Thymosin Beta-4

Thymosin beta-4 (Tβ4) is an endogenous 43-amino-acid peptide present in most cells and body fluids. Platelets and immune cells release it around injury sites. It participates in cell movement and tissue repair, but wellness-market recovery products are not approved medicines.

TB-500 is a different, synthetic acetylated seven-amino-acid fragment, Ac-LKKTETQ, corresponding to residues 17–23. The ophthalmic Phase II/III program and a 2025 cardiac randomized trial concern full-length Tβ4. The fragment does not have a comparable human trial program in the published account, and FDA identified no human exposure data for TB-500.

Tβ4 sequesters G-actin monomers, allowing cells such as keratinocytes to reorganize their cytoskeleton and migrate toward damaged tissue. Experimental work also investigates stem/progenitor-cell mobilization, angiogenesis, reduced inflammation and less scarring across wound, ocular, cardiac and nervous-system models.

In the foundational 1999 rat full-thickness-wound experiment, reepithelialization increased 42% at day 4 and up to 61% at day 7. These are animal observations; no large-scale human wound-healing randomized trial is described in these reports.

Tβ4 is not FDA-approved. Published reports describe that the RGN-259 program uses 0.1% Tβ4 eye drops, with Phase III dry-eye trials completed and a neurotrophic-keratopathy Phase III study listed as recruiting. Those development milestones are not marketing authorization.

The 2026 FDA advisory review concerned TB-500, not full-length Tβ4. FDA announced adviser consideration of 12 peptides on April 15, 2026. After nomination withdrawal, TB-500 was moved off Category 2 by April 22; that action did not declare it safe or put it on the 503A bulks list or into Category 1. An 8–6 advisory vote on July 23 supported TB-500 for wound healing, but was nonbinding and still required FDA rulemaking.

The 2026 WADA Section S2 prohibition covers Tβ4 and TB-500 both in and out of competition. Tβ4 is not a legal US over-the-counter medicine; online products are unregulated and may misstate their contents.

Human evidence includes early safety studies, a randomized dose-escalation venous-ulcer study and ophthalmic development, alongside a substantial preclinical literature. It does not establish a general wellness or recovery benefit.

The p value was 0.0656, a trend that did not reach the usual threshold for statistical significance. This result concerns eye drops for an ocular condition, not chronic subcutaneous recovery use.

Phase I reports by Ruff and colleagues (2010) and Wang and colleagues (2021) described tolerability in healthy volunteers after single and repeated intravenous exposures up to 1,260 mg. These are reported trial exposures, not a recommended injection regimen. No significant adverse effects were observed in the neurotrophic-keratopathy eye-drop trial, while chronic subcutaneous and long-term safety remain insufficiently characterized.