Thiopurine methyltransferase phenotype and genotype in relation to azathioprine therapy in autoimmune hepatitis

MMF Is an Effective and Safer Treatment Options for Treatment-Naïve Patients With Autoimmune Hepatitis Compared to Azathioprine: A Systematic Review and Meta-Analysis

OBJECTIVES

Autoimmune Hepatitis (AIH) is a chronic inflammatory liver disease with significant morbidity and mortality if untreated. Current first-line treatment involves corticosteroids and azathioprine (AZA), which are effective but are associated with significant adverse effects and treatment intolerance. Mycophenolate mofetil (MMF), an immunosuppressive agent with a potentially better safety profile, has emerged as an alternative. This meta-analysis evaluated the efficacy and safety of MMF compared to AZA in treatment-naïve AIH patients.

METHODS

We conducted a systematic review and meta-analysis in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Databases were searched for articles published up to May 2024. Statistical analysis was performed using RevMan, employing a random-effects model.

RESULTS

Five studies involving 621 patients were included. MMF showed significantly higher rates of complete biochemical response compared to AZA (odds ratio [OR] 3.64, 95% confidence interval [CI] 2.07-6.40, p < 0.00001) and lower non-response rates (OR 0.45, 95% CI 0.24-0.85, p = 0.01). Corticosteroid withdrawal rates were also higher in the MMF group (OR 2.89, 95% CI 1.69-4.94, p = 0.0001). Relapse rate and cumulative prednisolone dose were comparable between the two groups. MMF demonstrated a better safety profile, with significantly lower rates of gastrointestinal symptoms (OR 0.46, 95% CI 0.27-0.79, p = 0.005).

CONCLUSIONS

MMF shows superior efficacy and tolerability compared to AZA in treatment-naïve AIH patients and may serve as a preferred first-line therapy, offering improved patient adherence and clinical outcomes. Further randomized controlled trials are warranted to confirm these findings.

British Society of Gastroenterology guidelines for diagnosis and management of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease which, if untreated, often leads to cirrhosis, liver failure and death. The last British Society of Gastroenterology (BSG) guideline for the management of AIH was published in 2011. Since then, our understanding of AIH has advanced in many areas. This update to the previous guideline was commissioned by the BSG and developed by a multidisciplinary group. The aim of this guideline is to review and summarise the current evidence, in order to inform and guide diagnosis and management of patients with AIH and its variant syndromes. The main focus is on AIH in adults, but the guidelines should also be relevant to older children and adolescents.

An open-label randomised-controlled trial of azathioprine vs. mycophenolate mofetil for the induction of remission in treatment-naive autoimmune hepatitis

BACKGROUND & AIMS

Patients with autoimmune hepatitis (AIH) almost invariably require lifelong immunosuppressive treatment. There is genuine concern about the efficacy and tolerability of the current standard combination therapy of prednisolone and azathioprine. Mycophenolate mofetil (MMF) has emerged as an alternative option. The aim of this study was to compare MMF to azathioprine as induction therapy for AIH.

METHODS

In this 24-week, prospective, randomised, open-label, multicentre superiority trial, 70 patients with treatment-naive AIH received either MMF or azathioprine, both in combination with prednisolone. The primary endpoint was biochemical remission defined as normalisation of serum levels of alanine aminotransferase and IgG after 24 weeks of treatment. Secondary endpoints included safety and tolerability.

RESULTS

Seventy patients (mean 57.9 years [SD 14.0]; 72.9% female) were randomly assigned to the MMF plus prednisolone (n = 39) or azathioprine plus prednisolone (n = 31) group. The primary endpoint was met in 56.4% and 29.0% of patients assigned to the MMF group and the azathioprine group, respectively (difference, 27.4 percentage points; 95% CI 4.0 to 46.7; p = 0.022). The MMF group exhibited higher complete biochemical response rates at 6 months (72.2% vs. 32.3%; p = 0.004). No serious adverse events occurred in patients who received MMF (0%) but serious adverse events were reported in four patients who received azathioprine (12.9%) (p = 0.034). Two patients in the MMF group (5.1%) and eight patients in the azathioprine group (25.8%) discontinued treatment owing to adverse events or serious adverse events (p = 0.018).

CONCLUSIONS

In patients with treatment-naive AIH, MMF with prednisolone led to a significantly higher rate of biochemical remission at 24 weeks compared to azathioprine combined with prednisolone. Azathioprine use was associated with more (serious) adverse events leading to cessation of treatment, suggesting superior tolerability of MMF.

IMPACT AND IMPLICATIONS

This randomised-controlled trial directly compares azathioprine and mycophenolate mofetil, both in combination with prednisolone, for the induction of biochemical remission in treatment-naive patients with autoimmune hepatitis. Achieving complete remission is desirable to prevent disease progression. Patients assigned to the mycophenolate mofetil group reached biochemical remission more often and experienced fewer adverse events. The findings in this trial may contribute to the re-evaluation of international guidelines for the standard of care in treatment-naive patients with autoimmune hepatitis.

TRIAL REGISTRATION NUMBER

#NCT02900443.

Autoimmune Hepatitis: A Diagnostic and Therapeutic Overview

Autoimmune hepatitis is an immune-mediated inflammatory condition of the liver of undetermined cause that affects both sexes, all ages, races, and ethnicities. Its clinical presentation can be very broad, from having an asymptomatic and silent course to presenting as acute hepatitis, cirrhosis, and acute liver failure potentially requiring liver transplantation. The diagnosis is based on histological abnormalities (interface hepatitis), characteristic clinical and laboratory findings (increased aspartate aminotransferase, alanine aminotransferase, and serum IgG concentration), and the presence of one or more characteristic autoantibodies. The large heterogeneity of these clinical, biochemical, and histological findings can sometimes make a timely and proper diagnosis a difficult task. Treatment seeks to achieve remission of the disease and prevent further progression of liver disease. First-line therapy includes high-dose corticosteroids, which are later tapered to decrease side effects, and azathioprine. In the presence of azathioprine intolerance or a poor response to the standard of care, second-line therapy needs to be considered, including mycophenolate mofetil. AIH remains a diagnostic and therapeutic challenge, and a further understanding of the pathophysiological pathways of the disease and the implementation of randomized controlled trials are needed.

Towards personalised medicine in autoimmune hepatitis: Measurement of thiopurine metabolites results in higher biochemical response rates

BACKGROUND & AIMS

Patients with autoimmune hepatitis (AIH) usually receive maintenance therapy with thiopurines, such as azathioprine (AZA) or mercaptopurine. Genetic polymorphisms in AZA metabolism can lead to variations in thioguanine nucleotide (TGN) and 6-methylmercaptopurine, both of which can cause adverse drug reactions (ADRs). In inflammatory bowel disease, a therapeutic TGN range (225-450 pmol/8x10⁸ erythrocytes) has been identified to optimise effectiveness. We evaluated the benefits of a personalised medicine approach to thiopurine dosing, in comparison to standard weight-based dosing.

METHODS

A retrospective matched cohort study of 214 patients with AIH who were seen at King's College between 1999-2019 was performed. Metabolite levels were measured in 109 patients. The control group included 105 patients on weight-based thiopurine dosing with no metabolite monitoring.

RESULTS

Biochemical response (BR) occurred more frequently at 6-month follow-up in patients with metabolite monitoring compared to those on a weight-based regimen (77% vs. 60%, p = 0.008). This remained true with data analysis based on clinicians who measure metabolites and those who do not (BR at 6 months: 84% vs. 64%, p = 0.016). Patients with BR had TGN levels within the therapeutic range of 225-450 pmol/8x10⁸ erythrocytes significantly more often than those who failed to achieve or lost BR (40% vs. 13%, p <0.0001). Moreover, TGN levels within the pre-defined therapeutic range predicted more stable disease within 6 months of testing compared to levels outside the range (p <0.0001). A high proportion of patients with sub-therapeutic TGN levels (75-225 pmol/8x10⁸ erythrocytes) remained in BR (75% vs. 81%, p = 0.589) with fewer ADRs (44% vs. 86%, p = 0.0002) when compared to patients with therapeutic TGN levels.

CONCLUSION

A strategy of personalised medicine using metabolite levels can optimise treatment regimens in AIH, resulting in fewer ADRs whilst maintaining BR.

LAY SUMMARY

This study looked to see if measuring the breakdown products of a medication used in autoimmune hepatitis increases the chances of gaining good control of the disease, when compared to a group of patients who were on a dose of this medication based on their weight. A group of 214 patients with autoimmune hepatitis were split into 2 groups: roughly half had their medication dose adjusted according to measurements of breakdown products in the blood, whilst the other half received their weight-based dose as normal. The results confirmed that using a personalised approach and checking drug breakdown products resulted in fewer side effects and potentially improved control of disease.

Review article: opportunities to improve and expand thiopurine therapy for autoimmune hepatitis

BACKGROUND

Thiopurines in combination with glucocorticoids are used as first-line, second-line and maintenance therapies in autoimmune hepatitis and opportunities exist to improve and expand their use.

AIMS

To describe the metabolic pathways and key factors implicated in the efficacy and toxicity of the thiopurine drugs and to indicate the opportunities to improve outcomes by monitoring and manipulating metabolic pathways, individualising dosage and strengthening the response.

METHODS

English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

Thiopurine methyltransferase activity and 6-tioguanine (6-thioguanine) nucleotide levels influence drug efficacy and safety, and they can be manipulated to improve treatment response and prevent myelosuppression. Methylated thiopurine metabolites are associated with hepatotoxicity, drug intolerance and nonresponse and their production can be reduced or bypassed. Universal pre-treatment assessment of thiopurine methyltransferase activity and individualisation of dosage to manipulate metabolite thresholds could improve outcomes. Early detection of thiopurine resistance by metabolite testing, accurate estimations of drug onset and strength by surrogate markers and adjunctive use of allopurinol could improve the management of refractory disease. Dose-restricted tioguanine (thioguanine) could expand treatment options by reducing methylated metabolites, increasing the bioavailability of 6-tioguanine nucleotides and ameliorating thiopurine intolerance or resistance.

CONCLUSIONS

The efficacy and safety of thiopurines in autoimmune hepatitis can be improved by investigational efforts that establish monitoring strategies that allow individualisation of dosage and prediction of outcome, increase bioavailability of the active metabolites and demonstrate superiority to alternative agents.

Autoimmune hepatitis: Current and future therapeutic options

Autoimmune hepatitis (AIH) is a rare immune-mediated liver disease with few major advances in treatment options over the last several decades. Available options are effective in most patients albeit are imprecise in their mechanisms. Novel and more tolerable induction regimens and alternative options for management of patients intolerant or with suboptimal response to traditional therapies including in the post-transplant setting remain an important unmet need. This review aims to summarize recent data on pharmacological options and investigational drugs in development for patients with AIH. Standard therapy using prednisone with or without azathioprine remains the mainstay of therapy and is effective in most patients. Budesonide may be considered for induction in early disease and in those with mild fibrosis, but has not been approved for maintenance therapy. Mycophenolate mofetil (MMF) in combination with steroids might be an alternative first-line therapy, but results from a randomized trial are awaited. MMF as a second-line maintenance agent has moderate efficacy though more frequent adverse events in patients with cirrhosis may be seen. Tacrolimus may be an equally effective second-line option particularly in non-responders, but data remain limited. Management of recurrent AIH post-liver transplantation remains controversial with insufficient data to support long-term steroid use. Moving forward, expanding the scope of therapeutic options to include biologics including B-cell depleting agents may be a promising step. Recent insights in understanding the pathogenesis of AIH could serve as a basis for future therapies, including the elucidation of different immunoregulatory pathways and the potential role of the intestinal microbiome.

SNPs affecting the clinical outcomes of regularly used immunosuppressants

Recent studies have suggested that genomic diversity may play a key role in different clinical outcomes, and the importance of SNPs is becoming increasingly clear. In this article, we summarize the bioactivity of SNPs that may affect the sensitivity to or possibility of drug reactions that occur among the signaling pathways of regularly used immunosuppressants, such as glucocorticoids, azathioprine, tacrolimus, mycophenolate mofetil, cyclophosphamide and methotrexate. The development of bioinformatics, including machine learning models, has enabled prediction of the proper immunosuppressant dosage with minimal adverse drug reactions for patients after organ transplantation or for those with autoimmune diseases. This article provides a theoretical basis for the personalized use of immunosuppressants in the future.

[Usefulness of thiopurine methyltransferase polymorphism study and metabolites measurement for patients treated by azathioprine]

Azathioprine is widely used in internal medicine and frequently implicated in occurrence of adverse events. Among these adverse events the bone marrow suppression, a dose-related one, is the most serious because of is potential morbidity and mortality. Severe myelosuppression, associated with abnormal AZA metabolism, is linked to the thiopurine methyltransferase (TPMT) genetic polymorphism that results in a high variability of its activity with 89% of patients with a normal activity, 11% with an intermediate activity, and 0.3% with very low activity leading to a very high risk of bonne marrow suppression. TPMT status can be assessed prior to AZA treatment by measuring enzyme activity or genotyping techniques to identify patients for which the standard dose is not advisable. Furthermore, azathioprine metabolites monitoring is helpful for the follow up of patients, especially in therapeutic failure, to distinguish non-compliant patients from under-dosed, "shunters" or resistant patients.

BMSCs-derived miR-223-containing exosomes contribute to liver protection in experimental autoimmune hepatitis

Autoimmune hepatitis is a chronic inflammatory disease in the liver with potential to the development of liver fibrosis. Recent evidences suggest that bone marrow derived mesenchymal stem cells (BMSCs) may exert its therapeutic activity through exosomes. Moreover, miR-223 is highly expressed in BMSCs and plays an important role in autoimmune diseases. Therefore, in this study, hepatoprotective role of BMSCs and miR-223 was investigated in both mice and hepatocytes. Liver antigen S100 was used to establish autoimmune hepatitis model in mice while LPS and ATP were used to establish cell injury model in hepatocyte. Before the experiments, BMSCs were infected with pre-miR-223 and transfected with miR-223 inhibitor respectively. Exosomes from bone marrow stem cells were isolated by ultracentrifugation. Liver injury was evaluated by serum levels of ALT and AST as well as liver histology. Inflammation and cell death were examined by inflammatory cytokines and lactase dehydrogenase respectively. Both BMSCs-exo and BMSCs-exomiR-223(+) significantly reversed either S100 or LPS/ATP induced injury in mice and hepatocytes. Meanwhile, the expressions of cytokines, NLRP3 and caspase-1 were also downregulated by BMSCs-exo and BMSCs-exomiR-223(+) at both protein and mRNA levels in mice and hepatocytes. Moreover, BMSCs-exomiR-223(-) reverses the effects of BMSCs-exo and BMSCs-exomiR-223(+) in mouse AIH and in hepatocytes. In conclusion, bone marrow stem cell derived exosomes can protect liver injury in an experimental model of autoimmune hepatitis and the mechanism could be related to exosomal miR-223 regulation of NLRP3 and caspase-1.

6-Mercaptopurine modifies cerebrospinal fluid T cell abnormalities in paediatric opsoclonus-myoclonus as steroid sparer

The purpose of this study was to evaluate the capacity of 6-mercaptopurine (6-MP), a known immunosuppressant, to normalize cerebrospinal fluid (CSF) lymphocyte frequencies in opsoclonus-myoclonus syndrome (OMS) and function as a steroid sparer. CSF and blood lymphocytes were immunophenotyped in 11 children with OMS (without CSF B cell expansion) using a comprehensive panel of cell surface adhesion, activation and maturation markers by flow cytometry, and referenced to 18 paediatric controls. Drug metabolites, lymphocyte counts and liver function tests were used clinically to monitoring therapeutic range and toxicity. In CSF, adjunctive oral 6-MP was associated with a 21% increase in the low percentage of CD4⁺ T cells in OMS, restoring the CD4/CD8 ratio. The percentage of CD4⁺ T cells that were interferon (IFN)-γ⁺ was reduced by 66%, shifting the cytokine balance away from T helper type 1 (Th1) (proinflammatory) predominance. The percentage of natural killer (NK) cells decreased significantly in CSF (-32%) and blood (-67 to -82%). Low blood absolute lymphocyte count was more predictive of improvement in CSF lymphocyte proportions (correlated with % CD4⁺ T cells) than the 6-thioguanine level (no correlation). 6-MP was difficult to titrate: 50% achieved the target absolute lymphocyte count (< 1·5 K/mm); 20%, the 'therapeutic' 6-thioguanine level; and 40% the non-toxic 6-methylmercaptopurine level. Side effects and transaminase elevation were mild and reversible. Clinical steroid-sparing properties and lowered relapse frequency were demonstrated. 6-MP displayed unique pharmacodynamic properties that may be useful in OMS and other autoimmune disorders. Its steroid sparer capacity is limited to children in whom the therapeutic window can be reached without limiting pharmacokinetic factors or side effects.

Thiopurine S-methyltransferase testing for averting drug toxicity: a meta-analysis of diagnostic test accuracy

Thiopurine S-methyltransferase (TPMT) deficiency increases the risk of serious adverse events in persons receiving thiopurines. The objective was to synthesize reported sensitivity and specificity of TPMT phenotyping and genotyping using a latent class hierarchical summary receiver operating characteristic meta-analysis. In 27 studies, pooled sensitivity and specificity of phenotyping for deficient individuals was 75.9% (95% credible interval (CrI), 58.3-87.0%) and 98.9% (96.3-100%), respectively. For genotype tests evaluating TPMT*2 and TPMT*3, sensitivity and specificity was 90.4% (79.1-99.4%) and 100.0% (99.9-100%), respectively. For individuals with deficient or intermediate activity, phenotype sensitivity and specificity was 91.3% (86.4-95.5%) and 92.6% (86.5-96.6%), respectively. For genotype tests evaluating TPMT*2 and TPMT*3, sensitivity and specificity was 88.9% (81.6-97.5%) and 99.2% (98.4-99.9%), respectively. Genotyping has higher sensitivity as long as TPMT*2 and TPMT*3 are tested. Both approaches display high specificity. Latent class meta-analysis is a useful method for synthesizing diagnostic test performance data for clinical practice guidelines.The Pharmacogenomics Journal advance online publication, 24 May 2016; doi:10.1038/tpj.2016.37.

Thiopurine S-methyltransferase testing for averting drug toxicity in patients receiving thiopurines: a systematic review

AIM

Thiopurine S-methyltransferase (TPMT) testing is used in patients receiving thiopurines to identify enzyme deficiencies and risk for adverse drug reactions. It is uncertain whether genotyping is superior to phenotyping. The objectives were to conduct a systematic review of TPMT-test performance studies.

MATERIALS & METHODS

Electronic and grey literature sources were searched for studies reporting test performance compared with a reference standard. Sixty-six eligible studies were appraised for quality.

RESULTS

Thirty phenotype-genotype and six phenotype-phenotype comparisons were of high quality. The calculated sensitivity and specificity for genotyping to identify a homozygous mutation ranged from 0.0-100.0% and from 97.8-100.0%, respectively.

CONCLUSION

Clinical decision-makers require high-quality evidence of clinical validity and clinical utility of TPMT genotyping to ensure appropriate use in patients.

Diagnosis and Management of Autoimmune Hepatitis: Current Status and Future Directions

Autoimmune hepatitis is characterized by autoantibodies, hypergammaglobulinemia, and interface hepatitis on histological examination. The features lack diagnostic specificity, and other diseases that may resemble autoimmune hepatitis must be excluded. The clinical presentation may be acute, acute severe (fulminant), or asymptomatic; conventional autoantibodies may be absent; centrilobular necrosis and bile duct changes may be present; and the disease may occur after liver transplantation or with features that suggest overlapping disorders. The diagnostic criteria have been codified, and diagnostic scoring systems can support clinical judgment. Nonstandard autoantibodies, including antibodies to actin, α-actinin, soluble liver antigen, perinuclear antineutrophil antigen, asialoglycoprotein receptor, and liver cytosol type 1, are tools that can support the diagnosis, especially in patients with atypical features. Prednisone or prednisolone in combination with azathioprine is the preferred treatment, and strategies using these medications in various doses can ameliorate treatment failure, incomplete response, drug intolerance, and relapse after drug withdrawal. Budesonide, mycophenolate mofetil, and calcineurin inhibitors can be considered in selected patients as frontline or salvage therapies. Molecular (recombinant proteins and monoclonal antibodies), cellular (adoptive transfer and antigenic manipulation), and pharmacological (antioxidants, antifibrotics, and antiapoptotic agents) interventions constitute future directions in management. The evolving knowledge of the pathogenic pathways and the advances in technology promise new management algorithms.

Association between Thiopurine S-Methyltransferase Polymorphisms and Azathioprine-Induced Adverse Drug Reactions in Patients with Autoimmune Diseases: A Meta-Analysis

Purpose

Azathioprine (AZA) is widely used as an immunosuppressive drug in autoimmune diseases, but its use is limited by significant adverse drug reactions (ADRs). Thiopurine S-methyltransferase (TPMT) is an important enzyme involved in AZA metabolism. Several clinical guidelines recommend determining TPMT genotype or phenotype before initiating AZA therapy. Although several studies have investigated the association between TPMT polymorphisms and AZA-induced ADRs, the results are inconsistent. The purpose of this study is to evaluate whether there is an association between TPMT polymorphisms and AZA-induced ADRs using meta-analysis.

Methods

We explored PubMed, Web of Science and Embase for articles on TPMT polymorphisms and AZA-induced ADRs. Studies that compared TPMT polymorphisms with-ADRs and without-ADRs in patients with autoimmune diseases were included. Relevant outcome data from all the included articles were extracted and the pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated using Revman 5.3 software.

Results

Eleven published studies, with a total of 651 patients with autoimmune diseases, investigated associations between TPMT polymorphisms and AZA-induced ADRs, were included in this meta-analysis. Our meta-analysis demonstrated that TPMT polymorphisms were significantly associated with AZA-induced overall ADRs, bone marrow toxicity and gastric intolerance; pooled ORs were 3.12 (1.48–6.56), 3.76 (1.97–7.17) and 6.43 (2.04–20.25), respectively. TPMT polymorphisms were not associated with the development of hepatotoxicity; the corresponding pooled OR was 2.86 (95%CI: 0.32–25.86). However, the association in GI subset could be driven by one single study. After this study was excluded, the OR was 2.11 (95%CI: 0.36–12.42); namely, the association became negative.

Conclusions

Our meta-analysis demonstrated an association of TPMT polymorphisms with overall AZA-induced ADRs, bone marrow toxicity and gastric intolerance, but not with hepatotoxicity. The presence of the normal TPMT genotypes cannot preclude the development of ADRs during AZA treatment, TPMT genotyping prior to commencing AZA therapy cannot replace, may augment, the current practice of regular monitoring of the white blood cell. Because of small sample sizes, large and extensive exploration was required to validate our findings.

Diagnosis and management of autoimmune hepatitis

Autoimmune hepatitis is characterized by increased serum aminotransferase levels, autoantibodies, hypergammaglobulinemia, and interface hepatitis. Presentation can be acute, severe (fulminant), asymptomatic, or chronic. Diagnosis requires multiple findings and exclusion of similar diseases. Treatment with prednisone or prednisolone with azathioprine is recommended. Budesonide with azathioprine has normalized laboratory test with few side effects, but histologic resolution, durability of response, and target population are uncertain. Progressive worsening, incomplete improvement, drug intolerance, and relapse after drug withdrawal are suboptimal outcomes. Calcineurin inhibitors and mycophenolate mofetil are salvage agents in small series and liver transplantation is effective for liver failure.

Management of autoimmune hepatitis: Focus on pharmacologic treatments beyond corticosteroids

In autoimmune hepatitis, patients who are intolerant or with toxicity experience, non-responders, relapsers or refractory are challenging. Non-standard drugs are being tried to preemptively avoid corticosteroid-related side effects. Prognosis and quality of life of life rely on treatment optimization. Recently, emergence of powerful immunosuppressive agents, mainly from liver transplantation, challenged the supremacy of the corticosteroid regime and promise greater immunosuppression than conventional medications, offer site-specific actions and satisfactory patient tolerance. Successes in experimental models of related diseases have primed these molecular interventions. We performed a literature review on alternative treatments. Azatioprine intolerance is the principal indication for mycophenolate use but it can be used as a front-line therapy. Cyclosporine A and tacrolimus have been tested for non-responders or relapsers. Rituximab may be used as salvage therapy. Anti-tumor necrosis factor-alpha agents may be used for incomplete responses or non-responders. Methotrexate is possibly an alternative for induction of remission and maintenance in refractory patients. Cyclophosphamide has been included in the induction regimen with corticosteroids. Ursodeoxycholic acid action is mainly immunomodulatory. Non-standard treatments are coming slowly to the attention, but its use should be cautious performed by experienced centers.

Current and prospective pharmacotherapy for autoimmune hepatitis

INTRODUCTION

Corticosteroids alone or in combination with azathioprine are the mainstay therapies of autoimmune hepatitis. Suboptimal responses (treatment failure, partial response, drug toxicity), frequent relapse after drug withdrawal, and the emergence of alternative immunosuppressive medications have fueled the pursuit of new treatments. The goals of this review are to present current management strategies and evolving interventions.

AREAS COVERED

PubMed searches from 1970 - 2014 provide the bases for this review. Corticosteroid regimens should be administered until resolution of symptoms, laboratory tests, and liver tissue abnormalities. Treatment failure warrants high doses of the original regimen, and relapse warrants re-treatment followed by long-term maintenance with azathioprine. The calcineurin inhibitors, budesonide, and mycophenolate mofetil are evolving as frontline therapies, and they may be considered as salvage therapies with the exception of budesonide. Rapamycin, rituximab, and infliximab have also rescued refractory patients but experiences are limited. Anti-oxidants, recombinant molecules, mAbs, and modulators of critical cell populations are key prospects.

EXPERT OPINION

Autoimmune hepatitis must be managed by multiple medications that supplement or supplant current regimens depending on the clinical situation. Rescue therapies will emerge as adjunctive interventions to minimize tissue damage (prevent fibrosis and hepatocyte apoptosis) and improve immune tolerance (regulatory T cell manipulations).

Prevalence of TPMT polymorphism in Indian patients requiring immunomodulator therapy and its clinical significance

BACKGROUND

Thiopurine methyltransferase (TPMT) enzyme plays a key role in the metabolism of azathioprine/6-mercaptopurine (6-MP). Mutations in the enzyme lead to generation of excess thioguanine, which causes suppression of various cell lineages, especially neutrophils. Data on the prevalence of TPMT polymorphism are available from Western and some Asian countries; such data from India are sparse.

AIMS

The aim of this research is to study the prevalence of TPMT mutation in Indian patients requiring immunomodulator therapy and its relation to the development of neutropenia on azathioprine therapy.

METHODS

In this retrospective study, data of all patients who underwent TPMT genotyping by PCR-RFLP and allele-specific PCR prior to immunomodulator therapy were analyzed. The frequency of on-treatment development of neutropenia (total neutrophil count <1,500 per cubic millimeters) was noted.

RESULTS

Data were available on 126 patients (mean age, 42 [SD 13.6] years; 73 men and 53 women). The disease indications included ulcerative colitis (61), Crohn's disease (43), indeterminate colitis (1), autoimmune hepatitis (16), and others (5). TPMT genotype was wild in 120 patients (95.23 %) and heterozygous in 6 patients (4.77 %); no patient had homozygous mutation. Seven of 87 patients (6.8 %) who received azathioprine developed neutropenia; blood counts normalized on cessation of the drug in all. The incidence of neutropenia in patients with wild type was 6/84 (7.14 %) and with heterozygous type 1/3 (33 %) (p = 0.5764).

CONCLUSION

Nearly 5 % of this population of patients requiring immunomodulator therapy was heterozygous carriers of the TPMT gene. Neutropenia was equally common in patients without and with the mutation.

Autoimmune hepatitis

Autoimmune hepatitis is a disease of the hepatic parenchyma that can present in acute or chronic forms. In common with many autoimmune diseases, autoimmune hepatitis is associated with non-organ-specific antibodies in the context of hepatic autoimmunity. This dichotomy has made definition of a unifying hypothesis in the pathophysiology of the disease difficult, although data from the past 8 years have drawn attention to the role of regulatory T cells. Several triggers have been identified, and the disease arises in genetically susceptible individuals. Clinical and biochemical remission is achievable in up to 85% of cases. For the remaining patients, alternative immunosuppression strategies are an option. Liver transplantation provides an excellent outcome for patients with acute liver failure or complications of end-stage liver disease, including hepatocellular carcinoma. Variant or overlapping syndromes are worthy of consideration when unexpected disease features arise.

Review article: the management of autoimmune hepatitis beyond consensus guidelines

BACKGROUND

Consensus guidelines aid in the diagnosis and management of autoimmune hepatitis, but they are frequently based on low-quality clinical evidence, conflicting experiences and divergent opinions. Recommendations may be weak, discrepant or non-existent at critical decision points.

AIMS

To identify the decision points where guidelines are weak or non-existent and review the evidence essential in the decision process.

METHODS

Full-text articles published in English using the keyword 'autoimmune hepatitis' were identified by PubMed from 1972 to 2013. Personal experience and investigations in autoimmune hepatitis also identified important contributions.

RESULTS

Seventy per cent of the guidelines developed by the American Association for the Study of Liver Diseases and 48% of those proposed by the British Society of Gastroenterology are based on low-quality evidence, conflicting experiences or divergent opinions. The key uncertainties in diagnosis relate to the timing of liver biopsy, recognising acute severe (fulminant) disease, interpreting coincidental nonclassical histological changes, accommodating atypical or deficient features in non-White patients, differentiating drug-induced from classical disease and identifying overlap syndromes. The key uncertainties in management relate to pre-treatment testing for thiopurine methyltransferase activity, treating asymptomatic mild disease, determining treatment end points, managing suboptimal responses, incorporating nonstandard medications as front-line and salvage agents, using azathioprine in pregnancy and instituting surveillance for hepatocellular carcinoma.

CONCLUSIONS

Consensus guidelines are fraught with uncertainties in the diagnosis and management of autoimmune hepatitis. Each decision point must counterbalance the current available evidence and tailor the application of this evidence to the individual patient.

Systematic review: managing suboptimal treatment responses in autoimmune hepatitis with conventional and nonstandard drugs

BACKGROUND

Corticosteroid treatment for autoimmune hepatitis has been shown by randomised controlled clinical trials to ameliorate symptoms, normalise liver tests, improve histological findings and extend survival. Nevertheless, suboptimal responses to corticosteroid treatment still occur.

AIM

To describe the current definitions, frequencies, clinical relevance and treatment options for suboptimal responses, and to discuss alternative medications that have been used off-label for these occurrences.

METHODS

Literature search was made for full-text papers published in English using the keyword 'autoimmune hepatitis'. Authors' personal experience and investigational studies also helped to identify important contributions to the literature.

RESULTS

Suboptimal responses to standard therapy include treatment failure (7%), incomplete response (14%), drug toxicity (13%) and relapse after drug withdrawal (50-86%). The probability of a suboptimal response prior to treatment is higher in young patients and in patients with a severe presentation, jaundice, high MELD score at diagnosis, multilobular necrosis or cirrhosis, antibodies to soluble liver antigen, or inability to improve by clinical indices within two weeks or by MELD score within 7 days of conventional corticosteroid treatment. Management strategies have been developed for the adverse responses and nonstandard drugs, including mycophenolate mofetil, budesonide, ciclosporin, tacrolimus, sirolimus and rituximab, are emerging as rescue therapies or alternative frontline agents.

CONCLUSIONS

Once diagnosed, the suboptimal response should be treated by a highly individualised and well-monitored regimen, preferentially using first-line therapy. Nonstandard drugs warrant consideration as salvage or second-line therapies.

Drug choices in autoimmune hepatitis: part B--Nonsteroids

Nonsteroidal medications, previously unfamiliar in the management of autoimmune hepatitis, can supplement or replace conventional corticosteroid regimens, especially in problematic patients. Mycophenolate mofetil is a next-generation purine antagonist that has been useful in treating patients with azathioprine intolerance. It has been less effective in salvaging patients with steroid-refractory disease. Azathioprine is the choice as a corticosteroid-sparing agent in treatment-naive patients and in individuals with corticosteroid intolerance, incomplete response and relapse after drug withdrawal. Tacrolimus is preferred over cyclosporine for recalcitrant disease because of its established preference in organ transplantation, but replacement with cyclosporine should be considered if the disease worsens on treatment. Rapamycin has antiproliferative and proapoptotic actions that warrant further study in autoimmune hepatitis. The nonstandard, nonsteroidal medications are mainly salvage therapies with off-label indications that must be used in highly individualized and well-monitored clinical situations.

Azathioprine-related myelosuppression in a patient homozygous for TPMT*3A

BACKGROUND

A 50-year-old man who had received a simultaneous pancreas and kidney transplant 9 years earlier developed pancytopenia 3 weeks after starting azathioprine therapy to treat worsening proteinuria suspected to be caused by sirolimus.

INVESTIGATIONS

Laboratory tests, including complete blood counts, measurement of serum levels of vitamin B(12) and folate, liver function tests, virological assays, and thiopurine S-methyltransferase (TPMT) genotyping.

DIAGNOSIS

Severe myelosuppression as a consequence of azathioprine therapy in a patient homozygous for the TPMT*3A allele.

MANAGEMENT

Discontinuation of azathioprine, treatment with an erythropoiesis-stimulating agent, red blood cell transfusions, filgrastim (a granulocyte colony-stimulating factor analogue) and folic acid.

Management of autoimmune hepatitis

PURPOSE OF REVIEW

Autoimmune hepatitis (AIH) is a chronic, progressive hepatitis of uncertain cause which has fluctuating activity characterized by periods of flares and remissions. Initial placebo-controlled trials carried out in the 1970s demonstrated that immunosuppression with steroids was extremely effective in reducing flares and progression of disease. The late 1980s-1990s could be described as the 'Dark Ages' of AIH treatment research. Very few clinical studies were performed during this time, although it became increasingly apparent that not all patients tolerated or responded to traditional immunosuppression, and that not all patients were easy to diagnose because of overlapping features with other autoimmune conditions. Fortunately, clinical research in the treatment of AIH has experienced a renaissance in the 21st century.

RECENT FINDINGS

This review highlights some of the more important recent discoveries, including the creation of the clinically useful short form of the autoimmune hepatitis diagnostic scoring system; accumulation of data supporting the use of mycophenolate and tacrolimus as second-line treatment; and the recent completion of the largest, double-blind, placebo-controlled trial of AIH treatment to date, comparing budesonide to prednisone.

SUMMARY

These new findings are pertinent to the everyday clinical management of patients with AIH.

Azathioprine metabolite measurements are not useful in following treatment of autoimmune hepatitis in Alaska Native and other non-Caucasian people

BACKGROUND

In autoimmune hepatitis (AIH) patients treated with azathioprine, the utility of measuring thiopurine methyltransferase (TPMT) and azathioprine metabolites has been limited.

OBJECTIVE

To evaluate the association between TPMT genotype and enzyme activity, and the impact of TPMT enzyme activity on levels of azathioprine metabolites and leukopenia to assess the clinical utility of monitoring azathioprine metabolites in Alaska Native and other non-Caucasian AIH patients.

METHODS

Individuals with AIH were recruited at the Alaska Native Medical Center (Alaska, USA) and the University of Texas Southwestern Medical Center (Texas, USA). Identification of TPMT genotype and measurement of enzyme activity were performed. The metabolites 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) were measured in participants who were on azathioprine, and the associations with disease remission and leukopenia were assessed.

RESULTS

Seventy-one patients with AIH were included. The distribution of TPMT genotypes was similar to that reported in other populationbased studies. TPMT genotype and phenotype were strongly associated (P<0.0001). Levels of 6-TGN and 6-MMP correlated with azathioprine dose only in individuals with normal TPMT enzyme activity. Patients with leukopenia due to azathioprine were no more likely to have abnormal TPMT enzyme levels than those without leukopenia (P=1.0). No specific level of 6-TGN metabolites was associated with remission or leukopenia.

DISCUSSION

Results of the present study were consistent with previous studies in Caucasian populations. TPMT genotype and phenotype correlated well, and levels of 6-TGN and 6-MMP metabolites were not associated with remission of AIH or toxicity of azathioprine.

CONCLUSIONS

The present study confirmed the limited utility of monitoring levels of azathioprine metabolites in AIH patients.

[Autoimmune hepatitis: diagnostic and therapeutic up-to-date]

Autoimmune hepatitis is a disorder of unknown aetiology that occurs in children and adults of all ages with a female predominance. The spectrum of presentation is wide, ranging from no symptoms to acute liver failure. The diagnosis is based on high level serum gammaglobulins, characteristic circulating autoantibodies and histologic abnormalities (necrosis and inflammation). Autoimmune hepatitis is classified on the basis of the autoantibody pattern: type 1 (antinuclear and/or smooth muscle antibodies) is the classic form whereas type II (liver-kidney microsome 1 antibody) is much less common and occurs mainly in childhood. Mixed forms of autoimmune hepatitis that share features with other putative autoimmune liver diseases, primary biliary cirrhosis and primary sclerosing cholangitis, have been described. Because of therapeutic issues, it is important to distinguish autoimmune hepatitis from other forms of hepatitis and the use of diagnostic scoring systems may be helpful. The treatment of autoimmune hepatitis has not changed for the past 30 years. It consists of corticosteroids associated with azathioprine. This treatment is rapidly effective but usually only suspensive. Relapse after treatment withdrawal is the rule (80% of cases). The main risk factor of recurrence is the degree of residual inflammation on liver biopsy. The frequency of side effects justifies an attempt of drug discontinuation provided that criteria of clinical, biochemical and histological remission are achieved after at least 2 years of treatment.

Advances in the diagnosis, pathogenesis, and management of autoimmune hepatitis

Autoimmune hepatitis (AIH) is characterized by chronic inflammation of the liver, interface hepatitis (based on histologic examination), hypergammaglobulinemia, and production of autoantibodies. Many clinical and basic science studies have provided important insights into the pathogenesis and treatment of AIH. Transgenic mice that express human antigens and develop autoantibodies, liver-infiltrating CD4(+) T cells, liver inflammation, and fibrosis have been developed as models of AIH. AIH has been associated with autoantibodies against members of the cytochrome P450 superfamily of enzymes, transfer RNA selenocysteine synthase, formiminotransferase cyclodeaminase, and the uridine diphosphate glucuronosyltransferases, whereas alleles such as DRB1*0301 and DRB1*0401 are genetic risk factors in white North American and northern European populations. Deficiencies in the number and function of CD4(+)CD25(+) (regulatory) T cells disrupt immune homeostasis and might be corrected as a therapeutic strategy. Treatment can be improved by continuing corticosteroid therapy until normal liver test results and normal liver tissue are within normal limits, instituting ancillary therapies to prevent drug-related side effects, identifying problematic patients early, and providing long-term maintenance therapy after patients experience a first relapse. Calcineurin inhibitors and mycophenolate mofetil are potential salvage therapies, and reagents such as recombinant interleukin-10, abatacept, and CD3-specific antibodies are feasible as therapeutics. Liver transplantation is an effective salvage therapy, even in the elderly, and AIH must be considered in all patients with graft dysfunction after liver transplantation. Identification of the key defects in immune homeostasis and antigen targets will direct new therapies.

Are patients with intermediate TPMT activity at increased risk of myelosuppression when taking thiopurine medications?

Thiopurine S-methyltransferase (TPMT) metabolizes thiopurine medications, including azathioprine and 6-mercaptopurine. Absent TPMT activity (i.e., in individuals homozygous for a variant TPMT allele) is associated with an increased risk of myelosuppression in patients taking thiopurine drugs. However, it is not clear if there is also an increased risk for patients with intermediate TPMT activity (i.e., in individuals heterozygous for a variant TPMT allele).

AIMS

To quantify the increased risk of myelosuppression for patients with intermediate TPMT activity.

MATERIALS & METHODS

A systematic review identified published studies, up to 29 September 2008, that explored the relationship between TMPT and hematological adverse drug reactions to thiopurines. Following a critical appraisal of the quality of published studies, a meta-analysis calculated the odds ratio of myelosuppression for patients with intermediate TPMT activity compared with wild-type.

RESULTS

A total of 67 studies were identified, the majority retrospective cohort in design. Patients with two TPMT variant alleles who are TPMT deficient have a substantial increase in their risk of myelotoxicity (86% of deficient patients developed myelosuppression). The increase in odds ratio of developing leukopenia for patients with intermediate TPMT activity or one TPMT variant allele compared with wild-type was 4.19 (95% CI: 3.20-5.48).

CONCLUSION

This meta-analysis suggests that individuals with both intermediate and absent TPMT activity have an increased risk of developing thiopurine-induced myelosuppression, compared with individuals with normal activity. However, there is significant variability in the quality of the reported studies and large prospective studies to clarify the size of the effect of TPMT variant alleles on the risk of myelosuppression should be conducted. Accurate risk assessments will provide important data to inform clinical guidelines.

Difficult treatment decisions in autoimmune hepatitis

Treatment decisions in autoimmune hepatitis are complicated by the diversity of its clinical presentations, uncertainties about its natural history, evolving opinions regarding treatment end points, varied nature of refractory disease, and plethora of alternative immunosuppressive agents. The goals of this article are to review the difficult treatment decisions and to provide the bases for making sound therapeutic judgments. The English literature on the treatment problems in autoimmune hepatitis were identified by Medline search up to October 2009 and 32 years of personal experience. Autoimmune hepatitis may have an acute severe presentation, mild inflammatory activity, lack autoantibodies, exhibit atypical histological changes (centrilobular zone 3 necrosis or bile duct injury), or have variant features reminiscent of another disease (overlap syndrome). Corticosteroid therapy must be instituted early, applied despite the absence of symptoms, or modified in an individualized fashion. Pursuit of normal liver tests and tissue is the ideal treatment end point, but this objective must be tempered against the risk of side effects. Relapse after treatment withdrawal requires long-term maintenance therapy, preferably with azathioprine. Treatment failure or an incomplete response warrants salvage therapy that can include conventional medications in modified dose or empirical therapies with calcineurin inhibitors or mycophenolate mofetil. Liver transplantation supersedes empirical drug therapy in decompensated patients. Elderly and pregnant patients warrant treatment modifications. Difficult treatment decisions in autoimmune hepatitis can be simplified by recognizing its diverse manifestations and individualizing treatment, pursuing realistic goals, applying appropriate salvage regimens, and identifying problematic patients early.

Characterisation and utility of thiopurine methyltransferase and thiopurine metabolite measurements in autoimmune hepatitis

BACKGROUND & AIMS

Corticosteroids alone or in conjunction with azathioprine (AZA) is the standard treatment in autoimmune hepatitis (AiH). Individual variations in thiopurine (TP) metabolism may affect both drug efficacy and toxicity. Our aim was to investigate the utility of thiopurine methyltransferase (TPMT) as well as thioguanine nucleotide (TGN) and methylthioinosine monophosphate (meTIMP) metabolite measurements with regard to clinical outcome.

METHODS

Two hundred thirty-eight patients with AiH were included in this cross-sectional study. TPMT status was assessed in all patients, while TGN and meTIMP were measured in patients with ongoing TP medication. Clinical outcome was evaluated by liver tests and the ability to withdraw steroids.

RESULTS

TPMT genotyping (n=229) revealed 207 (90.4%) wild-type and 22 heterozygous patients. One hundred forty-three patients had ongoing TP therapy with AZA (n=134) or mercaptopurine (MP; n=9); response was judged as complete response (CR) in 113 patients and partial response (PR) in 30 patients. Both TP dose (1.64 vs 1.19 mg/kg; p=0.012) and TPMT activity (14.3 vs 13.5; p=0.05) were higher in PR, resulting in similar TGN levels (PR: 121 pmol/8 x 10(8) red blood cells [RBC]; CR: 113 pmol/8 x 10(8) RBC; p=0.33) but higher meTIMP levels in PR (1350 vs 400 pmol/8 x 10(8) RBC; p=0.004). Patients able to withdraw steroids or who were using 5 mg prednisolone daily were treated with lower TP doses than patients on higher steroid doses (1.15 vs 1.18 vs 1.82 mg/kg; p<0.001).

CONCLUSIONS

TP metabolite measurements are of clinical value in AiH patients who do not respond to standard TP treatment and for the identification of a shifted metabolism, which may demand an alternative treatment strategy.

[A case of autoimmune hepatitis]

Autoimmune hepatitis (AIH) is a disorder of unknown aetiology that occurs in children and adults of all ages with a female predominance. The spectrum of presentation is wide, ranging from no symptoms to acute liver failure. The diagnosis is based on high level or serum gammaglobulins, characteristic circulating autoantibodies and histologic abnormalities (necrosis and inflammation) in the absence of other causes. AIH is classified on the basis of the autoantibody pattern: type 1 (antinuclear and/or smooth muscle antibodies) is the classic form whereas type 2 (liver-kidney microsome 1 antibody) is much less common and occurs mainly in childhood. Mixed forms of AIH that share features with other putative autoimmune liver diseases, primary biliary cirrhosis and primary sclerosing cholangitis, have been described. Because of therapeutic issues, it is important to distinguish AIH from other forms of hepatitis and the use of diagnostic scoring systems may be helpful. Treatment basis of AIH have not changed for the last 30 years. Initial treatment consists of corticosteroids associated with azathioprine. Budesonide may be at least as effective as systemic corticosteroids and reduces the frequency of side effects in non-cirrhotic patients. Long-term treatment consists of azathioprine. This treatment is rapidly effective but usually only suspensive since relapse after treatment withdrawal is the rule (80 % of cases). The probability of relapse is lower in case of complete biochemical response defined by normalization of transaminases, gamma-globulins and IgG and in case of histological response defined by the lack of interface hepatitis. The frequency of side effects justifies an attempt of drug discontinuation provided that criteria of clinical, biochemical and histological remission are achieved after at least 2 years of treatment.

Individualization of thiopurine therapy: thiopurine S-methyltransferase and beyond

The metabolism of a given drug depends, not solely on a particular enzyme, but rather on a complex metabolic network. Thiopurine S-methyltransferase (TPMT) catalyzes the methylation, and thus deactivation, of 6-mercaptopurine, a thiopurine used in the treatment of acute lymphoblastic leukemia. Low TPMT activity has been associated with severe toxicity of 6-mercaptopurine. Determination of mutations in the TPMT gene before starting 6-mercaptopurine therapy constitutes a quick, simple and cost-effective strategy to individualize thiopurine dosing. However, TPMT phenotype-to-genotype correlation is not complete, indicating a need for identification of novel biomarkers. Based on our recent findings and reviewing seemingly unrelated literature reports we present a synthesis of the current understanding of factors that influence TPMT activity and consequently modulate responsiveness to thiopurine treatment. Identification and understanding of these factors is crucial for improving the efficacy and safety of acute lymphoblastic leukemia treatment.

Thiopurine methyltransferase and thiopurine metabolite testing in patients with inflammatory bowel disease who are taking thiopurine drugs

Thiopurine methyltransferase genotyping and thiopurine metabolite testing has been established as an adjunct to monitoring patients taking thiopurine drugs. This special report describes the clinical implications for this type of testing for patients with inflammatory bowel disease who are taking thiopurine drugs. A total of 10% of patients were found to be intermediate metabolizers and the mean dosage (in mg/kg equivalent) was lower in intermediate metabolizers than extensive metabolizers. The metabolite levels did not correlate with scores measuring clinical severity but levels of 6-methylmercaptopurine were related to the dosage of the drugs. Despite considerable study of thiopurine methyltransferase testing in the literature, it is still not widely used in many geographical areas. This study adds to the evidence about using such testing as well as expanding the role of simultaneously measuring thiopurine metabolites. Further work is planned to evaluate the uptake when such testing becomes available locally as a clinical service.

Current and future treatments of autoimmune hepatitis

Corticosteroid therapy induces clinical, laboratory and histological improvements in 80% of patients with autoimmune hepatitis. Prednisone, alone or at a lower dose in combination with azathioprine, increases the 20-year life expectancy to 80% and prevents or reduces hepatic fibrosis in 79% of patients. The combination regimen is preferred and treatment should be considered in all patients with active disease. The duration of therapy is finite and the medication should be discontinued after resolution of all manifestations of inflammatory activity, including the histological changes. Relapse after drug withdrawal occurs in 50-79% of patients, and it should be treated with long-term azathioprine (2 mg/kg daily). Salvage therapies for individuals intolerant of or refractory to the conventional regimens include high-dose corticosteroids, with or without high-dose azathioprine, 6-mercaptopurine, mycophenolate mofetil, tacrolimus or ciclosporin. Liver transplantation should be considered in patients with hepatic failure unresponsive to corticosteroid treatment, decompensated cirrhosis with a Model for End-Stage Liver Disease score of at least 15 points, or hepatocellular carcinoma that meets transplantation criteria. Autoimmune hepatitis recurs after transplantation in at least 17% of patients, and it typically improves after adjustments in the immunosuppressive regimen. Future therapies are likely to include mesenchymal stem cell transplantation, adoptive transfer of T regulatory cells, and cytokine manipulation. The emergence of new treatments will require the development of a collaborative network of clinical and basic investigators, as the complexity and specificity of current management problems require solutions that exceed the capabilities of single institutions.

Clinical pharmacology and pharmacogenetics of thiopurines

The thiopurine drugs-azathioprine (AZA), 6-mercaptopurine (6-MP), and thioguanine-are widely used to treat malignancies, rheumatic diseases, dermatologic conditions, inflammatory bowel disease, and solid organ transplant rejection. However, thiopurine drugs have a relatively narrow therapeutic index and are capable of causing life-threatening toxicity, most often myelosuppression. Thiopurine S-methyltransferase (TPMT; EC 2.1.1.67), an enzyme that catalyzes S-methylation of these drugs, exhibits a genetic polymorphism in 10% of Caucasians, with 1/300 individuals having complete deficiency. Patients with intermediate or deficient TPMT activity are at risk for excessive toxicity after receiving standard doses of thiopurine medications. This report reviews the recent advances in the knowledge of the mechanism of action as well as the molecular basis and interethnic variations of TPMT and inosine triphosphate pyrophosphatase (ITPase; EC 3.6.1.19), another enzyme implicated in thiopurine toxicity. In addition, an update on pharmacokinetics, metabolism, drug-drug interactions, safety, and tolerability of thiopurine drugs is provided.

Preventative hepatology: minimising symptoms and optimising care

Most care of liver disease is in the ambulatory setting, and therefore the clinical needs of patients represent those of any other chronic illness. Emphasis must be given to preventative strategies such that liver lifetime (including pre-emptive strategies related to potential allograft survival) is maximised through timely intervention and avoidance of side effects. This review addresses the pertinent practical clinical concerns faced by clinicians as they manage adult patients with chronic liver disease, with an emphasis on preventing and managing symptoms and complications directly and indirectly related to the underlying disease.

Safety issues in the management of autoimmune hepatitis

BACKGROUND

Prednisone and azathioprine are effective in the treatment of autoimmune hepatitis, but diverse side effects can diminish their net benefit.

OBJECTIVES

Describe the frequency and nature of these side effects and propose management strategies to minimize their impact.

METHODS

Pertinent articles published from 1970 to 2007 were identified by Medline search and through a personal library.

RESULTS

Medication is prematurely discontinued in 13% of patients mainly because of cosmetic changes, cytopenia, or osteopenia. Populations at high risk are the elderly, those with pre-existent co-morbidities, patients with near-zero thiopurine methyltransferase activity, individuals who are treatment-dependent, pregnant women, and asymptomatic patients who are over-treated.

CONCLUSIONS

Proper patient selection, effective pre-treatment counseling, preemptive protective measures, realistic treatment objectives, and early identification of problematic patients can reduce complications. Individualized dosing schedules and the emergence of non-steroidal medications are realistic expectations.

Assessment of thiopurine methyltransferase enzyme activity is superior to genotype in predicting myelosuppression following azathioprine therapy in patients with inflammatory bowel disease

BACKGROUND

Myelosuppression occurs in 2-7% of inflammatory bowel disease (IBD) patients treated with azathioprine, and can be associated with reduced activity of thiopurine methyltransferase (TPMT) in some patients. It has been proposed that pretreatment assessment of TPMT status reduces the incidence of toxicity and is cost-effective.

AIMS

To determine if screening for TPMT status predicts side-effects to azathioprine in patients with IBD and to ascertain whether screening by TPMT enzyme activity or genotype is superior.

METHODS

Sequential IBD patients were identified and azathioprine tolerance recorded. Blood was collected for measurement of TPMT activity and TPMT*3C, TPMT*3A and TPMT*2 genotypes.

RESULTS

Of 130 patients, 25% stopped azathioprine because of toxicity. Four patients experienced severe myelosuppression (WCC < 2). Eleven of 17 patients with reduced TPMT activity were heterozygotes, including one patient with marked TPMT deficiency who experienced severe myelosuppression. There was no association between intermediate TPMT deficiency and any side-effect.

CONCLUSIONS

Moderate reduction of TPMT activity in heterozygotes was not associated with toxicity, but very low TPMT activity caused severe myelosuppression in one patient. This would have been predicted by measuring TPMT activity but not by genotyping. Measurement of TPMT activity may therefore be superior to genotype in predicting severe myelosuppression.

Current therapy for autoimmune hepatitis

The treatment of autoimmune hepatitis is evolving as the pathogenic pathways that underlie the disease are defined, new immunosuppressive agents are tested, and site-specific molecular interventions become feasible. Prednisone alone or at a reduced dose combined with azathioprine is the conventional treatment. Patients with HLA genotype DRB1*0301 have a poorer treatment response and a more frequent need for liver transplantation than those with HLA genotype DRB1*0401. Therapy to the point when liver test results and histological findings are normal reduces, but does not eliminate, the occurrence of relapse. Treatment failure warrants reassessment with regard to the accuracy of the original diagnosis and the exclusion of variant forms of hepatitis or concomitant alternative diseases. Ciclosporin might be effective as short-term, front-line therapy in infants and adults, and calcineurin inhibitors might salvage patients who are refractory to corticosteroid regimens. Mycophenolate mofetil can induce an improvement in laboratory test results and reduce the requirement for corticosteroids. Sirolimus is effective for treatment of de novo autoimmune hepatitis that develops after liver transplantation. Synthetic peptides that block autoantigen presentation, cytokine manipulations, oral tolerance regimens, T-cell vaccination, and gene therapy are all interventions that will be able to emerge after a reliable animal model of the human disease has been developed.

Thiopurine S-methyltransferase gene polymorphism in Japanese patients with autoimmune liver diseases

BACKGROUND AND AIM

Thiopurine S-methyltransferase (TPMT) genotypes or phenotypes may be a predictive factor for azathioprine-induced toxicities. We investigated the genotypic status of TPMT to evaluate the risk of azathioprine-related adverse effects in Japanese patients with different liver diseases, including autoimmune hepatitis (AIH).

METHODS

49 patients with AIH, 67 with primary biliary cirrhosis (PBC), and 120 with hepatitis C virus (HCV) were examined. TPMT genotypes were determined by PCR-restriction fragment length polymorphism-based assays.

RESULTS

The distribution of TPMT genotypes was 90% TPMT*1/TPMT*1, 8% TPMT*1/TPMT*3C, and 2% TPMT*3C/TPMT*3C in AIH, and 94% TPMT*1/TPMT*1, 4.5% TPMT*1/TPMT*3C, and 1.5% TPMT*3C/TPMT*3C in PBC. All except 1 patient with HCV had the TPMT*1/TPMT*1 genotype. Severe myelosuppression occurred in two of nine patients with AIH who received azathioprine, one of whom was homozygous for TPMT*3C.

CONCLUSIONS

TPMT*3C variants are more frequent in patients with AIH or PBC than in patients with viral hepatitis or healthy volunteers in Japan. Pharmacogenetic screening for TPMT polymorphisms before commencing azathioprine therapy may help to prevent severe hematotoxicity in patients with TPMT deficiency.

Utility of thiopurine methyltransferase genotyping and phenotyping, and measurement of azathioprine metabolites in the management of patients with autoimmune hepatitis

BACKGROUND/AIMS

Azathioprine is a key drug in the management of autoimmune hepatitis (AIH), with effects mediated via conversion to 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP), the latter controlled by thiopurine methyltransferase (TPMT). Our aims were to evaluate the role of TPMT genotyping and phenotyping and to examine 6-TG and 6-MMP metabolite levels in patients with AIH.

METHODS

TPMT genotyping and phenotyping was performed on 86 patients with AIH, and metabolites evaluated in assessable patients.

RESULTS

Eighty-six patients with AIH received azathioprine; 22 developed toxicity and 4/22 were heterozygous for TPMT alleles. Cirrhosis was more common amongst patients who developed toxicity (12/22 (54.5%) versus 19/64 (29.6%), P=0.043). Patients who required persistent prednisone at equivalent azathioprine doses had a higher mean fibrosis stage (P=0.044). TPMT activity, but not metabolites, was lower in patients with stage III/IV fibrosis versus stage I/II fibrosis (30+/-1.92 versus 35.2+/-1.93, P=0.044). Azathioprine dose significantly correlated with measured 6-TG levels (r=0.409, P<0.0001) and 6-MMP levels (r=0.387, P<0.001).

CONCLUSIONS

Advanced fibrosis but not TPMT genotype or activity predicts azathioprine toxicity in AIH. Overlap in 6-TG and 6-MMP metabolite levels is noted whether or not steroid therapy is used to maintain remission.

Azathioprine in dermatology: The past, the present, and the future

For several decades, dermatologists have utilized azathioprine to treat numerous debilitating skin diseases. This synthetic purine analog is derived from 6-mercaptopurine. It is thought to act by disrupting nucleic acid synthesis and has recently been found to interfere with T-cell activation. The most recognized uses of azathioprine in dermatology are for immunobullous diseases, generalized eczematous disorders, and photodermatoses. In this comprehensive review, the authors present recent advancements in the understanding of azathioprine and address aspects not covered in prior reviews. They (1) summarize the history of azathioprine; (2) discuss metabolism, integrating information from recent publications; (3) review the mechanism of action with attention paid to the activities of azathioprine not mediated by its 6-mercaptopurine metabolites and review new data about inhibition by azathioprine of the CD28 signal transduction pathway; (4) thoroughly examine thiopurine s-methyltransferase genetics, its clinical relevance, and interethnic variations; (5) review prior uses of azathioprine in the field of dermatology and grade the level of evidence; (6) discuss the use of azathioprine in pregnancy and pediatrics; review (7) key drug interactions and (8) adverse effects; (9) suggest a dosing and monitoring approach different from prior recommendations; and (10) explore the future of azathioprine, focusing on laboratory considerations and therapeutic application.

Thiopurine methyltransferase deficiency and azathioprine intolerance in autoimmune hepatitis

Thiopurine methyltransferase deficiency has been associated with intolerance to azathioprine. Our goals were to assess the frequency of enzyme deficiency in autoimmune hepatitis and correlate deficiency states with azathioprine intolerance. Eighty-six patients receiving azathioprine (50-150 mg daily) were evaluated for enzyme activity and azathioprine-related complications. Their findings were compared to 89 similarly treated but untested patients. Thirteen patients (15%) had low thiopurine methyltransferase levels (11.4+/- 0.9 U/ml RBC; range, 3.5-14.9 U/ml RBC). Azathioprine intolerance occurred as commonly in patients with normal or above normal enzyme levels as in patients with below normal levels (12% versus 15%, p = 0.7). Patients treated without enzyme testing had the same frequency of complications (9% versus 13%, p = 0.5) as tested patients. We conclude that routine screening of blood thiopurine methyltransferase levels has a low yield for identifying individual patients at risk for azathioprine toxicity during conventional low dose therapy for autoimmune hepatitis.

Cost-effectiveness of pharmacotherapy for autoimmune hepatitis

In > 80% of patients with autoimmune hepatitis, steroid therapy alone or in combination with azathioprine results in disease remission. Treatment response results in reversal of fibrosis and excellent long-term survival in many patients, whereas untreated patients may expect a 10-year survival of < 30%. The use of azathioprine monotherapy (2 mg/kg/day) has gained widespread acceptance in maintaining remission in clinical practice. Although all patients with autoimmune hepatitis may not need treatment, particularly those with mild disease, alternative strategies are required in patients who have failed to achieve remission on standard therapy of steroids with or without azathioprine, or patients with azathioprine-induced drug toxicity. In such circumstances, the use of salvage therapy in the form of ciclosporin, tacrolimus or mycophenolate mofetil may be warranted. Liver transplantation is the treatment of choice for patients who present with subacute liver failure or decompensated cirrhosis. Salvage therapy results in an exponential rise in cost with each increment in therapeutic escalation. As an alternative to standard therapy, it has also been suggested that novel therapies such as ciclosporin, tacrolimus or mycophenolate mofetil be initiated to achieve remission. However, a > 10-fold cost differential exists between the charges associated with more potent immunosuppression and standard therapy. Therefore, in evaluating novel immunosuppression in autoimmune hepatitis, it behoves clinicians not only to consider end points pertaining to efficacy, but also end points pertaining to cost-effectiveness. Moreover, the exact role of pharmacogenomics and genotyping of thiopurine methyltransferase in patients with autoimmune hepatitis needs to be fully defined.