Guanine ribonucleotide depletion inhibits T cell activation. Mechanism of action of the immunosuppressive drug mizoribine

Novel approaches to primary membranous nephropathy: Beyond the KDIGO guidelines

Primary membranous nephropathy (PMN) is an immune-mediated glomerular disease. Rituximab (RTX) is recommended as a first-line immunosuppressive therapy and shows high clinical efficacy, but the optimal doses remain controversial. Approximately 20%-40% of PMN patients experience RTX resistance and failure. Reduced bioavailability, RTX internalization and attack, anti-RTX antibody production, autoreactive B-cell reservoirs and chronic and irreversible renal damage may contribute to this problem. Therefore, new treatment modalities are needed to compensate for this deficit. New interventions and new dose combinations are being proposed. Multiple drug combination therapies show comparable clinical efficacy to conventional treatments by blocking the production of disease-causing antibodies in multiple directions, and can reduce single-agent doses without increasing adverse effects. New therapies that directly target B cells, plasma cells, and antibody production have shown encouraging results. In addition, new techniques for sweeping antibodies and chimeric antigen receptor T-cell therapy also may be promising strategies for PMN. Immunoadsorption could be used as an auxiliary choice for severe cases. This article explores new treatments for PMN and highlights possible mechanisms for potential new technologies that offer new ideas for treatment.

Mizoribine Promotes Molecular Chaperone HSP60/HSP10 Complex Formation

It has been reported that Mizoribine is an immunosuppressant used to suppress rejection in renal transplantation, nephrotic syndrome, lupus nephritis, and rheumatoid arthritis. The molecular chaperone HSP60 alone induces inflammatory cytokine IL-6 and the co-chaperone HSP10 alone inhibits IL-6 induction. HSP60 and HSP10 form a complex in the presence of ATP. We analyzed the effects of Mizoribine, which is structurally similar to ATP, on the structure and physiological functions of HSP60-HSP10 using Native/PAGE and transmission electron microscopy. At low concentrations of Mizoribine, no complex formation of HSP60-HSP10 was observed, nor was the expression of IL-6 affected. On the other hand, high concentrations of Mizoribine promoted HSP60-HSP10 complex formation and consequently suppressed IL-6 expression. Here, we propose a novel mechanism of immunosuppressive action of Mizoribine.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Host Cell Amplification of Nutritional Stress Contributes To Persistence in Chlamydia trachomatis

Persistence, a viable but non-replicating growth state, has been implicated in diseases caused by Chlamydia trachomatis. Starvation of distinct nutrients produces a superficially similar persistent state, implying convergence on a common intracellular environment. We employed host-pathogen dual RNA-sequencing under both iron- and tryptophan-starved conditions to systematically characterize the persistent chlamydial transcriptome and to define common contributions of the host cell transcriptional stress response in shaping the intracellular environment. The transcriptome of the infected host cells was highly specific to each nutritional stress, despite comparable effects on chlamydial growth and development in each condition. In contrast, the chlamydial transcriptomes between nutritional conditions were highly similar, suggesting some overlap in host cell responses to iron limitation and tryptophan starvation that contribute to a common persistent phenotype. We demonstrate that a commonality in the host cell responses is the suppression of GTP biosynthesis, a nucleotide for which Chlamydia are auxotrophic. Pharmacological inhibition of host IMP dehydrogenase (IMPDH1), which catalyzes the rate-limiting step in de novo guanine nucleotide synthesis, resulted in comparable GTP depletion to both iron and tryptophan starvation and induced chlamydial persistence. Moreover, IMPDH1 inhibition and iron starvation acted synergistically to control chlamydial growth. Thus, host cell reduction in GTP levels amplifies the nutritional stress to intracellular chlamydiae in infection-relevant models of persistence, illustrating the determinative role the infected host cell plays in bacterial stress responses. IMPORTANCE Bacteria respond to nutritional stress through universal and unique mechanisms. Genome reduction in the Chlamydiaceae, a consequence of coevolution with their obligate eukaryotic hosts, has reduced their repertoire of stress response mechanisms. Here, we demonstrate that the infected host cell may provide the context within which universal stress responses emerge for Chlamydia trachomatis. We report that during starvation of the essential nutrients iron or tryptophan, a common response of the infected epithelial cell is the suppression of GTP biosynthesis, which induces a persistent developmental state in the pathogen. Thus, chlamydial persistence results from the combined effects of primary stresses on the pathogen and the host, with the latter eliciting a secondary host cell response that intensifies the inhospitable intracellular environment.

Mizoribine halts kidney fibrosis in childhood IgA nephropathy: association with modulation of M2-type macrophages

BACKGROUND

The immunosuppressant mizoribine (Miz) can reduce progression of childhood IgA nephropathy (IgAN). This study examined whether Miz affects CD163⁺ M2-type macrophages which are associated with kidney fibrosis in childhood IgAN.

METHODS

A retrospective cohort of 90 children with IgAN were divided into groups treated with prednisolone (PSL) alone (P group; n = 42) or PSL plus Miz (PM group; n = 48) for a 2-year period. Normal human monocyte-derived macrophages were stimulated with dexamethasone (Dex), or Dex plus Miz, and analyzed by DNA microarray.

RESULTS

Clinical and histological findings at first biopsy were equivalent between patients entering the P and PM groups. Both treatments improved proteinuria and haematuria, and maintained normal kidney function over the 2-year course. The P group exhibited increased mesangial matrix expansion, increased glomerular segmental or global sclerosis, and increased interstitial fibrosis at 2-year biopsy; however, the PM group showed no progression of kidney fibrosis. These protective effects were associated with reduced numbers of glomerular and interstitial CD163⁺ macrophages in the PM versus P group. In cultured human macrophages, Dex induced upregulation of cytokines and growth factors, which was prevented by Miz. Miz also inhibited Dex-induced expression of CD300E, an activating receptor which can prevent monocyte apoptosis. CD300e expression by CD163⁺ macrophages was evident in the P group, which was reduced by Miz treatment.

CONCLUSION

Miz halted the progression of kidney fibrosis in PSL-treated pediatric IgAN. This was associated with reduced CD163⁺ and CD163⁺CD300e⁺ macrophage populations, plus in vitro findings that Miz can suppress steroid-induced macrophage expression of pro-fibrotic molecules. A higher resolution version of the Graphical abstract is available as Supplementary information.

Targeting nucleotide metabolism: a promising approach to enhance cancer immunotherapy

Targeting nucleotide metabolism can not only inhibit tumor initiation and progression but also exert serious side effects. With in-depth studies of nucleotide metabolism, our understanding of nucleotide metabolism in tumors has revealed their non-proliferative effects on immune escape, indicating the potential effectiveness of nucleotide antimetabolites for enhancing immunotherapy. A growing body of evidence now supports the concept that targeting nucleotide metabolism can increase the antitumor immune response by (1) activating host immune systems via maintaining the concentrations of several important metabolites, such as adenosine and ATP, (2) promoting immunogenicity caused by increased mutability and genomic instability by disrupting the purine and pyrimidine pool, and (3) releasing nucleoside analogs via microbes to regulate immunity. Therapeutic approaches targeting nucleotide metabolism combined with immunotherapy have achieved exciting success in preclinical animal models. Here, we review how dysregulated nucleotide metabolism can promote tumor growth and interact with the host immune system, and we provide future insights into targeting nucleotide metabolism for immunotherapeutic treatment of various malignancies.

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.

Efficacy and Safety of Mizoribine Combined With Tacrolimus in Living Donor Kidney Transplant Recipients: 3-Year Results by a Chinese Single Center Study

BACKGROUND

Mizoribine (MZR) was effective and safe for living Chinese donor kidney transplantation (LDKT) on tacrolimus-based treatment 1 year after transplantation. We investigated whether MZR was effective and safe for LDKT on tacrolimus-based treatment with long follow-up periods.

METHODS

We compared 22 LDKT recipients who were administered MZR, tacrolimus, and corticosteroids with a control group (n = 20) treated with mycophenolate mofetil (MMF), tacrolimus, and corticosteroids. Primary efficacy endpoints were 3-year patient survival, 3-year graft survival, and acute rejection (AR) rate within 3 years after transplantation.

RESULTS

The 3-year patient and graft survival rates for the MZR and MMF groups were 100%. The AR rate after transplantation was 18.2% for the MZR group and 10.0% for the MMF group; the difference was not significant (P = .665). There was no significant difference in serum creatinine levels, glomerular filtration rates (eGFR), serum urate levels, blood urea nitrogen, and cystatin C levels 12, 24, and 36 months after transplantation. No significant differences in the CD3, CD4, CD8, CD4/CD8, and CD45 were observed between the 2 groups 12, 24, and 36 months after transplantation. There were no significant differences in adverse events among the MZR or the MMF group, whereas the prevalence of gastrointestinal symptoms were significantly lower in the MZR treatment group (P = .003), especially acid reflux (P = .007). Compared with the MMF group, the MZR group should lighten the burden on patients.

CONCLUSION

MZR with tacrolimus and corticosteroids provides satisfactory immunosuppression and higher safety for Chinese LDKT over a 3-year follow-up.

Usefulness of mizoribine administration in children with frequently relapsing nephrotic syndrome, and the relationship between pharmacokinetic parameters and efficacy: a multicenter prospective cohort study in China

BACKGROUND

Mizoribine (MZR) is an immunosuppressant used to treat adult nephropathy. There is little experience with the drug in treating Chinese children with frequently relapsing nephrotic syndrome (FRNS). We investigated the efficacy and safety for treating MZR with FRNS. Furthermore, the relationship between efficacy and serum concentration was investigated.

METHODS

A prospective multicenter observational 12-month study was performed for evaluating the usefulness of MZR with FRNS. Serum MZR concentration was measured, and the relationships between pharmacokinetic parameters (C_max, AUC), number of relapses, and urinary protein were evaluated.

RESULTS

Eighty-two pediatric patients from four hospitals were treated with MZR and prednisone. MZR treatment significantly reduced the number of relapses and steroid doses. A correlation between pharmacokinetic parameters and relapses was observed, which fits well with the sigmoidal E_max model. Even in the relationship between pharmacokinetic parameters and urinary proteins, it was recognized that there was a threshold in the pharmacokinetic parameters for the therapeutic effect similar to the results obtained with the sigmoidal E_max model. Eleven patients (13.4%) experienced mild adverse events.

CONCLUSIONS

MZR therapy was effective in reducing the number of relapses and steroid doses. No severe adverse reactions were observed. Therapeutically effective serum concentrations were estimated to be C_max ≥ about 2 μg/mL or AUC ≥ about 10 μg h/mL. MZR and steroid treatment were effective and safe for pediatric FRNS.

3-Trifluoromethylpyrazolones derived nucleosides: Synthesis and antiviral evaluation

Dengue (DENV) viral infection is a global public health problem that infrequently develops life threatening diseases such as dengue hemorrhagic fever (DFS) and dengue shock syndrome (DSS). Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human corona virus with 38% fatality rate of infected patients. A series of 4-arylhydrazono-5-trifluoromethyl-pyrazolones, their ribofuranosyl, and 5'-deoxyribofuranosyl nucleosides were synthesized, geometry optimized using Density functional theory (DFT), and evaluated for their antiviral activity. 2-Nitrophenylhydrazonopyra-zolone derivative 5 showed significant activity against MERS-CoV (EC50 = 4.6 μM). The nucleoside analog 8 showed moderate activity against DENV-2 (EC50 = 10 μM), while the activity was abolished with the corresponding 5'-deoxyribonucleoside analogs. The identified hits in this study set this category of compounds for further future optimizations.

Prediction of mizoribine pharmacokinetic parameters by serum creatinine in renal transplant recipients

PURPOSE

Mizoribine (MZR) is an immunosuppressive agent with extensive inter-individual differences in pharmacokinetics (PK). Here, we investigated the PK characteristics of MZR in renal transplant recipients and gave equations for prediction of some critical PK parameters.

METHODS

A total of 40 renal transplant recipients participated in this prospective study and were administered MZR orally twice daily in the range of 1.1-8.9 mg kg^-1 day^-1. Steady-state concentrations of MZR were detected before (0 h) and 0.5, 1, 2, 3, 4, 5, 6, 8, and 12 h after administration by high-performance liquid chromatography method. Another 38 patients with newly detected trough concentration (C₀) were enrolled to validate the obtained C₀ predictive equation.

RESULTS

Significant inter-individual differences in MZR PK parameters were observed. Patients with decreasing creatinine clearance rate (CCr) had significantly decreased terminal elimination rate constant (k_el) and apparent total body clearance (Cl/F), while other PK parameters including apparent terminal half-life (t_1/2), peak time (T_max), peak concentration (C_max), area under the curve (AUC_0-12h), apparent volume of distribution (V/F), and mean residence time (MRT) were significantly increased. Correlation coefficients between AUC_0-12h and C₀/C_max were 0.894 and 0.916, respectively (both p < 0.001). A serum creatinine (SCr)-based predictive C₀ equation [C₀ = (2.160 × SCr - 54.473) × Dose] was established and validated by C₀ from another 38 patients. Besides, significant linear correlations between k_el/t_1/2 and CCr were also found (r² = 0.668 and 0.484, respectively), and equations predicting k_el/t_1/2 were also obtained (k_el = 0.015 + 0.002 × CCr, t_1/2 = 13.601 - 0.139 × CCr).

CONCLUSIONS

Renal function plays as an essential factor that contributes to great inter-individual MZR PK variation. Both C₀ and C_max are suitable for evaluating MZR exposure in the body. SCr could be applied to predict C₀ and t_1/2 of MZR.

Uptake and metabolism of mizoribine, an immunosuppressant, in L5178Y-R mouse lymphoma cells in vitro and peripheral blood mononuclear cells of rats and kidney transplant recipients in vivo

The cellular uptake of mizoribine (MZR), an immunosuppressant, and metabolism of MZR to MZR-5'- monophosphate (MZRP), an active metabolite, were evaluated in L5178Y-R mouse lymphoma cells and peripheral blood mononuclear cells (PBMCs) of rats and kidney transplant recipients (KTRs, n = 22). Real-time PCR analysis revealed the expression of ENT1 and ENT2 mRNAs, but not of CNTs, in L5178Y-R cells and rat's PBMCs. In L5178Y-R cells, the uptake of MZR was suppressed by adenosine, a substrate for ENT1 and ENT2, but not by 5-(4-nitrobenzyl)-6-thioinosine (0.1 μM), an ENT1 inhibitor. Saturable metabolism of MZR to MZRP was observed. In rats, peak plasma concentrations of MZR and peak concentrations of MZR and MZRP in PBMCs were observed 3 h after oral administration. MZR disappeared from PBMCs in parallel with plasma MZR, but the disappearance of MZRP from PBMCs appeared to be slow. In KTRs, the mean plasma concentration of MZR 3-4 h after ingestion was 3.14 μg/ml and the mean MZRP concentration in PBMCs was 16.8% of MZR, reflecting the involvement of ENT in the uptake of MZR. A linear relationship was observed between plasma MZR concentrations ranging from 1 to 6 μg/ml and PBMC's MZRP concentrations ranging from 90 to 200 ng/ml.

Toward Developing Chemical Modulators of Hsp60 as Potential Therapeutics

The 60 kDa heat shock protein (Hsp60) is classically known as a mitochondrial chaperonin protein working together with co-chaperonin 10 kDa heat shock protein (Hsp10). This chaperonin complex is essential for folding proteins newly imported into mitochondria. However, Hsp60, and/or Hsp10 have also been shown to reside in other subcellular compartments including extracellular space, cytosol, and nucleus. The proteins in these extra-mitochondrial compartments may possess a wide range of functions dependent or independent of its chaperoning activity. But the mechanistic details remain unknown. Mutations in Hsp60 gene have been shown to be associated with neurodegenerative disorders. Abnormality in expression level and/or subcellular localization have also been detected from different diseased tissues including inflammatory diseases and various cancers. Therefore, there is a strong interest in developing small molecule modulators of Hsp60. Most of the reported inhibitors were discovered through various chemoproteomics strategies. In this review, we will describe the recent progress in this area with reported inhibitors from both natural products and synthetic compounds. The former includes mizoribine, epolactaene, myrtucommulone, stephacidin B, and avrainvillamide while the latter includes o-carboranylphenoxyacetanilides and gold (III) porphyrins. The potencies of the known inhibitors range from low micromolar to millimolar concentrations. The potential applications of these inhibitors include anti-cancer, anti-inflammatory diseases, and anti-autoimmune diseases.

Population Pharmacokinetic Analysis of Mizoribine in Chinese Renal Transplant Recipients

BACKGROUND

We calculated the population pharmacokinetics of mizoribine in adult Chinese patients and compared the parameters with those of Japanese patients to determine whether there are any ethnic differences in blood concentration transition between these 2 populations.

METHODS

The blood concentrations of mizoribine in 21 Chinese patients who were administered mizoribine after renal transplantation were measured at 304 time points. The absorption lag time, absorption rate constant, apparent distribution volume, and oral clearance were thereafter calculated and compared with the respective Japanese references.

RESULTS

The absorption lag time, absorption rate constant, and apparent distribution volume calculated in this study were, respectively, 0.353 hour, 0.856 hour^-1, and 0.776 L/kg. The oral clearance was calculated as 2.18 times the creatinine clearance using creatinine clearance as a function. The absorption rate constant, apparent distribution volume, and oral clearance are determinants of the maximum blood concentration, trough, and area under the blood concentration time curve. The relative absorption rate constant, apparent distribution volume, and oral clearance were 0.9-, 0.9-, and 1.2-fold, respectively, in Chinese patients compared with those in Japanese patients. These values are within the confidence limit, suggesting that there is no significant PK difference between the 2 ethnic groups.

CONCLUSIONS

Results of this study showed no ethnic difference in blood mizoribine concentration transition between Chinese and Japanese patients. In addition, the population pharmacokinetic parameters obtained in this study are useful in determining the initial dosage or in the Bayesian analysis of mizoribine concentrations using scarce time points.

Internally ratiometric fluorescent sensors for evaluation of intracellular GTP levels and distribution

GTP is a major regulator of multiple cellular processes, but tools for quantitative evaluation of GTP levels in live cells have not been available. We report the development and characterization of genetically encoded GTP sensors, which we constructed by inserting a circularly permuted yellow fluorescent protein (cpYFP) into a region of the bacterial G protein FeoB that undergoes a GTP-driven conformational change. GTP binding to these sensors results in a ratiometric change in their fluorescence, thereby providing an internally normalized response to changes in GTP levels while minimally perturbing those levels. Mutations introduced into FeoB to alter its affinity for GTP created a series of sensors with a wide dynamic range. Critically, in mammalian cells the sensors showed consistent changes in ratiometric signal upon depletion or restoration of GTP pools. We show that these GTP evaluators (GEVALs) are suitable for detection of spatiotemporal changes in GTP levels in living cells and for high-throughput screening of molecules that modulate GTP levels.

Ancillary Activity: Beyond Core Metabolism in Immune Cells

Immune cell function and fate are intimately linked to engagement of metabolic pathways. The contribution of core metabolic pathways to immune cell bioenergetics has been vigorously investigated in recent years. However, precisely how other peripheral metabolic pathways support immune cells beyond energy generation is less well understood. Here we survey the literature and highlight recent advances in our understanding of several ancillary metabolic pathways and how they support processes beyond ATP production and ultimately contribute to protective immunity.

Comparison of Mizoribine and Mycophenolate Mofetil With a Tacrolimus-Based Immunosuppressive Regimen in Living-Donor Kidney Transplantation Recipients: A Retrospective Study in China

BACKGROUND

A retrospective study was conducted to investigate the prevalence of gastrointestinal (GI) symptoms as well as the efficacy and safety of mizoribine (MZR) and mycophenolate mofetil (MMF) in Chinese living-donor kidney transplantation (LDKT).

METHODS

Forty-two recipients enrolled between January 2012 and March 2014 were treated with either MZR (n = 22) or MMF (n = 20). All patients were treated in combination with a tacrolimus-based immunosuppressive regimen, besides the study drugs.

RESULTS

GI symptoms were observed in 1 of 22 patients (4.5%) and 10 of 20 patients (50%) in MZR treatment group and MMF treatment group, respectively (P = .001), during the post-transplantation 1 year. No significant differences in the incidence of acid reflux, bloated stomach feeling, and constipation were observed between the two groups. No recipient developed diarrhea in the MZR treatment group, whereas 30% of the MMF treatment group developed diarrhea (P = .007). The averages of GI symptom severity total score and diarrhea score were significantly lower in the MZR treatment group compare with MMF treatment group. There were no inter-group differences in background characteristics. There were no significant differences in acute rejection rate and clinical findings between these two groups, whereas the prevalence of cytomegalovirus infection and leukopenia were significantly lower in the MZR treatment group. There was no significant difference on adverse events such as hyperuricemia or other adverse events.

CONCLUSIONS

This study demonstrated a significantly lower incidence of GI symptoms for treatment with MZR compared with MMF and good efficacy and safety in Chinese LDKT with MZR.

A four-drug combination therapy consisting of low-dose tacrolimus, low-dose mycophenolate mofetil, corticosteroids, and mizoribine in living donor renal transplantation: A randomized study

OBJECTIVE

We compared a three-drug combination therapy (control group) consisting of tacrolimus, mycophenolate mofetil, and corticosteroids in living donor renal transplantation with a four-drug combination therapy (study group), in which the doses of tacrolimus and mycophenolate mofetil were halved and the immunosuppressive drug mizoribine was added, in order to determine whether the incidence rates of acute rejection after transplantation between the study group and the control group are similar, whether the study group regimen prevents the occurrence of calcineurin inhibitor-induced renal damage, and whether the study group regimen prevents adverse effects such as diarrhea caused by mycophenolate mofetil.

METHODS

We investigated the incidence of acute rejection, serum creatinine levels, and estimated glomerular filtration rate and the incidence of adverse effects such as diarrhea.

RESULTS

There was no significant difference between the two groups in the incidence of acute rejection. Renal function (estimated glomerular filtration rate and serum creatinine) was maintained in the control group whereas in the study group renal function gradually improved, with a statistical difference observed at 12 months. The incidence of gastrointestinal symptoms including diarrhea was significantly higher in the control group than in the study group. There was no significant difference in the incidence of cytomegalovirus infection and other adverse effects.

CONCLUSION

These results suggest the study group therapy is an effective regimen in preventing acute rejection and the deterioration of renal function. These results also show this therapy can reduce the incidence of adverse effects such as gastrointestinal symptoms.

Pyruvate kinase isoform expression alters nucleotide synthesis to impact cell proliferation

Metabolic regulation influences cell proliferation. The influence of pyruvate kinase isoforms on tumor cells has been extensively studied, but whether PKM2 is required for normal cell proliferation is unknown. We examine how PKM2 deletion affects proliferation and metabolism in nontransformed, nonimmortalized PKM2-expressing primary cells. We find that deletion of PKM2 in primary cells results in PKM1 expression and proliferation arrest. PKM1 expression, rather than PKM2 loss, is responsible for this effect, and proliferation arrest cannot be explained by cell differentiation, senescence, death, changes in gene expression, or prevention of cell growth. Instead, PKM1 expression impairs nucleotide production and the ability to synthesize DNA and progress through the cell cycle. Nucleotide biosynthesis is limiting, as proliferation arrest is characterized by severe thymidine depletion, and supplying exogenous thymine rescues both nucleotide levels and cell proliferation. Thus, PKM1 expression promotes a metabolic state that is unable to support DNA synthesis.

Synthesis and antimicrobial evaluation of novel pyrazolones and pyrazolone nucleosides

The synthesis of a novel series of 4-arylhydrazono-5-methyl-1,2-dihydropyrazol-3-ones 4a-h, and their N (2)-alkyl and acyclo, glucopyranosyl, and ribofuranosyl derivatives is described. K(2)CO(3) catalyzed alkylation of 4a-h with allyl bromide, propargyl bromide, 4-bromobutyl acetate, 2-acetoxyethoxymethyl bromide, and 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide proceeded selectively at the N (2)-position of the pyrazolinone ring. Glycosylation of 4a with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose under Vorbruggen glycosylation conditions gave the corresponding N (2)-4-arylhydrazonopyrazolone ribofuranoside 9a in good yield. Conventional deprotection of the acetyl protected nucleosides furnished the corresponding 4-arylhydrazonopyrazolone nucleosides in good yields. Selected numbers of the newly synthesized compounds were screened for antimicrobial activity. Compounds 4b, 12a, and 14 d showed moderate activities against Aspergillus flavus, Penicillium sp., and Escherichia coli.

Refractory Proliferative Lupus Nephritis

Objective: To review the literature available regarding treatment of lupus nephritis (LN) refractory to cyclophosphamide, mycophenolate mofetil, azathioprine, and glucocorticoids. Data Sources: PubMed-MEDLINE and SCOPUS databases were searched through June 2013 using the terms lupus nephritis, refractory, induction, systemic lupus erythematosus, diffuse proliferative glomerulonephritis, rituximab, cyclosporine, tacrolimus, leflunomide, mizoribine, intravenous immunoglobulin, and belimumab. Study Selection and Data Extraction: Included studies were limited to human studies that evaluated clinical efficacy and English language articles. Articles assessing treatment with first-line agents such as glucocorticoids, cyclophosphamide, mycophenolate, and azathioprine were excluded from this review. Data Synthesis: There are an increasing number of medications being used in refractory LN, making the selection of an appropriate agent more difficult. Thirty studies evaluating the treatment of LN with alternative agents were identified. Although rituximab and calcineurin inhibitors have demonstrated the ability to induce remission in approximately 60% of patients with LN, large randomized trials have not confirmed these results. Leflunomide, mizoribine, and intravenous immunoglobulin have revealed potential benefits in some patient populations; however, there is not enough data to support the regular use of these agents for refractory LN. Conclusions: Rituximab and calcineurin inhibitors have the most evidence to support their use and should be the preferred agents in the treatment of refractory LN at this time. Further studies may elucidate the efficacy of other agents for refractory LN.

Therapeutic effect of mizoribine on pemphigus vulgaris and pemphigus foliaceus

We evaluated the effectiveness of mizoribine, a newly developed immunosuppressive agent, as an adjuvant therapy in the treatment of both pemphigus vulgaris and pemphigus foliaceus. Eleven pemphigus patients (eight pemphigus vulgaris and three pemphigus foliaceus) received the combination therapy of prednisolone and mizoribine. Complete remission was observed in three of the eight patients with pemphigus vulgaris and in one of the three patients with pemphigus foliaceus. The four patients with complete remission had a rapid clinical response and achieved remission at a median of 11.8 months. Partial remission was achieved in two of the three patients with pemphigus foliaceus. The median time to achieve partial remission was 16.0 months. Six (55.6%) of the 11 patients with pemphigus had complete or partial remission and were able to taper their prednisolone. The cumulative probability of having a complete remission was 64.3% at 19 months of follow-up using Kaplan-Meier analysis. The effectiveness of the additional mizoribine therapy could be attributed to its corticosteroid-sparing properties as well as its immunosuppressive effects. The serum concentration titer of mizoribine was around 1.0 μg/mL 2 hours after administration. Patients who were not improved by the additional mizoribine might require a continuously higher dose of mizoribine to achieve effective therapy.

Chronopharmacology of mizoribine in collagen-induced arthritis rats

We previously reported that higher therapeutic effects were obtained in rheumatoid arthritis (RA) patients and RA model animals when the dosing-times of methotrexate and tacrolimus were chosen according to the 24-h rhythms of the inflammatory response. Mizoribine (MZR) is an immunosuppressive agent and is used against RA in the same manner as methotrexate and tacrolimus. In this study, we examined whether a dosing-time dependency of the therapeutic effect of MZR could be detected in collagen-induced arthritis (CIA) rats. To measure C-reactive protein (CRP) and tumor necrosis factor (TNF)-α levels, blood was collected from CIA rats at different times. MZR was administered at two different dosing-times based on these findings and its effects and toxicity were examined. CRP and TNF-α concentrations in blood showed significant 24-h rhythms. The exacerbation of arthritis and excessive increase in leukocytes in CIA rats were markedly lower in the group treated with MZR at the dark phase than those of the group treated with MZR at the light phase. These findings suggest that the therapeutic index of RA therapy may be improved by administering MZR at a time in the day when the inflammatory reaction begins to activate.

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 of weekly mizoribine pulse therapy in refractory lupus nephritis

OBJECTIVE

We investigated the efficacy of a high-dose intermittent dosing treatment method (weekly mizoribine pulse therapy) conceived in the hope of achieving better efficacy by increasing the peak blood levels of mizoribine in patients with refractory lupus nephritis.

METHODS

Seventeen patients with lupus nephritis who had been resistant to corticosteroid and immunosuppressant therapy received weekly mizoribine pulse therapy. Mizoribine (350 mg) was administered three times at 12 h intervals over 2 consecutive days (700 mg for day 1 and 350 mg for day 2), followed by a washout period from day 3 to day 7.

RESULTS

This therapeutic strategy enabled the peak blood levels of mizoribine to be increased to more than 3 μg/mL in most of the patients. Although SLEDAI, anti-ds-DNA antibody titer, CH-50, and serum albumin level did not significantly improve, urinary protein levels decreased, and it was possible to taper the dose of concomitant steroids. Using our definition of clinical response, 10 of the 17 patients were responders and 4 of them were nonresponders. The average peak serum mizoribine concentration of the responders was as high as 3.5 μg/mL. Elevation of serum liver enzymes was seen in 1 patient, and hyperuricemia occurred in 4 cases, but none of these adverse events were serious.

CONCLUSION

Intermittent administration of mizoribine can increase blood levels and may be effective for refractory lupus nephritis.

Mizoribine provides effective treatment of sequential histological change of arteritis and reduction of inflammatory cytokines and chemokines in an animal model of Kawasaki disease

The incidence of panvasculitis in the coronary arteries and aortic root was 100% in the control group. The incidence of panvasculitis in the MZR group decreased to 50%. Moreover, the scope and severity of the inflammation of those sites were significantly reduced in the MZR group as well as the IgG group. On the other hand, increased cytokines and chemokines, such as IL-1α, TNF-α, KC, MIP-1α, GM-CSF, and IL-13, in the nontreatment group were significantly suppressed by treatment with MZR, but the MCP-1 level increased. In addition, IL-1α, TNF-α, IL-10, IL-13, and MIP-1α were suppressed by treatment in the IgG group.

BACKGROUND

Intravenous immunoglobulin (IVIg) treatment results in an effective response from patients with acute-phase Kawasaki disease (KD), but 16.5% of them remain nonresponsive to IVIg. To address this therapeutic challenge, we tried a new therapeutic drug, mizoribine (MZR), in a mouse model of KD, which we have established using injections of Candida albicans water-soluble fractions (CAWS).

METHODS

CAWS (4 mg/mouse) were injected intraperitoneally into C57BL/6N mice for 5 consecutive days. MZR or IgG was administered for 5 days. After 4 weeks, the mice were sacrificed and autopsied, the hearts were fixed in 10% neutral formalin, and plasma was taken to measure cytokines and chemokines using the Bio-Plex system.

RESULTS

The incidence of panvasculitis in the coronary arteries and aortic root was 100% in the control group. The incidence of panvasculitis in the MZR group decreased to 50%. Moreover, the scope and severity of the inflammation of those sites were significantly reduced in the MZR group as well as the IgG group. On the other hand, increased cytokines and chemokines, such as IL-1α TNF-α, KC, MIP-1α, GM-CSF, and IL-13, in the nontreatment group were significantly suppressed by treatment with MZR, but the MCP-1 level increased. In addition, IL-1α, TNF-α, IL-10, IL-13, and MIP-1α were suppressed by treatment in the IgG group.

CONCLUSION

MZR treatment suppressed not only the incidence, range, and degree of vasculitis, but also inflammatory cytokines and chemokines in the plasma of the KD vasculitis model mice, suggesting that MZR may be useful for treatment of KD.

Mizoribine protects against bleomycin-induced lung injury

Bleomycin (BLM)-induced lung injury has become a model for studies of interstitial pneumonitis and pulmonary fibrosis. BLM induces lung injury in two phases: early inflammation characterized by infiltration of inflammatory cells into the lungs, followed by a late phase of fibrosis characterized by deposition of collagen. In this study, we examined the role of mizoribine (MZB) in the regulation of inflammatory tissue injury caused by BLM. We examined the role of MZB using a mouse model of BLM-induced lung injury. We demonstrated that mice subjected to instillation of BLM into the lungs had a significantly increased number of macrophages and lymphocytes in bronchoalveolar lavage fluid (BALF), but that those treated with MZB in the early phase showed a significant reduction in the total number of BALF macrophages and lymphocytes. However, MZB was unable to inhibit fibrosis in the late phase of BLM injury. Our findings suggest that MZB inhibits the proliferation of both lymphocytes and macrophages in the early phase of the BLM-induced acute inflammatory response, as well as its development and amplification, but does not inhibit fibrotic change in the late phase.

Novel anticytomegalovirus activity of immunosuppressant mizoribine and its synergism with ganciclovir

Cytomegalovirus (CMV) infection is a prominent infection in transplant recipients. The immunosuppressive drug mizoribine was shown to have anti-CMV activity in vitro and was reported to have an anti-CMV effect in renal transplantation. This study characterized the anti-CMV activity of mizoribine in vitro and its synergistic activity with ganciclovir. Mizoribine suppressed replication and at the EC(50) for plaque inhibition of 12.0 microg/ml. Mizoribine and ganciclovir exerted a strong synergism in anti-CMV activity. Mizoribine depletes guanosine nucleotides by inhibiting inosine monophosphate dehydrogenase and may increase the ratio of ganciclovir to guanosine in treated cells, resulting in a strong synergistic augmentation of the anti-CMV activity of ganciclovir. Two clinical isolates with UL97 mutations were less susceptible to mizoribine than the Towne strain but were equally susceptible in the presence of guanine. Two mizoribine-resistant strains were isolated after culture for 3 months with 100 microg/ml mizoribine, but they were as sensitive to ganciclovir as the parent Towne strain. The anti-CMV activity of mizoribine was antagonized by 2'-deoxyguanosine. Mizoribine inhibited CMV replication directly, and the sequence of mizoribine-resistant mutants of UL97 and UL54 was identical to that of the parent Towne strain, indicating the different anti-CMV action from ganciclovir, foscarnet, and maribavir. Mizoribine as an immunosuppressive and anti-CMV drug in the clinical regimen was suggested to suppress replication of CMV in vivo and control CMV infection in transplant recipients in combination with ganciclovir.

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.

Usefulness of initial histological features for stratifying Sjogren's syndrome responders to mizoribine therapy

OBJECTIVES

To evaluate the response of patients with SS to mizoribine therapy in relation to histological features of minor salivary glands.

METHODS

Forty patients definitely diagnosed as having SS were treated with mizoribine (150 mg/day). Thirty-four untreated patients matched for age, baseline salivary secretion, etc., served as controls. Salivary secretion volume (measured by the Saxon test) and serum IgG level were measured before and after 24 weeks of treatment. Each histological finding (lymphocytic infiltration, acinar atrophy and intralobular fibrosis) was graded at baseline and the therapeutic responses were compared with the grade at 24 weeks in both the groups.

RESULTS

There was a significant increase of the salivary secretion volume after treatment with mizoribine as compared with the untreated control group. The effect of mizoribine on salivary secretion was more marked in patients having moderate lymphocytic infiltration and moderate or less severe acinar atrophy and intralobular fibrosis at baseline.

CONCLUSIONS

Mizoribine was clinically effective in patients with SS whose minor salivary glands had moderate cell infiltration and were free of intralobular fibrosis. The drug was less effective in patients who presented intralobular fibrosis. Histological evaluation of the minor salivary glands may serve to predict the response of SS patients to mizoribine therapy.

d‐penicillamine‐induced pemphigus successfully treated with combination therapy of mizoribine and prednisolone

A 63-year-old woman had D-penicillamine-induced pemphigus with a high index value of circulating autoantibodies against desmoglein 1. Because of the lack of response to prednisolone monotherapy, the patient was treated with a combination therapy of mizoribine and low-dose prednisolone. The skin eruption was improved by this combination with a declined value of circulating anti-desmoglein 1 antibody. Currently, a remission of 2 months has been achieved, and prednisolone could be tapered.

A sudden onset of diabetic ketoacidosis and acute pancreatitis after introduction of mizoribine therapy in a patient with rheumatoid arthritis

Mizoribine has been recognized to have an acceptable toxicity profile compared with other immunosuppressants. In this study, however, we report a case of diabetic ketoacidosis and acute pancreatitis that suddenly occurred in a rheumatoid arthritis patient 2 weeks after introduction of mizoribine therapy. To the best of our knowledge, this is the first case in the literature to show mizoribine-induced diabetic ketoacidosis. Through prompt diagnosis and treatment, the patient recovered from these extremely rare but potentially lethal complications.

Efficacy and safety of mizoribine for the treatment of Sjögren's syndrome: a multicenter open-label clinical trial

This multicenter clinical trial was performed to evaluate the efficacy and safety of mizoribine for the treatment of Sjögren's syndrome. Fifty-nine patients with a definite diagnosis of Sjögren's syndrome received 150;Smg of mizoribine daily for 16 weeks. The salivary secretion volume was determined at baseline, at weeks 8 and 16 after the start of the study treatment by the Saxon test, and clinical manifestations were assessed by the investigator and the patients using a 10-cm visual analog scale (VAS). Adverse drug reactions were reported in 18 patients, of whom 6 patients had to discontinue the study due to such adverse reactions; however, no serious adverse drug reactions definitely related to the study drug were noted. The salivary secretion volume, the rate of change in salivary secretion, the patients' own assessments of dry mouth and dry eyes, the investigators' assessment of oral sicca symptoms, and the investigators' overall assessment improved following the treatment regimen with statistical significance at week 16 after the start of treatment in comparison to the baseline values. These results suggested that mizoribine may be effective in producing a subjective and objective amelioration of the glandular symptoms in patients with Sjögren's syndrome, without observing any serious adverse effects related to this drug.

Effects of mizoribine on MHC-restricted exogenous antigen presentation in dendritic cells

Mizoribine (MZR) has been shown to possess immunosuppressive activity that selectively inhibits the proliferation of lymphocytes by interfering with inosine monophosphate dehydrogenase. The efficacy of MZR is not only in patients who have had renal transplantation, but also in patients with rheumatoid arthritis (RA), lupus nephritis, and primary nephritic syndrome. Because the exact mechanism of its immunosuppressive action is not clear, the object of this study was to examine the ability of MZR to regulate the antigen presenting cells (APCs), dendritic cells (DCs). In this work, we tested whether MZR (1-10 microg/mL) could inhibit the cross-presentation of DCs. DC2.4 cells (H-2K(b)) or bone marrow-derived DCs (BM-DCs) generated from BM cells of C57BL/6 mouse (H-2K(b)) were cultured in the presence of MZR with OVA-microspheres, and the amount of OVA peptide-class I MHC complexes was measured by a T cell hybridoma, B3Z, that recognizes OVA (257-264 : SIINFEKL)-H-2Kb complex and expresses-galactosidase. MZR profoundly inhibited the expression of SIINFEKL-H-2K(b) complexes. This inhibitory activity of MZR appeared to affect the phagocytic activity of DCs. MZR also decreased IL-2 production when we examined the effects of MZR on CD4+ T cells. These results provide an understanding of the mechanism of immunosuppressive activity of MZR on the inhibition of MHC-restricted antigen presentation and phagocytic activity in relation to their actions on APCs.

Safety, tolerability and pharmacokinetics of higher-dose mizoribine in healthy male volunteers

AIMS

Mizoribine is an oral immunosuppressive agent approved in several countries for prevention of rejection in renal transplantation. Its therapeutic window is based on trough concentrations staying at > or =0.5 but <3 microg ml(-1). It has been postulated that as renal function returns to normal, higher doses may be needed to maintain efficacy than the current clinical dosage of 2-5 mg kg(-1) day(-1). The safety, tolerability and pharmacokinetics from two clinical trials of higher-dose mizoribine treatments in healthy male volunteers are presented.

METHODS

Forty-eight healthy White male nonsmokers participated in two randomized, double-blind, placebo-controlled trials: 32 in a single-dose study (3, 6, 9 and 12 mg kg(-1)) and 16 in a multiple-dose study [6 mg kg(-1) day(-1) once daily for 5 days or twice daily (12 mg kg(-1) day(-1)) for 7 days]. Standard assessments of safety, tolerability and pharmacokinetics were performed.

RESULTS

The safety profiles of both studies were generally unremarkable, except for elevated serum uric acid concentrations at the highest dose (12 mg kg(-1) day(-1)) in the multiple-dose study. Orally administered mizoribine reached peak concentrations within 2-3 h and was eliminated mostly via the kidney (65-100% of dose) with a 3-h half-life. Only the 12 mg kg(-1) day(-1) group achieved trough concentrations that were within the therapeutic window. Conclusions Based on the favourable safety profile and current pharmacokinetic information, a new starting dose in the 6-12 mg kg(-1) day(-1) range is recommended in the up to 3 months acute phase following transplantation, with dose reduction recommended only if the function of the transplanted kidney is impaired.

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.

Differential effect of insulin and elevated glucose level on adenosine handling in rat T lymphocytes

Reduced proliferation potential is among other T cell functional defects long known feature of diabetes. However, the mechanism responsible for this impairment is still unknown. Our study was undertaken to investigate the effect of changes in glucose and insulin concentrations on adenosine metabolism, transport and receptor-mediated action in rat T lymphocytes. Presented results indicate that vulnerability of T cells to metabolic stress is determined by insulin but not by glucose concentration. However, glucose and insulin differentially affected the activities of adenosine metabolizing enzymes in resting and proliferating T cells. The Con A-induced proliferation of cultured T lymphocytes did not depended on expression level and functional state of nucleoside transporters. Inhibition of adenosine kinase (AK) with 5-iodotubercidin lowers the proliferation potential of T cells to the level observed for insulin-deprived cells. Moreover, insulin-deprived T lymphocytes but not cells cultured in the presence of insulin released significant quantities of adenosine. Under resting conditions, the cAMP level was fivefold higher in cells deprived of insulin comparing to cells cultured in the presence of insulin. Exposition of insulin-deprived T lymphocytes to specific antagonist (ZM241385) of A2a receptor but not to specific antagonist (Alloxazine) of A2b receptor suppressed cAMP elevation and completely restored the proliferation potential of T cells. Concluding, adenosine released by insulin-deprived T cells due to suppressed AK activity by acting on A2a receptors leads to increases in cAMP level and suppression of T cell proliferation. We assume that this mechanism may significantly contribute to immune impairment observed in diabetes.

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.

High-dose mizoribine therapy for childhood-onset frequently relapsing steroid-dependent nephrotic syndrome with cyclosporin nephrotoxicity

Cyclosporin A (CsA) is an effective treatment for frequently relapsing steroid-dependent nephrotic syndrome (FR-SDNS), but its use can be complicated by renal toxicity and a high incidence of relapses after withdrawal. We report 9 adolescent patients with childhood-onset FR-SDNS who had been treated with long-term CsA that resulted in moderate-to-severe CsA nephropathy (CsAN). They were treated with high-dose (mean: 10.1 mg/kg per day) mizoribine (MZR) in an attempt to allow weaning of CsA and/or steroid therapy, and reduce the frequency of relapses. Seven out of 9 patients were weaned off CsA by 1-year follow-up, although in the remaining 2 patients, MZR did not show any beneficial effects. Overall, this high-dose MZR therapy results in significant steroid sparing and reduction in relapse rates in our patients. Our experience shows that high-dose MZR therapy in patients with FR-SDNS who are also CsA-dependent appears to be effective in reducing CsA exposure as well as in decreasing the frequency of relapses.

Novel inosine monophosphate dehydrogenase inhibitor VX-944 induces apoptosis in multiple myeloma cells primarily via caspase-independent AIF/Endo G pathway

Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme required for the de novo synthesis of guanine nucleotides from IMP. VX-944 (Vertex Pharmaceuticals, Cambridge, MA, USA) is a small-molecule, selective, noncompetitive inhibitor directed against human IMPDH. In this report, we show that VX-944 inhibits in vitro growth of human multiple myeloma (MM) cell lines via induction of apoptosis. Interleukin-6, insulin-like growth factor-1, or co-culture with bone marrow stromal cells (BMSCs) do not protect against VX-944-induced MM cell growth inhibition. VX-944 induced apoptosis in MM cell lines with only modest activation of caspases 3, 8, and 9. Furthermore, the pan-caspase inhibitor z-VAD-fmk did not inhibit VX-944-induced apoptosis and cell death. During VX-944-induced apoptosis, expressions of Bax and Bak were enhanced, and both apoptosis-inducing factor (AIF) and endonuclease G (Endo G) were released from the mitochondria to cytosol, suggesting that VX-944 triggers apoptosis in MM cells primarily via a caspase-independent, Bax/AIF/Endo G pathway. Importantly, VX-944 augments the cytotoxicity of doxorubicin and melphalan even in the presence of BMSCs. Taken together, our data demonstrate a primarily non-caspase-dependent apoptotic pathway triggered by VX-944, thereby providing a rationale to enhance MM cell cytotoxicity by combining this agent with conventional agents which trigger caspase activation.