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Summary

Background  Randomized, placebo controlled trials are used to assess the efficacy of therapies for Crohn’s disease. The placebo response and remission rates vary among studies.

Aim  To analyse how the placebo response and remission rates in Crohn’s trials have changed over time in the era of parenteral biologic therapies.

Methods  A search for randomized, placebo-controlled trials of parenteral biologic therapies for active Crohn’s disease was conducted using online databases. The placebo response and remission rates and study week of evaluation were recorded for each trial. The placebo response and remission rates were analysed as functions of publication date and study week of evaluation.

Results  The odds of a placebo-induced remission and response significantly increased as the week of evaluation increased. The placebo remission rate increased significantly with year of publication. Adjusted for week of evaluation, this increase in placebo remission rate over time was no longer significant. The increase in the placebo response over this time period was not statistically significant.

Conclusion  The observed increase in placebo remission rates over time in trials of parenteral biologic therapies in Crohn’s disease is explained by longer times to the primary endpoint in more recent trials.