Pharmacogenetic investigation of the TNF/TNF-receptor system in patients with chronic active Crohn's disease treated with infliximab

Genetic and genomic predictors of anti-TNF response

The introduction of anti-TNF therapy has dramatically improved the outlook for patients suffering from a number of inflammatory conditions including rheumatoid arthritis and inflammatory bowel disease. Despite this, a substantial proportion of patients (approximately 30-40%) fail to respond to these potentially toxic and expensive therapies. Treatment response is likely to be multifactorial; however, variation in genes or their expression may identify those most likely to respond. By targeted testing of variants within candidate genes, potential predictors of anti-TNF response have been reported; however, very few markers have replicated consistently between studies. Emerging genome-wide association studies suggest that there may be a number of genes with modest effects on treatment response rather than a few genes of large effect. Other potential serum biomarkers of response have also been explored including cytokines and autoantibodies, with antibodies developing to the anti-TNF drugs themselves being correlated with treatment failure.

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.

Predicting response to Anti-TNF Agents for the treatment of crohn's disease

The arrival of anti-tumor necrosis factor (TNF) agents has led to a dramatic improvement in the care of patients with Crohn's disease. Since these medications do not work in everyone, and are associated with rare, but serious side effects, we want to selectively treat patients who have the highest chance of responding. A number of variables have been studied to determine their association with response to anti-TNF agents. Clinical parameters include patient characteristics, smoking status and disease phenotype, and biologic markers include C-reactive protein, serum TNF levels and immune responses to microbial antigens. More recently, research has focused on genetics to identify polymorphisms associated with treatment response. Results from individual studies of these factors have not yet allowed for solid clinical applicability. However, further work in this area along with multivariate clinical prediction modeling may soon allow us to deliver 'personalized medicine' by predicting individualized treatment response in patients with Crohn's disease.

Personalized approach to the selection of therapy for patients with psoriasisbased on the results of molecular and genetic tests

The article presents the results of tests aimed at revealing biomarkers of patients clinical response to treatment with Infliximab and phototherapy with the use of molecular and genetic technologies. The authors revealed that the predictor of evident clinical response to treatment of psoriasis patients with Infliximab is the homozygous TT genotype at the 676 locus of exon 6 of the TNFR- II gene; predictors of high efficacy and safety of treatment of psoriasis patients with Infliximab with the use of ultraviolet therapy (PUVA and mid-wavelength ultraviolet therapy (311 nm)) are: heterozygous GA genotype at the 19007 locus of the ERCC gene and homozygous CC genotype at the 27945 locus of the XPF gene.

Infliximab dependency is related to decreased surgical rates in adult Crohn's disease patients

BACKGROUND

Infliximab dependency in children with Crohn's disease (CD) has recently been described and found to be associated with a decreased surgery rate.

AIM

To assess infliximab dependency of adult CD patients, evaluate the impact on surgery, and search for possible clinical and genetic predictors.

METHODS

Two hundred and forty-five CD patients treated with infliximab were included from Danish and Czech Crohn Colitis Database (1999-2006). Infliximab response was assessed as immediate outcome, 1 month after infliximab start: complete, partial, and no response. Three months outcome, after last intended infusion: prolonged response (maintenance of complete/partial response), infliximab dependency (relapse requiring repeated infusions to regain complete/partial response or need of infliximab >12 months to sustain response).

RESULTS

Forty-seven percent obtained prolonged response, 29% were infliximab dependent and 24% nonresponders. The cumulative probability of surgery 40 months after infliximab start was 20% in prolonged responders, 23% in infliximab-dependent patients and 76% in nonresponders (P<0.001). The cumulative probability of surgery at 40 months in patients on maintenance versus on demand regime was 33 and 31%, respectively (P=0.63). No relevant clinical or genetic predictors were identified.

CONCLUSION

The infliximab dependency response seems to be equivalent to the prolonged response in adult CD patients when comparing surgery rates.

Genome wide association (GWA) predictors of anti-TNFalpha therapeutic responsiveness in pediatric inflammatory bowel disease

BACKGROUND

Interindividual variation in response to anti-TNFalpha therapy may be explained by genetic variability in disease pathogenesis or mechanism of action. Recent genome-wide association studies (GWAS) in inflammatory bowel disease (IBD) have increased our understanding of the genetic susceptibility to IBD. The aim was to test associations of known IBD susceptibility loci and novel "pharmacogenetic" GWAS identified loci with primary nonresponse to anti-TNFalpha in pediatric IBD patients and develop a predictive model of primary nonresponse.

METHODS

Primary nonresponse was defined using the Harvey Bradshaw Index (HBI) for Crohn's disease (CD) and partial Mayo score for ulcerative colitis (UC). Genotyping was performed using the Illumina Infinium platform. Chi-square analysis tested associations of phenotype and genotype with primary nonresponse. Genetic associations were identified by testing known IBD susceptibility loci and by performing a GWAS for primary nonresponse. Stepwise multiple logistic regression was performed to build predictive models.

RESULTS

Nonresponse occurred in 22 of 94 subjects. Six known susceptibility loci were associated with primary nonresponse (P < 0.05). Only the 21q22.2/BRWDI loci remained significant in the predictive model. The most predictive model included 3 novel "pharmacogenetic" GWAS loci, the previously identified BRWD1, pANCA, and a UC diagnosis (R(2) = 0.82 and area under the curve [AUC] = 0.98%). The relative risk of nonresponse increased 15-fold when number of risk factors increased from 0-2 to > or =3.

CONCLUSIONS

The combination of phenotype and genotype is most predictive of primary nonresponse to anti-TNFalpha in pediatric IBD. Defining predictors of response to anti-TNFalpha may allow the identification of patients who will not benefit from this class of therapy.

Role of genetics in prediction of disease course and response to therapy

The clinical course of Crohn’s disease and ulcerative colitis is highly variable between patients, and this has therapeutic implications. A number of clinical features have been identified, which predict a mild or more severe outcome. However, several of these are subjective and/or not persistent over time. With the progress in genetics research in inflammatory bowel disease (IBD), genetic markers are increasingly being proposed to improve stratification of patients. Genetics have the major advantage of being stable over time and not prone to subjective interpretation. Nevertheless, none of the genetic variants associated with particular outcomes have shown sufficient sensitivity or specificity to have been implemented in daily management. Along the same line of thinking, pharmacogenetics or the study of association between variability in drug response and genetic variation has also received more attention as part of the endeavor for personalized medicine. The ultimate goal in this area of medicine is to adapt medication to a patient’s specific genetic background and therefore improve on efficacy and safety rates. Although pharmacogenetic studies have been performed for all classes of drugs applied in IBD, few have generated consistent findings or have been replicated. The only genetic test approved for clinical practice is thiopurine S-methyltransferase testing prior to starting treatment with thiopurine analogues. The other reported associations have suffered from lack of confirmation or still need replication efforts. Nevertheless, the importance and necessity of pharmacogenetic studies will increase further as more therapeutic classes are being developed.

Pharmacogenomics in the treatment of inflammatory bowel disease

In recent years, the benefits of early aggressive treatment paradigms for inflammatory bowel disease have emerged. Symptomatic improvement is no longer considered adequate; instead, the aim of treatment has become mucosal healing and altered natural history. Nonetheless, we still fail to achieve these end points in a large number of our patients. There are many reasons why patients fail to respond or develop toxicity when exposed to drugs used for inflammatory bowel disease, but genetic variation is likely to account for a significant proportion of this. Some examples, notably thiopurine methyltransferase polymorphism in thiopurine treatment, are already established in clinical practice. We present a review of the expanding literature in this field, highlighting many interesting developments in pharmacogenomics applied to inflammatory bowel disease and, where possible, providing guidance on the translation of these developments into clinical practice.

Molecular Markers In Forecasting The Clinical Efficacy Of Infliximab In Psoriasis Patients

Biosamples (skin tissue samples taken from affection foci and blood serum) from 22 patients suffering from severe to medium psoriasis (8 women and 14 men) aged 19-57 treated with Infliximab were analyzed. As for skin tissue samples, the molecular structure of genes TNF-a, TNF-R-I and TNF-R-II, contents of cytokine TNF-a and its soluble receptors (sTNF-RI and sTNF-RII) and proteome composition was analyzed in skin tissue samples; contents of TNF-a, IL2, IL4, IL6, IL-8 and IL-10 were analyzed in the blood serum. The homozygous TT genotype of TNF-R-II gene at the 676 locus and high IL10 level in the blood serum (>2.7 pg/ml) was associated with the high intensity of the psoriasis patient response to treatment with Infliximab; the homozygous GG genotype of TNF-R-II gene at the 676 locus and low level of IL10 in the blood serum (

[Markers of the course of inflammatory bowel disease treated with immunomodulators or biological agents]

Immunosuppressive or biological treatment in patients with inflammatory bowel disease can modify the natural history of their disease, although these treatments are not universally effective and can have severe adverse effects. Attempts have been made to identify predictive factors of response to the various therapeutic options in order to aid the choice of the most appropriate therapeutic alternative in each patient. The possibility of modifying any one of these predictive factors would be of great interest since it would provide the opportunity to alter the course of the disease. Epidemiological, biological, clinical, endoscopic, radiological, genetic and even proteomic markers have been studied, in addition to others related to the disease itself or to specific treatments. The present article briefly discusses the real use of each of these markers and the evidence supporting their utility.

The TNF/ADAM 17 system: implication of an ADAM 17 haplotype in the clinical response to infliximab in Crohn's disease

Infliximab, a chimeric anti-tumour necrosis factor (TNF)-alpha antibody induces a clinical response in 70% of Crohn's disease patients and the response to infliximab therapy could be partially determined by genetic factors. The implication of both transmembrane and soluble forms of the TNF-alpha in the mechanism of action of infliximab has been demonstrated. The aim of our work was first to perform a complete study of TNF variants role in the response to infliximab in Crohn's disease. Secondly, considering the role of ADAM 17 in TNF-alpha shedding, the ADAM 17 locus was also studied. The response to infliximab was evaluated in 222 Caucasian Crohn's disease patients with a luminal (n=160) or fistulizing (n=62) form of the disease. Clinical and biological response evaluation was based on the Crohn's Disease Activity Index score and C-reactive protein level evolutions, respectively. The entire TNF gene was sequenced on the complete cohort. Twelve single nucleotide polymorphisms spanning the ADAM 17 locus were studied and haplotypes rebuilt. A clinical response was observed in 64% of the patients and biological response in 77.1% of patients. No association was found between the TNF gene and the response to infliximab. One haplotype in the ADAM 17 region was associated with a clinical response to infliximab in CD patients (adjusted P=0.045). In conclusion, our results exclude, with a reasonable power, an implication of the TNF gene in the response to infliximab in Crohn's disease, but reveal a potential role of the ADAM 17 gene in this response.

Infliximab for the treatment of active scleritis

OBJECTIVE

This study aimed to evaluate the possible safety and effectiveness of infliximab in patients with active scleritis.

STUDY DESIGN

Prospective, nonrandomized, open-label pilot study (Protocol No. 04-EI-0065).

PARTICIPANTS

Five patients with active anterior scleritis.

METHODS

This single-centre, pilot study of infliximab for the treatment of active anterior scleritis was conducted at the National Eye Institute, National Institutes of Health, between 2003 and 2007. Scleritis patients with active disease who had used at least 1 conventional immunosuppressive agent in the past were included. Primary outcome was a 2-step decrease in scleral inflammation within 14 weeks. Patients received infliximab (5 mg/kg) at baseline, at weeks 2 and 6, and every 4 weeks through week 30, after which the infusion interval was increased (week 36, 48).

RESULTS

All patients met the primary outcome by achieving quiescence of their active scleritis by week 14 with no additional immunosuppressives. However, after 14 weeks 1 patient developed new-onset intraocular inflammation that did not respond to reinduction and was terminated from the study. Side effects attributable to infliximab included ear infection with transient decreased hearing, urinary tract infection, lower respiratory tract infection, and facial rash in 1 patient and urinary tract infection, diarrhea, upper respiratory tract infection, nasal congestion and headache, mouth sores, head tremor, and occasional numbness and tingling in extremities in another patient, all of which resolved spontaneously or with appropriate treatment.

CONCLUSIONS

Infliximab may be considered as a viable option in treating patients with active scleritis; however, patients should be monitored closely for potentially serious side effects.

Pharmacogenetics of Crohn’s disease

The considerable interindividual differences in efficacy and side effects of commonly used medications in Crohn’s disease are partly owing to genetic polymorphisms. Many genetic variants have been studied in genes possibly involved in the metabolism or mechanism of action of therapeutic agents such as glucocorticosteroids, azathioprine/6-mercaptopurine, methotrexate, calcineurin inhibitors or anti-TNF agents. However, the only test translated into clinical practice is thiopurine S-methyltransferase (TPMT) genotyping for hematological toxicity of thiopurine treatment. To date, there are no other meaningful applications for pharmacogenomics in clinical practice of Crohn’s disease. In the future, designed therapeutic trials should possibly permit the development of predictive models including genotypic markers, such as that proposed for the clinical outcome after infliximab therapy, which includes an apoptotic pharmacogenetic index. The recent identification of new susceptibility genes provides additional candidate markers that have possible effects on the outcomes of therapies, and prioritizes new therapeutic targets, such as the IL-23 pathway. Futher innovative approaches might be relevant for the pharmacogenetic investigation of gene variants implied in innate immune pattern recognition and autophagy.

Genetic polymorphisms of tumour necrosis factor receptor superfamily 1A and 1B affect responses to infliximab in Japanese patients with Crohn's disease

BACKGROUND

Tumour necrosis factor alpha is the key inflammatory cytokine involved in the pathogenesis of Crohn's disease. Infliximab, a chimaeric monoclonal antibody of tumour necrosis factor-alpha is successfully used for the treatment of Crohn's disease, although the response to infliximab therapy differs among patients. The genetic background of the individual may partially explain the differences of the responsiveness.

AIM

To investigate whether the polymorphisms in these genes are associated with the response to infliximab treatment as tumour necrosis factor-alpha exerts its biological activity through TNF receptor superfamily 1A and 1B.

METHODS

Eighty Crohn's disease patients were enrolled in the study and classified into responder and nonresponder according to the efficacy of infliximab treatment. Single nucleotide polymorphisms of TNF receptor superfamily 1A (rs767455 and rs4149570) and TNF receptor superfamily 1B (rs1061622, rs1061624 and rs3397) were determined.

RESULTS

The minor allele carrier of rs767455 showed a significant association with a lack of efficacy compared to the major genotype (OR = 0.26; 95% CI: 0.08-0.91). A TNF receptor superfamily 1B haplotype inferred by rs1061624 and rs3397 also showed significant differences in the distribution between responder and nonresponder (P = 0.01).

CONCLUSION

These results suggest that tumour necrosis factor receptor genotypes may be involved in the different responses to infliximab in Japanese patients with Crohn's disease.

Pharmacogenomics in gastrointestinal disorders

It is anticipated that unraveling the human genome will have a direct impact on the management of specific diseases. Variations or mutations in genes involved in drug metabolism or disease pathophysiology in gastroenterology and hepatology are expected to have effect on response to therapy. The spectrum of diseases is vast. Thus, we focus this review on clinical pharmacogenetics of inflammatory bowel disease, Helicobacter pylori infections, gastroesophageal reflux disease, irritable bowel syndrome, liver transplantation, and colon cancer. Although only a few genotyping tests are used regularly in clinical practice, we anticipate that in the future there will be more routine use of many of the tests described in this review.

The genetics of inflammatory bowel disease

Great progress in the understanding of the molecular genetics of inflammatory bowel disease (IBD) has been made over the last 10 years. Strong epidemiological evidence, based initially on concordance data in twin/family studies, led to the application of genome-wide linkage analysis involving multiply affected families and the identification of a number of susceptibility loci. Further characterization of the IBD1 locus on chromosome 16 led to the discovery of the NOD2/CARD15 gene as the first susceptibility gene in Crohn's disease for 2001. This landmark finding has led to a redirection of basic research in IBD with interest focused principally on regulation of the innate immune response and mucosal barrier function. Within the last year, the use of genome-wide association studies has provided new insights into primary pathogenetic mechanisms; several new genes such as the Interleukin-23 receptor (IL23R) and ATG16L1 (autophagy-related 16-like 1) genes are strongly implicated. Overall, these studies promise to change our fundamental understanding of IBD pathophysiology and to have implications for clinical practice.

A single tumour necrosis factor haplotype influences the response to adalimumab in rheumatoid arthritis

OBJECTIVE

To determine whether tumour necrosis factor (TNF) gene polymorphisms and/or the shared epitope are genetic predictors of the response to adalimumab (ADA) in rheumatoid arthritis (RA).

METHODS

This ancillary study to the Research in Active Rheumatoid Arthritis (ReAct) Phase IIIb study included a large cohort of Caucasian patients with RA from France (n = 388) treated with ADA plus methotrexate (MTX) (n = 182), ADA plus any other DMARD (n = 98) or ADA alone (n = 108). The primary outcome was ACR50 at 12 weeks. Patients underwent genotyping for HLA-DRB1 and three TNF gene polymorphisms (-238A/G,-308A/G and-857C/T). Extended haplotypes involving HLA-DRB1 and TNF loci were reconstructed using the PHASE program.

RESULTS

A total of 151 patients (40%) had an ACR50 response at week 12. Neither the number of HLA-DRB1 shared epitope copies nor presence of the three TNF polymorphisms tested separately was significantly associated with ACR50 response at week 12. However, haplotype reconstruction of the TNF locus revealed that the GGC haplotype (-238G/-308G/-857C) in a homozygous form (i.e. present in more than half of the patients) was significantly associated with a lower ACR50 response to ADA at 12 weeks (34% vs. 50% in patients without the haplotype) (p = 0.003; pa = 0.015). This effect was more important in the subgroup of patients concomitantly treated with MTX.

CONCLUSION

This large pharmacogenetic study provides preliminary data indicating that a single TNF locus haplotype (-238G/-308G/-857C), present on both chromosomes is associated with a lower response to ADA, mainly in patients treated with ADA and MTX.

Infliximab use in children and adolescents with inflammatory bowel disease

Infliximab is a chimeric monoclonal antibody (75% human, 25% murine) against tumor necrosis factor-alpha, a cytokine with a central role in the pathogenesis of inflammatory bowel disease. Large randomized controlled trials have shown the efficacy and safety of infliximab for the induction and maintenance of remission in adult patients with active Crohn disease (CD). In children and adolescents, mostly small, nonrandomized, non-placebo-controlled studies have supported the notion that infliximab is a potent drug in a population that does not respond to standard therapies. The safety of infliximab is of major concern, and the most frequent severe adverse events are related to severe infections and reactivation of tuberculosis. Non-life-threatening infusion reactions occur rather frequently and seem to be related to the formation of antibodies. The indications for infliximab treatment are therapy-resistant luminal CD (no efficacy or insufficient efficacy of conventional treatment) and therapy-resistant fistulas. An efficient remission induction strategy consists of 3 initial infliximab infusions at 0, 2, and 6 weeks in a dosage of 5 mg/kg to sustain remission. Patients needing maintenance therapy are subsequently treated with an infliximab infusion every 8 weeks. There are indications that the early stages of CD may be more susceptible to immunomodulation, and the natural history of CD may be altered by the introduction of infliximab early in the disease process instead of waiting until conventional therapy has failed. Major points of discussion are whether infliximab maintenance treatment should be episodic (on demand) or scheduled and when infliximab therapy can be discontinued.

Predictive model for the outcome of infliximab therapy in Crohn's disease based on apoptotic pharmacogenetic index and clinical predictors

BACKGROUND

Infliximab (IFX) is an effective therapy for refractory luminal and fistulizing Crohn's disease (CD). Predictors of response could improve selection of patients with a higher probability of favorable outcomes and could improve the safety profile. We aimed to develop a predictive model for the response to infliximab in CD.

METHODS

Genetic and clinical data collected in a previous pharmacogenetic study of apoptosis genes were analyzed using SAS Enterprise miner modeling software and SPSS 12.0. We proposed a novel apoptotic pharmacogenetic index (API) with a score ranging from 0 (low apoptotic response) to 3 (high apoptotic response) and subsequently developed a decision tree model.

RESULTS

Response and remission rates significantly increased with API score (P = 0.005 in the group of patients with luminal CD, P = 0.02 in the group of patients with fistulizing CD). Patients with an API < or = 1 (n = 59) had the lowest response and remission rates in both the luminal CD (50% and 39.5%, respectively) and fistulizing CD (61.9% and 28.6%, respectively) groups, compared to those with an API of 2 (n = 158), whose response and remission rates were 73.8% and 56.1%, respectively, in the luminal CD group and 85.7% and 44.9%, respectively, in the fistulizing CD group; and those with an API of 3 (n = 10), whose response and remission rates were 100% and 85.7%, respectively, in the luminal CD group and 100% and 0% in the fistulizing CD group. Response in patients with an API < or = 1 was significantly influenced by concurrent azathioprine therapy in the luminal CD (21.4% versus 78.9%, P < 0.001) and in the fistulizing CD (46.6% versus 100%, P = 0.04) groups. In patients with an API of 2, we saw an interaction with age older than 40 years and location of disease (response 52.2% versus 83.9%, P = 0.008) in the luminal CD group and with baseline CRP greater than 5 mg/L (73.9% versus 93.9%, P = 0.04) in the fistulizing CD group.

CONCLUSIONS

From our newly proposed apoptotic pharmacogenetic index and clinical predictors, we developed a model for prediction of low, medium, and high responses to the first infusion of IFX in patients with CD. Further studies are needed to confirm the hypothesis generated by our study.

Biologic therapies in rheumatology: lessons learned, future directions

During the past decade biologic therapies such as monoclonal antibodies and fusion proteins have revolutionized the management of rheumatic disease. By targeting key cytokines and immune cells biologics have provided more specific therapeutic interventions with less immunosuppression. Clinical use, however, has revealed that their theoretical simplicity hides a more complex reality. Efficacy, toxicity and even pharmacodynamic effects can deviate from those predicted, as poignantly illustrated by the catastrophic effects witnessed during the first-into-human administration of TGN1412. This review summarizes lessons gleaned from practical experience and discusses how these can inform future discovery and development of new biologic therapies for rheumatology.

Potential role of pharmacogenetics in anti-TNF treatment of rheumatoid arthritis and Crohn's disease

Etanercept, infliximab and adalimumab have shown clinical benefit in immune-mediated inflammatory diseases; however, the outcome of treatment with these tumour-necrosis factor inhibitors remains insufficient in approximately 40-60% and approximately 25-40% of individuals with rheumatoid arthritis and Crohn's disease, respectively. Moreover, their use is accompanied by adverse events and unintentional immune suppression. Pharmacogenetics has the potential to increase efficacy and ameliorate adverse events and immune suppression, and its application might be of clinical benefit for patients with rheumatoid arthritis and Crohn's disease. Pharmacogenetic studies have shown associations between single nucleotide polymorphisms in genes encoding enzymes related to the pharmacodynamics of these drugs and treatment outcome. As we discuss here, replication and prospective validation are warranted before pharmacogenetics can be used in clinical practice.

Review article: interactions between genotype and response to therapy in inflammatory bowel diseases

BACKGROUND

More than half of the patients with inflammatory bowel diseases are candidates for immunosuppressive therapy. However, even the most effective drugs used in inflammatory bowel disease are only successful in about two-thirds of patients. Adverse events limit their use in a further substantial proportion of patients. Recent research has focussed on the possibility of predicting a drugs' efficacy and/or toxicity by identifying polymorphic variants in the genes encoding enzymes involved in metabolic pathways.

AIM

To highlight recent advances and limitations in the field of pharmacogenetics in inflammatory bowel disease.

RESULTS

Recent pharmacogenetic studies have mainly focussed on immunosuppressive agents including corticosteroids, azathioprine, methotrexate and infliximab. Several polymorphic genes encoding enzymes involved in the metabolism of these drugs have been identified including the inosine triphosphate pyrophosphatase in thiopurine therapy, the methylene tetrahydrofolate reductase in methotrexate therapy and polymorphisms in apoptosis genes in infliximab therapy. However, at the present time, genotyping for the variants of the thiopurine methyltransferase gene, an enzyme important for the metabolism of the thiopurine drugs, is the only useful test in clinical practice.

CONCLUSIONS

Although the field of pharmacogenetics in inflammatory bowel disease is promising most new targets have so far failed to translate into clinical practice. Future pharmaceutical trials should include pharmacogenetic research to test appropriate candidate genes in a prospective manner.

Clinical application of pharmacogenetics in gastrointestinal diseases

As knowledge of the human genome grows, there will be a direct impact on the management of specific diseases. Within gastroenterology and hepatology, there has been a change in the understanding of how variations or mutations in genes involved in drug metabolism or disease pathophysiology affect response to therapy. This review discusses the application of clinical pharmacogenetics to the following diseases and disorders: inflammatory bowel disease, Helicobacter pylori infections, gastroesophageal reflux disease, irritable bowel syndrome, functional dyspepsia, liver transplantation and colon cancer. Although only a few genotyping tests are regularly used in clinical practice, it is anticipated that studies will propel the routine use of many of the tests described in this review, in the future.

Review article: genetic susceptibility and application of genetic testing in clinical management of inflammatory bowel disease

The volume of research undertaken on the genetic susceptibility of inflammatory bowel disease (IBD) has been tremendous, and over 10 chromosomal regions have been identified by genome-wide scanning. Fine-mapping approaches and candidate gene studies have already led to the identification of several susceptibility genes, including CARD15 (NOD2), DLG5, novel organic cation transporter (OCTN) 1 and 2, and CARD4 (NOD1). The CARD15 gene is the most understood at present and explains around 20% of the genetic predisposition to Crohn's disease. Although the clinical implications of genetic testing are limited at present, genetic research has advanced our understanding of the clinical heterogeneity and the complex interactions between genetic and environmental risk factors in IBD. Genes also interfere with the metabolism of drugs and may influence the clinical response and drug-related toxicity. Ultimately, researchers and clinicians aim to personalize medicine based on a patient's genotype, although azathioprine (thiopurine methyltransferase polymorphisms) is the only drug to date where pharmacogenetics has shown clinical relevance in IBD. In the future, it is anticipated that genetic markers will be implemented in an integrated molecular diagnostic and prognostic approach to managing our patients.

Genetic variants and the risk of Crohn's disease: what does it mean for future disease management?

Genetic research in inflammatory bowel disease, especially in Crohn's disease, has made significant progress during recent years. There have been > 10 total genome scans that have been performed, and susceptibility loci on several chromosomes have been identified. Together with candidate gene studies, these scans have led to the identification of several susceptibility genes, with CARD15 being the most important. These genetic data have already provided important insights into the pathophysiology of inflammatory bowel disease and are stimulating future research. On the other hand, genotype-phenotype associations have illustrated the heterogenic nature of the disease. Although the clinical application of this knowledge is so far limited, there is significant optimism that an individual management of patients based on genetic data will be possible in the near future.

Lymphotoxin alpha gene in Crohn's disease patients: absence of implication in the response to infliximab in a large cohort study

A haplotype in the lymphotoxin alpha (LTA) gene has been associated with a lack of response to infliximab in a small cohort of Crohn's disease (CD) patients. The present study aimed to confirm the implication of this haplotype in the response to infliximab in a larger cohort of Caucasian patients. The response to the first infusion with infliximab was evaluated in 214 Caucasian patients with either luminal (n=150) or fistulising (n=64) CD. Clinical response was based on the decrease in CD Activity Index (luminal) or on the evolution in the fistula discharge (fistulising). Biological response was assessed in 139 patients who had elevated C-reactive protein (CRP) before treatment and for whom CRP values were also available after treatment. A positive biological response was defined as a decrease in CRP of at least 25%. The patients were genotyped for six polymorphisms in the LTA gene. A positive clinical response was present in 65.4% of the patients and a positive biological response was observed in 80.6% of the patients. No association was found with any of the studied polymorphisms, nor with the previously published LTA haplotype and the response to infliximab. We could not confirm an association between the LTA locus and clinical or biological response to infliximab in a large cohort of CD patients.

Protein therapeutics: new applications for pharmacogenetics

Pharmacogenetic studies have traditionally focused on genes involved in processes that affect the pharmacokinetics of small-molecule drugs, such as drug metabolism. However, attention is shifting to the effects of genetic variations in drug targets and associated pathway components on drug responses. We describe how these variations are important for understanding differences in responses to the growing number of protein therapeutics that are entering clinical practice. Pharmacogenetic studies of these drugs are surveyed, and issues important to the success of such endeavours are discussed. As novel protein therapeutics are introduced, we anticipate that the use of pharmacogenetics will assume a key role in their development and clinical application.

Pharmacogenetics in inflammatory bowel disease

Pharmacogenetics is the study of the association between variability in drug response and (or) drug toxicity and polymorphisms in genes. The goal of this field of science is to adapt drugs to a patient's specific genetic background and therefore make them more efficacious and safe. In this article we describe the variants in genes that influence either the efficacy or toxicity of common drugs used in the treatment of inflammatory bowel diseases (IBD), ulcerative colitis (UC), and Crohn's disease (CD) including sulfasalazine and mesalazine, azathioprine (AZA) and 6-mercaptopurine (6-MP), methotrexate (MTX), glucocorticosteroids (CSs) and infliximab. Furthermore, difficulties with pharmacogenetic studies in general and more specifically in IBD are described. Although pharmacogenetics is a promising field that already contributed to a better understanding of some of the underlying mechanisms of action of drugs used in IBD, the only discovery translated until now into daily practice is the relation between thiopurine S-methyltransferase (TPMT) gene polymorphisms and hematological toxicity of thiopurine treatment. In the future it is necessary to organize studies in well characterized patient cohorts who have been uniformly treated and systematically evaluated in order to quantitate drug response more objectively. An effort should be made to collect genomic DNA from all patients enrolled in clinical drug trials after appropriate informed consent for pharmacogenetic studies.

Current status of genetics research in inflammatory bowel disease

The research on genetic susceptibility of inflammatory bowel diseases (IBD) has been tremendous and over 10 chromosomal regions have been identified by genome-wide scanning. Further fine mapping as well as candidate gene studies have already led to the identification of a number of susceptibility genes including CARD15, DLG5, OCTN1 and 2, NOD1, HLA, and TLR4. The CARD15 gene is undoubtedly replicated most widely and most understood at present. CARD15 is involved in the recognition of bacterial peptidoglycan-derived muramyl dipeptide (MDP) and will stimulate secretion of antimicrobial peptides including alpha-defensins (also called cryptdins) to protect the host from invasion. Genetic research in IBD has advanced our understanding of the clinical heterogeneity of the disease and has started to tackle the complex interactions between genetic risk factors and environmental risk factors in IBD. Genes also interfere with the metabolization of drugs and may influence the clinical response and the drug-related toxicity. Interesting pharmacogenetic data with respect to steroids, azathioprine, and infliximab have been generated in IBD. Overall, it is anticipated that genetic markers in the future will be implemented in an integrated molecular diagnostic and prognostic approach of our patients.

Association of TNF-alpha polymorphisms in Crohn disease

Clinical and molecular studies implicate tumor necrosis factor alpha (TNF-alpha) as a key mediator in the initiation and propagation of Crohn disease (CD). Genetic associations have been documented between promoter polymorphisms of TNF-alpha and CD; however, these associations have not been universally replicated. In this study, we set out to examine the association of five promoter TNF-alpha polymorphisms in CD subjects from a founder population. In total, 128 CD subjects and 103 ethnically matched healthy controls were genotyped with time-of-flight mass spectrometry for the following five single nucleotide polymorphisms (SNPs) in the 5' flanking region of TNF-alpha gene: -1031 (T-->C), -863 (C-->A), -857 (C-->T), -308 (G-->A), and -238 (G-->A). Primer sequences, termination mixes, and multiplexing were determined with Sequenom SpectroDESIGNER software v1.3.4. The minor allele frequency for the TNF-alpha SNPs in subjects with CD and healthy controls, respectively, were -238 (5.5% vs. 5.3%); -308 (17.6% vs. 18.9%); -857 (5.1% vs. 7.8%); -863 (19.1% vs. 17.5%), and -1031 (24.6% vs. 22.8%). Thus, none of the TNF-alpha variants was associated with CD. Furthermore, no genotype/phenotype correlations were observed for the mutant allele of the TNF-alpha variants and selected clinical outcomes. In conclusion, there was no significant association for any of the TNF-alpha promoter polymorphism tested and CD in the Newfoundland population.

Polymorphisms in apoptosis genes predict response to infliximab therapy in luminal and fistulizing Crohn's disease

BACKGROUND

Infliximab treatment is effective in 70-80% of patients with refractory luminal and fistulizing Crohn's disease. The effect of infliximab is ascribed to induction of apoptosis.

AIM

To study whether polymorphisms in apoptosis genes predict the response to infliximab and whether they interact with clinical predictors.

METHODS

Cohort of 287 consecutive patients treated with infliximab for refractory luminal (n = 204) or fistulizing (n = 83) Crohn's disease was genotyped for 21 polymorphisms in apoptosis genes. Short-term clinical response was assessed at week 4 (luminal Crohn's disease) or 10 (fistulizing Crohn's disease) after the first infliximab infusion.

RESULTS

The response rate was 69% in luminal and 80% in fistulizing Crohn's disease. In luminal Crohn's disease, two genetic predictors were identified: (i) patients with the Fas ligand -843 CC/CT genotype (n = 135) responded in 75%, with the TT genotype (n = 21) in 38% only (P = 0.002; OR = 0.11; 95% CI: 0.08-0.56). (ii) Patients with the caspase-9 93 TT (n = 9) genotype all responded, in contrast with 67% (n = 147) with the CC and CT genotype (P = 0.04; OR = 1.50; 95% CI: 1.34-1.68). Concomitant azathioprine/mercaptopurine therapy overcame the effect of unfavourable genotypes. In the fistulizing Crohn's disease cohort, the same Fas ligand -843 CC/CT genotype was the only predictor of response (P = 0.002; OR = 1.66; 95% CI: 1.21-2.29), interacting with caspase-9 93 polymorphism but not with azathioprine/mercaptopurine.

CONCLUSION

We observed that polymorphisms in FasL/Fas system and caspase-9 influence the response to infliximab in luminal and fistulizing Crohn's disease. The strongest association was seen between the Fas ligand -843 TT genotype and non-response. Concomitant mercaptopurine/azathioprine therapy, however, was able to overcome the effect of unfavourable genotypes in luminal disease.

Are there predictors of Remicade treatment success or failure?

Infliximab (Remicade) is an antitumor necrosis factor (TNF) therapy effective in both induction and maintenance of remission in Crohn's disease. Identifying predictors of response or relapse to infliximab is important given the potential toxicities and cost of this therapy. Currently available data suggest that concurrent immunosuppressant therapy, certain clinical characteristics, biological and immunological markers, and gene polymorphism may correlate with response to infliximab. However, no single variable has been consistently shown or definitely proven in studies to be a predictor of response to infliximab to be of practical value in current clinical practice. Data from the literature in these areas are reviewed in this article, pointing to the need for additional research in this topic.

Genetic Testing in Crohn Disease

Inflammatory bowel disease (IBD), with its two subforms of Crohn disease and ulcerative colitis, is a polygenic disease that manifests due to environmental trigger factors on the background of a complex genetic predisposition. The first risk gene underlying susceptibility to Crohn disease has been identified as CARD15 (located on chromosome 16q12, encoding NOD2). Three single nucleotide polymorphisms in the leucine rich region (LRR) of this gene are strongly and independently associated with Crohn disease susceptibility and explain up to 20% of the total genetic predisposition for Crohn disease. These variants have been consistently replicated as associated with a particular sub-phenotype characterized by small bowel (ileum) involvement and early age at onset. Presently, genetic testing for the CARD15 variants has only a modest relevance in clinical practice. The most attractive use of genetic testing is for the prediction of response to therapy. Most therapies only show efficacy in subgroups of patients and no clinical parameters are available to distinguish, prior to therapy, whether the patients will be responders or non-responders, or if the patients will experience adverse effects. The pharmacogenetic basis of toxicity is well known for azathioprine: several thiopurine methyltransferase (TPMT) polymorphisms that are associated with reduced activity of this thiopurine drug metabolizing enzyme result in cytotoxic and immunosuppressive adverse effects of azathioprine. Genetic screening, which has found its way into routine clinical diagnostics, allows the identification of the patients who will not tolerate a standard dose of the drug. The extensive search for genetic predictors of response to the anti-tumor necrosis factor treatment with infliximab, which results in a remission rate of 30-40%, has, however, failed to identify a variation associated with a differential response.

The role of pharmacogenomics in the prediction of efficacy of anti-TNF therapy in patients with Crohn's disease

TNF-alpha plays a central role in the pathophysiology of Crohn's disease. Infliximab, a chimeric monoclonal antibody against TNF-alpha, has been shown to be effective and well-tolerated in several large placebo-controlled trials and has become a common treatment for Crohn's disease. The blockade of TNF through the infusion of infliximab is characterized by high clinical efficacy and rapid onset of action. A single infusion of infliximab results in a remission rate of 30-40%. Lack of response appears to be a stable trait even after repeated infusions, suggesting that it might be genetically determined. Mutations in the TNF-alpha gene have been extensively studied as predictors of response with various results. Polymorphisms in the TNF-alpha receptors TNF-R1 and TNF-R2 have been found not to be associated with treatment response. Similarly, the three mutations in the CARD15 gene, which are independently associated with susceptibility to Crohn's disease, have also been found not to be associated with treatment response.

Review article: exploration of the genetic aetiology of inflammatory bowel disease--implications for diagnosis and therapy

Genomic technologies offer new approaches to the investigation of the aetiology and pathophysiology of inflammatory bowel disease. An important field relevant to inflammatory bowel disease therapy is the pharmacogenetic investigation of gene variations that may predict responses to certain medications in order to target these therapeutic interventions more precisely. To date, only about 12,000 of the estimated 30,000-50,000 human genes have been characterized. Therefore, the use of techniques for a global analysis of gene expression may allow the identification of new pathways or molecules in the therapeutic mechanisms of drugs. Recently, NOD2 has been identified as the first disease gene in inflammatory bowel disease. DLGS and OCTN-1 have been named as further disease genes. Although the detection of disease-associated variants has greatly advanced our understanding of the primary events that lead to the development of inflammatory bowel disease in a subgroup of patients with Crohn's disease, the implications of the findings for diagnostic and therapeutic algorithms are less clear. However, it appears that there is a clear association between certain subphenotypes of Crohn's disease and the disease-associated variants in the NOD2 gene. It can be anticipated that genomic findings will profoundly influence the future therapy of inflammatory bowel disease.

Perianal Crohn's disease and infliximab therapy

INTRODUCTION

Perianal manifestations occur in almost half of patients with Crohn's disease and often respond poorly to conventional therapies. The introduction of anti-tumour necrosis factor alpha agents (e.g. infliximab) has altered the management of patients who fail first and second line medical and surgical therapies.

METHODS

We performed a literature search of the PubMed database using the Medical Search Headings infliximab, perianal Crohn's disease, fistulae, cost and safety. We also performed a manual search using references from these articles, review articles and proceedings from major gastroenterology meetings.

RESULTS

Use of infliximab, at a dose of 5mg/kg at intervals of 0, 2 and 6 weeks, results in significant improvement in disease in approximately 70% of patients with fistulae. Prior examination under anaesthesia with placement of non-cutting seton sutures in fistula tracks is a useful adjunct in many patients. Preliminary results show a benefit from maintenance infliximab therapy and from concomitant use of immunosuppressants such as azathioprine. No clinical or biochemical markers have been identified which predict non-response to infliximab, although its use is contraindicated in patients with strictures. Acute infusion reactions are the most common side-effect of infliximab therapy and they are usually mild. Despite initial fears, the incidence of opportunistic infection is low. There is inadequate information, at present, regarding a possible increase in incidence of lymphoma with infliximab therapy. Infliximab is expensive compared with established therapies and its use will increase the lifetime cost of treating Crohn's disease.

CONCLUSION

While infliximab is a useful adjunct in selected patients, the cornerstones of management of perianal Crohn's are essentially unchanged.

Tumour necrosis factor-alpha receptor 1 and 2 polymorphisms in inflammatory bowel disease and their association with response to infliximab

BACKGROUND

The role of tumour necrosis factor-alpha in the pathogenesis of inflammatory bowel disorders is well-known and is underscored by the effectiveness of antitumour necrosis factor-alpha treatment. Tumour necrosis factor-alpha exerts its effect by binding TNFR1 and TNFR2, which genes map to inflammatory bowel disorders susceptibility loci.

AIMS AND METHODS

Since TNFR1 and TNFR2 are good candidate genes for inflammatory bowel disorders, we studied the functional TNFR2T587G and the TNFR1A36G mutation in 344 Crohn's disease and 152 ulcerative colitis patients and investigated the relation with disease phenotypes. An association with response to infliximab was evaluated in 166 Crohn's disease patients.

RESULTS

The TNFR2 587G allele was more frequent in ulcerative colitis compared with controls (P = 0.03). Both single nucleotide polymorphisms were negatively associated with smoking at diagnosis in Crohn's disease (TNFR1A36G odds ratio: 0.614, 95% confidence interval: 0.452, 0.99 and TNFR2T587G odds ratio: 0.572, 95% confidence interval: 0.820, 0.875). There was a positive association between pancolitis and the TNFR1A36G polymorphism in ulcerative colitis (odds ratio: 5.341, 95% confidence interval: 1.484, 19.39). The biological response to infliximab was lower in patients carrying TNFR1 36G (odds ratio: 0.47, 95% confidence interval: 0.234, 0.946).

CONCLUSION

The TNFR2 587G allele was more frequent in ulcerative colitis. Both single nucleotide polymorphisms were negatively associated with smoking in Crohn's disease. A relation between TNFR1A36G and pancolitis was found in ulcerative colitis. There was no clear effect of the polymorphisms on infliximab response although, the TNFR1 minor was associated with a lower response to infliximab.

Smoking and immunomodulators do not influence the response or duration of response to infliximab in Crohn's disease

OBJECTIVE

Clinical predictors for infliximab response are still unknown. Identifying predictors of response to infliximab in Crohn's disease may improve our selection of patients.

METHODS

Two hundred patients with luminal (61%) or fistulous (39%) Crohn's disease and at least 6 months of follow-up following a total of 416 infliximab infusions were evaluated. Clinical response and duration of response were the primary endpoints.

RESULTS

Patients with fistulous disease had a higher response rate (83% versus 70%, P = 0.044) and a significantly longer duration of response compared with patients with luminal disease (17.4 versus 10.1 wks, P = 0.017). For luminal disease, nonsmokers and smokers had similar response rates (74% versus 64%, P = 0.5) and similar durations of response (9.4 wks versus 8.4 wks P = 0.6) while patients taking concurrent immunomodulators had similar response rates compared with those not taking immunomodulators (74% versus 71%, P = 0.9) and similar durations of response (10.4 wks versus 10.6 wks, P = 0.9). For fistulous disease, response rates (89% versus 83% P = 0.9) and duration of response (16.9 wks versus 10.1 wks, P = 0.10) were similar between nonsmokers and smokers and concurrent immunomodulators had no effect on response (89% versus 86%, P = 0.9) or duration of response (19.8 wks versus 15.4 wks, P = 0.46). Multivariable analysis confirmed that neither smoking, corticosteroids, immunomodulator therapy, gender, age, age of disease onset, disease duration, nor luminal disease location significantly influenced response or duration of response.

CONCLUSIONS

Patients with fistulous disease had a higher response rate and a significantly longer duration of response compared with patients with luminal disease. However, among patients with luminal or fistulous disease, neither smoking nor immunomodulators had any effect on response or duration of response.

Pharmacogenetics of inflammatory bowel disease

The therapeutic efficacy and toxicity of many commonly employed drugs show interindividual variations that relate to several factors, including genetic variability in drug-metabolizing enzymes, transporters or targets. The study of the genetic determinants influencing interindividual variations in drug response is known as pharmacogenetics. The ability to identify, through preliminary genetic screening, the patients most likely to respond positively to a medication should facilitate the best choice of treatment for each patient; drugs likely to exhibit low efficacy or to give negative side-effects can be avoided. Among the medications used for inflammatory bowel disease, the best studied pharmacogenetically is azathioprine. The hematopoietic toxicity of azathioprine is due to single nucleotide polymorphisms in the thiopurine S-methyltransferase enzyme. Additionally, likely gene targets have been investigated to predict the response to glucocorticoids and infliximab, a monoclonal antibody against tumour necrosis factor that induces remission in approximately 30-40% of patients. However, no genetic predictor of response has been identified in either case.

NOD2/CARD15: relevance in clinical practice

So far, the relevance of NOD2/CARD15 genotyping for clinical practice is modest. The current data almost unanimously show that NOD2/CARD15 mutations in Crohn's disease are associated with small-bowel involvement. More studies are needed to determine whether NOD2/CARD15 mutations are also associated with a fibrostenotic behaviour of the disease. If CARD15 variants would predict a more aggressive disease course, then a more aggressive treatment is justified in these patients after NOD2/CARD15 genetic testing. It is not clear whether NOD2/CARD15 genotyping is helpful in differentiating indeterminate colitis patients. Although CARD15 variants do not predict response to the TNF alpha monoclonal antibodies, the role of the gene in response to other drugs is not known. Finally, screening unaffected relatives of CD patients is not recommended until preventive strategies are available.

The contribution of HLA genes to IBD susceptibility and phenotype

The human leukocyte antigen (HLA) region located on chromosome 6p encodes the highly polymorphic, classical class I and II genes essential for normal lymphocyte function; it also encodes a further 224 genes. Many early studies investigating this region were limited by small sample size, poor statistical methodology, population stratification and variable disease definition. Although more recent studies have improved study design, investigators are still challenged by the complex patterns of linkage disequilibrium across this gene-dense region, and by the disease heterogeneity characteristic of all genetically complex disorders. However, a number of important observations have emerged from recent studies: (1) the HLA harbours gene(s) that determine susceptibility to colonic inflammation in both ulcerative colitis (UC) and Crohn's disease (CD); (2) most of the specific associations with UC and CD appear to differ; (3) associations between different ethnic groups differ; (4) markers in the HLA might predict the course of disease and the development of complications, notably the extraintestinal manifestations of disease.

Clinical relevance of advances in genetics and pharmacogenetics of IBD

Crohn's disease and ulcerative colitis result from an inappropriate response of the mucosal immune system to the normal enteric flora in a genetically susceptible individual. During the past decade, exciting progress has been made in our understanding of the contribution of genetics to inflammatory bowel disease susceptibility and phenotype. This article reviews recent advances in the genetics of inflammatory bowel disease and explores how they might impact on clinical practice. Current knowledge of the genetic basis for disease susceptibility, phenotype, and response to therapy is explored and the factors currently limiting the translation of this knowledge to clinical practice is discussed.

Optimizing anti-TNF treatment in inflammatory bowel disease

Infliximab, the chimeric monoclonal immunoglobulin (Ig)G1 antibody to tumor necrosis factor (TNF) has changed our therapy of Crohn's disease. Infliximab is indicated in refractory luminal and fistulizing Crohn's disease. In patients with luminal disease, a single intravenous (i.v.) dose of 5 mg/kg is efficacious; in fistulizing disease, an i.v. loading therapy of 5 mg/kg at weeks 0, 2, and 6 is advocated. Because the majority of patients will relapse if not re-treated, a long-term strategy is necessary. The optimal long-term approach is systematic re-treatment with 5 mg/kg every 8 weeks. Episodic therapy on relapse also is possible but is less efficacious and frequently is associated with problems resulting from the formation of antibodies to infliximab (ATI). If treatment is episodic, maintenance therapy with immunosuppression (azathioprine [AZA]/6-mercaptopurine [6-MP] or methotrexate) is mandatory. Trial data suggest that systematic maintenance with 8 weekly doses of infliximab decreases the rate of complications, hospitalizations, and surgeries. These effects probably are achieved thanks to thorough healing of the bowel. Infliximab also is indicated in treating corticosteroid-dependent Crohn's disease and extraintestinal manifestations of Crohn's disease. There are no data yet that support its use as first-line therapy. The data in ulcerative colitis (UC) are conflicting and we should await the results of 2 large controlled trials (ACT1 and ACT2) to position infliximab in the treatment of UC. Other anti-TNF strategies have been less effective than infliximab in the treatment of IBD until now. The results with thalidomide are promising but much more research into small molecules inhibiting TNF and other proinflammatory cytokines is necessary. Safety problems with antibody treatment mainly concern immunogenicity leading to infusion reactions, loss of response, and serum sickness-like delayed infusion reactions. The rate of opportunistic infections is increased mainly in patients treated concomitantly with immunosuppression. Other adverse events associated with anti-TNF strategies are demyelinating disease and worsening of congestive heart failure. Malignancy rates in patients treated with anti-TNF strategies do not seem to be increased.

Association between polymorphism in IgG Fc receptor IIIa coding gene and biological response to infliximab in Crohn's disease

AIM

To test the hypothesis of an association between polymorphism in FCGR3A (the gene coding for FcgammaRIIIa, which is expressed on macrophages and natural killer cells, is involved in antibody-dependent cell-mediated cytotoxicity and has recently been associated with a positive response to rituximab, a recombinant immunoglobulin G1 antibody used in non-Hodgkin's lymphomas) and response to infliximab in Crohn's disease.

METHODS

FCGR3A-158 polymorphism was determined using an allele-specific polymerase chain reaction assay in 200 Crohn's disease patients who had received infliximab for either refractory luminal (n = 142) or fistulizing (n = 58) Crohn's disease. Clinical and biological responses (according to C-reactive protein levels) were assessed in 200 and 145 patients, respectively.

RESULTS

There were 82.9% clinical responders in V/V patients vs. 72.7% in V/F and F/F patients (N.S.). Globally, the decrease in C-reactive protein was significantly higher in V/V patients than in F carriers (P = 0.0078). A biological response was observed in 100% of V/V patients, compared with 69.8% of F carriers (P = 0.0002; relative risk, 1.43; 95% confidence interval, 1.27-1.61). In the sub-group of patients with elevated C-reactive protein before treatment, the multivariate analysis selected the use of immunosuppressive drugs and FCGR3A genotype as independent factors influencing the clinical response to infliximab (P = 0.003).

CONCLUSION

Crohn's disease patients with FCGR3A-158 V/V genotype have a better biological and, possibly, clinical response to infliximab.