Larazotide common uses, half-life, side effects and more

Larazotide is an eight amino acid peptide taken by mouth. It was developed as an add-on for people with celiac disease who still had symptoms on a gluten-free diet. It works on the surface of the gut lining and does not enter the bloodstream in measurable amounts. The Phase 3 trial stopped early. The company developing it liquidated in 2023. Larazotide is approved nowhere. People now buy compounded capsules and research powder for leaky gut and digestive claims that no trial has tested. The FDA has named larazotide acetate among the ingredients that pharmacies may not compound.

• Persistent celiac symptoms on a gluten-free diet
• Leaky gut and intestinal permeability claims
• Irritable bowel and inflammatory bowel claims
• Recovery research after COVID-19 in children

Three oral doses daily about 15 minutes before meals

Celiac trials used 0.25 mg to 8 mg orally three times daily about 15 minutes before meals. The 342-person trial that met a symptom endpoint tested 0.5 mg, 1 mg, and 2 mg three times daily and only the 0.5 mg arm worked. The terminated Phase 3 used 0.25 mg and 0.5 mg three times daily. The largest dose given to a celiac patient was 12 mg once daily for three days. The children's inflammatory syndrome study used 10 mcg per kilogram four times daily with a 500 mcg ceiling per dose. An ongoing long COVID study uses a fixed 250 or 500 mcg four times daily split at 25 kilograms of body weight. Compounded capsules sold online copy the 0.5 mg trial strength.

• Trial capsules held enteric-coated beads timed to release past the stomach into the duodenum and jejunum
• Doses were taken about 15 minutes before meals rather than on a clock schedule
• The capsule that reached Phase 3 is discontinued and no sold product reproduces its release profile

No human plasma half-life exists. Blood levels stayed below the limit of measurement at every oral dose tested including the largest. The peptide is built to work inside the gut rather than enter the blood. Every half-life figure in the literature comes from pigs, averaging about 0.65 to 0.76 hours for clearance from intestinal fluid and about 35 minutes in injured jejunum tissue.

• Diarrhea, nausea, constipation, abdominal pain, and headache were recorded at rates mostly matching or below placebo
• Abdominal pain, headache, and constipation each ran higher on the 8 mg dose than on placebo in one trial, on counts of about six patients against two
• Placebo groups were either fed gluten on purpose or already symptomatic and that makes the comparison with placebo weak
• Individual symptoms ran from 4 to 97 percent during an all-placebo run-in before anyone received the drug
• Nothing is known about exposure beyond 12 weeks

Larazotide is meant to tighten the junctions between the cells lining the small intestine. Its sequence was said to come from a cholera toxin fragment. It was described as blocking the receptor for a protein called zonulin that pulls those junctions open. That receptor has never been identified. The paper that named it called it putative. Zonulin itself was later identified as a form of haptoglobin. The larazotide sequence does not occur anywhere in human haptoglobin and differs by one residue from a common antibody framework motif. Researchers have put that mismatch down to a sequencing error in the original report. The barrier effect still holds up in injured pig intestine with no gluten or zonulin present. That animal work comes from one laboratory and has not been replicated elsewhere.

Intestinal permeability was the registered primary endpoint in two placebo-controlled celiac trials and failed in both. A meta-analysis pooling four trials and 626 patients found no difference on that measure. One 342-person trial met its symptom endpoint at 0.5 mg three times daily. The 1 mg and 2 mg arms of that same trial did nothing. No dose has reproduced a symptom benefit across two trials. All three doses in the 2013 gluten-challenge trial did suppress the rise in celiac antibodies. A Phase 3 built to confirm the low dose stopped early at 307 of a planned 525 patients. No larazotide trial has posted results to the public registry. The zonulin hypothesis behind it traces to one research group.

• Bulk powder is not what was tested because the trials used capsules engineered to release past the stomach
• The code AT-1001 also names an unrelated Fabry disease drug dosed in the hundreds of milligrams and a dose copied from that search would be hundreds of times too high
• Vials sold as 5 mg larazotide carry injectable-grade specifications even though no registered study has ever given this peptide by injection
• Blood tests sold as zonulin tests have been shown to bind other proteins and do not track gut permeability measured directly
• No reproductive toxicity data, drug interaction study, or contraindication list has ever been published
• Pregnant and breastfeeding women were excluded from every celiac trial and no child with celiac disease has taken it in a published trial