Tocilizumab in the Treatment of Chronic Antibody-Mediated Rejection Post Kidney Transplantation: Clinical and Histological Monitoring

A Population Pharmacokinetic Model of Tocilizumab in Kidney Transplant Patients Treated for Chronic Active Antibody-Mediated Rejection: Comparison of Plasma Exposure Between Intravenous and Subcutaneous Administration Schemes

BACKGROUND

Tocilizumab prevents the clinical worsening of chronic active antibody-mediated rejection (CAAMR) in kidney transplant recipients. Following a global shortage of the intravenous pharmaceutical form in 2022, patients were switched from monthly intravenous administration of 8 mg/kg to weekly subcutaneous injection of 162 mg, raising the question of bioequivalence between these schemes of administration.

AIMS

We aimed to compare the areas under the curve (AUC) of tocilizumab in virtual simulations of populations treated with the two administration schemes and to identify the covariates that could contribute to pharmacokinetic variability of tocilizumab in kidney transplant patients with CAAMR who received tocilizumab as salvage treatment.

METHODS

This retrospective monocentric study included 43 kidney transplant patients (202 tocilizumab concentrations) with CAAMR treated with intravenous or subcutaneous tocilizumab between December 2020 and January 2023. We developed a population pharmacokinetic model using nonlinear mixed effects modeling and identified the covariates that could contribute to tocilizumab AUC variability. Monte Carlo simulations were then performed to assess the subcutaneous and intravenous tocilizumab AUC for 0-28 days (M1), 56-84 days (M3), 140-168 days (M6), and 308-336 days (M12). Bioequivalence was defined by SC/IV AUC geometric mean ratios (GMRs) between 0.80 and 1.25.

RESULTS

A two-compartment model with parallel linear and nonlinear elimination best described the concentration-time data. Significant covariates for tocilizumab clearance were body weight, urinary albumin-to-creatinine ratio (ACR), and inflammation status [C-reactive protein (CRP) ≥ 5 mg/L]. The GMR values and their 90% confidence intervals at M3, M6, and M12 were within the 0.8-1.25 margin for equivalence. Conversely, the 90% prediction intervals of the GMR were much wider than the 90% confidence intervals and did not fall within 0.8 and 1.25.

CONCLUSIONS

From month 3 of treatment, the subcutaneous and intravenous tocilizumab administration schemes provided average bioequivalent pharmacokinetic exposure at the population level but not at the individual level. Body weight, inflammation, ACR, and administration scheme should be considered to personalize the dose of tocilizumab for patients with CAAMR. Further studies are required to determine the target of tocilizumab exposure in kidney transplant patients with CAAMR.

Granulomatous Tubulointerstitial Nephritis in a Kidney Allograft: Treatment with Interleukin-6 Receptor Antagonist Stabilises Kidney Function

Granulomatous tubulointerstitial nephritis (GTIN) attributed to early onset sarcoidosis is an ultrarare finding in an allograft kidney biopsy. We present the case of a young man with allograft dysfunction who had GTIN upon biopsy. We performed a thorough case review based on recovered records from early childhood and reassessed genetic testing results. We revised his underlying diagnosis from cryopyrin-associated periodic syndrome to early-onset sarcoidosis with wild-type NOD2 and established a rationale to use the interleukin-6 (IL-6) receptor blocker tocilizumab (TCZ). This suppressed his inflammatory disease and stabilised kidney function. We performed a literature review related to the emerging role of IL-6 pathway blockade in kidney transplantation. We identified 18 reports with 417 unique patients treated with TCZ for indications including HLA-desensitisation, transplant immunosuppression induction, treatment of chronic antibody-mediated rejection, and treatment of subclinical rejection. Both TCZ and the direct IL-6 inhibitor clazakizumab are being studied in ongoing randomised control trials.

Absence of IL-6 Receptor Blockade Effect on the Outcomes of Transplant Glomerulopathy in the Absence of Anti-HLA Donor-specific Antibodies

Background

Transplant glomerulopathy (TG) is the hallmark of chronic antibody-mediated rejection but often occurs without anti-HLA donor-specific antibodies (DSAs) in the assumption that other DSAs may be the effectors of the tissue injury. Recently, we reported a positive effect of interleukin-6 (IL-6) receptor blocker tocilizumab (TCZ) in TG/DSA+. In the present study, we investigate the effect of TCZ in a cohort of TG cases without detectable anti-HLA DSAs.

Methods

Single-center retrospective analysis of TG cases without anti-HLA DSAs (TG/DSA) treated with TCZ for chronic antibody-mediated rejection as first-line therapy evaluated through clinical, protocol biopsies, and gene expression analyses was included.

Results

Differently from TG/DSA+, TG/DSA- showed a progressive reduction in the estimated glomerular filtration rate at 12 mo and after that with no significant modification in microvascular inflammation or C4d+. No upregulation in tight junction protein-1, aldo-keto reductase family 1 member C3, and calcium/calmodulin-dependent serine protein kinase, documented in TG/DSA+, was noted in post-TCZ biopsies. The reduction of microvascular inflammation was associated with natural killer-cell reduction in TG/DSA+, whereas TG/DSA- tends to maintain or increase periglomerular/interstitial infiltration.

Conclusions

In the absence of anti-HLA DSAs, TG behavior seems not to be modified by IL-6 receptor blockade. These results are at variance with observational studies and previous trials with IL-6 inhibitors in TG associated with anti-HLA DSAs. These data may fuel the hypothesis of different mechanisms underlying TGs (including the potentially different roles of natural killer cells) and suggest carefully selecting patients with TG for clinical trials or off-label treatment based on their antidonor serologic status.

Early Exposure of Kidney Transplant Recipients with Chronic Antibody-Mediated Rejection to Tocilizumab-A Preliminary Study

Tocilizumab prevents clinical worsening of chronic antibody-mediated rejection (CAMR) of kidney transplant recipients. Optimization of this treatment is necessary. We identified the determinants of early tocilizumab exposure (within the first three months) and investigated the relationship between early plasma tocilizumab exposure and graft function. Patients with CAMR who started treatment with tocilizumab were retrospectively included. Demographic, clinical, and biological determinants of the tocilizumab trough concentration (Cmin) were studied using a linear mixed effect model, and the association between early exposure to tocilizumab (expressed as the sum of Cmin over the three first months (M) of treatment (ΣCmin)) and the urinary albumin-to-creatinine ratio (ACR) determined at M3 and M6 were investigated. Urinary tocilizumab was also measured in seven additional patients. Seventeen patients with 51 tocilizumab Cmin determinations were included. In the multivariate analysis, the ACR and time after tocilizumab initiation were independently associated with the tocilizumab Cmin. The ΣCmin was significantly lower (p = 0.014) for patients with an ACR > 30 mg/mmol at M3 and M6 than for patients with an ACR < 30 mg/mmol. Tocilizumab was detected in urine in only 1/7 patients. This study is the first to suggest that early exposure to tocilizumab may be associated with macroalbuminuria within the first six months in CAMR patients.

Emerging Therapies for Antibody-Mediated Rejection in Kidney Transplantation

Despite the advances in immunosuppressive medications, antibody-mediated rejection (AMR) continues to be a major cause of kidney allograft failure and remains a barrier to improving long-term allograft survival. Recently, there have been significant advances in the understanding of the pathophysiological process of AMR, along with the development of new therapeutic options. Additionally, surveillance protocols with donor-derived cell-free DNA and gene profile testing have been established, leading to the early detection of AMR. A multitude of clinical trials are ongoing, opening numerous opportunities for improving outcome in kidney transplant recipients. In this brief review, we discuss the emerging therapies for managing both active and chronic active AMR and highlight the ongoing clinical trials.

New insights into maladaptive vascular responses to donor specific HLA antibodies in organ transplantation

Transplant vasculopathy (TV) causes thickening of donor blood vessels in transplanted organs, and is a significant cause of graft loss and mortality in allograft recipients. It is known that patients with repeated acute rejection and/or donor specific antibodies are predisposed to TV. Nevertheless, the exact molecular mechanisms by which alloimmune injury culminates in this disease have not been fully delineated. As a result of this incomplete knowledge, there is currently a lack of effective therapies for this disease. The immediate intracellular signaling and the acute effects elicited by anti-donor HLA antibodies are well-described and continuing to be revealed in deeper detail. Further, advances in rejection diagnostics, including intragraft gene expression, provide clues to the inflammatory changes within allografts. However, mechanisms linking these events with long-term outcomes, particularly the maladaptive vascular remodeling seen in transplant vasculopathy, are still being delineated. New evidence demonstrates alterations in non-coding RNA profiles and the occurrence of endothelial to mesenchymal transition (EndMT) during acute antibody-mediated graft injury. EndMT is also readily apparent in numerous settings of non-transplant intimal hyperplasia, and lessons can be learned from advances in those fields. This review will provide an update on these recent developments and remaining questions in our understanding of HLA antibody-induced vascular damage, framed within a broader consideration of manifestations and implications across transplanted organ types.

Novel therapies for treatment of antibody-mediated rejection of the kidney

PURPOSE OF REVIEW

We aim to discuss current literature on novel therapies for antibody-mediated rejection (AMR) in kidney transplantation with a focus on chronic AMR.

RECENT FINDINGS

IL-6/IL-6 receptor blockers appear promising in the treatment of chronic AMR. Blocking this pathway was shown to reduce human leucocyte antigen-antibodies, improve histologic inflammation and increase T-regulatory cells. Based on experience in desensitization, IgG degrading endopeptidase, imlifidase, could be effective in AMR. There have been case reports describing the successful use of plasma cell/natural killer-cell-directed anti-CD38 antibody in the treatment of AMR. Off-target effects have been noted and strategies to mitigate these will be needed when using these agents. Complement inhibitors could be an effective add-on strategy to antibody-depleting therapies but their role in AMR needs to be better defined. Combining proteasome inhibitors and costimulation blockers has shown encouraging results in the prevention of AMR in animal models and is now being investigated in humans. Other novel strategies such as Fc neonatal receptor blockers which inhibit the recycling of pathogenic IgG and bispecific antibodies against B-cell maturation antigen/CD3+ T cells warrant further investigation.

SUMMARY

There are now a number of emerging therapies with varied targets and mechanism(s) of action that hold promise in the management of AMR and improving allograft survival.

Tocilizumab for the treatment of chronic antibody mediated rejection in kidney transplant recipients

BACKGROUND

Chronic active antibody-mediated rejection (CAAMR) constitutes a dominant form of late allograft failure. Several treatment strategies directed at CAAMR have been attempted but proven ineffective at delaying kidney function decline or reducing donor-specific antibodies (DSA). We describe our single-center experience using tocilizumab in patients with CAAMR.

METHODS

This is a retrospective analysis using electronic medical records. 38 kidney transplant recipients at Columbia University Irving Medical Center who had been prescribed tocilizumab and followed for at least 3 months between August 2013 through December 2019 were included.

RESULTS

Tocilizumab use was associated with a decrease in the rate of estimated glomerular filtration rate (eGFR) decline in the 6 months following treatment initiation as compared to the 3 months before tocilizumab was initiated (difference between slopes before and after initiation of treatment = 2.6 mL/min/1.73 m² (SE = .8, p = .002) per month for up to 6 months following Tocilizumab initiation). Allograft biopsies showed significant improvement in interstitial inflammation scores (score 1(0,1) to 0 (0,1), p = .03) while other histologic scores remained stable. There was no significant change in proteinuria or DSA titers post-treatment with tocilizumab.

CONCLUSIONS

Treatment of CAAMR with tocilizumab was associated with a decrease in the rate of eGFR decline and a reduction in interstitial inflammation scores in patients with CAAMR.

Impact of interleukin-6 on T cells in kidney transplant recipients

Interleukin-6 (IL-6), a multifunctional proinflammatory cytokine, plays a key role in T cell activation, survival, and differentiation. Acting as a switch that induces the differentiation of naïve T cells into Th17 cells and inhibits their development into regulatory T cells, IL-6 promotes rejection and abrogates tolerance. Therapies that target IL-6 signaling include antibodies to IL-6 and the IL-6 receptor and inhibitors of janus kinases; several of these therapeutics have demonstrated robust clinical efficacy in autoimmune and inflammatory diseases. Clinical trials of IL-6 inhibition in kidney transplantation have focused primarily on its effects on B cells, plasma cells, and HLA antibodies. In this review, we summarize the impact of IL-6 on T cells in experimental models of transplant and describe the effects of IL-6 inhibition on the T cell compartment in kidney transplant recipients.

Rationale for the IMAGINE study for chronic active antibody-mediated rejection (caAMR) in kidney transplantation

Chronic active antibody-mediated rejection (caAMR) in kidney transplantation is a major cause of late graft loss and despite all efforts to date, there is no proven effective therapy. Indeed, the Transplant Society (TTS) consensus opinion called for a conservative approach optimizing baseline immunosuppression and supportive care focused on blood pressure, blood glucose, and lipid control. This review provides the rationale and early evidence in kidney transplant recipients with caAMR that supported the design of the IMAGINE study whose goal is to evaluate the potential impact of targeting the IL6/IL6R pathway.

Collaboration between local nephrologists and the transplant centre ensures good outcomes in post-transplant care

Background

Despite substantial improvements in short-term kidney allograft survival, median long-term survival remains at a standstill. It is unclear whether and to what extent a transplant centre's post-transplant care influences long-term outcomes.

Methods

We retrospectively analysed 501 single kidney transplant recipients (KTRs) who underwent transplantation between 2009 and 2018 and did not develop rejection or de novo donor-specific antibodies (dnDSA) within the first post-transplant year. After that, KTRs were either followed exclusively every 3 months by the transplant centre (n = 197) or every 3 months by local nephrologists (n = 304) with only yearly follow-up by the transplant centre. We analysed kidney allograft outcomes regarding estimated glomerular filtration rate (eGFR) decline, proteinuria, development of dnDSA and rejection.

Results

No differences between the two groups were observed in the baseline characteristics and the characteristics at the end of the first post-transplant year (P > .05). KTRs followed by local nephrologists were comparable to KTRs followed by the transplant centre concerning patient survival (P = .541), kidney allograft survival (P = .385), eGFR decline (P = .488), progression of proteinuria (P > .05), the development of dnDSA (P = .335) and T-cell-mediated rejection (P = .480). KTRs followed by the transplant centre were more likely to undergo indication biopsies in case of allograft dysfunction and dnDSA (P < .001). Antibody-mediated rejection was diagnosed earlier and more frequently (P = .059), recurrent glomerulonephritis was diagnosed earlier and more frequently (P = .026) and immunosuppression was modified earlier and more frequently in response to histological findings (P = .038).

Conclusions

Our findings suggest that close collaboration between local nephrologists and the transplant centre ensures good allograft outcomes independent of the caregiver. Greater biopsy activity in the transplant centre allows for earlier diagnosis of allograft dysfunction as the basis for novel treatment options.

Emerging drugs for antibody-mediated rejection after kidney transplantation: a focus on phase II & III trials

INTRODUCTION

Antibody-mediated rejection (ABMR) is a leading cause of kidney allograft failure. Its therapy continues to be challenge, and no treatment has been approved for the market thus far.

AREAS COVERED

In this article, we discuss the pathophysiology and phenotypic presentation of ABMR, the current level of evidence to support the use of available therapeutic strategies, and the emergence of tailored drugs now being evaluated in systematic clinical trials. We searched PubMed, Clinicaltrials.gov and Citeline's Pharmaprojects for pertinent information on emerging anti-rejection strategies, laying a focus on phase II and III trials.

EXPERT OPINION

Currently, we rely on the use of apheresis for alloantibody depletion and intravenous immunoglobulin (referred to as standard of care), preferentially in early active ABMR. Recent systematic trials have questioned the benefits of using the CD20 antibody rituximab or the proteasome inhibitor bortezomib. However, there are now several promising treatment approaches in the pipeline, which are being trialed in phase II and III studies. These include interleukin-6 antagonism, CD38-targeting antibodies, and selective inhibitors of complement. On the basis of the information that has emerged so far, it seems that innovative treatment strategies for clinical use in ABMR may be available within the next 5-10 years.

Tocilizumab and Active Antibody-Mediated Rejection in Kidney Transplantation: A Literature Review

Introduction

Chronic kidney disease (CKD) is a major public-health problem that increases the risk of end-stage kidney disease (ESKD), cardiovascular diseases, and other complications. Kidney transplantation is a renal-replacement therapy that offers better survival compared to dialysis. Antibody-mediated rejection (ABMR) is a significant complication following kidney transplantation: it contributes to both short- and long-term injury. The standard-of-care (SOC) therapy combines plasmapheresis and Intravenous Immunoglobulins (IVIg) with or without steroids, with or without rituximab: however, despite this combined treatment, ABMR remains the main cause of graft loss. IL-6 is a key cytokine: it regulates inflammation, and the development, maturation, and activation of T cells, B cells, and plasma cells. Tocilizumab (TCZ) is the main humanized monoclonal aimed at IL-6R and appears to be a safe and possible strategy to manage ABMR in sensitized recipients. We conducted a literature review to assess the place of the anti-IL-6R monoclonal antibody TCZ within ABMR protocols.

Materials and Methods

We systematically reviewed the PubMed literature and reviewed six studies that included 117 patients and collected data on the utilization of TCZ to treat ABMR.

Results

Most studies report a significant reduction in levels of Donor Specific Antibodies (DSAs) and reduced inflammation and microvascular lesions (as found in biopsies). Stabilization of the renal function was observed. Adverse events were light to moderate, and mortality was not linked with TCZ treatment. The main side effect noted was infection, but infections did not occur more frequently in patients receiving TCZ as compared to those receiving SOC therapy.

Conclusion

TCZ may be an alternative to SOC for ABMR kidney-transplant patients, either as a first-line treatment or after failure of SOC. Further randomized and controlled studies are needed to support these results.