By: Natalia Jucha, PharmD Candidate c/o 2022 and Helen Li, PharmD Candidate c/o 2023
Celiac disease is classified as an autoimmune disorder and occurs in individuals who cannot tolerate gluten. Dietary gluten induces an immune response and causes damage to the small intestine, particularly the duodenum and proximal jejunum. A small peptide called gliadin, present in wheat and several other cereals, is responsible for the pathogenesis of celiac disease. It is resistant to degradation by gastric pepsin and proteases in the small intestine.2 Currently, there are no treatment options available for patients with celiac disease other than dietary restrictions.
Gliadin causes the disassembling of inter-enterocyte tight junctions, which are structures between cells that regulate the permeability of ions, macromolecules, and cells. Disassembling of tight junctions causes upregulation of zonulin, a peptide that is involved in tight-junction (TJ) regulation and that is responsible for gut permeability.2 The upregulation of zonulin causes an increase in gut permeability which allows for gliadin to enter the lamina propria where it activates T-lymphocytes. The CD4+ cells produce inflammatory cytokines which can induce different inflammatory responses. Gliadin peptides can also activate CD8+ T-lymphocytes by interleukin (IL)-15. The increased density of CD8+ cells is the distinguishing factor of celiac disease as extensive infiltration of epithelium by CD8+ cells is associated with intestinal lesions of the villous surface.2
Tranglutaminase-2 is a celiac autoantigen in the intestinal mucosa. It modifies gluten peptides through deamidation; the removal of an amino group from a compound. This then allows for the presentation of these gluten-peptides by HLA-DQ2 and HLA-DQ8, two genetic markers which, when present, result in an increased risk for developing celiac disease. The gluten-peptide then induces CD4+ T helper cells, which cause activation of proinflammatory cytokines.1 This inflammatory response causes villous atrophy and crypt hyperplasia and causes the production of transglutaminase-2 immunoglobulin A (IgA); a marker of celiac disease.
Currently, there are no treatment options available on the market and individuals must adjust their lifestyles to a “gluten-free” diet to prevent further damage. Based on the pathophysiology of celiac disease, transglutaminase-2 inhibitors could be a potentially helpful treatment option. A randomized, double-blind, multicenter, and placebo-controlled trial, aimed to determine the utility of a transglutaminase-2 inhibitor as a plausible treatment option. The primary endpoint of the study was the attenuation of gluten-induced deterioration of intestinal mucosal morphologic features. The intestinal mucosal morphologic feature was measured by the ratio of villus height to crypt depth in duodenal biopsy samples. The secondary endpoint assessed the changes from baseline to week 6 by measuring the density of CD3+ intraepithelial lymphocytes, and the modified Marsh-Oberhuber classification, which is the accepted scale for determining celiac disease severity.3
Individuals enrolled were asked to undergo a screening period that lasted 8 weeks. Within 4 weeks of screening, an upper gastrointestinal (GI) endoscopy with duodenal biopsies was performed before the administration of the first dose in order to provide histological data. The sample population included adults aged 18 to 65 years old who had received a biopsy- confirmed diagnosis of celiac disease 12 months prior to screening, who were HLA-DQ2 or HLA-DQ8 positive, who adhered to a strict gluten-free diet for at least 12 months, who presented with negative serologic testing for transglutaminase-2 antibodies, and who had a mean villus height to crypt depth ratio greater than 1.5. Overall, it was intended for 163 patients to undergo randomization, however four patients were excluded. Out of the 159 patients who underwent randomization, 17 patients were excluded from analysis pertaining to the effect of study drug treatment on the ratio of villus height to crypt depth. Sixteen patients were excluded because they did not undergo final endoscopy, while an additional patient was excluded because one of the samples obtained was not adequate for analysis.4
The trial was conducted at 20 sites in 7 different countries from May 16, 2018 to February 27, 2020.4 Prior to taking the transglutaminase-2 inhibitor, each patient had at least 6 hours of fasting. The patients took either 10 mg, 50 mg, or 100 mg of ZED1227, the investigational medication, or a placebo. After 30 minutes, the patients ate a sponsor-provided biscuit containing 3 grams of gluten. For 6 weeks, patients were asked to continue their strict gluten-free diet, aside from the biscuit. Patients presented at week 0 to receive their drug or placebo, along with their sponsor-provided biscuit. Patients returned at week 2, 4, and 6 for assessments and at week 10 for a follow-up visit. A second endoscopy with biopsies was performed at week 6 or at the withdrawal visit. Patients kept a diary to record their daily use of ZED1227 or placebo, biscuit, food intake, other medications, and stool frequency/characteristics.4
Results show that the trial maintained 80% power as there were at least 34 patients in each assigned group. There were 35 patients in the 10 mg group, 39 patients in the 50 mg group, 38 patients in the 100 mg group, and 30 patients in the placebo group. For 10 mg, the ratio of villus height to crypt depth decreased to 1.85 from a baseline of 2.01 with a 95% confidence interval (CI) of –0.33 to –0.01. For 50 mg, the ratio decreased to 1.91 from a baseline of 2.04 with a 95% CI of –0.27 to 0.03. For 100 mg, the ratio decreased to 1.94 from a baseline 2.09 with a 95% CI of –0.28 to 0.03. For the placebo, the ratio decreased to 1.39 from a baseline of 1.98 with a 95% CI of −0.78 to −0.44. All four group’s ratio of villus height to crypt depth displayed decreases from baseline after 6 week treatment. However, only the 10 mg and placebo group showed a statistically significant decline, as the confidence intervals for the 50 mg and 100 mg group crossed zero (0).4
For 10 mg, the estimated difference in the ratio of villus height to crypt depth versus placebo at week 6 was 0.44, with a 95% CI of 0.15 to 0.73 (p=0.01). For 50 mg, the difference was 0.49 with a 95% CI of 0.20 to 0.77 (p=0.001). For 100 mg, the difference was 0.48 with a 95% CI of 0.20 to 0.77 (p<0.001). These values all showed statistical significance. The differences from placebo in the change in intraepithelial lymphocyte density were −2.7 cells per 100 epithelial cells with a 95% CI of −7.6 to 2.2 in the 10 mg group, −4.2 cells per 100 epithelial cells with a 95% CI of−8.9 to 0.6 in the 50 mg group and −9.6 cells per 100 epithelial cells with a 95% CI of −14.4 to −4.8 in the 100 mg group.4 Although the data meets statistical significance in terms of the study’s adjusted p-value, the confidence intervals for the 10 an 50 mg groups crossed 0, showing that there could be potentially no difference between those groups and placebo regarding change in intraepithelial lymphocyte density.
There were limitations in this study. One of the limitations of this study is that patients were followed for a short duration of six weeks which one could argue is not enough time to assess the long term effects of the treatment. Of note, the drug manufacturing company responsible for producing ZED1227 was responsible for conducting and overseeing this study, resulting in potential bias due to sponsorship. In the demographic characteristics of the patients, 100% were white and about 80% were women. Unfortunately, the study did not include a racially/ethnically diverse population of subjects. Additionally, after week 6, there was damage present in all 4 assigned groups as there were decreases in the ratio of villus height to crypt depth.
Transglutaminase-2 inhibitors such as ZED1227 can be a potential avenue for manufacturing companies to explore for the treatment of celiac disease; however, trials would have to be longer, larger, and more diverse to truly determine statistical and clinical significance. In the meantime, it is important that pharmacists continue to encourage patients to implement the current lifestyle modification recommendations as more research surfaces.
References:
- Caio G, Volta U, Sapone A, et al. Celiac disease: a comprehensive current review. BioMed Central. 2019;17(1):142. https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-019-1380-z. Accessed August 8,2021.
- Gianfrani C, Troncone R, Mugione P, et al. Celiac Disease Association with CD8+ T Cell Responses: Identification of a Novel Gliadin-Derived HLA-A2-Restricted Epitope. The Journal of Immunology. 2003; 170(5):2719–2726. https://doi.org/10.4049/jimmunol.170.5.2719. Accessed August 8,2021.
- Rouse R. Celiac Disease. Standford Medicine Surgical Pathologic Criteria. https://surgpathcriteria.stanford.edu/gi/celiac-disease/. Published November 11, 2009, Updated December 3, 2014 and Accessed August 8,2021.
- Schuppan D, Mäki M, Lundin KEA, et al. A Randomized Trial of a Transglutaminase 2 Inhibitor for Celiac Disease. NEJM. 2021;385(1):35-45. doi:10.1056/NEJMoa2032441 Accessed August 8,2021.
