Gastroenterology · Clinical trials
Chronic Constipation Clinical Trials
Approved therapies, the pivotal-trial endpoints they were judged on, the magnitude of benefit — and the drugs that failed their endpoints, and why.
Indication overview
About chronic constipation — and why its trials are hard
Chronic idiopathic constipation (CIC) and constipation-predominant irritable bowel syndrome (IBS-C) are common functional GI disorders defined by infrequent, hard, or difficult-to-pass stools, often with bloating and abdominal discomfort. First-line management uses fiber, osmotic laxatives (polyethylene glycol), and stimulant laxatives. When these fail, prescription secretagogues and prokinetics are used. The guanylate cyclase-C agonists linaclotide and plecanatide and the chloride-channel activator lubiprostone increase intestinal fluid secretion and transit; the 5-HT4 agonist prucalopride enhances colonic motility; and the gut-restricted NHE3 inhibitor tenapanor (approved for IBS-C) reduces sodium and phosphate absorption to increase luminal water. Regulatory endpoints center on complete spontaneous bowel movement (CSBM) responder rates over 12 weeks, and for IBS-C a combined abdominal-pain-plus-CSBM responder. Safety and tolerability, especially diarrhea, drive discontinuation. The therapeutic history also includes cautionary tales: the 5-HT4 agonist tegaserod was withdrawn in 2007 over cardiovascular safety concerns before a limited 2019 reintroduction, illustrating how tolerability and cardiovascular signals shape this class.
Approved therapies & pivotal evidence
What's been approved — and by how much it moved the endpoint
| Drug (brand) | Approved | Setting | Pivotal trial | Primary endpoint | Magnitude of benefit |
|---|---|---|---|---|---|
| Linaclotide (Linzess) | 2012 | CIC and IBS-C; guanylate cyclase-C agonist | Phase 3 CIC trials (Lembo et al., NEJM 2011) | 12-week CSBM responder (>=3 CSBMs/week and increase >=1 from baseline) | ~16-21% responders vs ~3-6% placebo |
| Plecanatide (Trulance) | 2017 | CIC (IBS-C added 2018); guanylate cyclase-C agonist | Phase 3 CIC trials (DeMicco et al.) | Durable overall CSBM responder over 12 weeks | ~20-21% vs ~10-13% placebo |
| Lubiprostone (Amitiza) | 2006 | CIC (IBS-C in women 2008; OIC 2013); ClC-2 chloride-channel activator | Phase 3 CIC trials | Spontaneous bowel movement (SBM) frequency, week 1 and over treatment | Significant increase in SBMs vs placebo (nausea a common adverse effect) |
| Prucalopride (Motegrity) | 2018 | CIC; selective 5-HT4 receptor agonist (earlier EU approval as Resolor) | Phase 3 CIC trials (e.g., Camilleri et al., NEJM 2008) | Average >=3 CSBMs/week over 12 weeks | ~19-28% vs ~10-13% placebo |
| Tenapanor (Ibsrela) | 2019 | IBS-C; gut-restricted NHE3 inhibitor | T3MPO-1 and T3MPO-2 | Combined responder (>=30% abdominal pain reduction plus >=1 CSBM increase) for >=6 of 12 weeks | ~27% vs ~19% placebo (T3MPO-1) |
Where trials have failed
Drugs that missed their endpoint — and what contributed
The most instructive lessons in chronic constipation development come from programmes that failed the endpoint that mattered.
| Drug / trial | Endpoint outcome | What contributed |
|---|---|---|
| Tegaserod — Post-marketing cardiovascular safety analysis (originally approved 2002) | Withdrawn from US market in 2007 after an imbalance of cardiovascular ischemic events (MI, stroke, unstable angina) | Rare but serious cardiovascular signal in a largely young female population; later reintroduced in 2019 for IBS-C in women under 65 without cardiovascular risk factors |
| Renzapride — Phase 3 IBS-C program (5-HT4 agonist/5-HT3 antagonist) | Failed to demonstrate clinically meaningful benefit over placebo on core symptom endpoints; development discontinued | Insufficient efficacy separation and a crowded class made further development unattractive (magnitude details unverified) |
Choosing the right endpoint
Primary endpoints that matter in chronic constipation trials
- CSBM responder rate — Complete spontaneous bowel movement responder over 12 weeks is the primary regulatory endpoint for CIC.
- Combined responder (IBS-C) — FDA composite requiring both abdominal pain improvement and CSBM increase for a defined proportion of weeks.
- Spontaneous bowel movement (SBM) frequency — Change in SBMs per week, used for lubiprostone and supportive analyses.
- Abdominal pain/bloating scores — Patient-reported symptom severity, key for IBS-C where pain is definitional.
How iNGENū runs chronic constipation trials
Physician-led design, built for FDA submission
Endpoint & biomarker strategy
Board-certified specialists design endpoints and patient selection aligned to current FDA guidance for this indication.
FDA-ready data
Built to ICH-GCP and 21 CFR 312.120, with direct FDA submission — data accepted by the FDA, EMA and MHRA.
Faster, lower-cost delivery
~4-week ethics via the TGA CTN scheme, up to 43.5% R&D rebate, and 80–90% below US CRO cost.
Request a fixed-milestone proposal and a tailored endpoint & feasibility summary for this indication.
Frequently asked questions
Chronic Constipation clinical trials — FAQs
How is CIC different from IBS-C?
What is the most common side effect of the secretagogues?
Why was tegaserod withdrawn and then reintroduced?
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