Nara
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Experimental and investigational

TB-500

A thymosin beta-4 fragment marketed for tissue repair.

Nara’s current positionClinical-trial only
Evidence briefing

Strongest directness: Other animal evidence. Last reviewed 2026-08-12.

Nara’s evidence view

Clinical-trial context only

Insufficient or conflictingNon-canine preclinical evidenceVery low confidence

The claim we’re evaluating

Chemically defined TB-500 or a specified thymosin beta-4-derived product improves clinically meaningful wound or tissue-healing outcomes in dogs.

Nara’s interpretation

TB-500 should not inherit the evidence base of full-length thymosin beta-4 merely because the molecules are related. For chemically defined TB-500 itself, evidence of meaningful tissue-healing efficacy is extremely limited, no peer-reviewed canine intervention study was identified, and an exact-parent in-vitro experiment produced a null wound-closure result while one metabolite was active. Nara should treat current commercial healing claims as investigational and highly formulation-dependent.

This is an umbrella assessment. The evidence differs materially depending on the outcome and the specific form of the intervention, so Nara evaluates those narrower claims separately.

Personalized

What this means for your dog.

Loading your dog’s context…

Evidence briefing

What Nara knows now.

A bounded position while the full claim-level dossier is still being completed.

What is known

Full-length thymosin beta-4 and the unacetylated LKKTETQ actin-binding sequence have produced wound-healing effects in rodent models. Commercially referenced TB-500, however, is commonly described as the N-acetylated fragment Ac-LKKTETQ and is not the same substance as full-length thymosin beta-4. In a 2024 metabolism and fibroblast study, parent TB-500 did not significantly improve wound closure versus control, whereas the metabolite Ac-LKKTE did. FDA's 2026 review found no in-vivo pharmacology demonstrating wound-healing efficacy for the exact TB-500 substances under evaluation and no adequate human clinical or toxicology evidence.

What is not known

No peer-reviewed canine TB-500 intervention or clinical-outcome study was identified in the targeted search. Much of the apparent evidence base comes from full-length endogenous thymosin beta-4 or related peptide fragments rather than chemically defined TB-500. Acetylation state, peptide length, salt form, active moiety, metabolites, and commercial nomenclature are not interchangeable details. The 2024 exact-parent wound assay was in cultured fibroblasts and therefore cannot establish efficacy or non-efficacy in whole animals, but it directly weakens simple attribution of wound-healing activity to the parent compound. In-vivo efficacy, dose-response, canine pharmacokinetics, chronic toxicity, reproductive toxicity, carcinogenicity, and clinically relevant safety information for defined TB-500 remain substantially undeveloped. Commercial use of the same 'TB-500' name for potentially different chemical preparations creates an additional translational and safety problem.

Current position

TB-500 should not inherit the evidence base of full-length thymosin beta-4 merely because the molecules are related. For chemically defined TB-500 itself, evidence of meaningful tissue-healing efficacy is extremely limited, no peer-reviewed canine intervention study was identified, and an exact-parent in-vitro experiment produced a null wound-closure result while one metabolite was active. Nara should treat current commercial healing claims as investigational and highly formulation-dependent.

Full-length thymosin beta-4 and the unacetylated LKKTETQ actin-binding sequence have produced wound-healing effects in rodent models. Commercially referenced TB-500, however, is commonly described as the N-acetylated fragment Ac-LKKTETQ and is not the same substance as full-length thymosin beta-4. In a 2024 metabolism and fibroblast study, parent TB-500 did not significantly improve wound closure versus control, whereas the metabolite Ac-LKKTE did. FDA's 2026 review found no in-vivo pharmacology demonstrating wound-healing efficacy for the exact TB-500 substances under evaluation and no adequate human clinical or toxicology evidence.