Bile Acid Deficiency in a Subgroup of Patients With Irritable Bowel Syndrome With Constipation Based on Biomarkers in Serum and Fecal Samples

Safety and efficacy of elobixibat for chronic constipation: results from a randomised, double-blind, placebo-controlled, phase 3 trial and an open-label, single-arm, phase 3 trial

BACKGROUND

A subset of patients with constipation has reduced colonic bile acid concentrations, which are associated with slow colonic transit. In a previous study, elobixibat, a locally acting ileal bile acid transporter inhibitor, accelerated colonic transit in Japanese patients with functional constipation. In this study, we aimed to determine the efficacy of elobixibat for short-term treatment of chronic constipation, and safety, patient satisfaction, and quality of life with long-term treatment.

METHODS

We did two phase 3 studies of patients aged 20-80 years in Japan with at least 6 months of chronic constipation, who satisfied Rome III criteria for functional constipation, including fewer than three spontaneous bowel movements per week. The first trial, including patients enrolled at 16 clinics, was a 2-week, randomised, double-blind, placebo-controlled study in which (after a 2-week run-in period) patients were randomly assigned (1:1) to either elobixibat 10 mg/day for 2 weeks or placebo. Randomisation was done with permuted block method (block size six) without stratification. Masking to treatment allocation was achieved with identical appearances of elobixibat and placebo, which were supplied in sealed, opaque containers. Group assignment was concealed from patients, investigators, and analysts. The second trial, including patients enrolled at 34 clinics or hospitals, was an open-label, 1-year study in which all patients received elobixibat; participants could titrate the dose to 5 mg/day or 15 mg/day, or maintain the 10 mg/day dose. In both studies, participants took the study drug as an oral tablet once per day before breakfast. The primary outcome of the 2-week randomised trial was the change from baseline (ie, last week of the 2-week run-in) in the frequency of spontaneous bowel movements during week 1 of treatment. The primary outcome of the 52-week open-label trial was safety (type, severity, and incidence of adverse drug reactions) at all times from treatment initiation. All efficacy analyses were based on the modified intention-to-treat (ITT) population without imputation for any missing data. Safety analyses included all patients who received at least one dose of study drug. These trials are registered with the Japan Pharmaceutical Information Center (numbers JapicCTI-153061 and JapicCTI-153062) and have been completed.

FINDINGS

Between Nov 4, 2015, and June 11, 2016, we assigned 133 patients to treatment in the 2-week randomised trial: 70 to elobixibat (69 included in the modified ITT and safety populations) and 63 to placebo. The frequency of spontaneous bowel movements per week during week 1 of treatment was greater with elobixibat (least-squares mean 6·4, 95% CI 5·3-7·6) than with placebo (1·7, 1·2-2·2), p<0·0001). Between Oct 31, 2015, and March 15, 2017, we allocated 341 patients to 52 weeks of elobixibat (340 included in the modified ITT and safety populations). 163 (48%) patients in the 52-week trial had an adverse drug reaction, the most common of which were mild gastrointestinal disorders (in 135 [40%] patients). Inguinal hernia was reported in one patient with elobixibat in the 52-week study as a moderate adverse drug reaction. The most common adverse drug reactions in both trials were mild abdominal pain (13 [19%] patients with elobixibat and one [2%] with placebo in the 2-week randomised trial, and 82 [24%] patients in the 52-week trial) and diarrhoea (nine [13%] patients with elobixibat and none with placebo in the 2-week randomised trial and 50 [15%] in the 52-week trial).

INTERPRETATION

Elobixibat resolved constipation in the short-term, and was well tolerated with both short-term and long-term treatment. The evidence supports the use of this novel approach to increase intracolonic concentrations of endogenous bile acid for the treatment of chronic constipation.

FUNDING

EA Pharma and Mochida Pharmaceutical.

Update on Bile Acid Malabsorption: Finally Ready for Prime Time?

PURPOSE OF REVIEW

To provide an update on the prevalence, pathophysiology, disease associations, and treatment options for bile acid malabsorption (BAM).

RECENT FINDINGS

•Molecular mechanisms-BAs prevent water reabsorption and increase water secretion by intracellular mediators, increasing aquaporin channels and intracellular permeability. •Inflammatory bowel disease-new molecular mechanisms of BAM are identified in patients without ileal disease, including changes in expression of ileal BA transporter and nuclear receptors involved in BA homeostasis. •Microscopic colitis-BAM is one of the mechanisms leading to microscopic colitis. •Diagnostic testing-new diagnostic tests have been launched in the USA (serum C4 and fecal 48-h BA excretion); stimulated FGF19 has higher detection of BAM compared to fasting sample alone. •Treatment-investigational FXR agonists may provide a daily, oral option for treatment of BAM instead of BA sequestrants. There is a greater appreciation of the biological role of bile acids across multiple fields of medicine, including gastrointestinal indications.

Modulating bile acid pathways and TGR5 receptors for treating liver and GI diseases

Bile acids are central signals in enterohepatic communication and also integrate microbiota-derived signals into this signaling axis. Discovery of the tissue distribution and signaling pathways activated by the natural receptors for bile acids, farnesoid X receptor and G protein-coupled bile acid receptor 1 (GPBAR1) also known as TGR5, and bile acid transporters has led to the development of therapeutic agents that target these molecules. Obeticholic acid, a selective FXR agonist, and NGM282, a non-mitogenic FGF-19 analog, are two of the agents in this pipeline. Obeticholic acid has been approved by regulatory agencies for use in patients with primary biliary cholangitis.