TB-500
Synthetic peptide related to the active region of thymosin beta-4.
Also known as: Thymosin beta-4 fragment, TB4 fragment 17-23
TB-500 is a synthetic peptide that reproduces or mimics the active region of thymosin beta-4, a naturally occurring protein involved in cell structure and tissue repair. It has been studied primarily in preclinical animal models and remains a research compound without approval for human use.
Key facts
- Class
- Research peptide related to thymosin beta-4
- Regulatory status
- Not approved for human or veterinary use in the United States
- WADA status
- Prohibited at all times under S2 Peptide Hormones
- Parent molecule
- Thymosin beta-4 (TB4), a 43 amino acid protein
- Primary research focus
- Tissue repair, angiogenesis, cell migration in preclinical models
What is TB-500?
Thymosin beta-4 is a small protein found in virtually all human cells. It is one of the most abundant actin-binding proteins and plays a structural role in cytoskeletal dynamics. Researchers have also identified TB4 in wound fluid and platelets, where it appears to participate in tissue repair processes.
TB-500 refers to a synthetic peptide sold primarily as a research chemical. Commercial TB-500 preparations are commonly described as containing either full-length thymosin beta-4 or a shorter fragment representing the active region, but quality and identity vary across suppliers and are not regulated.
Mechanism of action
In cell culture and animal studies, thymosin beta-4 has been reported to promote migration of endothelial cells and keratinocytes, influence angiogenesis, and affect the inflammatory response to injury. Its primary biochemical role is sequestering G-actin monomers, which influences how the actin cytoskeleton assembles and disassembles during cell movement.
- •Sequesters free actin monomers as the main biochemical function
- •Reported effects in preclinical models on endothelial cell migration and tube formation
- •Reported effects in animal wound healing models on closure time and scar formation
- •Mechanisms in humans for therapeutic use have not been established through phase 3 trials
Research context
Most published research on thymosin beta-4 and related peptides involves in vitro work and animal models. A company called RegeneRx Biopharmaceuticals conducted early-phase human trials of a thymosin beta-4 formulation for dry eye, pressure ulcers, and epidermolysis bullosa over the past two decades. These were small trials in specific clinical contexts and are distinct from the material sold under the TB-500 label online.
There is no published phase 3 clinical trial of TB-500 for the indications most commonly associated with it in fitness and athletic recovery communities.
Safety and regulatory context
The FDA has not approved TB-500 for any indication. The World Anti-Doping Agency lists TB-500 explicitly on its Prohibited List under S2 Peptide Hormones, Growth Factors, Related Substances, and Mimetics. Athletes subject to WADA rules face anti-doping consequences for using it.
Because TB-500 from online sources is unregulated, purity and identity cannot be verified without independent testing. Material sold as a research chemical is intended strictly for laboratory use and is not cleared for human administration.
Research sourcing
TB-500 is listed by our research partner, GLP1 Research Lab, which supplies lyophilized peptides for laboratory use. Listings include product identifiers relevant to research documentation.
View TB-500 listing at GLP1 Research LabAffiliate partnership. Metabolic Playbook may earn a commission on purchases made through this link at no additional cost to the researcher.