The "leaky gut" drug that got furthest — and still failed Phase 3. Larazotide is unusual in this register: a first-in-class, FDA Fast-Tracked, Phase 3-stage pharmaceutical — the most clinically advanced non-dietary celiac-disease drug ever — not a typical gray-market peptide. Three threads: (1) its
Larazotide (AT-1001) is a synthetic octapeptide and a first-in-class "tight-junction regulator" — the first drug ever aimed at intestinal permeability, the "leaky gut" concept. Taken orally and acting only inside the gut, it works as a zonulin antagonist: in celiac disease, gluten makes the junctions between intestinal cells spring open (via zonulin), letting gliadin through to trigger the immune attack — and larazotide is designed to hold those junctions shut. It's genuinely notable for how far it got: developed across three companies (Alba → Innovate → 9 Meters), it became the most clinically advanced non-dietary celiac drug, the only Phase 3-stage one, with FDA Fast Track and positive Phase 2b data. But in June 2022 its pivotal Phase 3 (CeDLara) was stopped for futility — an interim analysis showed it couldn't feasibly beat placebo — a major blow to the whole zonulin/"leaky gut" drug hypothesis. As of 2026 it's approved for nothing. The honest, and broadly important, takeaway: the most rigorously developed "leaky gut" drug in history failed its decisive trial — which should temper the far larger, far less tested wellness-market hype around "leaky gut" supplements. A real drug, a real mechanism, a real (negative) answer.
not approved for any indication (the Phase 3 celiac program failed in 2022). It had FDA Fast Track during development, but never reached approval. Investigational.
An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.
A credentialed reviewer (PharmD / PhD / MD) will be named before this entry is finalised. Until then, treat it as a working draft. Last updated July 2026 (status: celiac Phase 3 failed 2022, no approved indication; watch only for revived development in adjacent barrier-disease indications).
Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.
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