Larazotide acetate for persistent symptoms of celiac disease despite a gluten-free diet: a randomized controlled trial
Leffler DA, Kelly CP, Green PHR, Fedorak RN, DiMarino A, Perrow W, Rasmussen H, Wang C, +3 more
Gastroenterology (2015) · n=342
Larazotide acetate at 0.5 mg three times daily improved celiac-disease symptom scores versus placebo (ANCOVA p=0.022) in adults with persistent symptoms despite a gluten-free diet — the Phase IIb signal that licensed an attempt at registration that the Phase 3 program failed to confirm in 2022.
This is the Phase IIb randomized controlled trial of larazotide acetate (AT-1001) — a synthetic 8-amino-acid peptide that antagonizes zonulin, the principal endogenous regulator of intercellular tight-junction permeability in the small intestine — in adults with celiac disease and persistent gastrointestinal symptoms despite at least 12 months of strict gluten-free diet. The molecule was developed by Alba Therapeutics (and subsequently 9 Meters Biopharma) on the hypothesis that residual symptomatology in the gluten-free-diet-adherent celiac population reflects ongoing tight-junction dysregulation and gluten micro-exposure responses that a zonulin antagonist could attenuate at the apical brush border. Larazotide was designed to act locally in the small intestinal lumen with minimal systemic absorption — a pharmacokinetic profile that supports the gut-restricted-action argument and constrained the safety considerations the regulatory dossier had to address.
Investigators conducted a 12-week multicenter randomized, double-blind, placebo-controlled trial across approximately 70 sites in North America and Europe, randomizing 342 adults with biopsy-confirmed celiac disease and ongoing symptoms (gastrointestinal, extraintestinal, or both) to one of four arms: larazotide acetate at 0.5, 1, or 2 mg taken three times daily before meals, or matching placebo. The primary endpoint was the on-treatment difference in the Celiac Disease Gastrointestinal Symptom Rating Scale (CeD GSRS) — a validated patient-reported outcome instrument — between each active arm and placebo. Standard-of-care strict gluten-free diet was maintained across all arms throughout the trial.
The 0.5 mg three-times-daily dose met the primary endpoint with a statistically significant improvement in CeD GSRS score versus placebo (ANCOVA p = 0.022; mixed-model analysis p = 0.005), with parallel directional improvements on exploratory non-gastrointestinal symptom and quality-of-life endpoints. The 1 mg and 2 mg doses produced no significant effect on the primary or secondary endpoints — an inverted dose-response that the authors did not fully resolve and that was speculated at the time to reflect dose-related differences in luminal-binding pharmacokinetics or paradoxical receptor-occupancy effects at higher doses. The safety profile was acceptable across all doses with no signal of class-specific concern.
Cross-link to the IBD-and-peptides dossier, where the larazotide trajectory is the most-informative recent worked example of how a credible GI-peptide program plays out under modern regulatory scrutiny — and to the broader failed-peptide-trials archive for the cross-indication framing on primary-endpoint outcomes and their downstream development consequences.
The most consequential post-publication update is the Phase 3 failure. The pivotal CeD-PRO Phase 3 program (NCT04486313) was designed to enroll approximately 525 patients across three dose arms in the same persistent-symptom celiac population that responded in this Phase IIb. 9 Meters Biopharma discontinued the program in mid-2022 following an interim futility analysis indicating the sample size required to demonstrate a clinically significant treatment effect over placebo was substantially larger than the design supported — a futility outcome in which the prespecified powering assumptions did not survive contact with the observed effect size in the larger trial. No successor sponsor has advanced the molecule for celiac, IBD, or any related indication; the program is dormant as of 2026.
The inverted dose-response in this Phase IIb (positive at 0.5 mg, negative at 1 mg and 2 mg) is the structural feature that should have raised caution about Phase 3 reproducibility. Modern Phase IIb-to-Phase-3 statistics literature treats non-monotonic dose-response signals as elevating Phase 3 failure risk, and the larazotide trajectory is a representative example of that pattern resolving negatively. The 12-week trial duration is short relative to the chronic-therapy framing the indication requires. Industry sponsorship by Alba Therapeutics is disclosed; the manuscript and trial design were academically credible and the methodology was appropriate for the Phase IIb proof-of-concept question. The peptide remains the most-informative recent precedent for how a GI-permeability-modulating peptide program plays out under modern regulatory scrutiny — and the most-informative recent caution against extrapolating positive Phase II signals to Phase 3 success in the GI-peptide field. Within the IBD-peptide conversation specifically, larazotide is the cleanest negative control point: an oral, gut-restricted, mechanism-coherent peptide with a positive Phase IIb that still failed to survive Phase 3 futility analysis.
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