TB-500
Also known as: Thymosin Beta-4 Fragment, TB4-Frag, Ac-LKKTETQ
A synthetic 7-amino-acid fragment of thymosin beta-4, corresponding to the active region responsible for cell migration and wound healing. Widely used in anti-aging and sports recovery, though human clinical data is very limited. Previously banned from compounding but expected to return to legal status in 2026.
How it works
TB-500 contains the active actin-binding domain of thymosin beta-4. It promotes cell migration, which is essential for wound healing. It also reduces inflammation, encourages new blood vessel formation (angiogenesis), and supports the production of extracellular matrix proteins needed for tissue repair.
Common uses
- Muscle and tendon injury recovery
- Wound healing and tissue repair
- Joint pain and inflammation
- Sports recovery
- Hair regrowth (topical applications)
Side effects
- Very limited human safety data
- Injection site redness or irritation
- Headache (anecdotal reports)
- Mild fatigue or flu-like feelings initially
- Unknown long-term effects
Key research
- Animal studies show thymosin beta-4 promotes wound healing, reduces inflammation, and aids tissue regeneration
- In vitro studies demonstrate enhanced cell migration and angiogenesis
- No completed human clinical trials specifically for TB-500 fragment
Safety notes
- Was placed on FDA Category 2 restricted list (banned from compounding) in 2023-2024
- Expected to return to Category 1 status following HHS Secretary RFK Jr.'s February 2026 announcement, pending formal FDA publication
- Banned by WADA (World Anti-Doping Agency) under S2 at all times
- Not FDA-approved for any human use
- Quality varies significantly between sources
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