TB-500 has no published human studies. It is a short synthetic fragment of thymosin beta-4, a protein the body makes, and the small human trials often quoted in its favor tested the whole protein rather than the fragment. The FDA states it has identified no human exposure data for TB-500 at all. What exists is animal work, and a mechanism borrowed from the parent protein. On this site it sits under the recovery goal as a research-only compound.
A fragment, not the protein
The FDA identifies TB-500 as “thymosin beta-4, fragment (LKKTETQ)”, a stretch of seven amino acids [1]. The parent protein, thymosin beta-4, is 43 amino acids long and is thought to promote the migration of skin and blood-vessel cells, collagen deposition and new vessel growth [2]. The idea behind the fragment is that it carries the part of the protein responsible for those effects. That is a reasonable hypothesis, but it is a hypothesis: the fragment and the full protein are different molecules, and a result for one does not transfer to the other without a study.
What the human trials of the full protein found
Thymosin beta-4 itself has been tested in small phase 2 trials. In a trial of topical thymosin beta-4 for venous leg ulcers at eight European sites, 73 patients were randomized across doses and placebo [2]. Safety was comparable to placebo. The authors report that a 0.03% dose may have the potential to speed healing, with complete healing within three months in about 25% of patients, mainly those with smaller wounds.
In a phase 2 trial of thymosin beta-4 eye drops for severe dry eye, 9 patients were treated six times a day for 28 days (n = 9) [3]. At day 56, the treated group had 35.1% less ocular discomfort than the vehicle group (p = 0.0141), with 12 treated eyes compared against 6 control eyes.
What the animal work shows
A 2026 rat study compared TB-500, BPC-157 and the two combined after surgical repair of the Achilles tendon [4]. Thirty-two rats were split into four groups of eight and treated by abdominal injection for four weeks, with TB-500 at 60 micrograms per kilogram a day. The TB-500 group had a significantly higher load to failure than controls and better tendon structure on histology (Bonar score p = 0.016). Combining TB-500 with BPC-157 conferred no additional benefit over either alone. The authors call the study exploratory.
A 2026 review for orthopedic and sports medicine physicians summarizes the wider record: in preclinical models, thymosin beta-4 and TB-500 promoted new vessel growth and tissue repair, but human orthopedic data are lacking, and both remain banned substances in sport [5].
The first trial of TB-500 itself
A randomized, placebo-controlled phase 1/2 dose-escalation study registered in 2026 plans to give TB-500 to 80 adults with stable atherosclerotic cardiovascular disease [7]. Its primary outcomes are adverse events over 12 weeks and serious adverse events over 28 days, with heart biomarkers as exploratory measures. It was recruiting at its last update, with primary completion estimated for February 2027. It will be the first human safety data on the fragment, and it does not test injury recovery.
What regulators and reviewers say about risk
The FDA reviewed TB-500 when it was nominated for compounding. Its summary states that compounded TB-500 may pose a risk of immunogenicity for certain routes because of potential aggregation and peptide-related impurities [1]. It lacks important information on safety, including whether TB-500 would cause harm if given to people. A 2026 review of unregulated injectables lists TB-500 among unapproved peptides without established human safety profiles, naming contamination, impurities and inaccurate dosing among the risks [6].
On July 23, 2026, the FDA’s Pharmacy Compounding Advisory Committee discussed TB-500 for the 503A bulks list [8]. The FDA’s own briefing document concluded that the balance of criteria weighs against listing it, finding the substance not well characterized [9]. The committee voted 8–6 to recommend listing it anyway, with one abstention [10]. The vote does not bind the FDA, and a listing would still need notice-and-comment rulemaking, so TB-500 remains on no list.
TB-500 is often paired with BPC-157, which has slightly more human data; the three small reports are read in the human evidence for BPC-157, and its safety record in BPC-157 side effects. How this site keeps a parent protein’s results from being credited to a fragment is part of the methodology.