Larazotide (AT-1001)

The biology behind it is real

The intestinal mucosa is a single layer of cells, wafer-thin, and it has to do two contradictory things at the same time: let nutrients through and keep everything else out. Between the cells there are therefore connections that can open and close, the so-called tight junctions.

These connections can become more permeable, and that is not an invention of supplement sellers. There is a protein produced by the body, zonulin, that loosens them; this was discovered during research on celiac disease. When zonulin rises, the connections open, and what should not get through gets through.

What exists and what does not

Increased intestinal permeability exists and can be measured — in celiac disease, in inflammatory bowel disease, in severe illness. What does not exist is a diagnosis called leaky gut syndrome as a stand-alone clinical picture that would be responsible for fatigue, skin problems and difficulty concentrating.

It is precisely in this gap between a proven mechanism and a claimed clinical picture that the value of larazotide lies. The drug targets exactly the mechanism used to justify the entire market. It is thus the best test this market has ever had.

The trial was a home game

CedLara was randomized, double-blind and placebo-controlled. 525 patients were planned in three groups, two dose levels and placebo, with 175 participants each; 307 had been enrolled by the time it was stopped. Enrolled were celiac patients who continued to have symptoms despite a strictly gluten-free diet.

That is the most favorable starting position imaginable. These people have a proven disease, proven damage to the intestinal mucosa and proven symptoms. If zonulin and the tight junctions play a role anywhere, it is here. Anyone who wants to test a principle of action looks for exactly such patients.

What stopping for futility means

The trial was ended on June 21, 2022. An interim analysis by an independent statistician at about half the planned number of participants found that the number of additional patients that would be needed to demonstrate any difference from placebo at all was too large to justify continuing.

That is not the same as harmful, and not quite the same as ineffective either. It means: if there is something there, it is so small that it can no longer be found with reasonable effort. The analysis was carried out by an independent statistician.

What the studies show

Leffler 2015 — phase 2b, 342 adults with celiac disease

342 adults who had symptoms despite at least one year of a gluten-free diet received one of three dose levels or placebo for twelve weeks. The lowest level improved symptoms, with about a quarter fewer symptom days; the two higher levels did not differ from placebo on any endpoint. Side effects were at placebo level.

Kelly 2013 — gluten challenge, 184 participants

Under daily gluten exposure over six weeks, the sugar test for intestinal permeability (lactulose-mannitol) showed no difference between larazotide and placebo. At the lowest dose level, symptoms were less pronounced, and under larazotide celiac antibodies rose considerably less than under placebo.

CedLara — phase 3, 525 planned, 307 patients with celiac disease enrolled

CedLara was a randomized, double-blind, placebo-controlled phase 3 trial. 525 patients with celiac disease who continued to have symptoms despite a strictly gluten-free diet were planned, in three groups: two dose levels of larazotide and placebo, with 175 participants each; 307 had been enrolled by the time it was stopped. The trial was terminated on June 21, 2022. An interim analysis at about half the target size found that the number of additional patients needed to demonstrate a difference from placebo was too large to justify continuing. The trial was stopped for futility, not because of safety problems.

What the termination proves — and what it does not

The termination does not prove that intestinal permeability is unimportant. It proves something narrower but important: tightening these connections pharmacologically did not noticeably help patients. The mechanism is real — the assumption that it can be turned and that people then feel better did not pass the test.

All the more unsupported, then, is everything claimed beyond that. On the shelves are glutamine, collagen, zinc and herbal blends, promoted with the same rationale, offered to people without a diagnosed bowel disease, and without a single study of this size. If the most specific drug in the most favorable patient group is not enough, the burden of proof for the non-specific products has become higher, not lower. The useful question to ask of any leaky gut program is therefore: where is the study that shows the treatment improves symptoms — not the study that shows intestinal permeability exists. These are two completely different questions, and only the first one counts. The lesson beyond this topic: a clean mechanism is not proof of efficacy, and the chain from mechanism to effect breaks more often than it holds.

Status, approval and legal

Larazotide is not approved anywhere. After the phase 3 trial was stopped in 2022, development in celiac disease was discontinued, and the developer 9 Meters Biopharma filed for insolvency in 2023. Larazotide was continued only in academic phase 2 trials: in the severe inflammatory reaction of children after COVID (MIS-C, 12 children, Sci Transl Med 2025) and in long COVID (107 participants, completed in June 2026, results pending). There is no finished medicinal product, no tested quality and no medical use. What is offered under this name on the gray market is not a medicine and is not subject to any batch control. For the complaints in question, by contrast, there are real diagnoses with real tests and real treatments: celiac disease, irritable bowel syndrome, inflammatory bowel disease, intolerances.

Safety

Larazotide failed on efficacy, not on safety — that is an important difference. Development was not ended because of harm, but because a difference from placebo was no longer within reach. The real risk of this topic lies elsewhere: anyone who explains persistent bowel complaints for months with a leaky gut narrative delays the investigation that would lead to a treatable diagnosis. Anyone with persistent complaints has a real problem and deserves a real investigation. That larazotide failed does not mean the complaints are imagined. It means that the explanation on offer is probably the wrong one.

Sources

• ClinicalTrials.gov NCT03569007 (CedLara, phase 3 trial of larazotide in celiac disease)
• Leffler et al., Gastroenterology 2015 (phase 2b, 342 adults with persistent celiac symptoms)
• Kelly et al., Aliment Pharmacol Ther 2013 (gluten challenge, permeability test with no difference from placebo)
• Khaleghi et al., Ther Adv Gastroenterol 2016 (larazotide as a tight junction regulator)
• Fasano, Physiol Rev 2011 (zonulin and the regulation of tight junctions)
• Increased intestinal permeability in celiac disease and inflammatory bowel disease
• Camilleri, Gut 2019 (leaky gut, mechanisms, measurement and clinical significance)