Effect of EP4 agonist (ONO-4819CD) for patients with mild to moderate ulcerative colitis refractory to 5-aminosalicylates: A randomized phase II, placebo-controlled trial

To the Editor: Prostanoids constitute a group of cyclooxygenase (COX)-derived metabolites of arachidonic acid, and include prostaglandin (PG) D2, PGE2, PGF2α, PGI2, and thromboxane A2. They are synthesized in response to various physiological and pathophysiological stimuli and function to maintain local homeostasis in the body.1 PGE2 binds to either 1 of the 4 subtypes of PGE receptor, EP1–4. Among these receptors, EP4 is constitutively expressed in the colonic epithelium and its expression is increased during inflammatory bowel disease (IBD), accompanied by an increase in the amount of PGE2.2 We previously used knockout (−/−) mice deficient in each EP receptor subtype individually, and found that EP4−/− mice are most susceptible to dextran sulfate sodium (DSS)-induced colitis, and that administration of an EP4 agonist prevents DSS-induced colitis in the mouse through both regeneration of the intestinal epithelium and suppression of the immune response.3 Based on these findings, we proposed that an EP4 agonist could be used for the treatment of patients with IBD. In that there is no previous clinical trial examining the effects of EP4 agonists on patients with ulcerative colitis (UC), we designed a clinical trial to assess the efficacy of intravenous administration of an EP4 agonist, ONO-4819CD, on disease activity and peripheral cytokine phenotype in patients with mild to moderate UC. This study was a phase II, randomized, double-blind, placebo-controlled, multicenter trial that recruited patients from 3 centers (Kyoto University, Shiga University of Medical Science, and Osaka City University) in Japan. We defined eligible patients as those who were over the age of 20 years who were diagnosed as active UC by flexible endoscopic examination despite treatment with more than 4.5 g of salazosulfapyridine or more than 2.25 g of mesalazine for 2 or more consecutive weeks, and had symptoms of mild to moderate activity as determined by a Disease Activity Index (DAI) score of 3–9 at study entry as described by Sutherland et al.4 Exclusion criteria included Crohn's disease (CD), infectious or ischemic colitis. Patients were also excluded if they had severe UC requiring operation or fulminating disease, or had a history of malignancy, uncontrolled diabetes mellitus, or significant cardiac, pulmonary, hepatic, or renal diseases. The use of corticosteroids was not allowed within 2 weeks before enrollment and immunosuppressive medication for UC such as azathioprine, 6-mercaptopurine, methotrexate, tacrolimus, and cyclosporine were not allowed within 3 months before study entry. The study was approved by the institutional ethics committees at each site before patient enrollment and conducted according to the Good Clinical Practice Guidelines and the principles of the Declaration of Helsinki. We randomly assigned patients into either placebo or active drug group (ONO-4819CD) at a ratio of 1:1 by use of stratified block randomization. Patients assigned to active drug group received 2-week consecutive infusion of ONO-4819CD at a dose of 36 ng/kg body weight dissolved in physiological saline twice a day in combination with mesalamine or sulfasalazine, while those assigned to the placebo control group received infusion of the same volume of physiological saline alone. Eligible patients underwent a complete history taking and physical examination at the baseline study visit. The extent of UC was determined by colonoscopy. A flexible colonoscopy was performed at the baseline visit to confirm the presence of active disease. DAI score was calculated to confirm the presence of mild to moderate disease activity. Biopsy samples collected from the area representative of disease activity between 5 and 15 cm from the anal verge and histological findings were assessed by a central reference pathologist according to Matt's classification (1 = Matt's grade 1 through 5 = Matt's grade 5). We further performed intracellular cytokine assays for IL-10, IL-4, and IFN-γ on peripheral CD4 T cells before and after ONO-4819CD therapy by flow cytometry. The assessments were done at baseline and 2 weeks after treatment. The primary endpoint was clinical remission defined by a decrease in total DAI score of more than 3 points at 2 weeks after treatment. Secondary endpoints were changes in histological scoring according to Matt's grade, and peripheral cytokine phenotype of CD4 T cells. Safety was evaluated by adverse events and changes in plasma biochemistry and hematologic values. Planned sample size was 20 patients per arm, which will have 80% power to detect 50% improvement of response probability in ONO-4819CD group assuming response probability of 10% in the placebo group. All statistical analyses were performed using SAS v. 9.1 (SAS Institute, Cary, NC). Seven eligible patients were enrolled between February 2006 and March 2008 from 3 institutions. Although the planned sample size was 20 patients per arm, enrollment was finished at 7 patients. Four patients (4 male; mean age 39.7 ± 13.5; mean DAI 7.0 ± 2.0) received ONO-4819 CD and 3 (1 male, 2 female; mean age 54.4 ± 8.0; mean DAI 6.3 ± 1.5) had placebo. Four patients were afflicted with left-sided colitis and 2 patients had pancolitis. One patient had proctitis. Changes of DAI score are shown in Figure 1A. Three of 4 patients treated with ONO-4819CD showed a decrease of DAI score at 2 weeks. One of 3 responders to ONO-4819CD achieved clinical remission. On the other hand, 2 patients in the placebo group showed a decrease of DAI score but did not achieve clinical remission. Therefore, 1 of the patients treated with ONO-4819CD achieved clinical remission, whereas no patient in the placebo group showed remission. There was no statistically significant difference in changes of DAI score between the placebo and treatment groups. Histological score of biopsy specimen was decreased in all the patients treated with ONO-4819CD, while it did not change in patients receiving placebo (Fig. 1B). (A) Changes in DAI score in patients who received ONO-4819CD or placebo for 14 days. (B) Changes in histological score in patients who received ONO-4819CD or placebo for 14 days. Percentage of IL-10-producing cells of peripheral CD4 T cells was increased in 3 patients showing improvement of DAI score in ONO-4819CD group, while no increase was observed in patients treated with placebo. The Th1/Th2 ratio of peripheral CD4 T cells (as assessed by ratio of IFN-γ and IL-4-producing CD4 T cells) increased in 3 of 4 patients with ONO-4819CD, while this ratio decreased in patients treated with placebo. No serious adverse events were observed during this clinical study. The incidence of adverse events was similar among the groups (3 of 4 in ONO-4819CD group and 2 of 3 in placebo group). The adverse drug reaction observed in the ONO-4819CD group were neutropenia, elevated blood eosinophilis, headache, hot flashes, constipation, diarrhea, fever, and hypotension. All of these reactions were mild and transient. Here we report the first phase II, randomized, double-blind, placebo-controlled trial on the therapeutic effects of an EP4 agonist, ONO-4819CD, on patients with mild to moderate UC refractory to 5-ASA. In this study the decrease in DAI was observed in 3 of 4 patients treated with ONO-4819CD. One patient treated with ONO-4819CD achieved remission, while no patients on placebo achieved remission. Remarkably, although the number of patients is small, the improvement of histological scores was observed in all patients treated with ONO-4819CD. EP4 activation was shown to have both antiapoptotic action on intestinal epithelial cells and a stimulating effect on mucus secretion from Goblet cells.5 Thus, it appears reasonable to speculate that the histological improvement obtained by ONO-4819CD administration in our UC patients could be attributed to the enhanced mucosal defense through both antiapoptotic action on colonocytes and mucous secreting activity on Goblet cells of the EP4 agonist. Another possible mechanism for improvement of histological score may be modulation of cytokine balance by the EP4 agonist. Indeed, we previously reported that an EP4 agonist inhibited immune response in a mouse IBD model.2, 3 Moreover, in vitro study showed that PGE2 induces the production of IL-10 in bone marrow-derived dendritic cells.6 The present results showing that the percentage of IL-10-producing peripheral CD4 T cells was increased in all the patients treated by the EP4 agonist is well in accord with the previous studies. The pathophysiology of UC is associated with a Th2 cytokine phenotype. We reported that alteration of the Th1/Th2 ratio of peripheral CD4 T cells could be a biomarker of effectiveness of therapy for patients with UC and shifting toward a Th1-dominant cytokine profile reflected improvement of patients with UC.7 We found here that the increase of the Th1/Th2 ratio of peripheral CD4 T cells was observed in 3 of 4 patients treated with ONO-4819CD, while it was not observed in patients with placebo. Consistent with the elevation of the Th1/Th2 ratio observed in this trial, we recently found that EP4 stimulation can promote Th1 differentiation without an effect on Th2 cells.8 Thus, ONO-4819CD may improve colonic inflammation by not only an increase of IL-10-producing cells but also shifting toward a Th1 cytokine profile. In conclusion, although we could not obtain statistically significant therapeutic effects of an EP4 agonist, ONO-4819CD, in our UC patients, all the treated patients showed improvement of histological scores. This might suggest a clinical benefit of ONO-4819CD therapy for patients with mild to moderate UC. Because the number of patients was small in our study, further studies with a larger number of patients with UC would be required. The authors thank Tae Arai for secretarial work at the clinical trial office. This study was supported by a grant from the Program for Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation (NIBIO), Japan.