Larazotide

What is Larazotide?#

Larazotide acetate (AT-1001) is a synthetic octapeptide that acts as a zonulin receptor antagonist, designed to regulate intestinal tight junction permeability. Developed by 9 Meters Biopharma (previously Innovate Biopharmaceuticals and Alba Therapeutics), larazotide was the first drug candidate to reach Phase 3 clinical trials specifically for celiac disease.

The peptide is derived from a zonula occludens toxin (Zot) protein secreted by Vibrio cholerae. While the bacterial toxin opens tight junctions, larazotide was engineered to have the opposite effect: it blocks zonulin receptors to prevent tight junction opening, thereby reducing paracellular permeability.

Mechanism of Action#

Zonulin Pathway#

Zonulin is an endogenous human protein that regulates intestinal tight junction permeability. In celiac disease, gluten-derived peptides trigger excessive zonulin release, leading to:

1. Zonulin binding: Zonulin binds to receptors on the basolateral surface of intestinal epithelial cells
2. Tight junction opening: Zonulin-receptor interaction activates intracellular signaling that reorganizes tight junction proteins (claudins, occludin, ZO-1) and actin filaments
3. Increased permeability: Open tight junctions allow gluten-derived peptides (particularly gliadin fragments) to cross the epithelial barrier
4. Immune activation: Gliadin peptides reach the lamina propria, where tissue transglutaminase deamidates them, leading to HLA-DQ2/DQ8-mediated immune activation

Larazotide Mechanism#

Larazotide blocks step 2 of this cascade by antagonizing zonulin receptors:

• Receptor antagonism: Competitively blocks zonulin from activating its receptor
• Tight junction preservation: Prevents the reorganization of tight junction proteins and actin filaments
• Barrier maintenance: Maintains paracellular barrier integrity, reducing the flux of gluten peptides into the lamina propria
• Local action: Acts luminally in the gastrointestinal tract with minimal systemic absorption

Important Limitation#

Larazotide addresses intestinal permeability but does not treat the underlying autoimmune process of celiac disease. It was designed as an adjunctive therapy to reduce symptoms in celiac patients who maintain a gluten-free diet but continue to experience symptoms from inadvertent gluten exposure.

Research Overview#

Larazotide progressed through Phase 1, Phase 2a, Phase 2b, and Phase 3 clinical trials. The Phase 2b trial demonstrated significant symptom reduction at the 0.5 mg dose. However, the Phase 3 CeDLara trial was discontinued in 2022 after an interim analysis showed insufficient treatment effect to justify continuation.

Important Considerations#

• Larazotide is an investigational compound that failed to demonstrate adequate efficacy in Phase 3
• The Phase 3 discontinuation raises questions about its clinical viability
• The strong placebo response in celiac disease trials is a known challenge
• Larazotide acts locally in the gut with minimal systemic absorption, contributing to its favorable safety profile
• The zonulin pathway concept remains valid; larazotide's limitations may be dose or endpoint related

Key Research Findings#

Larazotide Acetate for Persistent Symptoms of Celiac Disease Despite a Gluten-Free Diet: A Randomized Controlled Trial, published in Gastroenterology (Kelly CP et al., 2015; PMID: 25683116):

• The study demonstrated dose significantly reduced celiac symptoms vs placebo of 0.5 mg
• The study demonstrated decrease of 26% in symptomatic days with 0.5 mg dose
• The study demonstrated increase of 31% in improved symptom days

Related Reading#

• Larazotide research studies and evidence
• Larazotide dosing protocols
• Larazotide side effects profile
• Linaclotide research guide
• Teduglutide research guide