Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of Larazotide and TB-500 — mechanism, side effects, legal status, and pricing.
Larazotide is a synthetic linear octapeptide (Gly-Gly-Val-Leu-Val-Gln-Pro-Gly) structurally derived from the Vibrio cholerae zonula occludens toxin. It is proposed to act on the zonulin/tight-junction signaling pathway, interrupting gliadin-triggered intestinal barrier disruption by preserving tight-junction integrity locally in the gut lumen. Larazotide has been studied in multiple human trials for celiac disease under the development codes AT-1001, INN-202, and SPD550, but has never received FDA or EMA approval; a Phase 3 trial (NCT03569007) was terminated by the sponsor in 2022 with no results posted. It is not systemically absorbed and is available only as a research chemical.
TB-500 is a synthetic N-acetylated heptapeptide (Ac-LKKTETQ) corresponding to amino acids 17–23 of thymosin β4, the actin-binding region of the native 43-residue protein. Despite widespread vendor labeling, TB-500 is NOT identical to full-length thymosin β4 (Tβ4); it is a short fragment containing the central actin-binding motif. It is sold as a research chemical and is not FDA-approved for any human indication.
Larazotide
TB-500
Category
Legal Status
Mechanism
Half-life
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
Larazotide
TB-500
COA corpus from Disclosed Labs — independently tested batches only.
Larazotide
1
COAs
98.3%
Avg purity
1
Labs
TB-500
170
COAs
99.3%
Avg purity
16
Labs
TB-500 is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. Larazotide remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
Larazotide has been studied in multiple completed human trials for celiac disease but has never received FDA or EMA approval. A Phase 1 single-dose study (Paterson et al. 2007, PMID 17697209) confirmed no systemic absorption. Phase 2 gluten-challenge trials (Leffler et al. 2012, PMID 22825365, n=86, doses 0.25/1/4/8 mg TID) did not meet the primary endpoint (intestinal permeability) due to high variability, though lower doses limited symptom worsening. A Phase 2b trial (Leffler et al. 2015, PMID 25683116, ~342 patients, no gluten challenge) met its primary endpoint at the 0.5 mg TID dose, showing symptom improvement versus placebo with an inverse dose-response. The Phase 3 CeDLara trial (NCT03569007, 307 patients, 0.25 mg and 0.5 mg TID) was terminated by the sponsor in 2022 for futility/impractically large required sample size, with no results posted. Across trials, no serious drug-related adverse events or hepatic/renal/bone toxicity signals were reported; headache and urinary tract infection were the most common adverse events without consistent excess versus placebo. In preclinical models, larazotide reduced gliadin-induced paracellular permeability and preserved tight-junction protein localization in Caco-2 human intestinal cell monolayers, prevented gliadin-induced permeability increases and reduced macrophage infiltration in HLA-DQ8 transgenic mice, and accelerated barrier recovery in a porcine jejunum ischemia-reperfusion injury model.
Key references
Animal studies of full-length Tβ4 show accelerated dermal wound reepithelialization (Malinda et al., 1999, PMID 10469335), increased angiogenesis, improved cardiac function after ischemic injury via an ILK/Akt pathway (Bock-Marquette et al., Nature 2004, PMID 15565145), and corneal healing (Sosne & Kleinman review, 2015, PMID 26241398). The short Ac-LKKTETQ peptide sold as TB-500 was characterized analytically in the anti-doping literature as a substance with suspected doping potential (Esposito et al., 2012, PMID 22962027); controlled human efficacy trials of injected TB-500 do not exist. Full-length synthetic Tβ4 (RGN-259) has been evaluated in Phase II/III ophthalmic trials for dry eye disease and neurotrophic keratopathy with mixed results — one Phase III NK trial met healing endpoints, while a later European Phase III missed its primary endpoint. No clinically validated human injection dose exists for the short TB-500 peptide; all circulating dosing figures derive from vendor and forum protocols, not controlled trials.
Larazotide (Immune) and TB-500 (Recovery) are in different categories and target different biological pathways. This is a common pattern in multi-compound research protocols. Researchers should monitor the biomarkers from both profiles and watch for interactions listed in each compound’s contraindications. Consult a licensed healthcare provider before combining any research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Side Effects
Contraindications
Lab Testing
Key references
Disclosed Labs