Protective effects of Mizoribine on Cyclosporine A nephropathy in rats

Oxidative stress-induced renal telomere shortening as a mechanism of cyclosporine-induced nephrotoxicity

Due to the association of oxidative stress and telomere shortening, it was aimed in the present study to investigate the possibility whether cyclosporine-A exerts its nephrotoxic side effects via induction of oxidative stress-induced renal telomere shortening and senescent phenotype in renal tissues of rats. Renal oxidative stress markers, 8-hydroxydeoxyguanosine, malondialdehyde, and protein carbonyl groups were measured by standard methods. Telomere length and telomerase activity were also evaluated in kidney tissue samples. Results showed that cyclosporine-A treatment significantly (P < 0.05) enhanced renal malondialdehyde, 8-hydroxydeoxyguanosine, and protein carbonyl groups levels, decreased renal telomere length, and deteriorated renal function compared with the controls. Renal telomerase activity was not affected by cyclosporine-A. Renal telomere length could be considered as an important parameter of both oxidative stress and kidney function. Telomere shortening and accelerated kidney aging may be caused by cyclosporine-induced oxidative stress, indicating the potential mechanism of cyclosporine-induced nephrotoxicity.

The first year results of mizoribine/tacrolimus-based multitarget treatment for consecutive patients with lupus nephritis

BACKGROUND

Despite the high efficacy of mycophenolate mofetil (MMF)/tacrolimus-based multitarget treatment, risks of infections are a matter of concern. In the present study, we clarified the potential of multitarget therapy using mizoribine opposed to MMF.

METHODS

A total of 36 patients with biopsy-proven lupus nephritis were treated with mizoribine, tacrolimus, and glucocorticoids and then retrospectively evaluated. To determine the efficacy, proteinuria remission (≤ 0.2 g/day), complete remission (Liu et al. in Ann Intern Med 162:18-26, 2015) and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) remission rates, and the prednisolone dose at months 6 and 12 were evaluated. The associations between serum mizoribine/tacrolimus levels and clinical parameters were investigated. To assess safety, adverse events were inspected.

RESULTS

All patients could continue the original treatment regimen without withdrawal or exacerbations through month 12. At month 6, the proteinuria remission, complete remission, SLEDAI remission rates, and prednisolone dose were 69, 53, 36%, and 12.1 mg/day, respectively, whereas the values at 12 months were 92, 67, 50%, and 8.8 mg/day, respectively. The treatment was efficacious for every histologic type of nephritis and non-renal manifestations of SLE. Excluding one patient who was hospitalized due to upper respiratory tract infection, serious infections, including pneumonia and cytomegalovirus disease, were not observed. Higher trough tacrolimus levels were associated with normalization of complement, whereas higher peak mizoribine levels with prevention of cytomegalovirus viremia.

CONCLUSIONS

Our results suggest that multitarget therapy using mizoribine opposed to MMF is highly safe and effective through 12 months. The therapy may enable faster dose reduction of concomitant glucocorticoids.

Calcineurin inhibitors in systemic lupus erythematosus

The calcineurin inhibitors (CNIs) belong to a group of immunosuppressive agents that block T-cell activation through the suppression of the calcium/calcimodulin-dependent phosphatase calcineurin. Agents such as cyclosporine A (CSA) and tacrolimus (TAC) have long been used in patients with systemic lupus erythematosus (SLE). TAC is preferred to CSA in SLE because of the lower frequency of cosmetic, hypertensive and dyslipidemic adverse effects. Recent randomised controlled trials have demonstrated noninferiority of TAC to mycophenolate mofetil (MMF) or cyclophosphamide (CYC) for induction therapy of lupus nephritis. Low-dose combination of TAC and MMF has also been shown to outperform CYC pulses in inducing remission of lupus nephritis in Chinese patients. TAC does not affect fertility and is relatively safe in pregnancy. In SLE patients who are intolerant or refractory to conventional immunosuppressives, or where contraindications to other immunosuppressive agents exist, TAC is an alternative option. However, the therapeutic window of TAC is narrow, and drug level monitoring is required to ensure drug exposure and minimise toxicities. Current evidence of TAC in lupus nephritis is limited to 6 months, and its long-term safety as maintenance therapy of SLE is yet to be determined. Newer chemical analogues of CNIs, such as voclosporin, with less variable plasma concentration are being tested in lupus nephritis.

Treatment of pediatric-onset lupus nephritis: a proposal of optimal therapy

Lupus nephritis (LN) is one of the major clinical manifestations of systemic lupus erythematosus (SLE) which occurs frequently in the early stages of pediatric-onset cases. Since SLE is a chronic disease associated with frequent disease flares and effective and safe maintenance therapy is required for achieving a favorable outcome, optimal treatment for LN in pubertal patients is a great challenge that remains to be overcome. Although its etiology remains unclear, it has been reported that the innate and adaptive immune systems have been reported to play an important role in the pathogenesis of SLE. However, studies of drugs that have been useful in controlling inflammatory pathways mediated by the innate and adaptive immune systems are now underway. In clinical practice, recent advances in the management of LN, together with earlier renal biopsy and selective use of aggressive immunosuppressive therapy, have contributed to a favorable outcome in children and adolescents with LN. However, the balance of the efficacy of treatment in terms of long-term prognosis and its adverse effects should be weighed in determining the treatment strategy.

Pro: The use of calcineurin inhibitors in the treatment of lupus nephritis

Renal disease in systemic lupus erythematosus (SLE) carries significant morbidity and mortality. Cyclophosphamide (CYC)- and mycophenolate mofetil (MMF)-based induction regimens are not ideal in terms of efficacy and toxicity. The adverse effects of CYC, such as infection risk, infertility, urotoxicity and oncogenicity, limit its use in lupus nephritis. Although MMF is non-inferior to CYC as induction therapy and has reduced gonadal toxicity and oncogenic potential, meta-analyses of clinical trials do not show a lower rate of infective and gastrointestinal complications. Tacrolimus (TAC) has recently been shown to have equal efficacy to either MMF or CYC for inducing remission of lupus nephritis. A low-dose combination of MMF and TAC appears to be more effective than intravenous CYC pulses in Chinese patients, and has potential to replace the more toxic CYC regimens in high-risk subgroups. TAC may be considered as another non-CYC alternative for induction therapy of lupus nephritis and in those with refractory disease or intolerance to CYC or MMF. TAC has no negative effect on fertility in younger women, and unlike MMF and CYC, it is safe in pregnancy. However, TAC has a narrow therapeutic window and drug level monitoring is required to ensure drug exposure and minimize acute toxicities. Current evidence for the efficacy of TAC in lupus nephritis is limited to 6 months and the incidence of renal flare after discontinuation of therapy or switching to azathioprine appears to be higher than other induction agents. Long-term data and the incidence of chronic nephrotoxicity of TAC as maintenance therapy in lupus nephritis are currently lacking and further prospective trials are needed to address these issues.

The effects of valsartan on renal glutathione peroxidase expression in alleviation of cyclosporine nephrotoxicity in rats

Introduction: Nephrotoxicity as a side effect caused by the immunosuppressive drug, cyclosporine-A (CsA), can be a major problem in transplant medicine. Oxidative stress may play an important role in the CsA-induced nephrotoxicity. It has been shown that the antihypertensive drug, valsartan (Val), has also renoprotective effects but, its molecular mechanism is largely unknown. In the present study, it was aimed to evaluate the Val effect in the alleviation of CsA nephrotoxicity via probable renal glutathione peroxidase (GPx) upregulation and oxidative stress decrease.

Methods: Thirty-two Sprague-Dawley rats were divided into four groups based on CsA and/or Val administration: group A (Control, 1 mL/kg/day of olive oil as vehicle), group B (CsA, 30 mg/kg/day), group C (CsA+Val, 30+30 mg/kg/day), and group D (Val, 30 mg/kg/day). After the administration period (six weeks), renal GPx expression was evaluated by real-time polymerase chain reaction (PCR). Plasma levels of GPx and 8-Hydroxydeoxyguanosine (8-OHdG) were measured by enzyme-linked immunosorbent assay (ELISA). Malondialdehyde (MDA) and protein carbonyl groups (PCG) were measured by spectrophotometer. Plasma levels of urea and creatinine were measured by an autoanalyzer.

Results: CsA treatment led to the decrease in renal expression and plasma levels of GPx in comparison to other study groups. Rats received CsA were detected to have significantly (p<0.05) higher plasma 8-OHdG, MDA, PCG, urea, and creatinine levels in comparison to other groups. Plasma urea and creatinine levels were negatively correlated with renal GPx expression and positively correlated with the oxidative stress markers.

Conclusion:Administration of Val may result in attenuating the nephrotoxic side effect of CsA via probable renal GPx upregulation, and subsequently oxidative stress decrease.

Safety and efficacy of mizoribine treatment in nephrotic syndrome complicated with hepatitis B virus infection: a clinical study

Objective The objective of this study is to explore the efficacy and safety of mizoribine (MZR) in treating nephrotic syndrome patients afflicted with hepatitis B virus (HBV). Methods The present study included 36 nephrotic syndrome patients accompanied with HBV infection. A draft of MZR (150-200 mg/d), methylprednisolone (0.6-0.8 mg/kg·d), and entecavir (0.5 mg/d) was administered to study patients over 24 weeks. The serum albumin (AlB), 24-h urine protein (24-U-TP), liver and renal functions, and HBV-DNA were quantified before and at 2, 4, 8, 12, 16, 20, and 24 weeks after the treatment. The adverse responses were recorded. Results The AlB levels of patients increased gradually after comprehensive treatment, while the 24-U-TP, serum cholesterol, and triglyceride (TG) levels declined gradually. The changes at 24 weeks post-treatment were statistically significant. Compared with the levels before treatment, the HBV-DNA, transaminase, and renal functions of the patients were not significantly altered after the treatment. No evident adverse response was found. Conclusion Treatment using MZR in combination with methylprednisolone and entecavir in HBV-positive nephrotic syndrome patients displays significant efficacy with a low incidence of adverse reactions.

Influence of cyclosporine A on glomerular growth and the effect of mizoribine and losartan on cyclosporine nephrotoxicity in young rats

The aim of this study was to evaluate the influence of cyclosporine A (CsA) on glomerular growth and the effect of mizoribine (MZR) and losartan (LSAR) on CsA-induced nephropathy in young rats. Six-week-old male Sprague-Dawley rats maintained on a low salt diet were given CsA (15 mg/kg), CsA and LSRT (30 mg/kg/day), CsA and MZR (5 mg/kg), or a combination of CsA, LSRT, and MZR for 4 and 7 weeks (two experiments) and compared with control group (olive oil-treated). Histopathology and glomerular size, inflammatory and fibrotic factors were studied. The score of acute CsA toxicity significantly decreased in the CsA + MZR group compared to the CsA group (p < 0.01). MZR and MZR + LSRT reduced tubulointerstitial fibrosis and TGF-β1 mRNA expression at 7 weeks. Osteopontin (OPN) mRNA expression was decreased at 7 weeks in MZR + LSRT (p < 0.01). Glomerular area decreased CsA group and recovered in MZR (p < 0.01) and MZR + LSRT (p < 0.01) at 7weeks. This study demonstrated that MZR and LSRT had suppressive effects on inflammatory process in chronic CsA nephropathy and led to improvement of tubular damage, tubulointerstitial fibrosis and arteriolopathy by down regulation of OPN and TGF-β1 and glomerular size contraction.

Mizoribine in the treatment of pediatric-onset glomerular disease

BACKGROUND

Mizoribine (MZR) is a selective inhibitor of inosine monophosphate dehydrogenase, a key enzyme in the pathway responsible for de novo synthesis of guanine nucleotides. As an immunosuppressant, MZR has been used successfully without any serious adverse effects in the treatment of renal diseases in children as well as adults. Besides its immunosuppressive effect, MZR has been reported to ameliorate tubulointerstitial fibrosis in rats via suppression of macrophage infiltration.

DATA SOURCES

In this review, we summarize reported possible benefits of MZR in the treatment of pediatriconset glomerular disease.

RESULTS

We recently observed that MZR itself selectively attenuates the expression of monocyte chemoattractant protein-1 at both the mRNA and protein levels in human mesangial cells. Since MZR binds specifically to 14-3-3 proteins and heat shock protein 60, both of which are reportedly expressed in inflamed glomeruli, MZR may bind directly to inflamed glomerular cells, thereby possibly preventing progressive damage from glomerulonephritis through a suppressive effect on activated macrophages and intrinsic renal cells. Moreover, it has recently been reported that MZR directly prevents podocyte injury through correction of the intracellular energy balance and nephrin biogenesis in cultured podocyte and rat models, suggesting a direct anti-proteinuric effect of MZR.

CONCLUSIONS

These beneficial mechanisms of action of MZR as well as its immunosuppressive effect would warrant its use in the treatment of pediatric-onset glomerular disease. Although further studies remain to be done, we believe that MZR may be an attractive treatment of choice for children with glomerular diseases from a histologic as well as clinical standpoint.

Efficacy of mizoribine-tacrolimus-based induction therapy for pediatric lupus nephritis

BACKGROUND

Recent advances in the management of lupus nephritis (LN) have also contributed to a favorable outcome in patients with pediatric-onset LN. Nevertheless, we believe that a more effective and less toxic treatment is needed to attain optimal control of pediatric-onset LN.

METHODS

Seven consecutive children with biopsy-proven LN (four with class III/IV and three with class V) received multitarget induction therapy consisting of mizoribine (MZR), tacrolimus (Tac), and prednisolone (PDN). They were prospectively evaluated at three, six, and 12 months, and at the latest observation point after a mean period of 32 months. Post-treatment renal biopsy was performed in two patients with class III/IV.

RESULTS

Despite gradually tapering the dose of concomitantly administered PDN, a significant improvement compared with baseline values was observed in the urinary, serological, and clinical assessment measures even at three months of treatment, and the favorable changes persisted throughout the treatment period in most of the study participants except for one. In two patients who underwent post-treatment renal biopsy, a marked histologic improvement was confirmed. No serious adverse events were observed.

CONCLUSIONS

Multitarget therapy may be an attractive option for the treatment of pediatric-onset LN. Further studies involving a larger number of patients are needed.

Synergistic protective effects of mizoribine and angiotensin II receptor blockade on cyclosporine A nephropathy in rats

BACKGROUND

Chronic cyclosporine A (CsA) nephrotoxicity is manifested by renal dysfunction, progressive histopathological kidney lesions characterized by afferent arteriolopathy, and tubulointerstitial fibrosis. In addition to the direct toxic effect of CsA, many other etiological factors such as angiotensin II, transforming growth factor (TGF)-β, and macrophage infiltration are involved in this pathogenesis. This study investigated the hypothesis that concomitant administration of mizoribine (MZR) and angiotensin II receptor blockade (ARB) may prevent CsA nephrotoxicity in rats.

METHODS

Sprague-Dawley male rats were divided into the following seven groups: group 1, treated with CsA; group 2, treated with CsA + MZR; group 3, treated with CsA + valsartan (Val); group 4, treated with CsA + MZR + Val; group 5, treated with MZR; group 6, treated with Val; and group 7, controls (n = 5 each). Renal histopathology and the effect of CsA-induced nephrotoxicity on inflammatory mediators were evaluated.

RESULTS

Results of this study demonstrated that ARB administration significantly decreased arteriolopathy and that in comparison with monotherapy, concomitant administration of MZR and ARB further decreased arteriolopathy, fibrosis, macrophage infiltration, and TGF-β1 mRNA expression associated with CsA nephrotoxicity.

CONCLUSION

These findings indicate that MZR and ARB combination treatment provides synergistic protective effects against chronic CsA nephrotoxicity.

Long-term tacrolimus-based immunosuppressive treatment for young patients with lupus nephritis: a prospective study in daily clinical practice

BACKGROUND

The optimal long-term treatment for lupus nephritis (LN) in pubertal patients remains to be determined. Tacrolimus (Tac) inhibits T cell activation, and is therefore expected to be effective in patients with LN. However, little has been published about the long-term efficacy and safety of Tac-based immunosuppressive treatment of young patients with LN in daily clinical practice.

METHODS

Nineteen consecutive patients with biopsy-proven LN were recruited for an open-label, prospective, long-term Tac-based treatment regimen. Tac was administered once daily at a dose of 3 mg as induction- or reinduction-maintenance treatment. Four patients (21%) with new-onset LN received mizoribine at a dose of 150 mg once daily in addition to Tac. Treatment outcomes were defined by the European Consensus Lupus Activity Measurement (ECLAM) index, urinary protein/creatinine ratio (Up/cr), serum creatinine and serological lupus markers (complement C3, complement hemolytic activity, CH50, and anti-dsDNA antibody titer). Data on these parameters were collected prospectively. The median follow-up was 42 months.

RESULTS

Baseline characteristics of the patients were as follows: mean age, 18 years; Up/cr, 0.89 ± 1.17; serum C3, 68.1 ± 23.2 mg/dl (normal, 79-152 mg/dl); serum CH50, 26.4 ± 10.5 U/ml (normal, 23-46 U/ml); serum anti-dsDNA antibody titer, 69.3 ± 67.5 IU/ml (normal, <12.0 IU/ml); serum creatinine, 0.55 ± 0.18 mg/dl, and ECLAM index, 4.6 ± 1.9. Despite gradually tapering the dose of concomitantly administered prednisolone, a marked improvement compared with baseline values was observed in all outcome measures as early as 3 months after the initiation of treatment, and the favorable changes persisted throughout the treatment period in most of the patients. Sustained improvements in the outcome measures compared with the baseline values were confirmed after a mean of 42 months of treatment: ECLAM index, 1.1 ± 1.1; serum CH50, 36.0 ± 12.8 U/ml, anti-dsDNA antibody titer, 22.5 ± 26.5 IU/ml (all p < 0.01); Up/cr ratio, 0.35 ± 0.58, and serum C3 level, 79.7 ± 17.6 mg/dl (both p < 0.05). Serum creatinine level remained within the normal range in all the study participants. Complete response was achieved in 12 patients (63%), and a partial response was achieved in 5 patients (26%). The remaining 2 patients showed no response. No serious adverse effects were observed.

CONCLUSION

The data suggest that long-term, relatively low-dose Tac-based immunosuppressive treatment is beneficial and has low cytotoxicity, and therefore represents an attractive option for the treatment of young patients with LN in daily clinical practice. Further studies involving a larger number of patients are needed to confirm these results.

Treatment of young patients with lupus nephritis using calcineurin inhibitors

Recent advances in the management of lupus nephritis, together with earlier renal biopsy and selective use of aggressive immunosuppressive therapy, have contributed to a favorable outcome in children and adolescents with systemic lupus erythematosus (SLE). Nevertheless, we believe that a more effective and less toxic treatment is needed to attain an optimal control of the activity of lupus nephritis. Recent published papers and our experiences regarding treatment of young patients with lupus nephritis using calcineurin inhibitors are reviewed. Although it has been reported that intermittent monthly pulses of intravenous cyclophosphamide (IVCY) are effective for preserving renal function in adult patients, CPA is a potent immunosuppressive agent that induces severe toxicity, including myelo- and gonadal toxicity, and increases the risk of secondary malignancy. Thus, treatment for controlling lupus nephritis activity, especially in children and adolescents, remains challenging. Cyclosporine A (CsA) and tacrolimus (Tac) are T-cell-specific calcineurin inhibitors that prevent the activation of helper T cells, thereby inhibiting the transcription of the early activation genes of interleukin (IL)-2 and suppressing T cell-induced activation of tumor necrosis factor-α, IL-1β and IL-6. Therefore, both drugs, which we believe may be less cytotoxic, are attractive therapeutic options for young patients with lupus nephritis. Recently, a multidrug regimen of prednisolone (PDN), Tac, and mycophenolate mofetile (MMF) has been found effective and relatively safe in adult lupus nephritis. Since the mechanisms of action of MMF and Tac are probably complementary, multidrug therapy for lupus nephritis may be useful. We propose as an alternative to IVCY, a multidrug therapy with mizoribine, which acts very similarly to MMF, and Tac, which has a different mode of action, combined with PDN for pediatric-onset lupus nephritis. We also believe that a multidrug therapy including CsA and Tac may be an attractive option for young patients with SLE and lupus nephritis.

Mitochondrial permeability transition pore opening induces the initial process of renal calcium crystallization

Renal tubular cell injury induced by oxidative stress via mitochondrial collapse is thought to be the initial process of renal calcium crystallization. Mitochondrial collapse is generally caused by mitochondrial permeability transition pore (mPTP) opening, which can be blocked by cyclosporine A (CsA). Definitive evidence for the involvement of mPTP opening in the initial process of renal calcium crystallization, however, is lacking. In this study, we examined the physiological role of mPTP opening in renal calcium crystallization in vitro and in vivo. In the in vitro study, cultured renal tubular cells were exposed to calcium oxalate monohydrate (COM) crystals and treated with CsA (2 μM). COM crystals induced depolarization of the mitochondrial membrane potential and generated oxidative stress as evaluated by Cu-Zn SOD and 4-HNE. Furthermore, the expression of cytochrome c and cleaved caspase 3 was increased and these effects were prevented by CsA. In the in vivo study, Sprague-Dawley rats were administered 1% ethylene glycol (EG) to generate a rat kidney stone model and then treated with CsA (2.5, 5.0, and 10.0 mg/kg/day) for 14 days. EG administration induced renal calcium crystallization, which was prevented by CsA. Mitochondrial collapse was demonstrated by transmission electron microscopy, and oxidative stress was evaluated by measuring Cu-Zn SOD, MDA, and 8-OHdG generated by EG administration, all of which were prevented by CsA. Collectively, our results provide compelling evidence for a role of mPTP opening and its associated mitochondrial collapse, oxidative stress, and activation of the apoptotic pathway in the initial process of renal calcium crystallization.

Complications of nephrotic syndrome

Nephrotic syndrome (NS) is one of the most common glomerular diseases that affect children. Renal histology reveals the presence of minimal change nephrotic syndrome (MCNS) in more than 80% of these patients. Most patients with MCNS have favorable outcomes without complications. However, a few of these children have lesions of focal segmental glomerulosclerosis, suffer from severe and prolonged proteinuria, and are at high risk for complications. Complications of NS are divided into two categories: disease-associated and drug-related complications. Disease-associated complications include infections (e.g., peritonitis, sepsis, cellulitis, and chicken pox), thromboembolism (e.g., venous thromboembolism and pulmonary embolism), hypovolemic crisis (e.g., abdominal pain, tachycardia, and hypotension), cardiovascular problems (e.g., hyperlipidemia), acute renal failure, anemia, and others (e.g., hypothyroidism, hypocalcemia, bone disease, and intussusception). The main pathomechanism of disease-associated complications originates from the large loss of plasma proteins in the urine of nephrotic children. The majority of children with MCNS who respond to treatment with corticosteroids or cytotoxic agents have smaller and milder complications than those with steroid-resistant NS. Corticosteroids, alkylating agents, cyclosporin A, and mycophenolate mofetil have often been used to treat NS, and these drugs have treatment-related complications. Early detection and appropriate treatment of these complications will improve outcomes for patients with NS.

Novel multidrug therapy for children with cyclosporine-resistant or -intolerant nephrotic syndrome

An effective treatment for children with refractory nephrotic syndrome (NS), especially in those with cyclosporine (CsA)-resistant or CsA-intolerant NS, has yet to be established. Recently, the efficacy of multidrug therapy consisting of tacrolimus (Tac), mycophenolate mofetil (MMF) in combination with prednisolone (PDN) in adult patients with refractory NS has been reported. We successfully treated 14 consecutive children with refractory CsA-resistant or CsA-intolerant NS using combination therapy consisting of relatively low-dose Tac, mizoribine (MZR), which has a mechanism of action very similar to that of MMF, and PDN. There were no serious clinical toxicities. Of the 14 children, 9 with a mean age of 13.0 years had steroid-dependent NS (SDNS) and 5 with a mean age of 9.6 years had steroid-resistant NS (SRNS). All SDNS patients had minimal change disease (MCD), 4 with SRNS had focal segmental glomerulosclerosis (FSGS), and the remaining child had MCD on renal biopsy. All patients were in a prospective cohort, but were evaluated retrospectively. The mean follow-up from the initiation of multidrug therapy was 18.4 months in SDNS and 18.6 months in SRNS patients. At the last observation point, the calculated relapse rate and minimum dose of PDN required for maintenance of clinical remission after the start of multidrug therapy were significantly decreased compared with those prior to this therapy, while on CsA, in SDNS patients (0.4 ± 0.5 times/year vs 2.9 ± 1.5 times/year, P = 0.0077, and 0.3 ± 0.2 mg/kg on alternate days vs 0.5 ± 0.2 mg/kg on alternate days, P = 0.0184 respectively). All SDNS and two SRNS patients (40%) achieved complete remission, allowing further decreases in the minimal doses of PDN required for maintenance of clinical remission in most our patients. However, one patient with FSGS remained refractory to multidrug therapy and subsequently developed end-stage renal disease. These clinical observations, although preliminary and involving a small number of patients, suggest that multidrug therapy consisting of relatively low-dose Tac, MZR, and PDN might be effective and safe for treating children with refractory CsA-resistant or CsA-intolerant NS. However, further studies involving larger numbers of patients are needed.