ABCB1 single-nucleotide polymorphisms determine tacrolimus response in patients with ulcerative colitis. Clin Pharmacol Ther. 2011;89:422-428. [PMID: 21289623 DOI: 10.1038/clpt.2010.348]

Genetic polymorphisms impacting clinical pharmacology of drugs used to treat inflammatory bowel disease: a precursor to multi-omics approach to precision medicine

INTRODUCTION

Inflammatory bowel diseases (IBDs), comprised of ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory diseases of the gastrointestinal tract. Clinicians and patients must vigilantly manage these complex diseases over the course of the patient's lifetime to mitigate risks of the disease, surgical complications, progression to neoplasia, and complications from medical or surgical therapies. Over the past several decades, the armamentarium of IBD therapeutics has expanded; now with biologics and advanced small molecules complementing conventional drugs such as aminosalicylates, corticosteroids and thiopurines. Significant attention has been paid to the potential of precision medicine to assist clinicians in tailoring therapeutics based on patients' genetic signatures to maximize therapeutic benefit while minimizing adverse effects.

AREAS COVERED

In this paper, we review the published literature on genetic polymorphisms relevant to each class of IBD therapeutics.

EXPERT OPINION

Finally, we envision a paradigm shift in IBD research toward an omics-based network analysis approach. Through global collaboration, organization and goal setting, we predict the next decade of IBD research will revolutionize existing disease frameworks by developing precise molecular diagnoses, validated biomarkers, predictive models and novel molecularly targeted therapeutics.

CYP3A5 influences oral tacrolimus pharmacokinetics and timing of acute kidney injury following allogeneic hematopoietic stem cell transplantation

Introduction: Polymorphisms in genes responsible for the metabolism and transport of tacrolimus have been demonstrated to influence clinical outcomes for patients following allogeneic hematologic stem cell transplant (allo-HSCT). However, the clinical impact of germline polymorphisms specifically for oral formulations of tacrolimus is not fully described. Methods: To investigate the clinical impact of genetic polymorphisms in CYP3A4, CYP3A5, and ABCB1 on oral tacrolimus pharmacokinetics and clinical outcomes, we prospectively enrolled 103 adult patients receiving oral tacrolimus for the prevention of graft-versus-host disease (GVHD) following allo-HSCT. Patients were followed in the inpatient and outpatient phase of care for the first 100 days of tacrolimus therapy. Patients were genotyped for CYP3A5 *3 (rs776746), CYP3A4 *1B (rs2740574), ABCB1 exon 12 (rs1128503), ABCB1 exon 21 (rs2032582), ABCB1 exon 26 (rs1045642). Results: Expression of CYP3A5 *1 was highly correlated with tacrolimus pharmacokinetics in the inpatient phase of care (p < 0.001) and throughout the entirety of the study period (p < 0.001). Additionally, Expression of CYP3A5 *1 was associated with decreased risk of developing AKI as an inpatient (p = 0.06). Variants in ABCB1 were not associated with tacrolimus pharmacokinetics in this study. We were unable to discern an independent effect of CYP3A4 *1B or *22 in this population. Conclusion: Expression of CYP3A5 *1 is highly influential on the pharmacokinetics and clinical outcomes for patients receiving oral tacrolimus as GVHD prophylaxis following allo-HSCT.

Oral Tacrolimus in Steroid Refractory and Dependent Pediatric Ulcerative Colitis-A Systematic Review and Meta-Analysis

BACKGROUND

There are limited treatment options for children with steroid-refractory or dependent ulcerative colitis (UC). A few observational studies suggest efficacy of oral tacrolimus. We performed a systematic review and meta-analysis to assess the efficacy of tacrolimus in pediatric UC.

METHODS

PubMed and Scopus were searched for publications related to the use of oral tacrolimus in pediatric UC. Data regarding the clinical response and colectomy-free survival were extracted from studies that met the selection criteria.

RESULTS

The search strategy yielded 492 articles of which 7 studies were included in the final review. They included 166 children (111 steroid-refractory, 52 steroid-dependent, 3 no steroids). Majority of cases (150/166 [90%]) were naïve to biologics. An initial response to tacrolimus therapy was seen in 84% (95% CI: 73%-93%) (n = 7 studies). No difference was observed between children with high (>10 ng/mL) or low tacrolimus levels (127/150 [85%] vs 12/16 [75%], P = 0.3). No difference in initial response between the children who were steroid refractory or dependent (92/111 [83%] vs 46/52 [88%], P = 0.36). The response in the biologic-exposed group (n = 10) was 70%. At 1-year follow-up, 15.2% (95% CI: 7%-21%) (n = 2 studies, 85 patients) had a sustained response on only tacrolimus. The pooled frequency of 1-year colectomy-free survival in children treated with initial oral tacrolimus was 64% (95% CI: 53%-75%). Twelve (7.2%) patients required cessation of therapy because of side effects.

CONCLUSION

Tacrolimus has a high initial response in biologic naïve UC children. It can be effectively used as a bridge to other therapies with a 1-year colectomy-free survival of 64%.

Current evidence and clinical relevance of drug-microbiota interactions in inflammatory bowel disease

Background

Inflammatory bowel disease (IBD) is a chronic relapsing-remitting disease. An adverse immune reaction toward the intestinal microbiota is involved in the pathophysiology and microbial perturbations are associated with IBD in general and with flares specifically. Although medical drugs are the cornerstone of current treatment, responses vary widely between patients and drugs. The intestinal microbiota can metabolize medical drugs, which may influence IBD drug (non-)response and side effects. Conversely, several drugs can impact the intestinal microbiota and thereby host effects. This review provides a comprehensive overview of current evidence on bidirectional interactions between the microbiota and relevant IBD drugs (pharmacomicrobiomics).

Methods

Electronic literature searches were conducted in PubMed, Web of Science and Cochrane databases to identify relevant publications. Studies reporting on microbiota composition and/or drug metabolism were included.

Results

The intestinal microbiota can both enzymatically activate IBD pro-drugs (e.g., in case of thiopurines), but also inactivate certain drugs (e.g., mesalazine by acetylation via N-acetyltransferase 1 and infliximab via IgG-degrading enzymes). Aminosalicylates, corticosteroids, thiopurines, calcineurin inhibitors, anti-tumor necrosis factor biologicals and tofacitinib were all reported to alter the intestinal microbiota composition, including changes in microbial diversity and/or relative abundances of various microbial taxa.

Conclusion

Various lines of evidence have shown the ability of the intestinal microbiota to interfere with IBD drugs and vice versa. These interactions can influence treatment response, but well-designed clinical studies and combined in vivo and ex vivo models are needed to achieve consistent findings and evaluate clinical relevance.

Lymphocyte to monocyte ratio and serum albumin changes predict tacrolimus therapy outcomes in patients with ulcerative colitis

Tacrolimus therapy for ulcerative colitis is ineffective in certain patients; these patients require biologics or colectomy. We examined the ability of serum albumin levels and leukocyte subtypes to predict the therapeutic efficacy of tacrolimus. Patients with ulcerative colitis treated with tacrolimus were divided into non-failure and failure (required colectomy or switch to biologics or systemic steroids) groups. Serum albumin levels and leukocyte subtypes at induction, week 1, and week 2 after reaching high trough levels were retrospectively examined. Tacrolimus therapy failed in 18/45 patients within 3 months. The week 2/week 1 albumin ratio was significantly different between the failure and non-failure groups (P < 0.001). The receiver operating characteristic curve analysis revealed optimal cut-off value of the week 2/week 1 albumin ratio was 1.06, and area under the curve was 0.815. Analysis of leukocyte subtypes revealed significant between-group difference in the week 1 lymphocyte to monocyte ratio (P < 0.001). Multivariate analysis showed week 2/week 1 albumin ratio ≤ 1.06 and week 1 lymphocyte to monocyte ratio ≤ 3.86. Therefore, a low week 2/week 1 albumin and low week 1 lymphocyte to monocyte ratio predicted failure within 3 months of tacrolimus induction; a combination of these markers could accurately predict failure.

Towards next-generation personalization of tacrolimus treatment: a review on advanced diagnostic and therapeutic approaches

The benefit of personalized medicine is that it allows the customization of drug therapy - maximizing efficacy while avoiding side effects. Genetic polymorphisms are one of the major contributors to interindividual variability. Currently, the only gold standard for applying personalized medicine is dose titration. Because of technological advancements, converting genotypic data into an optimum dose has become easier than in earlier years. However, for many medications, determining a personalized dose may be difficult, leading to a trial-and-error method. On the other hand, the technologically oriented pharmaceutical industry has a plethora of smart drug delivery methods that are underutilized in customized medicine. This article elaborates the genetic polymorphisms of tacrolimus as case study, and extensively covers the diagnostic and therapeutic technologies which aid in the delivery of personalized tacrolimus treatment for better clinical outcomes, thereby providing a new strategy for implementing personalized medicine.

Early serum albumin changes in patients with ulcerative colitis treated with tacrolimus will predict clinical outcome

BACKGROUND

Oral tacrolimus is a therapeutic agent for moderate to severe steroid-dependent or resistant ulcerative colitis (UC), but remission induction is difficult, and it is necessary to treat the patient while considering the next treatment.

AIM

To examine serum albumin (Alb) level as a prognostic factor for the therapeutic effect of tacrolimus in clinical practice.

METHODS

Forty-seven patients with UC treated with tacrolimus at our institution were divided into remission and failure groups (colectomy or switch to biologics), and the biological data at the start of observation and at weeks 1 and 2 were retrospectively examined. Kaplan-Meier and multivariate analyses were performed using Alb as a prognostic factor in UC treatment.

RESULTS

During the three months observed, 17 (36.2%) patients failed treatment with tacrolimus. A comparison between the failure and remission groups showed a significant difference only in Alb in week 2, and in the week 2/week 0 Alb ratio, which showed the rate of change in Alb. The cut-off value of the week 2/week 0 Alb ratio that predicted failure was 1, and its area under the curve was 0.751 (95%CI: 0.604-0.898). In the Kaplan-Meier analysis, a week 2/week 0 Alb ratio ≤ 1 had a significantly higher failure rate than that of > 1; Cox proportional hazard regression analysis also showed that a week 2/week 0 Alb ratio ≤ 1 was an independent prognostic factor for failure within 3 mo after the start of tacrolimus treatment.

CONCLUSION

A week 2/week 0 Alb ratio ≤ 1 predicts failure within 3 mo of tacrolimus administration for UC. High failure risk exists with week 2 Alb values ≤ 1 on admission.

Prevalence of pharmacogenomic variants in 100 pharmacogenes among Southeast Asian populations under the collaboration of the Southeast Asian Pharmacogenomics Research Network (SEAPharm)

Pharmacogenomics can enhance the outcome of treatment by adopting pharmacogenomic testing to maximize drug efficacy and lower the risk of serious adverse events. Next-generation sequencing (NGS) is a cost-effective technology for genotyping several pharmacogenomic loci at once, thereby increasing publicly available data. A panel of 100 pharmacogenes among Southeast Asian (SEA) populations was resequenced using the NGS platform under the collaboration of the Southeast Asian Pharmacogenomics Research Network (SEAPharm). Here, we present the frequencies of pharmacogenomic variants and the comparison of these pharmacogenomic variants among different SEA populations and other populations used as controls. We investigated the different types of pharmacogenomic variants, especially those that may have a functional impact. Our results provide substantial genetic variations at 100 pharmacogenomic loci among SEA populations that may contribute to interpopulation variability in drug response phenotypes. Correspondingly, this study provides basic information for further pharmacogenomic investigations in SEA populations.

CUBAP: an interactive web portal for analyzing codon usage biases across populations

Synonymous codon usage significantly impacts translational and transcriptional efficiency, gene expression, the secondary structure of both mRNA and proteins, and has been implicated in various diseases. However, population-specific differences in codon usage biases remain largely unexplored. Here, we present a web server, https://cubap.byu.edu, to facilitate analyses of codon usage biases across populations (CUBAP). Using the 1000 Genomes Project, we calculated and visually depict population-specific differences in codon frequencies, codon aversion, identical codon pairing, co-tRNA codon pairing, ramp sequences, and nucleotide composition in 17,634 genes. We found that codon pairing significantly differs between populations in 35.8% of genes, allowing us to successfully predict the place of origin for African and East Asian individuals with 98.8% and 100% accuracy, respectively. We also used CUBAP to identify a significant bias toward decreased CTG pairing in the immunity related GTPase M (IRGM) gene in East Asian and African populations, which may contribute to the decreased association of rs10065172 with Crohn's disease in those populations. CUBAP facilitates in-depth gene-specific and codon-specific visualization that will aid in analyzing candidate genes identified in genome-wide association studies, identifying functional implications of synonymous variants, predicting population-specific impacts of synonymous variants and categorizing genetic biases unique to certain populations.

A Functional Synonymous Variant in PDGFRA Is Associated with Better Survival in Acral Melanoma

Purpose: Polymorphisms of genes in the platelet-derived growth factor (PDGF) signaling pathway have been found to predict cutaneous melanoma (CM) survival, but their clinical effects in acral melanoma (AM) patients have not been explored. The aim of this study was to characterize the functional effect of the tag single-nucleotide polymorphism (SNP) rs2228230:C>T and assess its association with clinical outcomes in AM patients.

Methods: The effect of rs2228230:C>T on mRNA structures and codon usage values were evaluated using in silico analyses. PDGF receptor alpha (PDGFRA) expression vectors with the rs2228230:C or rs2228230:T allele were constructed to evaluate the expression and signaling activity of PDGFRA. The expression of PDGFRA in AM samples was measured using in situ RNAscope hybridization and immunohistochemical staining. The association of the rs2228230 genotype with survival was analyzed in two independent AM cohorts.

Results: In silico analyses indicated that the rs2228230:T allele increases the minimum free energy and reduces synonymous codon usage. The rs2228230:T allele decreased the expression of PDGFRA by reducing the stability of its mRNA and protein as well as the signaling activity of the MAPK and PI3K/AKT pathways. PDGFRA mRNA and protein expression was significantly reduced in AM tissues with the rs2228230:T allele. The progression-free survival and overall survival of AM patients with the rs2228230:T allele were significantly longer than those of patients with the CC genotype.

Conclusion: Our study indicated that rs2228230:T can reduce the expression of PDGFRA and downstream signaling activity and is associated with better survival in AM patients.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Treatment of Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) of unknown etiology, probably caused by a combination of genetic and environmental factors. The treatment of patients with active UC depends on the severity, localization and history of IBD medication. According to the classic step-up approach, treatment with 5-aminosalicylic acid compounds is the first step in the treatment of mild to moderately active UC. Corticosteroids, such as prednisolone are used in UC patients with moderate to severe disease activity, but only for remission induction therapy because of side effects associated with long-term use. Thiopurines are the next step in the treatment of active UC but monotherapy during induction therapy in UC patients is not preferred because of their slow onset. Therapeutic drug monitoring (TDM) of the pharmacologically active metabolites of thiopurines, 6-thioguanine nucleotide (6-TGN), has proven to be beneficial. Thiopurine S-methyltransferase (TMPT) plays a role in the metabolic conversion pathway of thiopurines and exhibits genetic polymorphism; however, the clinical benefit and relevance of TPMT genotyping is not well established. In patients with severely active UC refractory to corticosteroids, calcineurin inhibitors such as ciclosporin A (CsA) and tacrolimus are potential therapeutic options. These agents usually have a rather rapid onset of action. Monoclonal antibodies (anti-tumor necrosis factor [TNF] agents, vedolizumab) are the last pharmacotherapeutic option for UC patients before surgery becomes inevitable. Body weight, albumin status and antidrug antibodies contribute to the variability in the pharmacokinetics of anti-TNF agents. Additionally, the use of concomitant immunomodulators (thiopurines/methotrexate) lowers the rate of immunogenicity, and therefore the concomitant use of anti-TNF therapy with an immunomodulator may confer some advantage compared with monotherapy in certain patients. TDM of anti-TNF agents could be beneficial in patients with primary nonresponse and secondary loss of response. The potential benefit of applying TDM during vedolizumab treatment has yet to be determined.

Role of cytochrome P450 polymorphisms and functions in development of ulcerative colitis

Cytochromes P450s (CYPs) are terminal enzymes in CYP dependent monooxygenases, which constitute a superfamily of enzymes catalysing the metabolism of both endogenous and exogenous substances. One of their main tasks is to facilitate the excretion of these substances and eliminate their toxicities in most phase 1 reactions. Endogenous substrates of CYPs include steroids, bile acids, eicosanoids, cholesterol, vitamin D and neurotransmitters. About 80% of currently used drugs and environmental chemicals comprise exogenous substrates for CYPs. Genetic polymorphisms of CYPs may affect the enzyme functions and have been reported to be associated with various diseases and adverse drug reactions among different populations. In this review, we discuss the role of some critical CYP isoforms (CYP1A1, CYP2D6, CYP2J2, CYP2R1, CYP3A5, CYP3A7, CYP4F3, CYP24A1, CYP26B1 and CYP27B1) in the pathogenesis or aetiology of ulcerative colitis concerning gene polymorphisms. In addition, their significance in metabolism concerning ulcerative colitis in patients is also discussed showing a clear underestimation in genetic studies performed so far.

Pharmacotherapy of ulcerative colitis - current status and emerging trends

Ulcerative colitis (UC) is a chronic mucosal inflammation of the large intestine restricted to the rectum and colon. Its clinical course follows an intermittent pattern with episodes of relapse, followed by remission and eventually resulting in mucosal damage. Although there is no permanent cure for UC, the currently available pharmacotherapy aims to induce and maintain clinical remission, promote the healing of colonic mucosa and avert any surgical intervention. The conventional drug therapy comprising of 5-aminosalicylates, thiopurines and corticosteroids has advanced recently in terms of formulations and dosing schedule, resulting in improved efficacy, safety and compliance. Calcineurin inhibitors, such as cyclosporin and tacrolimus, have emerged as steroid sparing agents. The treatment paradigm of UC patients who are refractory to conventional drugs has changed in view of the availability of biologics. Currently, there are four biologics approved by the US FDA for the treatment of UC, namely, infliximab, adalimumab, golimumab and vedolizumab, and several others are undergoing clinical trial. In this comprehensive review, the advantages and limitations of the medical therapy of UC are elaborated with an emphasis on the pharmacokinetic and pharmacodynamic aspects of the drugs.

Individualized treatment based on CYP3A5 single-nucleotide polymorphisms with tacrolimus in ulcerative colitis

Background/Aims

The pharmacokinetics of tacrolimus (TAC) is known to be largely influenced by single-nucleotide polymorphisms (SNPs) in CYP3A5. Patients starting TAC require careful dose adjustment, owing to the wide range of optimal dosages, depending on their CYP3A5 expression status. Here, we evaluated whether individualization of TAC dosages based on CYP3A5 SNPs would improve its therapeutic efficacy in ulcerative colitis.

Methods

Twenty-one patients were prospectively treated, with their initial dosage adjusted according to their CYP3A5 status (0.1, 0.15, and 0.2 mg/kg/day for CYP3A5*3/*3, CYP3A5*1/*3, and CYP3A5*1/*1, respectively). Their clinical outcomes were compared with those of patients treated with a fixed dose (0.1 mg/kg/day).

Results

The first blood trough level of CYP3A5 expressors, CYP3A5*1/*3 or CYP3A5*1/*1, and the overall rate in achieving the target blood trough level within a week in the individualized-dose group were significantly higher than those in the fixed-dose group (5.15±2.33 ng/mL vs. 9.63±0.79 ng/mL, P=0.035 and 12.5% vs. 66.7%, P=0.01). The remission rate at 2 weeks in the expressors was as high as that in the nonexpressors, CYP3A5*3/*3, in the individualized-dose group.

Conclusions

Individualized TAC treatment is effective against ulcerative colitis regardless of the CYP3A5 genotype.

ATP-binding cassette subfamily B member 1 1236C/T polymorphism significantly affects the therapeutic outcome of tacrolimus in patients with refractory ulcerative colitis

BACKGROUND AND AIM

Tacrolimus is now considered to be one of the main therapeutic options for refractory ulcerative colitis. Both cytochrome P-450 3A5 (CYP3A5) and ATP-binding cassette subfamily B member 1 (ABCB1) associated with tacrolimus metabolism are known to have several genetic polymorphisms. However, it remains controversial whether these polymorphisms affect the therapeutic efficacy for ulcerative colitis. We aimed to investigate the influence of both CYP3A5 and ABCB1 polymorphisms on the efficacy of tacrolimus in ulcerative colitis treatment under the tight dose-adjusting strategy.

METHODS

Sixty-one Japanese patients with ulcerative colitis treated with tacrolimus were enrolled retrospectively. Tacrolimus treatment was performed using the tight dose-adjusting strategy. Genotyping for CYP3A5*3, ABCB1 1236C>T, 2677G>A,T, and 3435C>T were performed, and the clinical outcomes at 12 weeks after the initiation of tacrolimus were compared among the genotypes.

RESULTS

There was no association between the CYP3A5 genotypes and therapeutic efficacy. In contrast, a significant association was observed with the ABCB1 1236C > T polymorphism and therapeutic efficacy. The ABCB1 1236CC+CT groups (n = 41) had a significantly higher response rate (73% vs 35%; P = 0.004) and remission rate (61% vs 20%; P = 0.002) than the TT group (n = 20). The multivariate logistic regression analysis also revealed that ABCB1 1236C>T was identified as an independent factor associated with remission.

CONCLUSIONS

ABCB1 1236C>T polymorphism significantly affects the therapeutic efficacy of tarcolimus at 12 weeks under the tight dose-adjusting treatment for ulcerative colitis.

Impact of Genetic Polymorphisms of ABCB1 (MDR1, P-Glycoprotein) on Drug Disposition and Potential Clinical Implications: Update of the Literature

ATP-binding cassette transporter B1 (ABCB1; P-glycoprotein; multidrug resistance protein 1) is an adenosine triphosphate (ATP)-dependent efflux transporter located in the plasma membrane of many different cell types. Numerous structurally unrelated compounds, including drugs and environmental toxins, have been identified as substrates. ABCB1 limits the absorption of xenobiotics from the gut lumen, protects sensitive tissues (e.g. the brain, fetus and testes) from xenobiotics and is involved in biliary and renal secretion of its substrates. In recent years, a large number of polymorphisms of the ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1] gene have been described. The variants 1236C>T (rs1128503, p.G412G), 2677G>T/A (rs2032582, p.A893S/T) and 3435C>T (rs1045642, p.I1145I) occur at high allele frequencies and create a common haplotype; therefore, they have been most widely studied. This review provides an overview of clinical studies published between 2002 and March 2015. In summary, the effect of ABCB1 variation on P-glycoprotein expression (messenger RNA and protein expression) and/or activity in various tissues (e.g. the liver, gut and heart) appears to be small. Although polymorphisms and haplotypes of ABCB1 have been associated with alterations in drug disposition and drug response, including adverse events with various ABCB1 substrates in different ethnic populations, the results have been majorly conflicting, with limited clinical relevance. Future research activities are warranted, considering a deep-sequencing approach, as well as well-designed clinical studies with appropriate sample sizes to elucidate the impact of rare ABCB1 variants and their potential consequences for effect sizes.

Systems biology approaches to adverse drug effects: the example of cardio-oncology

Increased awareness of the cardiovascular toxic effects of chemotherapy has led to the emergence of cardio-oncology (or onco-cardiology), which focuses on screening, monitoring and treatment of patients with cardiovascular dysfunctions resulting from chemotherapy. Anthracyclines, such as doxorubicin, and HER2 inhibitors, such as trastuzumab, both have cardiotoxic effects. The biological rationale, mechanisms of action and cardiotoxicity profiles of these two classes of drugs, however, are completely different, suggesting that cardiotoxic effects can occur in a range of different ways. Advances in genomics and proteomics have implicated several genomic variants and biological pathways that can influence the susceptibility to cardiotoxicity from these, and other drugs. Established pathways include multidrug resistance proteins, energy utilization pathways, oxidative stress, cytoskeletal regulation and apoptosis. Gene-expression profiles that have revealed perturbed pathways have vastly increased our knowledge of the complex processes involved in crosstalk between tumours and cardiac function. Utilization of mathematical and computational modelling can complement pharmacogenomics and improve individual patient outcomes. Such endeavours should enable identification of variations in cardiotoxicity, particularly in those patients who are at risk of not recovering, even with the institution of cardioprotective therapy. The application of systems biology holds substantial potential to advance our understanding of chemotherapy-induced cardiotoxicity.

CTLA-4 and MDR1 polymorphisms increase the risk for ulcerative colitis: A meta-analysis

AIM: To evaluate the correlations between cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and multi-drug resistance 1 (MDR1) genes polymorphisms with ulcerative colitis (UC) risk.

METHODS: PubMed, EMBASE, Web of Science, Cochrane Library, CBM databases, Springerlink, Wiley, EBSCO, Ovid, Wanfang database, VIP database, China National Knowledge Infrastructure, and Weipu Journal databases were exhaustively searched using combinations of keywords relating to CTLA-4, MDR1 and UC. The published studies were filtered using our stringent inclusion and exclusion criteria, the quality assessment for each eligible study was conducted using Critical Appraisal Skill Program and the resultant high-quality data from final selected studies were analyzed using Comprehensive Meta-analysis 2.0 (CMA 2.0) software. The correlations between SNPs of CTLA-4 gene, MDR1 gene and the risk of UC were evaluated by OR at 95%CI. Z test was carried out to evaluate the significance of overall effect values. Cochran’s Q-statistic and I² tests were applied to quantify heterogeneity among studies. Funnel plots, classic fail-safe N and Egger’s linear regression test were inspected for indication of publication bias.

RESULTS: A total of 107 studies were initially retrieved and 12 studies were eventually selected for meta-analysis. These 12 case-control studies involved 1860 UC patients and 2663 healthy controls. Our major result revealed that single nucleotide polymorphisms (SNPs) of CTLA-4 gene rs3087243 G > A and rs231775 G > A may increase the risk of UC (rs3087243 G > A: allele model: OR = 1.365, 95%CI: 1.023-1.822, P = 0.035; dominant model: OR = 1.569, 95%CI: 1.269-1.940, P < 0.001; rs231775 G > A: allele model: OR = 1.583, 95%CI: = 1.306-1.918, P < 0.001; dominant model: OR = 1.805, 95%CI: 1.393-2.340, P < 0.001). In addition, based on our result, SNPs of MDR1 gene rs1045642 C > T might also confer a significant increases for the risk of UC (allele model: OR = 1.389, 95%CI: 1.214-1.590, P < 0.001; dominant model: OR = 1.518, 95%CI: 1.222-1.886, P < 0.001).

CONCLUSION: CTLA-4 gene rs3087243 G > A and rs231775 G > A, and MDR1 gene rs1045642 C > T might confer an increase for UC risk.

Tacrolimus for the Treatment of Ulcerative Colitis

Tacrolimus is a calcineurin inhibitor used for the treatment of corticosteroid-refractory ulcerative colitis (UC). Two randomized controlled trials and a number of retrospective studies have assessed the therapeutic effect of tacrolimus in UC patients. These studies showed that tacrolimus has excellent short-term efficacy in corticosteroid-refractory patients, with the rates of clinical response ranging from 61% to 96%. However, the long-term prognosis of patients treated with tacrolimus is disappointing, and almost 50% of patients eventually underwent colectomy in long-term follow-up. Tacrolimus can achieve mucosal healing in 40-50% of patients, and this is associated with a favorable long-term prognosis. Anti-tumor necrosis factor (TNF)-α antibodies are another therapeutic option in corticosteroid-refractory patients. A prospective head-to-head comparative study of tacrolimus and infliximab is currently being performed to determine which treatment is more effective in corticosteroid-refractory patients. Several retrospective studies have demonstrated that switching between tacrolimus and anti-TNF-α antibody therapy was effective in patients who were refractory to one of the treatments. Most adverse events of tacrolimus are mild; however, opportunistic infections, especially pneumocystis pneumonia, are the most important adverse events, and these should be carefully considered during treatment. Several issues on tacrolimus treatment in UC patients remain unsolved (e.g., use of tacrolimus as remission maintenance therapy). Further controlled studies are needed to optimize the use of tacrolimus for the treatment of UC.

Tacrolimus induction followed by maintenance monotherapy is useful in selected patients with moderate-to-severe ulcerative colitis refractory to prior treatment

BACKGROUND

Tacrolimus in refractory ulcerative colitis often serves as a bridge to long-term maintenance therapy with thiopurines. Our aim was to review efficacy and safety of tacrolimus in active ulcerative colitis resistant to conventional therapies, including anti-tumour necrosis factor.

METHODS

Charts of consecutive outpatients with refractory ulcerative colitis, in whom tacrolimus was orally administered as a 12 week-induction (target trough levels 10-15ng/mL) followed by a maintenance therapy (target trough levels 5-10ng/mL), were retrospectively reviewed. Clinical remission and response at weeks 4, 12 and 52 as well as adverse events within 1-year therapy were reported.

RESULTS

Twelve (40%) and six (20%) of the 30 patients included (14 males, mean age 37.1±1.4 years) achieved a clinical remission and response, respectively, at week 12. Three responders to tacrolimus initiation experienced drug-related adverse events requiring discontinuation. Among the 18 remaining initial responders who tolerated tacrolimus, 8 (27%) were in clinical remission at week 52, whereas the remainder either experienced adverse events requiring drug withdrawal (n=4) or relapsed (n=6). Overall adverse events were recorded in 14 patients (46%), mainly finger tremor and urinary infections.

CONCLUSION

Oral monotherapy with tacrolimus may be a valuable long-term therapeutic option in selected patients with moderate-to-severe active refractory ulcerative colitis.

Exposing synonymous mutations

Synonymous codon changes, which do not alter protein sequence, were previously thought to have no functional consequence. Although this concept has been overturned in recent years, there is no unique mechanism by which these changes exert biological effects. A large repertoire of both experimental and bioinformatic methods has been developed to understand the effects of synonymous variants. Results from this body of work have provided global insights into how biological systems exploit the degeneracy of the genetic code to control gene expression, protein folding efficiency, and the coordinated expression of functionally related gene families. Although it is now clear that synonymous variants are important in a variety of contexts, from human disease to the safety and efficacy of therapeutic proteins, there is no clear consensus on the approaches to identify and validate these changes. Here, we review the diverse methods to understand the effects of synonymous mutations.

Impact of CYP3A5 genetic polymorphisms on the pharmacokinetics and short-term remission in patients with ulcerative colitis treated with tacrolimus

BACKGROUND AND AIM

The pharmacokinetics of tacrolimus (Tac) differ among individuals, and genetic polymorphisms of cytochrome P-450 (CYP) 3A4, CYP3A5, and ABCB1 are thought to be involved. The aim of this study was to clarify whether these genetic polymorphisms affect the pharmacokinetics of Tac in patients with ulcerative colitis.

METHODS

The subjects in this study were 45 patients with moderate-to-severe ulcerative colitis who were resistant to other therapies and were treated with Tac. The subjects were tested for genetic polymorphisms of CYP3A4, CYP3A5, and ABCB1, and the relationship between Tac pharmacokinetics and the remission rate was investigated.

RESULTS

Of the 45 subjects, 24 (53.3%) were CYP3A5 expressers (Exp), and 21 (46.7%) were non-expressers (Non-Exp). The trough level and the dose-adjusted trough level on days 2-5 were significantly higher in the Non-Exp group than in the Exp group (10.16 ± 5.84 vs 4.47 ± 2.50 ng/mL, P < 0.0001, 139.36 ± 77.43 vs 61.37 ± 41.55 ng/mL per mg/kg/day, P < 0.0001). The percentage of patients achieving the optimal trough level on days 2-5 was significantly higher in the Non-Exp group than in the Exp group (40.0% vs 4.3%, P = 0.01). This trend was also observed on days 7-10. On multivariate analysis, factors associated with achievement of the optimal trough level were food non-intake and Non-Exp of CYP3A5. The remission rate was significantly higher in the Non-Exp group than in the Exp group (47.6% vs 16.7%, P = 0.046).

CONCLUSIONS

CYP3A5 genetic polymorphisms affected the pharmacokinetics of Tac, so that the short-term clinical remission rate was different between Exp and Non-Exp of CYP3A5.

Oral tacrolimus for pediatric steroid-resistant ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) occurring during childhood is generally extensive and is associated with severe flares that may require intravenous steroid treatment. In cases of corticosteroid resistance is necessary to introduce a second-line treatment to avoid or delay surgery.

AIMS

To describe the efficacy and safety of oral tacrolimus for the treatment of severe steroid-resistant UC.

METHODS

We performed a retrospective study that included all patients under age 18 suffering from severe steroid-resistant UC treated with oral tacrolimus during the period January 1998 to October 2012 and with a follow-up period after treatment of 24 months or more.

RESULTS

A total of ten patients were included. The age at baseline was 9.4±4.9 years, and the time from diagnosis was 1.3 months (IQR, 1-5.7). Seven of the patients were in their first flare of disease. All of them received an oral dose of 0.12 mg/kg/day of tacrolimus divided in two doses. Trough plasma levels of tacrolimus were maintained between 4 and 13 ng/ml. Response was seen in 5/10 patients at 12 months, colectomy was eventually performed in 60% of patients during the follow-up period.

CONCLUSIONS

Tacrolimus is useful in inducing remission in patients with severe steroid-resistant UC, preventing or delaying colectomy, and allowing the patient and family to prepare for a probable surgery. Tacrolimus may also be used as a treatment bridge for corticosteroid-dependent patients until the new maintenance therapy takes effect.

Mucosal healing with oral tacrolimus is associated with favorable medium- and long-term prognosis in steroid-refractory/dependent ulcerative colitis patients

BACKGROUND

Oral administration of tacrolimus is an effective remission induction therapy for steroid-refractory/dependent ulcerative colitis (UC).

AIM

This study aimed to evaluate the short- as well as medium- and long-term effectiveness of tacrolimus therapy.

METHODS

The medical records of 51 patients treated with tacrolimus for UC at our hospital between July 2009 and December 2011 were reviewed retrospectively. Clinical remission and improvement were defined as a Lichtiger score of 4 or less and as a Lichtiger score of ≤10 and a reduction in the score of ≥3 compared with the baseline score, respectively. Endoscopic findings were evaluated based on the endoscopic activity index and Mayo endoscopic score.

RESULTS

The clinical effectiveness combining clinical remission and improvement was observed in 62.7% of the patients at 3 months. Thirty-six patients underwent colonoscopy at 3 months, and 12 (33.3%) and 10 patients (27.8%) showed Mayo endoscopic scores of 0 and 1, respectively. On Kaplan-Meier analysis, the overall percentage of event-free survivors, who did not require colectomy nor switching to other induction therapy such as infliximab, was 73.0% at 6 months, 49.9% at 1 year, and 37.8% at 2 years. Patients with a Mayo endoscopic score of 0-1 at 3 months showed significantly better medium- and long-term prognosis than those with a score of 2-3 (p<0.01). All adverse events, including infections in 2 patients, were reversible.

CONCLUSIONS

Tacrolimus therapy was effective for inducing clinical and endoscopic remission of steroid-refractory/dependent UC. Endoscopic improvement was associated with favorable medium- and long-term prognosis.

Oral tacrolimus as maintenance therapy for refractory ulcerative colitis--an analysis of outcomes in two London tertiary centres

BACKGROUND

The medical management of refractory ulcerative colitis (UC) remains a significant challenge. Two randomised controlled studies have demonstrated tacrolimus therapy is effective for the induction of remission of moderate to severe UC. However, the long term outcomes of UC patients treated with tacrolimus as maintenance therapy are not certain.

AIMS

This study aims to assess the efficacy of tacrolimus maintenance therapy for refractory UC.

METHODS

A retrospective review of patients with UC treated with tacrolimus at two London tertiary centres was performed. Clinical outcomes were assessed at six months, at the end of tacrolimus treatment, or at the last follow-up for patients continuing tacrolimus treatment. Modified Truelove-Witts score (mTW) and Mayo endoscopy subscores were calculated.

RESULTS

25 patients with UC, treated with oral tacrolimus between 2005 and 2011, were identified. The median duration of tacrolimus treatment was 9 months (IQR 3.7-18.2 months). The median duration of follow-up was 27 months (range 3-66 months). At six months thirteen (52%) patients had achieved and maintained clinical response and eleven (44%) were in clinical remission. The mean mTW score decreased from 10+/-0.5 before therapy, to 5.8+/-0.8 (p≤0.001 95% CI 2.7-5.8) at cessation of treatment or last follow-up. Mayo endoscopy subscore decreased from 2.6+/-0.1 to 1.2+/-0.2 (p≤0.001 mean reduction 1.4, 95% CI 0.8-1.9). Eight patients (32%) subsequently underwent a colectomy within a mean time of 17 months (range 2-45 months).

CONCLUSION

Tacrolimus is effective for the maintenance of refractory UC and can deliver sustained improvement in mucosal inflammation.

A Markov chain model to evaluate the effect of CYP3A5 and ABCB1 polymorphisms on adverse events associated with tacrolimus in pediatric renal transplantation

The SNP A6986G of the CYP3A5 gene (*3) results in a non-functional protein due to a splicing defect whereas the C3435T was associated with variable expression of the ABCB1 gene, due to protein instability. Part of the large interindividual variability in tacrolimus efficacy and toxicity can be accounted for by these genetic factors. Seventy-two individuals were examined for A6986G and C3435T polymorphism using a PCR-RFLP-based technique to estimate genotype and allele frequencies in the Jordanian population. The association of age, hematocrit, platelet count, CYP3A5, and ABCB1 polymorphisms with tacrolimus dose- and body-weight-normalized levels in the subset of 38 pediatric renal transplant patients was evaluated. A Markov model was used to evaluate the time-dependent probability of an adverse event occurrence by CYP3A5 phenotypes and ABCB1 genotypes. The time-dependent probability of adverse event was about double in CYP3A5 non-expressors compared to the expressors for the first 12 months of therapy. The CYP3A5 non-expressors had higher corresponding normalized tacrolimus levels compared to the expressors in the first 3 months. The correlation trend between probability of adverse events and normalized tacrolimus concentrations for the two CYP3A5 phenotypes persisted for the first 9 months of therapy. The differences among ABCB1 genotypes in terms of adverse events and normalized tacrolimus levels were only observed in the first 3 months of therapy. The information on CYP3A5 genotypes and tacrolimus dose requirement is important in designing effective programs toward management of tacrolimus side effects particularly for the initial dose when tacrolimus blood levels are not available for therapeutic drug monitoring.

Influence of CYP3A5 6986A > G and ABCB1 3435C > T Polymorphisms on Adverse Events Associated With Tacrolimus in Jordanian Pediatric Renal Transplant Patients

The aim of the study is to investigate the influence of ABCB1(3435) and CYP3A5(6986) polymorphisms, tacrolimus troughs and clinical factors on the time of adverse events associated with tacrolimus in pediatric kidney transplant patients. Clinical data, adverse events, tacrolimus troughs, corresponding doses, ABCB1 3435C > T and CYP3A5 6986A > G genotypes were collected from 38 pediatric kidney transplant patients in a retrospective study for over 2 years post-transplant. We used a marginal Cox proportional hazard model to evaluate the influence of clinical factors and single nucleotide polymorphisms (SNPs) on tacrolimus-associated adverse events. CYP3A5 genotype, the Bayesian predicted tacrolimus concentrations, hematocrit and mean corpuscular volume are significant risk factors of adverse events over a 2-year-period. CYP3A5*1 genotype was associated with 36% relative risk of CYP3A5*3/*3 genotype. In the 9-month period, the additional factor, ABCB1 3435TT genotype, was shown to be associated with 38% relative risk of the CC and CT genotypes. For graft loss, acute and chronic rejection, only tacrolimus concentration and hematocrit, but not CYP3A5 or ABCB1 polymorphisms, are important factors influencing their occurrences.

The role of pharmacogenetics in nonmalignant gastrointestinal diseases

Genetic variation influences the absorption and efflux of drugs in the intestine, the metabolism of drugs in the liver and the effects of these drugs on their target proteins. Indeed, variations in genes whose products have a role in the pathophysiology of nonmalignant gastrointestinal diseases, such as IBD, have been shown to affect the response of patients to therapy. This Review provides an overview of pharmacogenetics in the management of nonmalignant gastrointestinal diseases on the basis of data from clinical trials. Genetic variants that have the greatest effect on the management of patients with IBD involve the metabolism of thiopurines. Variation in drug metabolism by cytochrome P450 enzymes also requires attention so as to avoid drug interactions in patients receiving tricyclic antidepressants and PPIs. Few genotyping tests are currently used in the clinical management of patients with nonmalignant gastrointestinal diseases, owing to a lack of data from clinical trials showing their effectiveness in predicting nonresponse or adverse outcomes. However, pharmacogenetics could have a beneficial role in enabling pharmacotherapy for nonmalignant gastrointestinal diseases to be targeted to the individual patient.

Understanding the contribution of synonymous mutations to human disease

Synonymous mutations - sometimes called 'silent' mutations - are now widely acknowledged to be able to cause changes in protein expression, conformation and function. The recent increase in knowledge about the association of genetic variants with disease, particularly through genome-wide association studies, has revealed a substantial contribution of synonymous SNPs to human disease risk and other complex traits. Here we review current understanding of the extent to which synonymous mutations influence disease, the various molecular mechanisms that underlie these effects and the implications for future research and biomedical applications.