Calcineurin Inhibitor Nephrotoxicity Research Articles

Anuria after kidney transplantation diagnosed as early recurrence of focal segmental glomerulosclerosis combined with acute calcineurin inhibitor nephrotoxicity: a case report and literature review

BackgroundPrimary focal segmental glomerulosclerosis (FSGS) is a glomerular disease that sometimes recurs in patients after kidney transplantation (KT) and increases the risk of graft loss. Proteinuria is a common early sign of recurrent FSGS, but an abrupt decrease in urine volume is rare. Herein, we report a patient with early recurrence of FSGS with anuria following KT.Case presentationA 55-year-old man with end-stage kidney disease caused by primary FSGS experienced anuria on postoperative day 2 following deceased donor KT. Laboratory results revealed that serum tacrolimus trough levels were consistently elevated at the time of anuria. At first, we considered acute calcineurin inhibitor (CNI) nephrotoxicity based on graft biopsy on light microscopy, laboratory findings, and clinical courses. However, the allograft function did not recover even after discontinuation of CNI, and recurrent FSGS was diagnosed 2 weeks later on electron microscopy. A total of 13 sessions of plasmapheresis and two administrations of rituximab (375 mg/m2) were required to treat recurrent FSGS. The patient achieved a partial response, and the spot urine protein-to-creatinine ratio decreased from 15.5 g/g creatinine to 5.2 g/g creatinine. At 5 months following KT, the serum creatinine level was stable at 1.15 mg/dL.ConclusionsThese findings highlight that anuria can occur in cases of early recurrence of FSGS combined with acute CNI nephrotoxicity.

Effect of delayed graft function on immediate and long-term kidney transplant outcomes

Objective: to analyze the immediate and long-term outcomes of kidney transplantation (KT) depending on the duration of delayed graft function (DGF). Materials and methods. The study conducted a retrospective analysis of KT outcomes in 312 patients operated on at Botkin Hospital from June 2018 to December 2022. Exclusion criteria were primary non-function, severe surgical complications that required emergency transplantectomy in the first week after KT and cases where a comprehensive approach to DGF prevention was applied. DGF was defined as the need for dialysis within the first 7 days of KT. The severity of this complication was assessed by the time it took the transplanted kidney function to normalize from mild DGF to severe. We analyzed the immediate and long-term outcomes of KT depending on the presence of initial function and the severity of DGF. Results. DGF developed in 25.3% of cases. The mean time for graft function normalization was 16.5 ± 6.8 days. Mild DGF occurred in 68% of cases, severe DGF was determined in the remaining cases (32%). The incidence of complications was statistically significantly higher in the severe DGF group: 14/25 (56%) vs. 15/54 (27.8%) (p = 0.047). There were also no significant differences in the rate of complications between recipients with immediate and mild DGF: 43/233 (18.4%) vs. 15/54 (27.8%) (p > 0.05). Severe DGF lasting for more than 2 weeks had a statistically significant association with postoperative complications (p = 0.047) and with decreased long-term graft survival (log-rank p = 0.021). Conclusion. Development of severe DGF mainly depends on donor characteristics, timing and peculiarities of graft preservation. Nevertheless, other factors, such as acute calcineurin inhibitor nephrotoxicity, should not be ignored. Therefore, prevention of all potentially modifiable risk factors for DGF should go hand in hand with the expansion of the indications for donation.

Sirolimus in combination with low-dose extended-release tacrolimus in kidney transplant recipients.

Many challenges remain for long-term survival of renal allografts. Once-daily sirolimus (SRL) combined with low-dose extended-release tacrolimus (LER-TAC) may improve medication adherence and reduce the potential nephrotoxicity of calcineurin inhibitors (CNI) compared with standard immunosuppression regimens, thus potentially improving long-term graft survival. This retrospective, observational, single-center, propensity score matching (PSM) study compared conversion to SRL combined with low-dose ER-TAC and mycophenolic acid (MPA) combined with standard-dose TAC in kidney transplant recipients. After PSM, there were 56 patients in each group. Efficacy, safety, and medication adherence were evaluated over 12 months. There was no significant difference between the two groups in terms of graft and recipient survival and incidence of biopsy-proven acute rejection (p = 1.000), and none of the recipients developed dnDSA after conversion. The mean eGFR improved in SRL + LER-TAC group after conversion compared to before conversion (51.12 ± 20.1 ml/min/1.73 m2 vs. 56.97 ± 19.23 ml/min/1.73 m2, p < 0.05). The medication adherence at 12 months after conversion was superior to before conversion (p = 0.002). Our findings suggest that an immunosuppressive regimen of SRL combined with low-dose ER-TAC is no less effective and safe than standard immunosuppressive regimens for renal transplant recipients and may improve graft renal function and medication adherence.

Diagnostic significance of TGF-β1 in kidney recipients with graft dysfunction

Development of minimally invasive diagnosis techniques for complications in recipients, based on analysis of the levels of molecular and genetic biomarkers, is an urgent task facing modern transplantology. Transforming growth factor beta 1 (TGF-β1), which has multiple effects in the body, among the potential indicators of complications.Objective: to assess the diagnostic significance of serum TGF-β1 in kidney recipients with graft dysfunction.Materials and methods. The study included 129 kidney recipients aged 17 to 68 years and 35 healthy subjects. Serum TGF-β1 levels in the recipients were determined by immunoenzyme technique.Results. Kidney recipients included 95 patients with laboratory and clinical signs of graft dysfunction, who underwent biopsy of the transplanted kidney, followed by morphological examination, and 34 recipients with normal graft function. Serum TGF-β1 levels in the kidney recipients were significantly higher than in their healthy counterparts (p = 0.00001); it did not correlate with most blood test parameters; with the glomerular filtration rate (GFR). Kidney recipients with graft dysfunction had significantly higher TGF-β1 levels than other recipients (p = 0.018). In recipients with graft dysfunction, morphological study revealed the following: acute tubular necrosis (ATN, n = 11), acute T-cell mediated rejection (ACR, n = 26), acute antibody-mediated rejection (AMR, n = 35), non-immune-mediated nephrosclerosis with signs of calcineurin inhibitor nephrotoxicity (CNI nephrotoxicity, n = 13), and recurrent glomerulonephritis (chronic graft rejection, n = 10). Recipients with immune-mediated graft injury (ACR, AMR and chronic rejection) had higher serum TGF-β1 levels than recipients with graft dysfunction resulting from other causes, p &lt; 0.0001. Kidney recipients with serum TGF-β1 levels above the threshold value of 94.3 ng/mL had a higher risk of immune-mediated graft dysfunction than other kidney recipients (RR = 2.2 ± 0.22 [95% CI 1.46–3.46]) with 77.5% test sensitivity and 60.3% specificity.Conclusion. The calculated threshold serum TGF-β1 level in kidney recipients can be considered as an auxiliary indicator of graft dysfunction resulting from acute or chronic rejection.

Chronic dehydration induces injury pathways in rats, but does not mimic histopathology of chronic interstitial nephritis in agricultural communities

CINAC-patients present renal proximal tubular cell lysosomal lesions which are also observed in patients experiencing calcineurin inhibitor (CNI) nephrotoxicity, suggesting that CINAC is a toxin-induced nephropathy. An alternative hypothesis advocates chronic dehydration as a major etiological factor for CINAC. Here, we evaluated histological and molecular changes in dehydrated versus toxin exposed rats. Wistar rats were divided in 3 groups. Group 1 (n = 6) had free access to drinking water (control group). Group 2 (n = 8) was water deprived for 10 h per 24 h, 5 days/week and placed in an incubator (37 °C) for 30 min/h during water deprivation. Group 3 (n = 8) underwent daily oral gavage with cyclosporine (40 mg/kg body weight). After 28 days, renal function, histopathology and proteomic signatures were analysed. Cyclosporine-treated rats developed focal regions of atrophic proximal tubules with associated tubulo-interstitial fibrosis. PASM staining revealed enlarged argyrophilic granules in affected proximal tubules, identified as lysosomes by immunofluorescent staining. Electron microscopy confirmed the enlarged and dysmorphic phenotype of the lysosomes. Overall, these kidney lesions resemble those that have been previously documented in farmers with CINAC. Dehydration resulted in none of the above histopathological features. Proteomic analysis revealed that dehydration and cyclosporine both induce injury pathways, yet of a clear distinct nature with a signature of toxicity only for the cyclosporine group. In conclusion, both cyclosporine and dehydration are injurious to the kidney. However, dehydration alone does not result in kidney histopathology as observed in CINAC patients, whereas cyclosporine administration does. The histopathological analogy between CINAC and calcineurin inhibitor nephrotoxicity in rats and humans supports the involvement of an as-yet-unidentified environmental toxin in CINAC etiology.

Association of high intra-patient variability in tacrolimus exposure with calcineurin inhibitor nephrotoxicity in kidney transplantation

Tacrolimus intra-patient variability (IPV) is a novel predictive marker for long-term kidney transplantation outcomes. We examined the association between IPV and calcineurin inhibitor (CNI) nephrotoxicity and the impact of pharmacogenes on CNI nephrotoxicity and IPV. Among kidney transplant recipients at our hospital between January 2013 and December 2015, the records of 80 patients who underwent 1-year protocol renal allograft biopsy and agreed to donate blood samples for genetic analysis were retrospectively reviewed. The cohort was divided into the low and high IPV groups based on a coefficient variability cutoff value (26.5%). In multivariate analysis, the IPV group was involved in determining CNI nephrotoxicity (HR 4.55; 95% CI 0.05–0.95; p = 0.043). The 5-year graft survival was superior in the low IPV group than in the high IPV group (100% vs 92.4% respectively, p = 0.044). Analysis of the time above therapeutic range (TATR) showed higher CNI nephrotoxicity in the high IPV with high TATR group than in the low IPV with low TATR group (35.7% versus 6.7%, p = 0.003). Genetic analysis discovered that CYP3A4 polymorphism (rs2837159) was associated with CNI nephrotoxicity (HR 28.23; 95% CI 2.2–355.9; p = 0.01). In conclusion, high IPV and CYP3A4 polymorphisms (rs2837159) are associated with CNI nephrotoxicity.

Long-Term Results in Recipients of Late Conversion to a Calcineurin Inhibitor-Free Regimen with Everolimus After Kidney Transplantation

Conversion to a calcineurin inhibitor (CNI)-free regimen in cases of CNI nephrotoxicity (CNIT) is a strategy to improve the long-term outcomes of kidney transplantation. However, the long-term results of late conversion to a CNI-free regimen using everolimus (EVR) remain uncertain. Nine kidney transplant recipients with biopsy-confirmed CNIT were enrolled. The median time of CNIT diagnosis was 9.0 years. All recipients underwent a conversion from CNI to EVR. We evaluated the clinical outcomes, development of donor-specific antibody (DSA), the incidence of rejection, alternativearteriolar hyalinosis (aah) scores, renal function changes, and T cell responses by mixed lymphocyte reaction (MLR) assay after conversion. The median follow-up after conversion was 5.4 years. Currently, 7 of 9 recipients have received a CNI-free regimen for 1.6 to 9.5 years. In the other 2 recipients, one experienced graft loss due to CNIT 3.8 years after conversion, and the other had to resume CNI due to acute T cell-mediated rejection (ATMR) a year after conversion. None of the recipients developed DSA. No rejection was observed in the kidney allograft histology except for the ATMR case. Moreover, improvement in aah scores was noted in one patient. Furthermore, serum creatinine levels were stable in recipients without proteinuria before the EVR add-on. In the MLR analysis, low responses against donors were observed in stable patients. Late conversion to an EVR-based regimen without CNI may be a promising therapeutic strategy against CNIT, particularly for recipients without proteinuria before the EVR add-on.

Prevalence of renal pathological disorders in kidney transplant recipients: an observational study in the north of Iran

Introduction: There are possible adverse effects and pathological disorders that can occur after kidney transplantation. The prevalence of these outcomes in kidney transplant patients is different worldwide. Objectives: In this study, we decided to take a general look at the prevalence of pathological disorders in kidney transplant patients undergoing biopsy. Patients and Methods: This cross-sectional study was conducted on 206 kidney transplant recipients who underwent biopsy of transplanted kidney at Razi medical education center in Rasht city between 2008 and 2019. Information was collected from medical records and interviewing patients. The data were analyzed using SPSS software version 26. They were summarized as the mean (SD) or as median (IQR). The frequency distribution (percentage) was conducted to describe the qualitative variables. Results: Out of 206 patients, 143 (69.4%) were male and the mean age at transplantation was 46.7±13.6 years. About 42.72% were non-relative donors, 47.57% were brain dead donors and 9.71% were family donors. The most common pathological disorder was nephrotoxic caused by calcineurin inhibitors (CNIs) (41.75%) and the most common type of graft rejection was antibody-dependent graft rejection (46.12%). In terms of transplant outcome, 35.92% of the patients suffered transplant rejection and 23.3% of them died. The results of this study did not show a significant relationship between the administration of immunosuppressive drugs and the pathological disorders. Conclusion: The present study showed that the most common pathological disorder in kidney transplant patients was CNIs nephrotoxicity, and the most common type of transplant rejection was antibody-dependent transplant rejection.

The Renal Histological Correlates of Refractory Renal Dysfunction After Liver Transplantation

Kidney dysfunction is common after liver transplantation (LT)and is often attributed to calcineurin inhibitors (CNIs). Very few studies have looked at histological causes. The study is a retrospective analysis of histological findings and diagnosis in all patients who underwent a kidney biopsy after LT from 2010 to 2020. Data are shown as mean±standard deviation or medians (25-75 interquartile range). The study cohort consisted of 26 patients (25 males, 1 female), aged 55±7 years at the time of the kidney biopsy. Kidney biopsies were done at 27.5 (6.7-60.7) months after LT. At the time of the kidney biopsy, the median serum creatinine was 2.10 (1.50-2.86) mg/dland proteinuria was 3.8 (1.8-5.9) gm/day. Twenty-four (92%) patients were on CNIs. The diagnoses on kidney biopsies were diabetic nephropathy (n=7), focal segmental glomerulosclerosis (n=4), CNI nephrotoxicity (n=3), IgA nephropathy (n=4), chronic glomerulonephritis (n=3), hypertensive nephropathy (n=1), membranous glomerulonephritis (n=1), acute on chronic interstitial nephritis (n=1), and C1q nephropathy (n=1), and the sample was inadequate in one patient. A total of sixteen patients had progression of kidney disease. The kidney function remained stable/improved in 6 (23%) patients, follow-up data were not available for 4 patients. Fourteen (53.8%) patients (including one with CNI nephrotoxicity) required hemodialysis at 13.5 (5.7-29) months after the kidney biopsy. Although the kidney biopsy diagnosed the cause of unexplained renal insufficiency in LT recipients, the majority of patients progressed to end-stage renal disease despite treatment modifications. The use of CNIs was an uncommon cause of renal impairment.

A Low Tacrolimus Concentration-to-Dose Ratio Increases Calcineurin Inhibitor Nephrotoxicity and Cytomegalovirus Infection Risks in Kidney Transplant Recipients: A Single-Center Study in Japan

Tacrolimus (TAC) has several problems due to its narrow therapeutic window and variations pharmacokinetics and pharmacodynamics. Recently, several studies reported that TAC metabolism, defined by TAC blood trough concentration to dose (C/D) ratio, was associated with TAC toxicity. Reports on once-daily extended-release TAC (TAC-ER) are limited. The present study aimed to investigate the effect of the TAC metabolic rate on TAC-ER and compare TAC area under the curve (AUC) between fast and slow metabolizers. A total of 58 recipients were included in this study. The optimal cut-off value and time of the C/D ratio on TAC-ER for fast and slow metabolizers was determined using receiver operating characteristic curve analysis for biopsy-proven calcineurin inhibitor (CNI) nephrotoxicity. The optimal time to evaluate the C/D ratio was 1 month after kidney transplantation (KT) and the cut-off value was 0.9. The multivariate analysis for CNI nephrotoxicity risk showed that only TAC metabolism was associated with CNI nephrotoxicity (hazard ratio 10.60, P=.005, 95% CI 2.03-55.22). Cytomegalovirus infection occurred more frequently in fast metabolizers when the cut-off value of the C/D ratio was set to 0.9 at 3 months after KT (P=.04). The TAC C4, AUC2-8, was higher in fast metabolizers than in slow metabolizers (P < .01, P=.03, respectively). The study revealed that TAC fast metabolizers on TAC-ER may be classified as a high-risk group for CNI nephrotoxicity and cytomegalovirus infection. The result of TAC AUC supported the hypothesis that fast metabolizers tended to be overexposed to immunosuppressive agents early after oral administration.

De novo collapsing glomerulopathy after kidney transplantation: Description of two cases.

Among different forms of de novo focal segmental glomerulosclerosis (FSGS), which can develop after kidney transplantation (KTx), collapsing glomerulopathy (CG) is the least frequent variant, but it is associated with the most severe form of nephrotic syndrome, histological findings of important vascular damage, and a 50% risk of graft loss. Here, we report two cases of de novo post-transplant CG. A 64-year-old White man developed proteinuria and worsening of renal function 5 years after KTx. Before the KTx, the patient was affected by an uncontrolled resistant hypertension, despite multiple antihypertensive therapies. Blood levels of calcineurin inhibitors (CNIs) were stable, with intermittent peaks. Kidney biopsy showed the presence of CG. After introduction of angiotensin receptor blockers (ARBs), urinary protein excretion progressively decreased in 6 months, but subsequent follow-up confirmed a progressive renal function decline. A 61-year-old White man developed CG 22 years after KTx. In his medical history, he was hospitalized twice to manage uncontrolled hypertensive crises. In the past, basal serum cyclosporin A levels were often detected above the therapeutic range. Low doses of intravenous methylprednisolone were administered due to the histological inflammatory signs shown on renal biopsy, followed by a rituximab infusion as a rescue therapy, but no clinical improvement was seen. These two cases of de novo post-transplant CG were supposed to be mainly caused by the synergic effect of metabolic factors and CNI nephrotoxicity. Identifying the etiological factors potentially responsible for de novo CG development is essential for an early therapeutic intervention and the hope of better graft and overall survival.

Reversible Chronic Interstitial Nephritis Induced by Tacrolimus &amp;lt;br/&amp;gt;—Tacrolimus Chronic Interstitial Nephritis

Calcineurin inhibitors (CNI) are potent immunosuppressive agents in prophylaxis against graft rejection and autoimmune diseases including primary glomerulopathies. Previous research showed reversible; acute afferent arteriolar vasculopathy and irreversible chronic interstitial fibrosis associated with CNI nephrotoxicity. In this case report we describe a patient, with minimal change disease, that had developed chronic and progressive renal disease while receiving therapeutic dose of Tacrolimus. His serum creatinine had reached 537 umol/L and his nephrotic state worsened. Kidney biopsy showed chronic interstitial nephritis. Tacrolimus was discontinued and he was treated with 1 mg/kg prednisone in addition to Mycophenolate mofetil (MMF) 1 g twice daily. By the 2nd month; serum creatinine returned to normal and by the 3rd month serum albumin too. After 1 month of therapy; the dose of Prednisone was tapered down gradually till 5 mg daily by the end of 3rd month. Moreover, the dose of MMF was reduced to 500 mg X2 by the end of 3rd month. After 2 years of follow up; he remained stable and without relapse of NS or renal failure. In conclusion, reversible renal disease, due to chronic interstitial nephritis can be induced by CNI which is amenable to treatment with Prednisone and MMF.

Mesangiolysis in Pathological Chronic Active Antibody-Mediated Rejection in Kidney Transplant Biopsies

Introduction: This study aimed to determine if immune or nonimmune and acute or chronic lesions associated with mesangiolysis (MGLS) occurred in biopsy-proven pathological chronic active antibody-mediated rejection (P-CAABMR) in kidney transplant biopsies. Methods: We evaluated MGLS in 41 patients with biopsy findings of P-CAABMR from January 2016 to December 2019. Histological scoring was evaluated by Banff classification. Multivariate logistic regression analysis was performed using a forward selection method. Results: Fifteen of the 41 P-CAABMR biopsies (36.6%) cases showed MGLS. The estimated glomerular filtration rate (eGFR) was significantly lower in the MGLS-positive compared with the MGLS-negative group, and proteinuria was significantly higher in the MGLS-positive compared with the MGLS-negative group. In the clinical model, multivariate analysis was performed using covariates of eGFR and duration after transplantation significantly correlated with MGLS by simple analysis, in addition to type of calcineurin inhibitor use (tacrolimus or cyclosporine), donor-specific antibodies, diabetes, and hypertension grade defined by use of antihypertensive therapy or/and blood pressure level. Only hypertension grade was significantly correlated with MGLS. In the pathological model, multivariate analysis was performed using the presence of FSGS and the aah and cg scores significantly correlated with MGLS by simple analysis, in addition to g and ptc scores. The cg score was significantly correlated with hypertension grade, duration after transplantation, g, ah, and aah. Conclusion: Lower graft function and higher proteinuria was observed in MGLS of P-CAABMR. The Banff cg score was independently related to MGLS in multivariate analysis. Sustained glomerulitis, calcineurin inhibitor nephrotoxicity, and hypertension may cause Banff cg lesions, leading to MGLS in P-CAABMR.

"Creating Blue Skies Overhead for All" Introduction of the 2022 Recipient of the Medawar Prize of the Transplantation Society: Professor Jeremy Chapman.

"Creating Blue Skies Overhead for All" Introduction of the 2022 Recipient of the Medawar Prize of the Transplantation Society: Professor Jeremy Chapman.

Acute Calcineurin Inhibitor Nephrotoxicity Diagnosed Using Kidney Doppler Ultrasonography After Heart Transplant: A Case Report

Acute calcineurin inhibitor (CNI) nephrotoxicity is a common complication associated with CNI exposure. However, it can be difficult to diagnose. Herein, we report a case of acute CNI nephrotoxicity after heart transplant that was visualized using kidney Doppler ultrasonography. A 38-year-old female patient underwent heart transplant 5 years after the use of left ventricular assist device support because of advanced heart failure due to ischemic cardiomyopathy. Corticosteroids, tacrolimus, and mycophenolate mofetil were administered as immunosuppressive regimens postoperatively. The patient gradually developed kidney dysfunction despite a favorable perioperative clinical course and hemodynamics. Serum creatinine increased to 1.89 mg/dL on postoperative day (POD) 9, and the kidney Doppler ultrasonography examination showed severely reduced blood flow in the renal and renal segmental arteries, indicating acute CNI nephrotoxicity due to vasoconstriction of the renal arterioles. After the cessation of tacrolimus, kidney function returned to baseline levels within 2 days, and the kidney Doppler ultrasonography examination on POD 19 revealed a significant increase in blood flow in the renal and renal segmental arteries. Basiliximab followed by everolimus were administered as alternative immunosuppressants. No organic stenosis of the renal artery was detected on the kidney magnetic resonance angiography, and the patient was discharged on POD 51, without any other adverse events, including rejection. Although CNIs are widely used after heart transplant, acute nephrotoxicity should always be considered. After heart transplant, a kidney Doppler ultrasonography should be performed routinely and promptly if there are any clinical manifestations related to kidney function.

New immunosuppressive agents in transplantation

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

Kidney Disease after Heart and Lung Transplantation

Chronic kidney disease (CKD) is not only common after lung and heart transplantation but also is associated with increased morbidity and mortality due to multiple pre-, peri- and post-transplant factors. While the exact incidence of CKD in this population is not well-defined, it seems to have gradually increased over the years as older recipients are more frequently considered. The increasing success of the procedure and expanding transplant candidate pool has allowed many with comorbid conditions to receive a transplant, which was considered prohibitive in the past. This review presents risk factors that have been linked to CKD as well as interventions that may help alleviate this serious problem. The impact of pretransplant renal function and the overexaggerated role of chronic nephrotoxicity of calcineurin inhibitors is discussed in detail. Until the exact pathophysiology of kidney disease is better understood, there is a dire need to expand the research agenda beyond observational studies.

P8.122: Tacrolimus Dose Reduction as an Effective Therapeutic Approach to the Patients With Active BK Virus Replication And Nephrotoxicity

Background: BK viral nephropathy (BKVN) affects a significant proportion of kidney grafts in the early post-transplant period and often leads to functional failure of these grafts. The intensity of immunosuppressive therapy plays a significant role in the activation of BK viral (BKV) replication. Methods: 457 per-protocol biopsies of kidney grafts were performed in a group of 161 newly transplanted patients. The incidence of histological signs of tacrolimus nephrotoxicity as a manifestation of excessive immunosuppression was calculated using the Calcineurin Inhibitor Nephrotoxicity Score (CINS). In case of detection of simultaneous toxicity and substantial BKV replication, the dose of tacrolimus and/or mycophenolate was reduced and the effect on the inhibition of BKV activation and regression of toxic changes were compared. In parallel, we studied the effect of pre-emptive reduction of tacrolimus dose on the development of BKV replication in isolated detections of toxicity during the subsequent period. Results: The reduction of tacrolimus and mycophenolate dose in patients with histological evidence of toxicity and significant BKV replication was associated with an early and significant decrease in the BKV plasma load compared to isolated mycophenolate reduction (P = 0.023), significant decrease in CINS (P = 0.001) and better functional parameters at the end of this one-year follow-up (P = 0.024). A pre-emptive dose reduction of tacrolimus in case of toxicity evidence led to a marked reduction in the incidence of substantial BKV viremia during the subsequent period. Conclusions: The reduction of tacrolimus and mycophenolate dose in patients with histologically verified tacrolimus nephrotoxicity represents a more effective approach to attenuate significant BKV replication than a single-dose reduction of mycophenolate, including the regression of toxic changes. Pre-emptive tacrolimus dose reduction in case of toxicity signs is associated with a lower incidence of significant BKV replication during the first year after transplantation, without increasing the risk of acute rejection. Supported by MH CZ – DRO (FNOl, 00098892) and by grant IGA_LF_2022_03.

P15.04: Human Primary Renal Tubuloids as Tools for Calcineurin Inhibitor Nephrotoxicity Assessment

P15.04: Human Primary Renal Tubuloids as Tools for Calcineurin Inhibitor Nephrotoxicity Assessment

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

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