TB-500 (thymosin beta-4 fragment)

FDA status

Not FDA-approved. The FDA says it has found no data on TB-500 in people. It was on FDA's compounding safety-risk list until the nomination was withdrawn. In July 2026 FDA advisers voted to add it to the pharmacy list for wound healing. On October 30, 2026 HHS published a draft policy: it does not intend to act against pharmacies and doctors that compound TB-500, as injections only, under set conditions while that list is worked out. That is not an approval. It covers only compounding for a patient's prescription, with peptide from an FDA-registered maker; HHS says it aims to move people away from research-use-only peptides from foreign suppliers to a more controlled alternative. FDA safety-risk list ↗McDermott ↗Federal Register ↗HHS ↗

Its research stage

Stage 1: trials in people gave the full thymosin beta-4 protein, not TB-500, the short piece of it sold online. A stage counts only trials of the peptide itself. The counts behind it

FDA advisers, July 2026

The FDA's compounding advisory committee recommended adding it to the substances pharmacies may use, for wound healing (8–6, 1 abstaining). The FDA hasn't decided. What's changing →

What's changing

A draft HHS policy, published October 30, 2026: no action against pharmacies that compound it under set conditions while the pharmacy list is worked out. Comments are open for two weeks. See what's changing →

In people so far

• 40 healthy volunteers were given full-length thymosin beta-4 into a vein for up to 14 days with no serious side effects. PubMed ↗
• In 9 people with severe dry eye, thymosin beta-4 eye drops eased discomfort and eye-surface damage more than a placebo. PubMed ↗

Safety

• The FDA says TB-500 may cause immune reactions and that it has no data on its use in people. FDA safety-risk list ↗
• Sold online without a prescription; doctors warn of contamination, impurities and inaccurate doses. PubMed ↗

In sport

Banned in sport at all times: WADA names “thymosin-β4 and its derivatives, e.g. TB-500” (class S2). WADA ↗

One of the peptides we follow. We don't give doses or say where to buy. Talk to your doctor before trying any of them.