Recent advances in the development of new treatments for celiac disease

Addressing proteolytic efficiency in enzymatic degradation therapy for celiac disease

Celiac disease is triggered by partially digested gluten proteins. Enzyme therapies that complete protein digestion in vivo could support a gluten-free diet, but the barrier to completeness is high. Current options require enzyme amounts on the same order as the protein meal itself. In this study, we evaluated proteolytic components of the carnivorous pitcher plant (Nepenthes spp.) for use in this context. Remarkably low doses enhance gliadin solubilization rates, and degrade gliadin slurries within the pH and temporal constraints of human gastric digestion. Potencies in excess of 1200:1 (substrate-to-enzyme) are achieved. Digestion generates small peptides through nepenthesin and neprosin, the latter a novel enzyme defining a previously-unknown class of prolyl endoprotease. The digests also exhibit reduced TG2 conversion rates in the immunogenic regions of gliadin, providing a twin mechanism for evading T-cell recognition. When sensitized and dosed with enzyme-treated gliadin, NOD/DQ8 mice did not show intestinal inflammation, when compared to mice challenged with only pepsin-treated gliadin. The low enzyme load needed for effective digestion suggests that gluten detoxification can be achieved in a meal setting, using metered dosing based on meal size. We demonstrate this by showing efficient antigen processing at total substrate-to-enzyme ratios exceeding 12,000:1.

Randomised clinical study: Aspergillus niger-derived enzyme digests gluten in the stomach of healthy volunteers

BACKGROUND

Aspergillus niger prolyl endoprotease (AN-PEP) efficiently degrades gluten molecules into non-immunogenic peptides in vitro.

AIM

To assess the efficacy of AN-PEP on gluten degradation in a low and high calorie meal in healthy subjects.

METHODS

In this randomised, double-blind, placebo-controlled, cross-over study 12 healthy volunteers attended to four test days. A liquid low or high calorie meal (4 g gluten) with AN-PEP or placebo was administered into the stomach. Via a triple-lumen catheter gastric and duodenal aspirates were sampled, and polyethylene glycol (PEG)-3350 was continuously infused. Acetaminophen in the meals tracked gastric emptying time. Gastric and duodenal samples were used to calculate 240-min area under the curve (AUC0-240 min ) of ?-gliadin concentrations. Absolute ?-gliadin AUC0-240 min was calculated using duodenal PEG-3350 concentrations.

RESULTS

AN-PEP lowered α-gliadin concentration AUC0-240 min, compared to placebo, from low and high calorie meals in stomach (low: 35 vs. 389 μg × min/mL; high: 53 vs. 386 μg × min/mL; P < 0.001) and duodenum (low: 7 vs. 168 μg × min/mL; high: 4 vs. 32 μg × min/mL; P < 0.001) and absolute α-gliadin AUC0-240 min in the duodenum from low (2813 vs. 31 952 μg × min; P < 0.001) and high (2553 vs. 13 095 μg × min; P = 0.013) calorie meals. In the placebo group, the high compared to low calorie meal slowed gastric emptying and lowered the duodenal α-gliadin concentration AUC0-240 min (32 vs. 168 μg × min/mL; P = 0.001).

CONCLUSIONS

AN-PEP significantly enhanced gluten digestion in the stomach of healthy volunteers. Increasing caloric density prolonged gastric residence time of the meal. Since AN-PEP already degraded most gluten from low calorie meals, no incremental effect was observed by increasing meal caloric density. ClinicalTrials.gov, Number: NCT01335503; www.trialregister.nl, Number: NTR2780.

Celiac disease 2015 update: new therapies

Celiac disease (CD) is a chronic, small intestinal, immune-mediated enteropathy triggered by exposure to dietary gluten in genetically susceptible individuals. Currently, lifelong adherence to a gluten-free diet (GFD) is the only available treatment. However, GFD alone is not sufficient to relieve symptoms, control small intestinal inflammation and prevent long-term complications in many patients. The GFD has its challenges including issues related to adherence, lifestyle restrictions and cost. As a result, there is growing interest in and a need for non-dietary therapies to manage this condition. In recent years, different targets in the immune-mediated cascade of CD have been identified in clinical and pre-clinical trials for potential therapies. This review will discuss the latest non-dietary therapies in CD, including endopeptidases, modulators of enterocyte tight junctions and agents involved in gluten tolerization and immunomodulation. We will also discuss the potential implications of approved therapeutics on CD clinical practice.

Glutenase ALV003 attenuates gluten-induced mucosal injury in patients with celiac disease

BACKGROUND & AIMS

Gluten ingestion leads to small intestinal mucosal injury in patients with celiac disease, necessitating strict life-long exclusion of dietary gluten. Despite adherence to a gluten-free diet, many patients remain symptomatic and still have small intestinal inflammation. In this case, nondietary therapies are needed. We investigated the ability of ALV003, a mixture of 2 recombinant gluten-specific proteases given orally, to protect patients with celiac disease from gluten-induced mucosal injury in a phase 2 trial.

METHODS

We established the optimal daily dose of gluten to be used in a 6-week challenge study. Then, in the intervention study, adults with biopsy-proven celiac disease were randomly assigned to groups given ALV003 (n = 20) or placebo (n = 21) together with the daily gluten challenge. Duodenal biopsies were collected at baseline and after gluten challenge. The ratio of villus height to crypt depth and densities of intraepithelial lymphocytes were the primary end points.

RESULTS

A daily dose of 2 g gluten was selected for the intervention study. Sixteen patients given ALV003 and 18 given placebo were eligible for efficacy evaluation. Biopsies from subjects in the placebo group showed evidence of mucosal injury after gluten challenge (mean villus height to crypt depth ratio changed from 2.8 before challenge to 2.0 afterward; P = .0007; density of CD3(+) intraepithelial lymphocytes changed from 61 to 91 cells/mm after challenge; P = .0003). However, no significant mucosal deterioration was observed in biopsies from the ALV003 group. Between groups, morphologic changes and CD3(+) intraepithelial lymphocyte counts differed significantly from baseline to week 6 (P = .0133 and P = .0123, respectively). There were no statistically significant differences in symptoms between groups.

CONCLUSIONS

Based on a phase 2 trial, the glutenase ALV003 appears to attenuate gluten-induced small intestinal mucosal injury in patients with celiac disease in the context of an everyday gluten-free diet containing daily up to 2 g gluten. Clinicaltrial.gov,

NUMBERS

NCT00959114 and NCT01255696.

Current trends and investigative developments in celiac disease

Celiac disease has become extensively studied. What could be the cause? Increasing the accuracy of diagnostic tests for celiac disease has led to more discovered cases. Serological diagnosis of celiac disease has undergone important changes in recent years. Application of serological tests has reflected the diagnostic performance of tissue transglutaminase antibody and endomysial antibody as screening tests for celiac disease but also the progress of new serological tests as the antibodies against synthetic deamidated gliadin peptides. Serological tests are largely responsible for the recognition that celiac disease is not a rare disease. The Consensus in celiac disease from 2008 conducted under the aegis of the European Society of Pediatric Gastroenterology, Hepatology and Nutrition jointly with North American Society of Pediatric Gastroenterology, Hepatology and Nutrition which agreed that "Celiac disease is an immune-mediated enteropathy that can affect any system or organ and that can present itself with a wide range of clinical manifestations of variable severity" was confirmed. But increasing prevalence of this disease has led to the need for new methods of treatment among patients with celiac disease. Studies on quality of life of patients with celiac disease have questioned the gluten-free diet. As such new therapies, like TG2 inhibitors, the copolymer P (HEMA-co-SS) and other new experimental therapies, have emerged in celiac disease. The new therapies in celiac disease are based on new investigations in gluten toxicity screening, like K562(S)-cell agglutination, A1 and G12 monoclonal antibodies and proteomics. In this paper we want to present the investigative developments in celiac disease. We also want to find whether a new treatment in celiac disease is necessary.

Validation of morphometric analyses of small-intestinal biopsy readouts in celiac disease

Background

Assessment of the gluten-induced small-intestinal mucosal injury remains the cornerstone of celiac disease diagnosis. Usually the injury is evaluated using grouped classifications (e.g. Marsh groups), but this is often too imprecise and ignores minor but significant changes in the mucosa. Consequently, there is a need for validated continuous variables in everyday practice and in academic and pharmacological research.

Methods

We studied the performance of our standard operating procedure (SOP) on 93 selected biopsy specimens from adult celiac disease patients and non-celiac disease controls. The specimens, which comprised different grades of gluten-induced mucosal injury, were evaluated by morphometric measurements. Specimens with tangential cutting resulting from poorly oriented biopsies were included. Two accredited evaluators performed the measurements in blinded fashion. The intraobserver and interobserver variations for villus height and crypt depth ratio (VH:CrD) and densities of intraepithelial lymphocytes (IELs) were analyzed by the Bland-Altman method and intraclass correlation.

Results

Unevaluable biopsies according to our SOP were correctly identified. The intraobserver analysis of VH:CrD showed a mean difference of 0.087 with limits of agreement from −0.398 to 0.224; the standard deviation (SD) was 0.159. The mean difference in interobserver analysis was 0.070, limits of agreement −0.516 to 0.375, and SD 0.227. The intraclass correlation coefficient in intraobserver variation was 0.983 and that in interobserver variation 0.978. CD3⁺ IEL density countings in the paraffin-embedded and frozen biopsies showed SDs of 17.1% and 16.5%; the intraclass correlation coefficients were 0.961 and 0.956, respectively.

Conclusions

Using our SOP, quantitative, reliable and reproducible morphometric results can be obtained on duodenal biopsy specimens with different grades of gluten-induced injury. Clinically significant changes were defined according to the error margins (2SD) of the analyses in VH:CrD as 0.4 and in CD3⁺-stained IELs as 30%.