The effect of 6-mercaptopurine on natural killer-cell activities in Crohn's disease

Drug safety in thyroid eye disease - a systematic review

INTRODUCTION

The autoimmune-induced thyroid eye disease (TED) is a frequent extrathyroidal manifestation of Graves' disease and less frequently of Hashimoto's thyroiditis. Pathognomonic clinical signs, i.e. exophthalmos, double vision, and inflammation of the orbital tissue cause physical, ophthalmic, and socio-psychological limitations.

AREAS COVERED

PubMed and MeSH database were searched for specific guidelines, randomized controlled trials, prospective clinical studies, systematic reviews and meta-analyses pertaining to the safety profile of currently administered immunosuppressive agents for the treatment of TED. Occurred adverse events (AE), severe AE (SAE), side effects (SE), and severe SE (SSE) were classified according to the standardized medical dictionary for regulatory activities (MedDRA).

EXPERT OPINION

This novel systematic analysis offers an overview of potential AE, SAE and SE for currently recommended immunosuppressive drugs for the treatment of TED. Non-specific, anti-inflammatory drugs and more specific, targeted biologicals are treatment options for active and severe TED. Critical evaluation of the pertinent literature confirms an evidence-based, beneficial efficacy/risk ratio of the current first-line and second-line treatment recommendations endorsed by the European Society of Endocrinology. However, further large, well-conceived trials are mandatory to enhance our knowledge and experience with novel specific small molecules and/or monoclonal antibodies targeting the key autoantigens in TED.

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

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

Combined Immunosuppression Impairs Immunogenicity to Tetanus and Pertussis Vaccination Among Patients with Inflammatory Bowel Disease

BACKGROUND

Pertussis epidemics have recently emerged across the United States, prompting broad public health recommendations for adult Tdap vaccination (tetanus, diphtheria, acellular pertussis). The impact of immunosuppressive regimens for inflammatory bowel disease (IBD) on vaccine responses to the Tdap vaccine is not known.

METHODS

We performed a prospective controlled trial between April 2011 and March 2012. Adults with IBD were consecutively stratified based on therapeutic regimen into one of 5 groups: A: no IBD therapy or 5-aminosalicylates alone; B: maintenance biologic monotherapy; C: maintenance immunomodulator monotherapy; D: combined biologic and immunomodulator therapy; and E: healthy age-matched controls. Subjects received Tdap, and serum antibody levels against tetanus toxoid, pertussis toxoid, and filamentous hemagglutinin (FHA) were drawn just before and approximately 4 weeks after vaccination. The primary outcome was the booster response rate to each antigen. Secondary outcomes included the differences in pregeometric and postgeometric mean titers.

RESULTS

A total of 98 subjects enrolled, and 84 completed the study. Tetanus response rates were 55%, 56%, 40%, 27%, and 63% across groups A to E, respectively. Group D rates were lower than those of group B (P = 0.02). Postvaccination pertussis toxoid responses were 59%, 72%, 47%, 45%, and 75%, while FHA responses were 86%, 72%, 80%, 64%, and 75% across groups A to E, respectively. Prevaccination and postvaccination geometric mean titer differences for FHA were lower in group D than those in group A (P = 0.05).

CONCLUSIONS

Antibody responses to tetanus and pertussis vaccination may be affected by therapeutic drug regimen. Patients with IBD should optimally receive Tdap before starting immunomodulators, particularly when used in combination with anti-tumor necrosis factor alpha agents.

Increased proportion of CD16(+) NK cells in the colonic lamina propria of inflammatory bowel disease patients, but not after azathioprine treatment

BACKGROUND

Distinct functional subsets of natural killer cells potentially contribute to the pathology of inflammatory bowel disease (IBD).

AIM

To report the phenotypic and functional characteristics of natural killer cells in blood and lamina propria of IBD patients, and the effect of azathioprine.

METHODS

Natural killer cells from blood and lamina propria of healthy controls or patients with Crohn's disease, or ulcerative colitis were studied by flow cytometry. Activation, cytokine production, proliferation and apoptosis of natural killer cell subsets were studied in vitro.

RESULTS

CD16(+) natural killer cells are increased in frequency in the lamina propria comparing Crohn's disease or ulcerative colitis with healthy controls. Azathioprine therapy was associated with a reduction in total natural killer cells in blood and lamina propria, preferentially of the CD16(+) subset. Azathioprine therapy did not impair natural killer degranulation, but reduced natural and cytokine-activated cytotoxicity and interferon-gamma (IFN-γ) production. Culture of resting peripheral blood mononuclear cells with azathioprine resulted in loss of natural killer cells and inhibition of activation and IFN-γ production. Azathioprine preferentially inhibited proliferation of CD16(+) natural killer cells and induced apoptosis in resting but not in pre-activated natural killer cells.

CONCLUSIONS

Natural killer cells with cytolytic potential are enriched in the colonic lamina propria of individuals with IBD. Azathioprine is associated with a reduction in these cells and a normalization of natural killer cell populations.

Association of 6-thioguanine nucleotide levels and inflammatory bowel disease activity: a meta-analysis

BACKGROUND & AIMS

6-Thioguanine nucleotide (6-TGN) levels have been proposed to correlate with inflammatory bowel disease (IBD) activity among patients treated with azathioprine or 6-mercaptopurine (6-MP). Previous studies, most with small sample sizes, yielded conflicting conclusions. Our aim was to pool the available data to provide a more precise estimate of the association between 6-TGN levels and IBD activity.

METHODS

We searched Medline and PubMed (from 1966 to November 2004) and reviewed the reference lists of selected articles. Fixed and random-effects models were used to test whether mean/median 6-TGN levels differed among patients with active disease vs remission and whether 6-TGN levels above a threshold of 230-260 pmol/8 x 10(8) red blood cells were associated with clinical remission. When studies reported multiple 6-TGN threshold values, we used the data for the lower value.

RESULTS

We identified 55 articles, 12 of which contained data sufficient for inclusion. The mean/median 6-TGN levels were higher among patients in remission than in those with active IBD (pooled difference, 66 pmol/8 x 10(8) red blood cells; 95% confidence interval, 18-113; P = .006), but with significant heterogeneity. Excluding the 1 outlier study eliminated this heterogeneity. Patients with 6-TGN levels above the threshold value were more likely to be in remission (62%) than those below the threshold value (36%) (pooled odds ratio, 3.3; 95% confidence interval, 1.7-6.3; P < .001), but with significant heterogeneity. Again, excluding the 1 outlier study eliminated this heterogeneity.

CONCLUSIONS

Although prior studies yielded inconsistent conclusions, this analysis strongly supports that higher 6-TGN levels are associated with clinical remission.

Treatment of inflammatory bowel disease with azathioprine and 6-mercaptopurine

6-Mercaptopurine and azathioprine have become important therapeutic options for patients with inflammatory bowel disease (IBD). Although accumulating data in the literature have supported the use of these immunomodulators in the management of IBD, marked variation exists in the pattern of clinical practice regarding azathioprine or 6-mercaptopurine therapy in patients with IBD. This article provides a critical review of the data on the clinical efficacy and toxicities of 6-mercaptopurine and azathioprine in the management of IBD. Emerging literature on the potential application of pharmacogenetic testing and metabolite monitoring are also discussed.

Treatment of inflammatory bowel disease with azathioprine and 6-mercaptopurine

6-Mercaptopurine and azathioprine have become important therapeutic options for patients with inflammatory bowel disease (IBD). Although accumulating data in the literature have supported the use of these immunomodulators in the management of IBD, marked variation exists in the pattern of clinical practice regarding azathioprine or 6-mercaptopurine therapy in patients with IBD. This article provides a critical review of the data on the clinical efficacy and toxicities of 6-mercaptopurine and azathioprine in the management of IBD. Emerging literature on the potential application of pharmacogenetic testing and metabolite monitoring are also discussed.

Topical azathioprine in the treatment of immune-mediated chronic oral inflammatory conditions: a series of cases

OBJECTIVES

After hematopoietic cell transplantation, a variety of complications can occur, including chronic graft-versus-host disease (GVHD), with 25% to 70% of these involving the oral cavity. Those lesions, as well as oral involvement of autoimmune mucocutaneous diseases, might present as painful, erythematous, and ulcerative oral lesions. Management includes topical and systemic immunosuppressive agents, including systemic azathioprine (AZA). The purpose of this study was to evaluate the efficacy of topical AZA in chronic oral GVHD and in oral autoimmune diseases in a series of patients.

METHODS

Four men and 2 women with GVHD and 2 men with autoimmune vesiculo-ulcerative oral lesions were treated with topical AZA. A rinse of 5 mL of 5 mg/mL AZA in methylcellulose were rinsed 3 to 4 times daily for over 1 minute and expectorated, or a gel in the same concentration in 3% methylcellulose was topically applied. The outcome was evaluated separately for total ulcer size, assessment of the erythema, and severity of pain by using a visual analogue scale. Global estimated improvements represented a proportional combined improvement of ulcers, erythema, and pain.

RESULTS AND CONCLUSIONS

The mean estimated global improvement for 6 patients with GVHD who used AZA rinse was 60% in a mean of 16.67 weeks. Ulcers improved by 58%, erythema by 55%, and pain was reduced by 63%. Two patients with oral lesions of vesiculo-ulcerative diseases (1 AZA rinse and 1 topical gel) improved by 95% and 96%, respectively, in 3 months. One patient with GVHD applied topical AZA gel in addition to mouthrinses, and a 29% estimated global improvement was achieved in addition to 50% of improvement achieved with AZA mouthrinses. The observed effect of topical AZA suggests that it can be used for management of oral immune-mediated inflammatory conditions, and for patients who are provided with systemic immunosuppressives it can allow control of oral findings with lower systemic dosing. The therapeutic potential of topical AZA as mouthrinse versus topical applications and the most effective concentration should be further investigated.

Azathioprine or 6-mercaptopurine for inflammatory bowel disease: do risks outweigh benefits?

The treatment of Crohn's disease and ulcerative colitis has evolved and has improved the quality of life of patients afflicted with these disorders. Immune modulators such as azathioprine and 6-mercaptopurine are an important class of medications used for the treatment of patients with inflammatory bowel disease. Controlled studies have demonstrated their efficacy in both induction and maintenance of remission in Crohn's disease, and similarly, for the induction and maintenance of remission in patients with ulcerative colitis. These agents have had an increasing importance in the management of steroid-resistant, steroid-dependent diseases, and fistulizing Crohn's disease. The primary limitations to these agents have been their slow onset of action and their side effect profile. Despite these limitations, these agents have demonstrated efficacy and have become paramount to the management of patients with these incurable potentially disabling disorders. The precise role of azathioprine/6-mercaptopurine, their limitations and their safety are reviewed in this paper.

Enhanced bioavailability of azathioprine compared to 6-mercaptopurine therapy in inflammatory bowel disease: correlation with treatment efficacy

BACKGROUND

Azathioprine and 6-mercaptopurine have proven efficacy in the treatment of Crohn's disease. Immunosuppression is mediated by their intracellular metabolism into active 6-thioguanine metabolites, and clinical responsiveness to therapy in patients with inflammatory bowel disease has been correlated with the measure of erythrocyte 6-thioguanine levels.

AIMS AND METHODS

To perform a dosing equivalency analysis and comparison of clinical efficacy in 82 patients with inflammatory bowel disease on long-term (> 2 months) therapy with either branded azathioprine (Imuran) (n=26), generic azathioprine (n=38), or 6-mercaptopurine (n=18), based on the measurement of erythrocyte 6-thioguanine metabolite levels.

RESULTS

Disease remission was achieved in 51% (42 out of 82) of patients treated with either azathioprine or 6-mercaptopurine therapy, and correlated well with high erythrocyte 6-thioguanine levels (> 250 pmoles/8 x 108 RBCs). Patients treated with either branded azathioprine or 6-mercaptopurine achieved significantly higher erythrocyte 6-thioguanine levels than patients treated with generic azathioprine, thereby suggesting that branded azathioprine has improved oral bioavailability compared to generic azathioprine. These data are consistent with the putative immunosuppressive role of 6-thioguanine metabolites in the treatment of inflammatory bowel disease, and provides a basis for developing a therapeutic index of clinical efficacy based on the measurement of erythrocyte 6-thioguanine metabolite levels.

CONCLUSIONS

Our results suggest that differences in bioavailability may have clinical relevance when considering the need to optimize erythrocyte 6-thioguanine metabolite levels in patients deemed unresponsive to treatment on conventional drug dosages.

Topical azathioprine in the combined treatment of chronic oral graft-versus-host disease

This paper presents the first report of the use of topical azathioprine in the management of persistent symptomatic chronic oral graft-versus-host disease (GVHD). Topical azathioprine suspension was used as an oral rinse and was swallowed, maintaining the previously prescribed systemic dose of azathioprine, and resulted in improvement in a case of oral GVHD that was resistant to other approaches to management. Topical azathioprine may provide additional therapy in the management of immune-mediated oral mucosal disease. Clinical trials appear warranted based upon the results of topical azathioprine use as presented in this case report.

6-Mercaptopurine metabolism in Crohn's disease: correlation with efficacy and toxicity

BACKGROUND

6-Mercaptopurine (6-MP) has confirmed short and longterm efficacy in the treatment of IBD. However, the relation between its metabolism, efficacy, and side effects is not well understood.

AIMS

To assay 6-MP metabolites and to correlate levels with drug compliance, disease activity, and adverse effects of treatment.

PATIENTS

Heparinised blood was obtained prior to daily administration of 6-MP in 25 adolescent Crohn's disease patients (14 ileocolitis, 11 colitis) receiving 1.2 (range 0.4-1.6) mg/kg/day for a mean of 17 (range 4-65) months.

METHODS

Erythrocyte free bases 6-thioguanine (6-TG) and 6-methyl-mercaptopurine (6-MMP) were measured (pmol/8 x 10(8) red blood cells) using reverse phase high performance liquid chromatography.

RESULTS

Disease activity (modified Harvey-Bradshaw index) improved significantly with 6-MP (p = 0.001). Clinical remission was achieved in 72% of patients, who stopped taking prednisone, or were successfully weaned to a low alternate day dose (< 0.4 mg/kg/OD). Remission correlated well with erythrocyte 6-TG (p < 0.05), but not 6-MMP levels. Neutropenia was associated with 6-MP use (p < 0.005), but did not correlate with erythrocyte 6-MP metabolite levels. One patient refractory to 6-MP had 6-TG, but no measureable 6-MMP production, suggesting deficient thiopurine methyl-transferase activity or poor compliance. 6-MP induced complications (hepatitis, pancreatitis, and marrow suppression) were generally associated with increased 6-MMP levels.

CONCLUSIONS

These results suggest that high performance liquid chromatography measurement of erythrocyte 6-MP metabolites may provide a quantitative assessment of patient responsiveness and compliance to treatment. The data support an immunosuppressive role for 6-TG, and potential cytotoxicity of raised 6-MMP levels.

Newer treatments for inflammatory bowel disease

Despite intense investigative efforts, the causes of ulcerative colitis and Crohn's disease remain elusive. The mainstay of medical therapy focuses on inhibition of the effects of the inflammatory mediators operant in inflammatory bowel disease because the causes of these two chronic disorders are unknown. During recent years, the physician's armamentarium for medical treatment of inflammatory bowel disease has increased substantially. In this article, the current standard medical therapies available for treatment of patients with inflammatory bowel disease are reviewed along with their efficacy; the side effects and status of other investigative drugs also are reviewed.

Treatment of inflammatory bowel disease from now to the millennium

After decades of therapeutic stasis, treatment advances are occurring in inflammatory bowel disease. Recognition that mesalazine was the active moiety of sulphasalazine has led to a number of new methods of delivering mesalazine without sulphapyridine, with improved toxicity ratios. Current attempts to deliver topical steroids directly to the large bowel have yet to be established as therapeutically effective. Immunosuppressive treatment has been used for many years but recent evidence has firmly established its value and cyclosporin has recently been added to the therapeutic armamentarium. Increasing understanding of the basic processes of inflammation has yielded targets for anti-inflammatory treatments aimed both at the processes of immune activation and of attraction by chemotaxis of neutrophils from the circulation to the lamina propria. Some of these novel treatments, which will be assessed in forthcoming years, involve large molecular weight bioengineered peptides and antibodies that are likely to be expensive and difficult to administer. Other treatment, e.g. 5-lipoxygenase or thromboxane synthesis inhibitors or platelet-activating factor antagonists, are conventional lower molecular weight compounds that are easier to produce and are orally active. It is predicted that 5-lipoxygenase inhibitors will be the next therapeutic advance in inflammatory bowel disease. Such a prediction may founder if blanket suppression of multiple inflammatory mechanisms, rather than targeted actions, is required in inflammation.

Review article: immunosuppressive therapy for inflammatory bowel disease

Refractory inflammatory bowel disease can be treated by surgery or using nutritional supplementation or replacement. Immunosuppressive agents may also play a role for refractory disease; they have gained widespread acceptance, due not only to trials that demonstrate efficacy but also to the realization that these side-effects are minor compared to those associated with long-term, high-dose corticosteroids. To date, 6-mercaptopurine and azathioprine remain the drugs of choice based upon extensive clinical experience, but both methotrexate and cyclosporin are promising immunosuppressants for otherwise refractory disease.

Inflammatory bowel disease revisited: newer drugs

The development of new drug therapy is an evolutionary process progressing from clinical success with current treatments through an understanding of interactions in the immune and inflammatory events that culminate in the tissue injury of IBD. The basic immunoinflammatory response is reviewed, with identification of the recognized and potential sites of activity of current therapies. Potential sites and implications for future interventions by newer therapies are discussed as we anticipate the discovery of the etiology and eventual cure for ulcerative colitis and Crohn's disease.

Immunosuppressive drugs in inflammatory bowel disease. A review of their mechanisms of efficacy and place in therapy

Immune effector mechanisms are central to the disease process in inflammatory bowel disease, but it is not clear whether the mucosal or systemic immunological abnormalities are primary phenomena, or are secondary to disease activity. Corticosteroid drugs remain the most effective treatment for active disease, but there is no evidence that they are useful for maintenance therapy. Some patients, however, are dependent on low-dose corticosteroids, and relapse when the drug is withdrawn. These drugs have widespread actions on the immune response, and monocytes are particularly sensitive to corticosteroids. In contrast, sulphasalazine and 5-aminosalicylic acid are effective in maintenance therapy, but do not act primarily by immunosuppressive mechanisms. They are effective in maintenance therapy of ulcerative colitis, and mild relapses of ulcerative colitis and colonic Crohn's disease. New preparations of 5-aminosalicylic acid have reduced side effects, many of which are due to sulphapyridine. Azathioprine and 6-mercaptopurine are used less widely: in Crohn's disease there is reasonable evidence for benefit in chronic active disease unresponsive to corticosteroids, and maintenance of remission. In ulcerative colitis, the position is less clearcut. Overall, trials favour an effect in chronic active disease, and there are pointers to an effect in maintenance of remission. Because of their side effects, in particular marrow suppression, these drugs should be reserved for second-line therapy. Similarly, other cytotoxic drugs are not used because of their side effects. More recently, cyclosporin A, with its selective action on interleukin-2 release and/or synthesis, and inhibition of helper T cell function, has been shown to be helpful in Crohn's disease. At present it should only be used in controlled trials, for patients with unresponsive disease in whom surgery is contraindicated. Renal toxicity may limit long term use. There is little data for cyclosporin A in ulcerative colitis. On the basis that there may be an underlying immune defect in Crohn's disease leading to mucosal inflammation, immunostimulant therapy has been used, but there is no evidence for benefit from treatment with BCG or levamisole in active disease or in maintenance therapy. 7S-Immunoglobulin, plasmapheresis or T-lymphocyte apheresis have been used in acute relapse, but evidence is anecdotal, and does not support their use except as a desperate measure to avoid surgery. Further well-designed controlled trials are needed to define the role of all these drugs, and further research into the mechanism of action on the immune response may shed light on the pathogenesis of inflammatory bowel disease.

A longitudinal study of the influence of azathioprine on natural killer cell activity

Natural killer (NK) cell activity against K562 target cells was studied in six patients with definite or classical rheumatoid arthritis before and during treatment with azathioprine. Azathioprine induced suppression of NK cell activity, but treatment with azathioprine for 5-8 months was necessary before NK cell activity was completely suppressed. In vitro incubation of mononuclear cells from a healthy donor with azathioprine or 6-mercaptopurine in concentrations not reducing cell viability did not inhibit NK cell activity, nor did sera from patients treated with azathioprine for more than 6 months.