as part of an immunosuppressive regimen in organ transplantation.

Conventional and novel approaches to immunosuppression

Immunosuppressive therapy has contributed significantly to improved survival after solid organ transplantation. Nevertheless, treatment-related adverse events and persistently high risk of chronic graft rejection remain major obstacles to long-term survival after lung transplantation. The development of new agents, refinements in techniques to monitor immunosuppression, and enhanced understanding of transplant immunobiology are essential for further improvements in outcome. In this article, conventional immunosuppressive regimens, novel approaches to preventing graft rejection, and investigational agents for solid organ transplantation are reviewed.

Targets of new immunosuppressants in renal transplantation

Although current immunosuppression is highly effective in avoiding acute rejection, it is associated with nephrotoxicity, cardiovascular morbidity, infection, and cancer. Thus, new drugs dealing with new mechanisms, as well as minimizing comorbidities, are warranted in renal transplantation. Few novel drugs are currently under investigation in Phase I, II, or III clinical trials. Belatacept is a humanized antibody that inhibits T-cell co-stimulation and has shown encouraging results in Phase II and III trials. Moreover, two new small molecules are under clinical development: AEB071 or sotrastaurin (a protein kinase C inhibitor) and CP-690550 or tasocitinib (a Janus kinase inhibitor). Refinement in selecting the best combinations for the new and current immunosuppressive agents is probably the main challenge for the next few years.

T-cell co-stimulatory blockade in kidney transplantation: back to the bench

It is believed that blocking positive T-cell co-stimulatory pathways should lead to long-term graft acceptance. Despite the exciting initial achievements in experimental animal models, targeting co-stimulatory pathways has shown to be much more complex in the clinic. In addition to multiple binding partners, some co-stimulatory interactions have been found to be inhibitory in nature, whereas others were demonstrated to be important in the development of regulatory T cells. Moreover, memory T cells have been shown to be resistant to co-stimulation blockade. Herein we focus on the B7:CD28 pathway and describe the evolution of targeting this pathway with cytotoxic T-lymphocyte antigen-4-Ig from bench to clinic. We also attempt to address possible causes for the unexpected high rejection rate observed in the phase III clinical trials with belatacept, using experimental data obtained from basic science research.

Costimulatory pathways in transplantation

Secondary, so-called costimulatory, signals are critically required for the process of T cell activation. Since landmark studies defined that T cells receiving a T cell receptor signal without a costimulatory signal, are tolerized in vitro, the investigation of T cell costimulation has attracted intense interest. Early studies demonstrated that interrupting T cell costimulation allows attenuation of the alloresponse, which is particularly difficult to modulate due to the clone size of alloreactive T cells. The understanding of costimulation has since evolved substantially and now encompasses not only positive signals involved in T cell activation but also negative signals inhibiting T cell activation and promoting T cell tolerance. Costimulation blockade has been used effectively for the induction of tolerance in rodent models of transplantation, but turned out to be less potent in large animals and humans. In this overview we will discuss the evolution of the concept of T cell costimulation, the potential of 'classical' and newly identified costimulation pathways as therapeutic targets for organ transplantation as well as progress towards clinical application of the first costimulation blocking compound.

Efficacy and safety of early cyclosporine conversion to sirolimus with continued MMF-four-year results of the Postconcept study

Calcineurin inhibitor (CNI) withdrawal has been used as a strategy to improve renal allograft function. We previously reported that conversion from cyclosporine A (CsA) to sirolimus (SRL) 3 months after transplantation significantly improved renal function at 1 year. In the Postconcept trial, 77 patients in the SRL group and 85 in the CsA group were followed for 48 months. Renal function (Cockcroft and Gault) was significantly better at month 48 (M48) in the SRL group both in the intent-to-treat population (ITT): 62.6 mL/min/1.73 m(2) versus 57.1 mL/min/1.73 m(2) (p = 0.013) and in the on-treatment population (OT): 67.5 mL/min/1.73 m(2) versus 57.4 mL/min/1.73 m(2) (p = 0.002). Two biopsy proven acute rejection episodes occurred after M12 in each group. Graft and patient survival were comparable (graft survival: 97.4 vs. 100%; patient survival: 97.4 vs. 97.6%, respectively). The incidence of new-onset diabetes was numerically increased in the SRL group (7 vs. 2). In OT, three cancers occurred in the SRL group versus nine in the CsA group and mean proteinuria was increased in the SRL group (0.42 ± 0.44 vs. 0.26 ± 0.37; p = 0.018). In summary, the renal benefits associated with conversion of CsA to SRL, at 3 months posttransplantation, in combination with MMF were maintained for 4 years posttransplantation.

Steroid and calcineurin inhibitor-sparing protocols in kidney transplantation

Recent improvements in kidney transplantation have been driven largely by lower acute rejection rates attributed to better immunosuppressive agents. In an effort to reduce the long-term toxicities of immunosuppressant drugs, corticosteroid- and calcineurin inhibitor (CNI)-sparing immunosuppression protocols have become increasingly popular in managing kidney transplant recipients. Nevertheless, these strategies may increase the risk of acute and chronic allograft injury (CAI) that may worsen the fate of transplant recipients. This article focuses on steroid and CNI sparing protocols to elucidate their safety and efficacy in patients receiving a kidney transplant. Steroid avoidance protocols are rapidly and increasingly being used. Studies have shown that corticosteroids are not essential to achieve excellent short- and intermediate-term results. However, the role of steroid withdrawal is only marginally beneficial and very often benefit overstated. CNI-sparing strategies have been used to help maintain the balance between allograft survival and nephrotoxicity. Trials evaluating CNI minimization have shown reduced incidence of CAI and preservation of allograft function. CNI withdrawal within 3 to 12 months after kidney transplantation improved graft function despite increased risk of acute rejection. This approach may be feasible with adequate exposure and proper usage of mammalian target of rapamacin inhibitors. Late withdrawal or conversion did not show a clear benefit. Timing and degree of renal dysfunction are key determining factors. With regards to CNI avoidance, earlier trials, such as the Symphony study, did not support the use of a CNI-free regimen of low-dose sirolimus as initial immunosuppression. However, recent studies using costimulatory blockade-based immusouppression showed that CNI avoidance is possible. The best maintenance immunosuppressive with CNI- or steroid-sparing is a work in progress and awaits longer term follow-up. The availability of newer biologics for costimulatory blockade and new immunosuppressive agents with novel mechanisms of action have the potential of using CNI- and steroid-sparing protocols to minimize the incidence of CAI and improve long-term outcomes in kidney transplant recipients.

Sotrastaurin, a novel small molecule inhibiting protein-kinase C: randomized phase II study in renal transplant recipients

Sotrastaurin, a selective protein-kinase-C inhibitor, blocks early T-cell activation through a calcineurin-independent mechanism. In this study, de novo renal transplant recipients with immediate graft function were randomized 1:2 to tacrolimus (control, n = 44) or sotrastaurin (300 mg b.i.d.; n = 81). All patients received basiliximab, mycophenolic acid (MPA) and steroids. The primary endpoint was the composite of treated biopsy-proven acute rejection (BPAR), graft loss, death or lost to follow-up at month 3. The main safety assessment was estimated glomerular filtration rate (eGFR); modification of diet in renal disease (MDRD) at month 3. Composite efficacy failure at month 3 was higher for the sotrastaurin versus control regimen (25.7% vs. 4.5%, p = 0.001), driven by higher BPAR rates (23.6% vs. 4.5%, p = 0.003), which led to early study termination. Median (± standard deviation [SD]) eGFR was higher for sotrastaurin versus control at all timepoints from day 7 (month 3: 59.0 ± 22.3 vs. 49.5 ± 17.7 mL/min/1.73 m(2) , p = 0.006). The most common adverse events were gastrointestinal disorders (control: 63.6%; sotrastaurin: 88.9%) which led to study-medication discontinuation in two sotrastaurin patients. This study demonstrated a lower degree of efficacy but better renal function with the calcineurin-inhibitor-free regimen of sotrastaurin+MPA versus the tacrolimus-based control. Ongoing studies are evaluating alternative sotrastaurin regimens.

Belatacept-based regimens are associated with improved cardiovascular and metabolic risk factors compared with cyclosporine in kidney transplant recipients (BENEFIT and BENEFIT-EXT studies)

BACKGROUND

Cardiovascular disease, the most common cause of death with a functioning graft among kidney transplant recipients, can be exacerbated by immunosuppressive drugs, particularly the calcineurin inhibitors. Belatacept, a selective co-stimulation blocker, may provide a better cardiovascular/metabolic risk profile than current immunosuppressants.

METHODS

Cardiovascular and metabolic endpoints from two Phase III studies (BENEFIT and BENEFIT-EXT) of belatacept-based regimens in kidney transplant recipients were assessed at month 12. Each study assessed belatacept in more intensive (MI) and less intensive (LI) regimens versus cyclosporine A (CsA). These secondary endpoints included changes in blood pressure, changes in serum lipids, and the incidence of new-onset diabetes after transplant (NODAT).

RESULTS

A total of 1209 patients were randomized and transplanted across the two studies. Mean systolic blood pressure was 6 to 9 mm Hg lower and mean diastolic blood pressure was 3 to 4 mm Hg lower in the MI and LI groups versus CsA (P ≤ 0.002) across both studies at month 12. Non-HDL cholesterol was lower in the belatacept groups versus CsA (P<0.01 MI or LI vs. CsA in each study). Serum triglycerides were lower in the belatacept groups versus CsA (P<0.02 MI or LI vs. CsA in each study). NODAT occurred less often in the belatacept groups versus CsA in a prespecified pooled analysis (P<0.05 MI or LI vs. CsA).

CONCLUSIONS

At month 12, belatacept regimens were associated with better cardiovascular and metabolic risk profiles, with lower blood pressure and serum lipids and less NODAT versus CsA. The overall profile of belatacept will continue to be assessed over the 3-year trials.

Improving long-term renal allograft survival via a road less traveled by

It has become cliché to state that improvements in early renal allograft survival over the past two decades have not led to increased long-term renal allograft survival. However, it is not clear how long-term graft survival can be improved. Here, we present the viewpoint that the road forward does not involve searching for new and more ideal immunosuppressive regimens, but rather detailed patient follow-up to identify specific causes of late renal allograft loss and the development of new therapy designed to address these problems before allograft damage becomes irreversible.

Novel strategies in immunosuppression: issues in perspective

Recent findings suggest that a chronic alloimmune response is playing the dominant role in late allograft loss, challenging the notion that most grafts are lost due to the inexorable progression of calcineurin inhibitor (CNI) nephrotoxicity. CNIs have failed to improve long-term outcomes and are associated with multiple metabolic derangements. Thus, improvement in long-term allograft outcomes may depend on new agents with novel mechanisms of action, devoid of the toxicities associated with CNIs. To meet this need, inhibitors of novel pathways in B cell and plasma cell activation have emerged to combat the humoral immune response including belimumab and atacicept, both promising targets of B-cell survival factors and bortezomib and eculizumab, agents currently in trials for desensitization protocols and treatment of antibody-mediated rejection. Promising agents for maintenance immunosuppression, used as monotherapy or synergistically, include monoclonal antibodies and fusion receptor proteins targeting the CD40-CD154 pathway (multiple anti-CD40 antibodies), the CD28-CD80/86 pathway (i.e., belatacept), the LFA3-CD2 pathway (i.e., alefacept), and small molecules such as tofacitinib, a janus kinase 1/3 inhibitor. The induction of allograft tolerance has been attempted with some success with simultaneous bone marrow/kidney transplantation from the same donor, albeit, limited by its associated toxicites. Finally, the exciting fields of tissue engineering and stem cell biology with the repopulation of decellularized organs is ushering in a new paradigm for transplantation. The era of simplified immunosuppression regimens devoid of toxicities is upon us with the promise of dramatic improvement in long term survival.

Safety and efficacy of intensified versus standard dosing regimens of enteric-coated mycophenolate sodium in de novo renal transplant patients

BACKGROUND

Efficacy and safety of an intensified dosing (ID) regimen of enteric-coated mycophenolate sodium (EC-MPS), which achieves higher mycophenolic acid exposure early posttransplantation, were evaluated in comparison with a standard dosing (SD) regimen.

METHODS

In total, 128 de novo kidney transplant recipients treated with basiliximab induction, cyclosporine A, and steroids were randomized (1:1) to receive EC-MPS as SD (1440 mg/day; n=65) or ID (days 0-14: 2880 mg/day; days 15-42: 2160 mg/day; followed by 1440 mg/day; n=63). Efficacy parameters, safety, and tolerability were assessed over a 6-month study period. The primary endpoint was mean time to first occurrence of treatment failure.

RESULTS

Mean time to treatment failure was 130 days (95% confidence interval [CI]: 81-n/a) in the ID group versus 114 days (95% CI: 15-155) in the SD group (P=0.36). Similar percentages (ID 30.2%; SD 36.9%) experienced treatment failure. Biopsy-proven acute rejection occurred in 2 (3.2%) ID versus 11 (16.9%) SD patients (P<0.001). Three (2.3%) deaths (2 SD, 1 ID) and five (3.9%) graft losses (3 SD, 2 ID) occurred. Renal function, incidence of infection, and hematologic disorders were comparable in both study cohorts. Gastrointestinal disorders occurred in 51 (81.0%) ID and 49 (75.4%) SD patients with overall similar tolerability as assessed by the Gastrointestinal Symptom Rating Scale.

CONCLUSION

In this exploratory study, the EC-MPS ID regimen reduced the incidence of rejection and showed a comparable safety and tolerability profile to SD. Further examination of this approach in a larger patient cohort is now warranted to confirm these findings.

Co-stimulation blockade as a new strategy in kidney transplantation: benefits and limits

New immunosuppressive drugs have greatly decreased the frequency of graft failure due to acute rejection but have had little impact on long-term graft survival. This is due, at least in part, to the broad non-immune effects of the current immunosuppressive drugs, which are involved in the death of patients and in chronic allograft dysfunction, particularly due to their nephrotoxicity. Recent progress in the development of biologicals, i.e. antibodies and fusion proteins, allows precise targeting of the immune system, preventing the non-immune side effects encountered with current protocols. In particular, targeting of the two most important co-stimulation pathways critical for T-cell activation, i.e. B7/CD28 and CD40/CD40L, has provided excellent results in many experimental models of organ transplantation. This has led to the clinical development of belatacept, a cytotoxic T-lymphocyte-associated antigen 4 immunoglobulin (CTLA4-Ig) fusion protein, which has proved to be efficient in preventing acute rejection in kidney transplant recipients. Its use is associated with improved renal function and a better metabolic profile than calcineurin inhibitors. However, because belatacept does not selectively target alloreactive T lymphocytes and must be combined with classical immunosuppressive drugs, infectious and neoplastic complications may occur, particularly post-transplantation lymphoproliferative disorders. We also address the current development of molecules targeting other co-stimulatory pathways (CD40/CD40L, leukocyte function-associated antigen [LFA]-1/intercellular adhesion molecule [ICAM], CD2/LFA-3). Many unresolved issues regarding the use of co-stimulation blocking agents are also discussed, e.g. their long half-life, which can be problematic in cases of serious adverse events, their long-term safety and efficacy, and the lack of monitoring tools to allow modulation of their use over time.

Report of a joint ESOT and AST meeting: highlights in biologic agents and transplantation

A joint meeting organized by the European (ESOT) and American (AST) Societies of Transplantation occurred in Nice, France, October 1-3, 2010. Focused on emerging use of biologic agents in solid organ transplantation, it served as a venue for state-of-the-art updates in basic immunology and clinical science, with an emphasis on the interrelatedness of the two. This meeting summary is designed to highlight important insights communicated in Nice, offer an overview of novel therapeutics in development, and entice members of all societies to consider attending a second joint symposium, under consideration for 2012.

The molecular phenotype of 6-week protocol biopsies from human renal allografts: reflections of prior injury but not future course

We assessed the molecular phenotype of 107 6-week protocol biopsies from human renal allografts, using Affymetrix microarrays. Transcript changes were summarized as nonoverlapping pathogenesis-based transcript sets (PBTs) reflecting inflammation (T cells, macrophages, IFNG effects) and the injury-repair response of the parenchyma, stroma and microcirculation-increased ('injury-up') and decreased ('injury-down') transcripts. The molecular changes were highly correlated with each other, even when all rejection and borderline cases were excluded. Inflammation and injury-down PBTs correlated with histologic inflammation and tubulitis, and the inflammation transcripts were greater in kidneys diagnosed as T cell-mediated or borderline rejection. Injury-up PBTs did not correlate with histopathology but did correlate with kidney function: thus functional disturbances are represented in transcript changes but not in histopathology. PBT changes correlated with prior delayed graft function. However, there was little difference between live donor kidneys and deceased donor kidneys that had not shown delayed graft function. Molecular changes did not predict future biopsies for clinical indications, rejection episodes, functional deterioration or allograft loss. Thus while detecting T cell-mediated inflammation, the molecular phenotype of early protocol biopsies mostly reflects the injury-repair response to implantation stresses, and has little relationship to future events and outcomes.

Rationale for using belatacept in combination with sirolimus

Kidney transplantation can be used to replace failing native kidneys; however, it requires long-term immunosuppression, and immunological tolerance for this is not yet achievable. The cornerstone of immunosuppression is based on calcineurin inhibitors, which are nephrotoxic. Therefore, new drugs are being developed that provide efficacious immunosuppression and almost no renal toxicity. The first family of drugs that have these properties are mammalian target of rapamycin inhibitors: these include sirolimus and everolimus. These two drugs, besides their immunosuppressive properties, also have beneficial effects regarding cytomegalovirus (CMV) infection, which is a very common posttransplantation complication. In phase III trials, belatacept, a costimulatory blocker, has also been shown to provide a good immunosuppressive effect and also gives a significantly better cardiovascular profile than cyclosporine-based immunosuppression. However, belatacept can potentially increase infections such as CMV. Thus, herein, we describe the rationale for combining belatacept with sirolimus for kidney transplant patients.

Optimal immunosuppression to prevent chronic allograft dysfunction

Prevention of chronic allograft dysfunction is currently one of the main goals in renal transplantation for the improvement of kidney graft survival. For this purpose, refinements in immunosuppressive regimens, both controlling alloimmune responses and avoiding calcineurin inhibitor (CNI)-derived nephrotoxicity, are mandatory. The majority of trials aiming to avoid CNI-related nephrotoxicity have only reported short-term data, with different rates of acute rejection depending on the strategy performed. First attempts of CNI-free strategies in micophenolate mofetil-based regimens showed unsatisfactory results in terms of increased acute rejection events. With the advent of mammalian target of rapamycin inhibitors, a new optimistic perspective seemed to appear. Despite an increased risk of rejection, better graft function and graft parenchyma preservation seem to be associated with such a strategy, at least in the short term, with a potential benefit in terms of less cardiovascular-related adverse events and malignancies. New biological agents such as belatacep have been developed as another interesting strategy for CNI avoidance. Importantly, in any case, longer-term analyses of all these CNI-avoidance strategies are warranted in order to confirm whether persistent immune-mediated graft damage can be safely overcome.

High levels of IDO-expressing CD16+ peripheral cells, and Tregs in graft biopsies from kidney transplant recipients under belatacept treatment

BACKGROUND

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-degrading enzyme that suppresses T-lymphocyte activity. Costimulation blockade through CTLA4lg increases IDO in antigen-presenting cells. The suppressive effect of IDO is thought to be mediated by Foxp3+CD4+CD25+ regulatory T-cells (Tregs).

OBJECTIVE

In this descriptive study, we evaluated the percentage of IDO-expressing peripheral cell subpopulations as well as Tregs in 27 stable kidney transplant recipients receiving either belatacept (LEA29Y), a daughter compound of abatacept (CTLA4lg; n = 19) or cyclosporine (n = 8).

METHODS

Blood samples were obtained at 24 ± 2 months (belatacept) and 23 ± 6 months (cyclosporine) of treatment. Intracellular IDO was analyzed by flow cytometry in CD14+, CD11c+, CD16+, CD56+, and CD8+ cell subpopulations. Tregs were assessed by intracellular Foxp3 detection in CD4+CD25+ cells. CD3+, CD4+, CD8+, CD20+, CD68+, IDO+, and Foxp3+ cells were evaluated by immunohistochemistry on graft biopsies obtained preimplantation, at 12 months posttransplant, and in subjects with dysfunction during the first 12 months.

RESULTS

Only percentages of CD16+/IDO+-expressing peripheral monocytes were significantly increased among the group receiving belatacept. No differences were observed in peripheral Tregs between the groups. In contrast, higher percentages of Tregs, CD4+, CD8+, and CD68+ cells were noted in dysfunction and at 12 months vs baseline among graft biopsies in subjects receiving belatacept, and also among dysfunction cohorts of belatacept vs Cyclosporine treatment.

CONCLUSION

Patients receiving belatacept showed greater amounts of peripheral blood CD16+/IDO+ cells and Tregs on graft biopsies than those under cyclosporine treatment.

Inflammation lesions in kidney transplant biopsies: association with survival is due to the underlying diseases

Assessment of kidney transplant biopsies relies on nonspecific inflammatory lesions: Interstitial infiltrates (i), tubulitis (t) and intimal arteritis (v). We studied the relationship between inflammation and prognosis in biopsies for clinical indications from 314 patients (median follow-up 25 months). We used a modified Banff classification, separately assessing inflammation (i-) in nonscarred (i-Banff), scarred (i-IFTA) and whole cortex (i-total), plus tubulitis and intimal arteritis. In early biopsies (<1 year), i- and t-lesions had no association with graft survival. In late (>1 year) biopsies, all i-scores correlated with progression to failure, due to the association of these infiltrates with progressive diseases: antibody-mediated rejection (ABMR) and glomerulonephritis. Tubulitis in nonscarred areas had no impact on survival. Severe tubulitis including scarred areas (tis3) was associated with worse survival, but reflected polyoma virus nephropathy or ABMR, not T-cell-mediated rejection. Intimal arteritis (v-lesions) had no association with allograft loss in early or late biopsies. In multivariate analysis, outcome was better predicted by the presence of progressive disease than by inflammation. Thus inflammation in late kidney transplants has no inherent prognostic impact, but predicts reduced survival because inflammation indicates actively progressing diseases. The most important predictor of outcome is the diagnosis of a progressive disease.

Regulatory T cells in lung transplantation--an emerging concept

Lung transplantation represents an option for patients with a variety of end-stage lung diseases. While surgical advances have led to improvements in short-term survival, long-term survival is limited by chronic rejection termed bronchiolitis obliterans syndrome (BOS). A growing body of work is devoted to determining why some patients develop BOS. One avenue of interest that has emerged recently is the role that regulatory T cells (Tregs) may have in protection from BOS. In this review, we will discuss the evidence that Tregs are relevant to outcomes following transplant. We will discuss the relevant animal models, in vitro assays, and human observational studies that support a role for Tregs. We will also explore the interplay between injurious T cells such as Th17 cells and Tregs as well as the effect that additional cell types and chemokines have on the balance between inflammation and regulation. Finally, we will review emerging therapies which may harness the ability of Tregs to lessen the effects of BOS.

Management of posttransplant lymphoproliferative disorders following solid organ transplant: an update

Development of secondary malignancies is a well-known complication of solid organ transplant, with skin cancer and lymphoproliferative disorders being most frequently observed. Posttransplant lymphoproliferative disorders, caused by diminished immune surveillance, represent a broad spectrum of pathological and clinical disorders, ranging from benign conditions to very aggressive lymphomas. Here we review treatment options for adult patients experiencing posttransplant lymphoproliferative disorders following solid organ transplant.