TB-500

TB-500 is sold online as a research chemical, described as thymosin beta-4 or a fragment of it — a 43-amino-acid protein that occurs naturally in platelets, white blood cells and most nucleated cells in the body. That protein regulates the actin cytoskeleton and is bound up in cell migration, wound healing, blood vessel growth and inflammatory control. The peptide has a following in biohacking and athletic recovery circles, where it is routinely stacked with BPC-157.

One distinction gets blurred almost everywhere online and decides how to read everything below. The thymosin beta-4 that entered formal clinical trials, developed as a pharmaceutical, was a precisely characterized protein given under regulated conditions. What vendors sell as TB-500 is an unlicensed research chemical: no standard formulation, nobody overseeing how it is made, and no trial ever run under that name. Whatever human evidence exists — the Phase I safety work, the small pilots — attaches to the pharmaceutical protein rather than to the vial.

Grade C. Thymosin beta-4 has a better developed preclinical and early clinical literature than most peptides in this category, and the distance between what was studied and what is sold remains substantial. Efficacy in humans has never been established by a randomized controlled trial, for any indication.

Its central action is binding up free actin monomers, which controls how actin polymerizes and lets cells move. That matters for repair: it is what allows keratinocytes, endothelial cells and fibroblasts to migrate into damaged tissue and start rebuilding [1]. Animal models show it driving re-epithelialization, collagen deposition and new vessel formation, damping inflammatory cytokines at the wound, and possibly helping heart muscle cells survive when starved of blood.

Sequestering actin sets it apart from an ordinary growth factor — it operates upstream of several repair pathways at once instead of hitting one receptor. Skin wounds, the cornea, oxygen-starved heart tissue and neurological injury have all been research targets [1]. Whether what is sold commercially retains the activity of the protein that was studied is unknown, because nobody has published a direct comparison of the two.

Read every human result here through one filter: which compound was actually used. The human data came from pharmaceutical thymosin beta-4 under Investigational New Drug conditions, not from research-chemical TB-500. A 2010 Phase I study gave it intravenously to healthy volunteers in single and repeated doses and found it generally well tolerated, sketching a preliminary safety picture [3]. In 2021 a first-in-human Phase I study of the recombinant version reported broadly favorable tolerability too [4]. Neither examined whether it treats anything.

The nearest thing to therapeutic evidence is two small studies and one indirect one. A 2012 report described thymosin beta-4 in skin wound healing across animal models and patients — but as a conference case series rather than a randomized trial [2]. A 2010 pilot in venous ulcers produced suggestive preliminary findings [6]. And a 2016 cardiac pilot used it to pretreat a patient's own endothelial progenitor cells before transplanting them after a heart attack, which is indirect — the protein acted outside the body, not injected into it — in a small sample [5].

An independent 2026 review in Sports Medicine assessed unapproved peptides in musculoskeletal injury and athletic performance, and found the clinical evidence for thymosin beta-4 fragments too thin to recommend them to either patients or athletes [7]. Nothing completed and peer-reviewed has shown either the research chemical or the protein improving muscle recovery, tendon healing or sports performance. Grade C.

No therapeutic human dose exists, because no trial established one. The Phase I safety work used intravenous dosing in the region of 6 to 42 mg, which does not translate to the subcutaneous injections sold as research chemicals. The unregulated market commonly quotes 2 to 5 mg injected under the skin once or twice weekly, sometimes with a heavier loading period for the first few weeks — none of it grounded in any validated human pharmacokinetics or pharmacodynamics.

Online recovery protocols habitually pair it with BPC-157. Neither compound has been studied in humans in a controlled trial, alone or together. Both are sold as research chemicals rather than medical products, and neither carries US approval for therapeutic use in people.

The full protein looked acceptably safe in Phase I trials in healthy adults [3] [4], with caveats that matter: those used pharmaceutical-grade material, given intravenously, under clinical supervision — not research chemicals of unknown purity injected at home. What it does over years, in any human population, has never been looked at. What ships as TB-500 is not made under Good Manufacturing Practice, and may carry the wrong dose, the wrong sequence, degraded peptide or outright contaminants.

Thymosin beta-4 and its fragments appear explicitly on the World Anti-Doping Agency Prohibited List under Section S2, covering peptide hormones, growth factors and related substances. For any athlete under WADA-aligned rules it is straightforwardly banned. Beyond sport, it is approved for no human indication anywhere, and use outside a licensed trial is unregulated. Anyone using it is accepting risk that nobody has measured, from a product whose manufacturing nobody inspects.