Research record / starter review

TB-500

Thymosin beta-4 fragment discussed in tissue-repair communities

Tested-sport concernLast reviewed 2026-07-13

Also called

Thymosin beta-4 fragment · LKKTETQ

What people ask about

Community claims

tissue-repair claimsrecovery claims

These are topics circulating in appearance, physique, or recovery communities. Listing them does not validate them.

What this record can say

Evidence snapshot

Do not merge TB-500 with full-length thymosin β4. Recent human studies found in this update concern different thymosin β4 molecules/formulations and unrelated eye or early-phase contexts; they are not evidence for TB-500 or recovery claims.

Safety context

Read uncertainty as information

FDA states it has not identified human-exposure data for compounded thymosin beta-4 fragment and lacks information needed to determine whether it would cause harm in humans.

Tested sport

Anti-doping context

WADA's 2026 List names thymosin-β4 derivatives, including TB-500, in S2.3 (growth factors and growth-factor modulators).

Regulatory scope

Context is not a universal answer

United States: this reflects FDA's compounding-safety source, not a global legal determination.

Study-level evidence

What the individual records actually say.

Every row preserves identity and context. A related molecule, a tissue experiment, or a trial registration cannot become proof for the community claim.

Published phase-I human study2021

A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers ↗

Wang X, et al. J Cell Mol Med. 2021;25(17):8222-8228. PMID: 34346165. DOI: 10.1111/jcmm.16693.

Identity: Related, not interchangeable: recombinant full-length human thymosin β4 (NL005), not the TB-500 fragment

Design & population: Randomised, double-blind phase-I programme in healthy adults. The published report describes single- and multiple-dose components with 54 and 30 participants respectively.

Question studied: Short-term tolerability, pharmacokinetics, and anti-drug antibodies for recombinant full-length thymosin β4.

Record finding: The authors report mild-to-moderate adverse events and no dose-limiting toxicities or serious adverse events during the study observation period.

Does not show: It is not evidence for TB-500, because the molecular identity differs. It also does not test tendon repair, athletic recovery, or long-term safety.

Related-molecule human evidence — do not transfer to TB-500Checked 2026-07-13

Published randomised placebo-controlled clinical trial2023

0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial ↗

Sosne G, et al. Int J Mol Sci. 2023;24(1):554. PMID: 36613994. DOI: 10.3390/ijms24010554.

Identity: Related, not interchangeable: thymosin β4 ophthalmic formulation (RGN-259), not the TB-500 fragment

Design & population: Small double-masked, placebo-controlled study in people with neurotrophic keratopathy; the abstract reports 10 active and 8 placebo-treated participants.

Question studied: Corneal epithelial healing and comfort in a specific eye disease with a topical ophthalmic formulation.

Record finding: The paper reports more complete healing in the active group but its reported comparison did not reach conventional statistical significance in this small sample.

Does not show: It is not evidence for TB-500 or for systemic recovery, tendon repair, physique, or appearance claims. Different molecule, formulation, route, disease, and outcome matter.

Related-molecule, formulation-specific human evidence — do not transfer to TB-500Checked 2026-07-13

Primary sources

Read the source, not only our summary.

regulatory / safetyCertain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksU.S. Food and Drug Administration ↗anti-doping2026 Prohibited ListWorld Anti-Doping Agency ↗