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FACTORS INFLUENCING PLACEBO RATES IN RANDOMIZED CONTROLLED TRIALS IN INFLAMMATORY BOWEL DISEASES: AN UMBRELLA REVIEW

Marianne Hupé 1,2, Yuhong Yuan 1,3, Vipul Jairath 1,4

Affiliations

1 University of Western Ontario, London, Canada

2 Grenoble University Hospital, Grenoble, France

3 London Health Science Centre, Ancaster, Canada

4 London Health Sciences Centre Research Institute, London, Canada

Summary

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This summary was generated by an AI large language model based on the content transcript. It is for informational purposes only and should not be considered a substitute for clinical judgment. Always rely on your professional expertise and the full clinical context when making clinical decisions.

Abstract

Introduction

There have been some anomalously high placebo rates in recent clinical trials for inflammatory bowel diseases (IBD). Thus, we conducted an umbrella review to summarize the best available evidence for factors which influence placebo rates to help inform trial design.

Aims & Methods

A systematic search was conducted on October 29, 2025 in MEDLINE, Embase, and the Cochrane CDSR to identify systematic reviews with meta-analysis focused on factors associated with placebo response and remission rates in placebo-controlled RCTs in IBD. Outcomes were clinical, endoscopic and histological response and remission for induction and maintenance phases. For each outcome, placebo rates, predictors of placebo outcomes and their effect estimates were extracted.

Results

Eighteen reviews between 2004-2025 were eligible. Pooled placebo rates and significant predictors of placebo outcomes varied widely across reviews. Some factors reflecting higher baseline disease activity were consistently associated with lower placebo rates. We identified predictors related to outcome measure: definition of outcomes, but also timing of measurement (earlier timepoint in induction yielding lower placebo rates) and with central endoscopy reading (consistently associated with lower placebo rates). Placebo rates increased with treatment route in the following order: oral, topical, subcutaneous and intravenous. Some consistent factors were related to trial design and location: longer maintenance phases, asymmetrical randomization, studies conducted outside of North America or with fewer sites consistently having higher placebo rates. The Table contains a summary of findings.

Table: factors associated with changes in response and remission rates on placebo in clinical trials in inflammatory bowel diseases.
Cells colored in blue indicate factors associated with a lower placebo effect. Cells colored in green indicate factors associated with a higher placebo effect.

Area concerned	Factors evaluated	Influence on placebo
Population characteristics at baseline	Disease severity, biologic exposure, Mayo endoscopic subscore, albumin, CRP (CD), extensive disease (UC), disease activity scores, age at diagnosis	Markers of higher severy associated with lower placebo rates
Endpoint	Subjective endpoints	Higher number of factors influencing placebo
	Definition of clinical response (CDAI decrease by ≥ 100 vs. ≥ 70-points from baseline)	Lower placebo rates
	Earlier outcome measure in induction	Lower placebo rates
	Central reading	Lower placebo rates
Design	Short duration of induction, longer duration of maintenance	Lower placebo rates
Design	Asymmetrical randomization (clinical remission, CD)	Higher placebo rates
Location	Northern America	Lower placebo rates
Location	Higher number of centers	Lower placebo rates

Conclusion

We identified several factors which consistently influence placebo rates across multiple clinical trials. Implementation of these into trial design may lower placebo rates.

Disclosure

Marianne Hupé: consulting/advisory board/lecture fees from Takeda, Pfizer, Johnson&Johnson, Lilly. Speaker fees from Abbvie, Pfizer, Lilly.
Yuhong Yuan declares no conflict of interest.
Vipul Jairath: Consulting/advisory board fees from AbbVie, Alimentiv Inc, Arena pharmaceuticals, Asahi Kasei Pharma, Asieris, Astra Zeneca, Bristol Myers Squibb, Celltrion, Eli Lilly,
Ferring, Flagship Pioneering, Fresenius Kabi, Galapagos, GlaxoSmithKline, Genentech, Gilead, Janssen, Merck, Mylan, Pandion, Pendopharm, Pfizer, Protagonist, Prometheus,
Reistone Biopharma, Roche, Sandoz, Second Genome,Takeda, Teva, Topivert, Ventyx, Vividion; speaker’s fees from, Abbvie, Ferring, Galapagos, Janssen Pfizer Shire,
Takeda, Fresenius Kabi.

Conference

UEG Week Barcelona 2026

Topics

IBD

Submission format

Abstract

Session

IBD (INCLUDING MICROSCOPIC COLITIS) (Posters)

Citation

2026: United European Gastroenterology Journal 2026; 14 (S1)

Published

2026

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Timepoint	Q1 2018	Q3 2020	Q1 2023
Surveyed gastroenterologists	207	211	220
Reported UC patients	816	844	880

		Multimodal	RS Plasma	RS Tissue	Metabolites
Epithelial barrier impairment	AUC % (95% CI)	84 (76 - 90)	59 (49 - 76)	65 (54 - 74)	59 (48 - 65)
	F1 score % (95% CI)	82 (78 - 86)	73 (69 - 76)	66 (54 - 74)	73 (67 - 78)
	Accuracy % (95% CI)	77 (70 - 82)	63 (61 - 66)	60 (48 - 67)	59 (51 - 66)
Vascular barrier impairment	AUC % (95% CI)	80 (74 - 90)	55 (44 - 65)	77 (71 - 84)	70 (55 - 82)
	F1 score % (95% CI)	73 (64 - 80)	53 (45 - 66)	70 (67 - 76)	67 (55 - 75)
	Accuracy % (95% CI)	76 (66 - 83)	54 (48 - 64)	72 (67 - 80)	68 (59 - 75)
Clinical outcome	AUC % (95% CI)	84 (75 – 93)	62 (52 - 71)	67 (59 - 74)	78 (68 - 87)
	F1 score % (95% CI)	73 (65 – 80)	57 (46 - 67)	64 (56 - 72)	70 (58 - 82)
	Accuracy % (95% CI)	74 (67 – 81)	57 (47 - 66)	62 (55 – 68)	71 (61 - 81)