Future treatment strategies for celiac disease

Potential therapeutic options for celiac Disease: An update on Current evidence from Gluten-Free diet to cell therapy

Celiac disease (CD) is a chronic autoimmune enteropathy and multifactorial disease caused by inappropriate immune responses to gluten in the small intestine. Weight loss, anemia, osteoporosis, arthritis, and hepatitis are among the extraintestinal manifestations of active CD. Currently, a strict lifelong gluten-free diet (GFD) is the only safe, effective, and available treatment. Despite the social burden, high expenses, and challenges of following a GFD, 2 to 5 percent of patients do not demonstrate clinical or pathophysiological improvement. Therefore, we need novel and alternative therapeutic approaches for patients. Innovative approaches encompass a broad spectrum of strategies, including enzymatic degradation of gluten, inhibition of intestinal permeability, modulation of the immune response, inhibition of the transglutaminase 2 (TG2) enzyme, blocking antigen presentation by HLA-DQ2/8, and induction of tolerance. Hence, this review is focused on comprehensive therapeutic strategies ranging from dietary approaches to novel methods such as antigen-based immunotherapy, cell and gene therapy, and the usage of nanoparticles for CD treatment.

Quality of life in coeliac disease: item reduction, scale development and psychometric evaluation of the Coeliac Disease Assessment Questionnaire (CDAQ)

BACKGROUND

A better understanding of coeliac disease can be achieved by assessing health-related quality of life alongside clinical factors. Existing patient-reported outcome measures (PROMs) evaluating quality of life in coeliac disease have not been developed in accordance with the US Food and Drug Administration guidelines.

AIM

To develop a PROM in accordance with best practice guidelines, capturing all aspects of quality of life important to adults with coeliac disease.

METHODS

Candidate items for the Coeliac Disease Assessment Questionnaire (CDAQ) were refined through item appraisal, expert review, cognitive interviews, and a translatability assessment. A cross-sectional survey determined further item reduction and the CDAQ's structure. The final CDAQ was administered alongside the Short Form Health Survey Version 2 (SF?36v2) in a second survey to assess construct validity and test-retest reliability.

RESULTS

Pre-testing the 64 candidate items revealed a range of issues which guided their refinement and reduction, resulting in the final CDAQ with 32 items representing 5 subscales: stigma (eight items), dietary burden (eight items), symptoms (five items), social isolation (five items), and worries and concerns (six items). Cronbach's alpha ranged between 0.82 and 0.88 for all domains. Further results showed CDAQ scores were more strongly correlated with the SF-36v2's mental health dimensions, as expected. Intraclass correlation coefficients ranged from 0.79 to 0.89.

CONCLUSION

The CDAQ is a reliable and valid coeliac-specific measure that captures all aspects of quality of life important to adults with coeliac disease. Further work is underway to assess the CDAQ's responsiveness to change.

Quality of life in coeliac disease: qualitative interviews to develop candidate items for the Coeliac Disease Assessment Questionnaire

Background

Coeliac-specific measures have been criticized for not complying with current guidance on the development of patient-reported outcome measures (PROMs). The aim of this study was to develop a measure to assess health-related quality of life in adults with coeliac disease (CD), in accordance with current guidance for PROM development.

Methods

In-depth qualitative interviews were conducted with adults with CD. A thematic analysis was undertaken to develop a coding framework. All interviews were analyzed according to this framework. Interviewing continued until data saturation was achieved. Candidate items were developed on the basis of the interview findings.

Results

The analysis revealed 6 themes: 1) symptoms, 2) gluten-free diet, 3) emotional health, 4) impact on activities, 5) relationships, and 6) financial issues. Data saturation was reached after 8 interviews, but a total of 23 interviews were conducted to include a wide enough range of diverse participants. From the themes, 64 candidate items (9 for symptoms, 15 for emotional health, 16 for gluten-free diet, 7 for relationships, 12 for impact on activities, and 5 for financial issues) were developed to form the first draft of the Coeliac Disease Assessment Questionnaire (CDAQ).

Conclusion

The 64 items reflect all the issues of importance to people with CD. Next, these items will be pretested and refined to lead to a shorter draft version of the CDAQ before it is administered in a survey to produce a final version with subscales.

Transglutaminase 2 in human diseases

Transglutaminase 2 (TG2) is an inducible transamidating acyltransferase that catalyzes Ca(2+)-dependent protein modifications. In addition to being an enzyme, TG2 also serves as a G protein for several seven transmembrane receptors and acts as a co-receptor for integrin β1 and β3 integrins distinguishing it from other members of the transglutaminase family. TG2 is ubiquitously expressed in almost all cell types and all cell compartments, and is also present on the cell surface and gets secreted to the extracellular matrix via non-classical mechanisms. TG2 has been associated with various human diseases including inflammation, cancer, fibrosis, cardiovascular disease, neurodegenerative diseases, celiac disease in which it plays either a protective role, or contributes to the pathogenesis. Thus modulating the biological activities of TG2 in these diseases will have a therapeutic value.

Current status of drugs in development for celiac disease

INTRODUCTION

Gluten is the main trigger for celiac disease, and the current treatment is based on its elimination from the diet. Although the symptoms usually disappear during the diet, it is restrictive and difficult to maintain. Further, despite a strict treatment the small-bowel mucosal damage does now always heal. Consequently, adherence is often poor and new treatment approaches are needed. With an increased understanding of the disease pathogenesis, several novel treatments have been suggested, and some of them have already entered Phase II clinical trials.

AREAS COVERED

This article reviews the latest status of the drugs in development for celiac disease. The article focuses mainly on synthetic drugs currently entering in clinical trials.

EXPERT OPINION

It is anticipated that some of the treatments under investigation will soon enter Phase III clinical trials, although challenges remain. For instance, histological studies are problematic in wide-scale clinical studies. On the other hand, the existing non-invasive serological methods and clinical outcome measures might be too insensitive for monitoring responses to the possible drug candidates. There is also no animal model which would accurately reflect celiac disease. Well-conducted basic and clinical research is required to develop better non-invasive surrogate markers and patient-related outcomes for future pharmacological studies.

Non-dietary forms of treatment for adult celiac disease

At present, treatment for celiac disease includes a strict gluten-free diet. Compliance, however, is difficult and gluten-free food products are costly, and, sometimes very inconvenient. A number of potential alternative measures have been proposed to either replace or supplement gluten-free diet therapy. In the past, non-dietary forms of treatment were used (e.g., corticosteroids) by some clinicians, often to supplement a gluten-free diet in patients that appeared to be poorly responsive to a gluten-free diet. Some of new and novel non-dietary measures have already advanced to a clinical trial phase. There are still some difficulties even if initial studies suggest a particularly exciting and novel form of non-dietary treatment. In particular, precise monitoring of the response to these agents will become critical. Symptom or laboratory improvement may be important, but it will be critical to ensure that ongoing inflammatory change and mucosal injury are not present. Therapeutic trials will be made more difficult because there is already an effective treatment regimen.

CYP3A4-catalyzed simvastatin metabolism as a non-invasive marker of small intestinal health in celiac disease

OBJECTIVES

Histological examination of duodenal biopsies is the gold standard for assessing intestinal damage in celiac disease (CD). A noninvasive marker of disease status is necessary, because obtaining duodenal biopsies is invasive and not suitable for routine monitoring of CD patients. As the small intestine is a major site of cytochrome P450 3A4 (CYP3A4) activity and also the location of the celiac lesion, we investigated whether patients with active CD display abnormal pharmacokinetics of an orally administered CYP3A4 substrate, simvastatin (SV), which could potentially be used for noninvasive assessment of their small intestinal health.

METHODS

Preclinical experiments were performed in CYP3A4-humanized mice to examine the feasibility of the test. Subsequently, a clinical trial was undertaken with 11 healthy volunteers, 18 newly diagnosed patients with CD, and 25 celiac patients who had followed a gluten-free diet (GFD) for more than 1 year. The maximum concentration (Cmax) of orally administered SV plus its major non-CYP3A4-derived metabolite SV acid (SV equivalent (SVeq)) was measured, and compared with clinical, histological, and serological parameters.

RESULTS

In CYP3A4-humanized mice, a marked decrease in SV metabolism was observed in response to enteropathy. In the clinical setting, untreated celiac patients displayed a significantly higher SVeq Cmax (46±24 nM) compared with treated patients (21±16 nM, P<0.001) or healthy subjects (19±11 nM, P<0.005). SVeq Cmax correctly predicted the diagnosis in 16/18 untreated celiac patients, and also the recovery status of all follow-up patients that exhibited normal or near-normal biopsies (Marsh 0-2). All patients with abnormal SVeq Cmax showed a reduction in the value after 1 year of following a GFD.

CONCLUSIONS

SVeq Cmax is a promising noninvasive marker for assessment of small intestinal health. Further studies are warranted to establish its clinical utility for assessing gut status of patients with CD.

Protein kinase C delta is a substrate of tissue transglutaminase and a novel autoantigen in coeliac disease

Post-translational modification of proteins by deamidation or transamidation by tissue transglutaminase (tTG) has been suggested as a possible mechanism for the development of autoimmunity. Sequence analysis of protein kinase C delta (PKCδ) identified an amino acid motif that suggested the possibility that PKCδ was a glutamine substrate of tTG and MALDI-TOF analysis of synthesised peptides from PKCδ proved that this was the case. Polymerisation experiments using recombinant tTG and biotinylated hexapeptide substrate incorporation assays demonstrated that PKCδ is a substrate for tTG-mediated transamidation. Elevated levels of anti-PKCδ antibodies were detected in sera from patients with coeliac disease (p<0.0001) but not from patients with other autoimmune disorders. These data suggest that a subset of patients with coeliac disease produce autoantibodies against PKCδ and that this response may stem from a tTG-PKCδ substrate interaction.