Long-term results in mizoribine-treated renal transplant recipients: a prospective, randomized trial of mizoribine and azathioprine under cyclosporine-based immunosuppression

Long-term Survival Analysis of Kidney Transplant Recipients Receiving Mizoribine as a Maintenance Immunosuppressant: A Single-Center Study

BACKGROUND

Mizoribine (MZR) has been developed as an immunosuppressant and is widely used in Asia. However, most studies on MZR have been performed in Japan, and there remains a lack of reports on long-term use in other countries. The purpose of this study is to evaluate the efficacy and safety of MZR's use in Korean kidney transplant recipients by observing their clinical courses and analyzing their long-term patent and graft survival rates.

METHODS

We studied 129 subjects who had received MZR as a maintenance immunosuppressant since January 2000. Our analysis was based on the patients' medical records from January 2000 to December 2017.

RESULTS

The overall survival rates of the kidney transplant recipients were 100% at 1 year, 99.1% at 5 years, 96.8% at 10 years, and 92.5% at 15 years. The graft survival rates were 100% at 1 year, 98.3% at 5 years, 93.2% at 10 years, and 82.2% at 15 years. There were differences in the recipient survival and graft survival rates according to the kidney donor and the use of renal replace therapy before transplant. There were no differences in the survival rates according to the MZR dose, the type of underlying disease, or other clinical factors.

CONCLUSIONS

The use of low doses of MZR as a maintenance immunosuppressant could be an effective means of ensuring relatively good long-term patient and graft survival rates in cases of kidney transplant.

Beneficial Effects of High-Dose Mizoribine on ABO-Incompatible Living-Related Kidney Transplantation: Two-Year Results by a Japanese Multicenter Study

BACKGROUND

Mizoribine (MZ) has been developed as an immunosuppressive agent in Japan, but it has a less-potent immunosuppressive effect up to 3 mg/kg/d. In the previous study, a Japanese multicenter study, we reported that high-dose MZ, at 6 mg/kg/d, with a calcineurin inhibitor was effective and safe in reducing the frequency of cytomegalovirus (CMV)-related events in ABO-incompatible (ABO-i) living-related kidney transplantation (LKT). In the present study, therefore, we investigated the effects of high-dose MZ with a CNI in ABO-i LKT recipients in a Japanese multicenter study.

METHODS

A total of 37 patients were treated with high-dose MZ (6 mg/kg), a CNI (cyclosporine [CsA] or tacrolimus [Tac]), basiliximab (Bas), rituximab (Rit), and corticosteroids. CsA was started at a dose of 7 mg/kg to maintain blood levels [200 ng/mL (C0), 6000 ng-h/mL (AUC 0-9)]. Tac was started at a dose of 0.2 mg/kg to maintain blood levels [8-10 ng/mL (C0), 100 ng-h/mL (AUC 0-9)]. Bas (20 mg/body) was administrated on day 0 and day 4 after transplantation. Rit (100-200 mg/body) was administrated on day -14 and day -7 before transplantation. MZ was adjusted to maintain target C0 levels of 1.5 to 2.0 μg/mL.

RESULTS

Patient and graft survival rates for 2 years were 100% in the CsA group (n = 22) and 93.3% in the Tac group (n = 15) (not significant, NS). Overall incidence of acute rejection for 2 years was 22.7% in the CsA group and 26.7% in the Tac group. Mean serum creatinine levels at 2 years were 1.29 ± 0.2 mg/dL in the CsA group and 1.21 ± 0.34 mg/dL in the Tac group (NS). The incidence of CMV disease was 0% in both groups, and positive rates of CMV antigenemia were 50.0% and 26.7% in the CsA and Tac groups, respectively (NS). Mean serum uric acid levels were 5.5 ± 1.3 mg/dL and 6.4 ± 1.2 mg/dL at 2 years (NS) in the CsA and Tac groups, respectively.

CONCLUSIONS

A high-dose MZ regimen including calcineurin inhibitor (CsA or Tac), Bas, Rit, and steroids was effective and safe in reducing the frequency of CMV-related events in ABO-i LKT.

Cyclophilin A as a target in the treatment of cytomegalovirus infections

BACKGROUND

Viruses are obligate parasites that depend on the cellular machinery of the host to regenerate and manufacture their proteins. Most antiviral drugs on the market today target viral proteins. However, the more recent strategies involve targeting the host cell proteins or pathways that mediate viral replication. This new approach would be effective for most viruses while minimizing drug resistance and toxicity.

METHODS

Cytomegalovirus replication, latency, and immune response are mediated by the intermediate early protein 2, the main protein that determines the effectiveness of drugs in cytomegalovirus inhibition. This review explains how intermediate early protein 2 can modify the action of cyclosporin A, an immunosuppressive, and antiviral drug. It also links all the pathways mediated by cyclosporin A, cytomegalovirus replication, and its encoded proteins.

RESULTS

Intermediate early protein 2 can influence the cellular cyclophilin A pathway, affecting cyclosporin A as a mediator of viral replication or anti-cytomegalovirus drug.

CONCLUSION

Cyclosporin A has a dual function in cytomegalovirus pathogenesis. It has the immunosuppressive effect that establishes virus replication through the inhibition of T-cell function. It also has an anti-cytomegalovirus effect mediated by intermediate early protein 2. Both of these functions involve cyclophilin A pathway.

Efficacy and safety of adding mizoribine to standard treatment in patients with immunoglobulin A nephropathy: A randomized controlled trial

Background

Mizoribine (MZR) is an immunosuppressive drug used in Japan for treating patients with lupus nephritis and nephrotic syndrome and has been also reportedly effective in patients with immunoglobulin A (IgA) nephropathy. However, to date, few randomized control studies of MZR are performed in patients with IgA nephropathy. Therefore, this prospective, open-label, randomized, controlled trial aimed to investigate the efficacy and safety of adding MZR to standard treatment in these patients, and was conducted between April 1, 2009, and March 31, 2016, as a multicenter study.

Methods

Patients were randomly assigned (1:1) to receiving standard treatment plus MZR (MZR group) or standard treatment (control group). MZR was administered orally at a dose of 150 mg once daily for 12 months.

Results

Primary outcomes were the percentage reduction in urinary protein excretion from baseline and the rate of patients with hematuria disappearance 36 months after study initiation. Secondary outcomes were the rate of patients with proteinuria disappearance, clinical remission rate, absolute changes in estimated glomerular filtration rate from baseline, and the change in daily dose of prednisolone. Forty-two patients were randomly assigned to MZR (n = 21) and control groups (n = 21). Nine patients in MZR group and 15 patients in the control group completed the study. No significant differences were observed between the two groups with respect to primary and secondary outcomes.

Conclusion

The addition of MZR to standard treatment has no beneficial effect on reducing urinary protein excretion and hematuria when treating patients with IgA nephropathy.

Excellent results of high-dose mizoribine combined with cyclosporine, basiliximab, and corticosteroids in renal transplant recipients--4-year results

BACKGROUND

Mizoribine (MZR) at 3 mg/kg/d shows less potent immunosuppressive effects, but high-dose MZR (6 mg/kg/d) was effective and safe in a 2-year study in conjunction with a regimen of cyclosporine (CsA), basiliximab, and corticosteroids.

METHODS

We compared 40 living-related kidney recipients administered MZR (6 mg/kg/d), CsA (7 mg/kg/d), prednisolone (maintenance dose 10 mg/d), and basiliximab (20 mg/body) with control group (n = 38) treated with CsA, mycophenolate mofetil (MMF; 25 mg/kg/d), basiliximab, and corticosteroids.

RESULTS

The 4-year graft survival rates for the MZR vs MMF groups were 92.5% vs 94.7%, respectively, with serum creatinine levels of 1.66 ± 1.0 mg/dL vs 1.41 ± 0.42 mg/dL at 3 years, and 1.72 ± 1.16 mg/dL vs 1.56 ± 1.26 mg/dL at 4 years. There was no significant difference in serum creatinine levels between the 2 groups. The MZR group demonstrated a significantly higher rate of elevated serum uric acid values (29.7%). The numbers of patients treated with allopurinol at 4 years were 11/37 (29.7%) for MZR vs 2/36 (5.6%) for the MMF subjects (P < .05). Mean serum uric acid levels of the MZR vs MMF group at 4 years were 7.1 ± 1.9 mg/dL vs 7.0 ± 1.6 mg/dL, respectively (NS). There was no significant difference between the 2 groups regarding bone marrow suppression or liver dysfunction. Severe cytomegalovirus infection was not observed at 3 and 4 years in either group. There were no severe gastrointestinal symptoms among the MZR or the MMF group at 3 or 4 years.

CONCLUSIONS

The combination of high-dose MZR with CsA, basiliximab, and corticosteroids displayed excellent results over a 4-year follow-up.

The argument for the use of mizoribine in renal transplantation: a meta-analysis and systemic review

OBJECTIVE

The aim of this study is to evaluate the efficacy and safety of mizoribine (MZR) for immunosuppressive therapy in renal transplantation.

METHODS

A systematic search of the eligible studies that compared MZR with azathioprine (AZA) for post renal transplant immunosuppressive therapy was performed by using MEDLINE, EMBASE, and the Cochrane Library. Meta-analyses were performed to study the pooled effects of relative risk (RR) and weighted mean difference with 95% confidence intervals (CI).

RESULTS

A total of 486 participants from seven clinical trials were included. MZR demonstrated comparable efficacy in terms of acute rejection, patient/graft survival, and serum creatinine. However, MZR was associated with a significantly lower incidence of adverse events as compared with AZA (RR 0.39, CI 0.21-0.73, p=0.003). Specifically, recipients receiving MZR suffered from significantly fewer episodes of myelosuppression (RR 0.12, CI 0.02-0.54, p=0.006) and leukopenia (RR 0.20, CI 0.06-0.70, p=0.01). Also, MZR seemed to offer more favorable outcomes in terms of hepatic dysfunction, infection and diabetes, although the differences were not statistically significant.

CONCLUSIONS

MZR is a safe, well-tolerated and effective immunosuppressive agent that can be recommended as an alternative to AZA in renal transplant recipients, although further studies are needed to balance its effect with mycophenolate mofetil.

Mizoribine as sole immunosuppressive agent in islet xenotransplantation models: a candidate immunosuppressant causing no adverse effects on islets

Mizoribine (MZ) inhibits the differentiation and proliferation of helper T and B cells after antigen recognition by suppressing the purine biosynthesis pathway and nucleic acid synthesis. MZ has been used in kidney transplantation, but distinct data are unavailable for islet transplantation. The present study investigated the efficacy of MZ for islet xenotransplantation. Immunosuppressive effects of MZ were determined by mixed lymphocyte reaction (MLR) assay in vitro. Toxicities for Wistar rat islets were determined by adenosine triphosphate (ATP) contents of islets during 3-day culture and stimulation index in response to glucose after culture. Immunosuppressive effects in vivo were tested in a Wistar-to-B6 islet xenotransplantation model. MZ was administered continuously for 28 days subcutaneously or intramuscularly. MZ inhibited MLR response by approximately 50% at 0.1 μg/ml. ATP contents decreased with MZ >100 μg/ml, while stimulation index was maintained. Continuous infusion of MZ at 10 mg/kg maintained blood concentrations at 0.13-0.19 μg/ml, while intramuscular injection of MZ at 100 mg/kg/day (peak 520 μg/ml at 1 h postinjection) resulted in below measurable levels (<0.03 μg/ml) within 24 h. Graft survival was significantly prolonged following continuous infusion of 10 mg/kg/day compared to controls (31.0 ± 9.5 vs. 13.2 ± 5.2 days; p = 0.002). Furthermore, animals with intramuscular injection at doses of 3.2, 10, or 100 mg/kg/day showed significantly longer graft survival (20.0 ± 7.5, 22.0 ± 7.31, and 24.5 ± 8.1 days, respectively; p < 0.05 each). Histological examination showed significant suppression of lymphocyte infiltration by MZ administration. MZ showed immunosuppressive effects in an experimental islet xenotransplantation model without adverse effects on endocrine function of islet grafts.

Current state of renal transplant immunosuppression: Present and future

For kidney transplant recipients, immunosuppression commonly consists of combination treatment with a calcineurin inhibitor, an antiproliferative agent and a corticosteroid. Many medical centers use a sequential immunosuppression regimen where an induction agent, either an anti-thymocyte globulin or interleukin-2 receptor antibody, is given at the time of transplantation to prevent early acute rejection which is then followed by a triple immunosuppressive maintenance regimen. Very low rejection rates have been achieved at many transplant centers using combinations of these agents in a variety of protocols. Yet, a large number of recipients suffer chronic allograft injury and adverse events associated with drug therapy. Regimens designed to limit or eliminate calcineurin inhibitors and/or corticosteroid use are actively being pursued. An ideal immunosuppressive regimen limits toxicity and prolongs the functional life of the graft. This article contains a critical analysis of clinical data on currently available immunosuppressive strategies and an overview of therapeutic moieties in development.

Efficacy and safety of multitarget therapy with mizoribine and tacrolimus for systemic lupus erythematosus with or without active nephritis

The prognosis of lupus nephritis (LN) has improved since the introduction of immunosuppressant therapies, but the safety and effectiveness of treatments can also be improved. We retrospectively assessed the treatment courses of 12 patients with systemic lupus erythematosus who were treated with glucocorticoid, mizoribine (MZR) and tacrolimus. This regimen was used as initial therapy for active LN in six patients (mean glucocorticoid dose, 66.6 mg); four of these six patients also received pulse methylprednisolone therapy. The starting doses of MZR and tacrolimus were 150 and 3 mg, respectively, and they were titrated as required. Five of six patients achieved complete remission and one achieved partial remission at 6 months. Five patients who completed 12-month analysis achieved complete remission. Another six patients were given the combination regimen for treating minor flares or for steroid sparing. The mean prednisolone doses were reduced from 11.0 mg at baseline to 6.6 mg at 12 months. Six patients experienced minor adverse events, including three minor infections. One patient stopped tacrolimus because of suspected toxicity. All 12 patients were successfully treated, and none experienced severe adverse events. Multitarget therapy combining glucocorticoid, MZR and tacrolimus may have the potential to become a treatment option which is effective and safe.

The beneficial effect of high-dose mizoribine combined with cyclosporine, basiliximab, and corticosteroids on CMV infection in renal transplant recipients

BACKGROUND

Mizoribine (MZR) has been developed as an immunosuppressive agent, but has a less potent immunosuppressive effect up to 3 mg/kg/day MZR. Therefore, we investigated whether high-dose MZR, at 6 mg/kg/day, would be effective and safe for kidney transplant patients in conjunction with cyclosporine (CsA), basiliximab, and corticosteroids.

METHODS

A total of 40 living related patients were administered MZR (6 mg/kg/day), CsA (7 mg/kg/day), prednisolone (maintenance dose 10 mg/day), and basiliximab (20 mg/body). A control group (n = 38) treated with CsA, mycophenolate mofetil (MMF, 25 mg/kg/day), basiliximab, and corticosteroids was also employed in this study.

RESULTS

The 2-year graft survival rates for the MZR and MMF groups were 100 and 94.7 %, respectively. The rejection rate in the MZR group (25 %) was not significantly higher than that in the MMF group (16 %). Serum creatinine level was not significant between the two groups. The number of patients who developed cytomegalovirus (CMV) disease was 0 (0 %) in the MZR group and 7 (18.4 %) in the MMF group (P < 0.05). The number of patients treated with ganciclovir was 3 (7.5 %) and 11 (28.9 %) (P < 0.05), respectively.

CONCLUSIONS

The combination of high-dose MZR with CsA, basiliximab, and corticosteroids can establish not only satisfactory immunosuppression but also a low rate of CMV infection in vivo.

Methylprednisolone pulse plus mizoribine in children with Henoch-Schoenlein purpura nephritis

We evaluated whether methylprednisolone and urokinase pulse therapy combined with mizoribine (MUPM) was effective in children with severe Henoch-Schoenlein purpura nephritis (HSPN). We studied 12 patients who had been diagnosed with HSPN of at least ISKDC type III. All patients were treated with MUPM. Clinical features, pathological findings, and prognosis were prospectively investigated. Ten patients (responders; nine with ISKDC grade IIIb and one with grade IVb) were treated with MUPM, whereas MUPM was discontinued due to the lack of response in two patients (non-responders; two with grade IVb). Among responders, urinary protein excretion had decreased significantly from 99.7 ± 37.8 to 25.9 ± 33.4 mg/m(2) per hour after 3 months of therapy. The acute index and tubulointerstitial scores decreased significantly from 5.8 ± 1.5 and 3.8 ± 0.6 at the first biopsy to 2.3 ± 1.3 and 1.0 ± 0.8 at the second biopsy, respectively. At the most recent follow-up, eight of the responders had normal urine, and two had minor urinary abnormalities. Non-responders demonstrated continued high levels of urinary protein excretion after 3 months of therapy, and MUPM was discontinued. Our study suggests that MUPM is effective in ameliorating the proteinuria and the histological severity of HSPN in patients with <50% crescents but is not so effective for HSPN in patients with >50% crescents.

Mizoribine: a new approach in the treatment of renal disease

Mizoribine (MZB) is an imidazole nucleoside and an immunosuppressive agent. The immunosuppressive effect of MZB has been reported to be due to the inhibition of DNA synthesis in the S phase of the cell cycle. Because of its relative lack of toxicity, during the past decade MZB has been frequently used instead of azathioprine as a component of immunosuppressive drug regimens. MZB is being used to treat renal transplantation patients, IgA nephropathy, lupus erythematosus, and childhood nephrotic syndrome (NS), and some recent studies have assessed the efficacy of oral MZB pulse therapy for severe lupus nephritis, steroid-resistant NS, and frequently relapsing-steroid-dependent NS. This review summarizes the published findings on the efficacy of MZB for renal disease including IgA nephropathy, lupus nephritis, and NS, as well as of oral MZB pulse therapy for severe lupus nephritis and NS, and also the mechanism of the effect of oral MZB pulse therapy on the lymphocyte cell cycle.

Combination effect of mycophenolate mofetil with mizoribine on cell proliferation assays and in a mouse heart transplantation model

BACKGROUND

Mycophenolate mofetil (MMF) is a highly potent immunosuppressant that suppresses the proliferation of T and B cells by the uncompetitive inhibition of inosine monophosphate dehydrogenase (IMPDH). Consequently, under MMF immunosuppression, good graft survival has been achieved in clinical organ transplantation, although MMF shows adverse gastrointestinal effects. Mizoribine (MZ) also inhibits IMPDH in a competitive manner and is used clinically for organ transplantation in Japan as an immunosuppressant with fewer adverse gastrointestinal effects. Therefore, in this study we investigated the synergistic effects on in vitro and in vivo assays of mice of a combination of MMF with MZ immunosuppression.

METHODS

Mixed lymphocyte reaction (MLR) assay and a mouse heart transplantation model were used to evaluate the immunosuppressive effect of MMF with MZ. The median-effect principle and a combination index (CI) were employed to determine synergism, an additive effect, or antagonism.

RESULTS

Combination of MMF with MZ resulted in mild synergistic effects in the inhibition of MLR (CI = 0.854-1.143). In the mouse heart transplantation model, C57BL/6 recipients who received a BALB/c heart under the combination of MMF and MZ at 40 + 40 or 80 + 80 mg/kg/day showed a strong synergistic prolongation of graft survival with 19.7 +/- 18.9 (P = 0.0012, CI = 0.438) and 78.4 +/- 36.9 days (P = 0.0002, CI = 0.317), respectively, compared with recipients treated with MMF or MZ monotherapy. CONCLUSIONS.: The combination of MMF and MZ showed mild synergistic effects in the inhibition of MLR and strong synergistic effects in a mouse heart transplantation model.

Revival of effective and safe high-dose mizoribine for the kidney transplantation

We investigated whether high-dose Mizoribine (MIZ: a water-soluble anti-metabolite), 4-6 mg/kg/d was as effective and safe as mycophenolate mofetil (MMF) for patients after kidney transplantation. Between January 2001 and December 2005, 36 recipients at a stable phase more than one month passed after transplantation underwent conversion from MMF to MIZ, two from Azathioprine to MIZ, and two cases on MIZ from the beginning. There were 24-male and 16-female patients whose average age was 43.3 yr old and average weight was 54.0 kg. The types of transplantations were living donor renal transplantation 25, cadaveric renal transplantation 11, and simultaneous pancreas-kidney transplantation four examples. Of these, 33 patients were on Tacrolimus-based triple regimen and seven patients on Cyclosporine A base. The drugs used together with MIZ were basically the same as those before conversion. The reasons for conversion to MIZ were infection in 18 cases (45.0%), bone marrow suppression in nine cases (22.5%) and diarrhea in eight cases (20.0%), and post-transplant lymphoproliferative disorder in one case (2.5%). We initiated 4-6 mg/kg/d of MIZ divided twice a day depending on the serum creatinine (sCr) value of each patient. There was no big difference in the sCr value before and after MIZ administration in each individual patient, 1.79 +/- 1.37 and 1.65 +/- 1.30 mg/dL, respectively. A 12 h pharmaco-kinetic study of MIZ revealed that a peak value reached 2.87 microg/mL on average at three h (C3) followed by a slow decrease afterward. Acute rejection occurred in two cases and adverse effects were seen in five cases. The results of analysis of 349 points divided into three groups by renal function were as follows; poor renal function Group A revealed a trough level of 2.21 +/- 0.99 microg/mL and dosage 2.20 +/- 1.06 mg/kg, good renal function Group B had a trough level of 1.06 +/- 0.82 microg/mL and dosage 4.40 +/- 1.72 mg/kg, and excellent function Group C had a trough level of 0.92 +/- 0.55 microg/mL and dosage of 4.36 +/- 1.08 mg/kg. High-dose MIZ 4-6 mg/kg/d is an anti-metabolite having an equivalent immunosuppressive effect, fewer serious adverse events and good cost-effectiveness as MMF even for patients with prolonged hemodialysis period and declined digestive function in Japan.

Combination therapy of prednisolone and mizoribine improves cryoglobulinemic vasculitis with purpura and skin ulcers

Conventional treatment is not standardized for hepatitis C virus-negative cryoglobulinemia, but corticosteroids, immunosuppressive agents, and plasma exchange typically improved the symptoms. Mizoribine is an immunosuppressive agent that was developed in Japan and has been found to inhibit the proliferation of lymphocytes, especially B cells. We have encountered an elder patient who had hepatitis C virus-negative, type II cryoglobulinemic vasculitis with leg purpura and skin ulcers. Her symptoms improved and cryoglobulin disappeared by the combination therapy of prednisolone and mizoribine. We speculate the action mechanism of this therapy is due to immunosuppressive effects including up-regulation of the efficacy of prednisolone by mizoribine.

Potential value of high-dose mizoribine as rescue therapy for ongoing acute humoral rejection

Mizoribine (MZ) inhibits the proliferation of lymphocytes selectively via inhibition of inosine monophosphate dehydrogenase, like mycophenolate mofetil (MMF). The clinical dosage of MZ (2-5 mg/kg) is much lower than that of MMF (20-60 mg/kg). The purpose of this study was to examine whether high-dose MZ would be effective for treatment of acute humoral rejection. Renal transplantation was performed in a different pig strain combination. Group 1 (n = 2) received no treatment. Group 2 (n = 4) received cyclosporine microemulsion (6 mg/kg) and prednisolone (0.1 mg/kg) as baseline immunosuppression. Groups 3 (n = 4), 4 (n = 4) and 5 (n = 4) were additionally treated with MZ for rescue therapy, 30, 10 and 3 mg/kg, respectively, immediately after rejection was observed. All pigs developed acute vascular rejection between days 4 and 8. Complete reversal of acute rejection including reduction of elevated serum creatinine, suppression of anti-donor antibody production and pathological finding, was obtained in 3/4 (group 3), 1/4 (group 4) and 0/4 (group 5). Rescue with high-dose MZ (30 mg/kg) reversed ongoing acute humoral rejection. Such a high dose of MZ was tolerable for pigs. However, leukocytopenia was observed when MZ trough level was maintained over 10 mug/ml. Treatment with high-dose MZ would be applicable to a clinical trial, if blood level is carefully monitored.

Treatment with the purine synthesis inhibitor mizoribine for ANCA-associated renal vasculitis

BACKGROUND

The common treatment for antineutrophil cytoplasmic autoantibody (ANCA)-associated renal vasculitis is oral cyclophosphamide (CYC)-corticosteroid combination therapy. However, there are serious complications associated with long-term use of CYC. In this study, we investigate the efficacy of a purine synthesis inhibitor, mizoribine, for patients at high risk for relapse.

METHODS

Our study included 5 patients, 4 patients with myeloperoxidase (MPO)-ANCA-associated renal vasculitis and 1 patient with proteinase 3 (PR3)-ANCA-associated renal vasculitis, who had achieved remission through treatment with methylprednisolone pulse therapy, corticosteroids, and CYC. When their ANCA titers were found to be greater than normal range after remission status, mizoribine treatment was initiated.

RESULTS

Median time from initial treatment to first administration of mizoribine was 40.0 months (range, 24 to 51 months). Median follow-up was 13.0 months (range, 6 to 16 months). Before initiation of mizoribine treatment, no patient had experienced relapse and ANCA titers were less than the detectable range in all patients at 3 months before mizoribine administration. When mizoribine administration was started, ANCA titers were elevated in all patients (median MPO-ANCA, 101 ELISA units [EU]; range, 65 to 154 EU; PR3-ANCA, 55 EU), but no new symptoms or signs of relapse were noted. After 2 months of mizoribine treatment, only 1 patient had experienced a relapse; however, ANCA titers had decreased in all other patients and normalized in 3 patients. No adverse effects appeared in any patient.

CONCLUSION

Considering the balance between suppression of disease activity and adverse effects of treatment, mizoribine may be useful for preemptive treatment for patients with ANCA-associated renal vasculitis at high risk for relapse.

Mizoribine as an effective combined maintenance therapy with prednisolone in child-onset systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is one of the major collagen diseases in childhood. However, the pathogenesis of this disease still remains unknown. The disease is known as a chronic inflammatory disease. Since oral and intravenous corticosteroid therapy has been introduced into the treatment of SLE, the prognosis of patients has improved significantly. However, it has now become clear that there are limitations in the effectiveness, as well as adverse reactions when corticosteroids therapy is administered for a long-term period. Therefore, we have been attempting to improve the maintenance therapy of child-onset SLE.

METHODS

We have proposed and tested a new type of combination therapy using prednisolone (PSL) and mizoribine (MZR) in pediatric patients with SLE for maintenance therapy after the induction of remission.

RESULTS

Our results showed that this combination therapy is more effective than the previous regimen. In addition, no significant side-effects were observed in our study.

CONCLUSION

This combination therapy is still not perfect. Efforts should be continued to establish an optimal therapy regimen for child-onset SLE.

Role of mizoribine in renal transplantation

Renal transplantation is the optimal form of therapy for children and adolescents with end-stage renal disease. Usually histocompatibility differences exist between donor and recipient, so it is necessary to modify or suppress the immune response to enable the recipient to accept a graft. Calcineurin inhibitors (CNI), which include cyclosporin (CsA) and tacrolimus (FK506), give many benefits on the outcome after renal transplantation, but have some toxic effects, especially nephrotoxicity. Therefore, inhibitors of purine synthesis revived as newer generation of more specific inhibitors, mizoribine (MZ) and mycophenolate mofetil (MMF). The Japanese pediatric renal transplantation clinical study group attempted to reduce and then discontinue steroid administration in combination with another three immunosuppressive drugs, CsA, MZ and anti-lymphocyte globulin (ALG). This study showed good clinical results. Mizoribine is an effective immunosuppressive drug in human renal transplantation. However, it is not as popular as other inhibitors of purine synthesis, such as azathioprine (AZA) and MMF, because MZ has been used mainly in Japan and infrequently in other countries. However, MZ is a more useful immunosuppressive drug than AZA, when it is used in combination with CNI.

New immunosuppressive drugs: an update

An increasing number of immunosuppressive drugs became available for clinical use over the past few decades. These include substances with recently recognized immunosuppressive properties, which needed careful evaluation in various trials before they could be approved for use in different diseases. The effectiveness of other agents was already established, but knowledge about their modes of action or the mechanisms that lead to side effects was acquired much later. This understanding also contributed to the development of new drugs that display synergistic effects or lack certain adverse effects. The greater choice afforded by such research endeavours allows us to select the best therapeutic strategy for an individual patient; however, this requires a comprehensive knowledge of the available options. The present review provides an update of current knowledge of the most important substances (including calcineurin and target of rapamycin inhibitors, regulators of gene expression, and inhibitors of purine and pyrimidine synthesis) and surveys some of the novel agents that are expected to play an important role in the future.

Current treatment practice in immunosuppression

New drugs have recently been added that may eventually replace the two-decade dominance of cyclosporin in solid organ transplantation. This cornerstone of immunosuppression was introduced by Borel [1] and Calne [2] in the mid-70s. In 1989, Starzl et al., after 2 years of preclinical experimentation, introduced tacrolimus (originally designated as FK506 by the Fujisawa Pharmaceutical Company of Japan) as a potent immunosuppressant for liver transplants [3]. Also, in recent years, a variety of novel purine and pyrimidine biosynthesis inhibitors have been tested for transplantation therapy. The leading agent which appears to be replacing the 35-year position occupied by azathioprine is the semi-synthetic morpholinoethyl ester of mycophenolic acid (MPA), mycophenolate mofetil (MMF), introduced by Allison [4] and Sollinger [5], and developed by the Syntex Corporation (now Roche Pharmaceuticals). Others, affecting different intra- or intercellular messages amplifying immunity, are in the pipeline.