Elobixibat

Overview

Elobixibat (also known as A3309) is a minimally absorbed ileal bile acid transporter (IBAT) inhibitor used to treat chronic idiopathic constipation (CIC) and constipation-predominant irritable bowel syndrome (IBS-C). It is approved in Japan and has been investigated in multiple global RCTs.

Mechanism of Action

The terminal ileum normally reabsorbs ~95% of intestinal bile acids via the apical sodium-dependent bile acid transporter (ASBT/IBAT). Elobixibat selectively inhibits this transporter, thereby:

Blocking ileal bile acid reabsorption → increased bile acid delivery to the colon
Stimulating colonic secretion (fluid and electrolytes) and enhancing colonic motility
Reducing colonic transit time → more frequent, softer stools

Because the drug is minimally absorbed systemically, its action is predominantly local in the gut lumen.

Clinical Efficacy

Chronic Constipation (CIC):

A Phase 2 RCT (n=190, 8 weeks) comparing 5 mg, 10 mg, and 15 mg once daily vs. placebo showed dose-dependent increases in spontaneous bowel movements (SBM) in week 1:
- 5 mg → +2.5 SBM/week
- 10 mg → +4.0 SBM/week
- 15 mg → +5.4 SBM/week
- Placebo → +1.7 SBM/week
Improvements were maintained over 8 weeks
Also improved abdominal bloating and straining
Improved stool transit, consistency, and ease of passage

IBS-C: Studies demonstrated improved stool transit, consistency, and ease of passage, though abdominal cramping was noted.

Special populations:

A 2024 RCT (CONST-PD study; PMID 38264844) evaluated elobixibat in Parkinson's disease patients with chronic constipation and found efficacy and acceptable safety.
A 2025 multicenter Phase III RCT from India (PMID 39985701) confirmed efficacy and safety.

Comparative Profile

A 2024 systematic review and meta-analysis (Rao et al., PMID 38166671) compared elobixibat with lubiprostone and linaclotide:

All three showed similar efficacy in increasing SBM (number needed to treat analysis)
Distinct safety profiles:
- Lubiprostone → highest risk of nausea
- Linaclotide → highest risk of diarrhea
- Elobixibat → highest risk of abdominal pain

Dosing

10 mg once daily, taken before breakfast (approved dose in Japan)
Available doses studied: 5 mg, 10 mg, 15 mg

Adverse Effects

Abdominal pain/cramping (most characteristic)
Diarrhea
Abdominal bloating

These are mechanistically predictable — excess bile acids in the colon stimulate motility and can cause cramping.

Key Differentiating Features

Feature	Elobixibat
Drug class	IBAT inhibitor
Route	Oral
Absorption	Minimally systemic
Primary site of action	Terminal ileum
Approval	Japan (chronic constipation)
Mechanism class	Bile acid modulation

Sources

Sleisenger and Fordtran's Gastrointestinal and Liver Disease — Elobixibat section
Yamada's Textbook of Gastroenterology, 7th ed. — Bile acid modulation & Agents targeting bile acid processing
Rao SS et al. BMC Gastroenterol 2024 [PMID 38166671] — Systematic review/meta-analysis vs. lubiprostone & linaclotide

This is a shared conversation. Sign in to Orris to start your own chat.