Are clinical trials different for Crohn's Disease vs Ulcerative Colitis?

Yes. While both are inflammatory bowel diseases and share some treatments, clinical trials differ significantly. Crohn's trials often focus on fistulising or stricturing complications and may test novel targeted therapies for small bowel involvement. Ulcerative Colitis trials more commonly study mucosal healing, colectomy prevention, and topical delivery methods. Trial eligibility criteria also differ based on disease location and behaviour.

Can I participate in an IBD trial if I'm not sure whether I have Crohn's or UC?

Most IBD clinical trials require a confirmed diagnosis of either Crohn's Disease or Ulcerative Colitis as part of their eligibility criteria. If your diagnosis is uncertain (sometimes called IBD-unclassified), there may be specific trials that include this population. Speak with your gastroenterologist about getting a definitive diagnosis, then use TrialConnect's Smart Matcher to find trials matching your specific condition.

Which IBD condition has more clinical trials available in the UK?

Both conditions have substantial trial availability in the UK. Crohn's Disease typically has slightly more trials due to its greater therapeutic complexity and unmet needs in fistulising and stricturing disease. However, Ulcerative Colitis has seen significant growth in trials recently, particularly in biologic and JAK inhibitor studies. Use TrialConnect to search both conditions and compare what's available near you.

IBD Comparison Updated 26 May 2026

Crohn's Disease vs Ulcerative Colitis — Clinical Trial Comparison

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Crohn's Disease

Transmural inflammation, any GI segment

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Ulcerative Colitis

Mucosal inflammation, colon only

Both Crohn's Disease and Ulcerative Colitis are types of Inflammatory Bowel Disease (IBD), but they differ in how they affect the digestive system, what treatments work best, and what clinical trials are available. If you're considering participating in a clinical trial, understanding these differences is essential for finding the right study.

Key Differences at a Glance

Feature	Crohn's Disease	Ulcerative Colitis
Area affected	Any part of GI tract (mouth to anus)	Colon and rectum only
Inflammation depth	Transmural (full thickness of bowel wall)	Mucosal (inner lining only)
Pattern	Patchy ("skip lesions")	Continuous from rectum
Common complications	Strictures, fistulas, perianal disease	Severe bleeding, toxic megacolon
Surgery potential	Not curative — disease can recur	Colectomy can be curative
Key biomarkers	CRP, faecal calprotectin, anti-TNF levels	CRP, faecal calprotectin

Clinical Trial Availability Comparison

Trial Aspect	Crohn's Disease	Ulcerative Colitis
UK trials actively recruiting	50–80 studies	40–65 studies
Most common trial phase	Phase 2–3	Phase 2–3
Top drug classes tested	Biologics, JAK inhibitors, antisense oligonucleotides	Biologics, JAK inhibitors, 5-ASA reformulations
Unique trial focus areas	Fistula healing, stricture management, fibrosis	Mucosal healing, colectomy prevention, topical delivery
Biomarker-driven trials	Common (CRP, calprotectin thresholds)	Common (CRP, calprotectin, endoscopic scores)
Paediatric trial availability	Moderate	Moderate

How Trial Eligibility Differs

Crohn's Disease Trial Criteria

Often classified by disease behaviour: inflammatory, stricturing, or fistulising (Montreal classification)
Many trials require a specific CDAI (Crohn's Disease Activity Index) score
Perianal fistula trials are a distinct subcategory with unique eligibility
Prior biologic failure is commonly required for later-line trials
Small bowel imaging (MRI or capsule endoscopy) often needed for confirmation

Ulcerative Colitis Trial Criteria

Classified by extent: proctitis, left-sided, or extensive/pancolitis
Mayo score or partial Mayo score commonly used for disease activity
Endoscopic evidence of active inflammation usually required at screening
Acute severe colitis has specific trial pathways (hospital-based)
Some trials exclude patients with prior colectomy

💡 Which trials might you be eligible for?

Some IBD trials accept both Crohn's and UC patients (especially biologic or JAK inhibitor studies), while others are disease-specific. Your exact diagnosis, disease location, prior treatments, and current disease activity all determine eligibility. Use our Smart Matcher to find trials tailored to your specific situation.

Treatment Approaches in Current Trials

Shared Treatment Classes

Both conditions see trials for similar drug classes, though the specific targets and endpoints may differ:

Anti-TNF biologics — adalimumab, infliximab, golimumab (UC only), certolizumab (Crohn's only)
Anti-integrin therapy — vedolizumab for both conditions
JAK inhibitors — tofacitinib, upadacitinib, filgotinib
IL-23 inhibitors — risankizumab, mirikizumab, guselkumab
TL1A inhibitors — emerging class in both conditions (e.g., tulisokibart)

Crohn's-Specific Trial Treatments

Antisense oligonucleotides targeting SMAD7 (e.g., mongersen)
Stem cell therapy for perianal fistulas
Anti-fibrotic agents for stricturing disease
Exclusive enteral nutrition (EEN) — mainly paediatric trials

Ulcerative Colitis-Specific Trial Treatments

Topical/rectal delivery formulations (foam, enema, suppository)
Combination oral + topical therapy optimisation
Colectomy-sparing approaches in acute severe colitis
Microbiome-based therapies (FMT — faecal microbiota transplant)

How to Decide Which Trials to Explore

If you have a confirmed diagnosis, the path is straightforward — search for your specific condition. If your diagnosis is classified as IBD-unclassified (IBDU), your gastroenterologist may need to clarify the diagnosis before you're eligible for most condition-specific trials.

Consider these factors when evaluating trials:

Disease severity: Mild disease may qualify for early intervention trials; severe disease may access refractory treatment studies
Treatment history: Biologic-naive patients have more trial options than biologic-experienced patients
Location: UK IBD trials are concentrated in major teaching hospitals — check if there's a site near you
Phase preference: Phase 3 trials are closest to market; Phase 2 may offer earlier access to novel mechanisms

🫄 Crohn's Disease Trials

Find actively recruiting Crohn's Disease clinical trials across the UK

View Crohn's Trials

🫄 Ulcerative Colitis Trials

Find actively recruiting Ulcerative Colitis clinical trials across the UK

View UC Trials

Not sure which condition applies to you?

Use our Smart Matcher to describe your situation and find relevant trials regardless of whether you search Crohn's, UC, or general IBD.

Open Smart Matcher