Thymosin alpha-1 and TB-500 are often confused because of the shared word thymosin. TB-500 is a synthetic version of thymosin beta-4, studied for cell migration and tissue repair. Thymosin alpha-1 is a separate peptide studied for immune modulation, including in chronic viral hepatitis. Neither is FDA-approved.
At a glance
| Thymosin alpha-1 | TB-500 | |
|---|---|---|
| What it is | Immune-modulating peptide studied for T-cell and natural killer cell function, including in chronic viral hepatitis | Synthetic version of thymosin beta-4, studied for cell migration, angiogenesis, and tissue repair |
| How it's thought to work | Studied for T-cell maturation, NK cell activity, cytokine modulation and dendritic cell function | Promotes actin polymerization and cell migration, supports angiogenesis, reduces inflammation, distributes systemically |
| Regulatory status | Not FDA-approved; reported to be approved in some countries outside the US. A 2024 FDA review found insufficient evidence of effectiveness | WADA prohibited substance; not FDA-approved for any human use |
| Strength of evidence | Randomized human trials with mixed results, such as one in chronic hepatitis C combined with interferon | Preclinical (animal and lab) studies; human data is limited |
| Reported side effects | Rare injection site reactions | Rare: fatigue, temporary mood changes, injection site reactions |
| Common vial sizes | 1.6mg, 3.2mg | 5mg, 10mg |
| Mixing math example | 3.2 mg + 1 mL BAC water = 3,200 mcg/mL, 32 mcg per unit | 5 mg + 1 mL BAC water = 5,000 mcg/mL, 50 mcg per unit |
Key differences
Thymosin alpha-1 is studied for supporting T-cell maturation, natural killer cell activity, cytokine production and dendritic cell function. TB-500 is studied for promoting actin polymerization and cell migration and for supporting angiogenesis and tissue repair.
Thymosin alpha-1 is reported to be approved in some countries outside the United States, but it is not FDA-approved, and a 2024 FDA review found insufficient evidence of effectiveness for the uses it evaluated. TB-500 is not FDA-approved and is on the World Anti-Doping Agency's prohibited list.
Thymosin alpha-1's reported side effects are rare injection site reactions. TB-500's reported side effects are rare and include fatigue, temporary mood changes and injection site reactions.
What the research covers
Thymosin alpha-1 has randomized human trials, including one in chronic hepatitis C combined with interferon, with mixed results. TB-500's tissue-repair findings come from animal and laboratory research, and human data is limited.
Sources
- Combination therapy with thymosin alpha1 and interferon for the treatment of chronic hepatitis C infection: a randomized, placebo-controlled double-blind trial. Sherman KE et al. Hepatology, 1998. Human trial
- Thymosin alpha1: the regulator of regulators?. Pierluigi B et al. Annals of the New York Academy of Sciences, 2010. Review
- Thymosin Alpha-1 (Ta1) Related Bulk Drug Substances (Pharmacy Compounding Advisory Committee briefing). U.S. Food and Drug Administration, 2024. Regulatory document
- Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Goldstein AL et al. Trends in Molecular Medicine, 2005. Review
- The effect of thymosin treatment of venous ulcers. Guarnera G et al. Annals of the New York Academy of Sciences, 2010. Human trial
- The Prohibited List. World Anti-Doping Agency, 2026. Regulatory document
Frequently asked questions
Is thymosin alpha-1 the same as thymosin beta-4?
No. They are different peptides. TB-500 is a synthetic version of thymosin beta-4, studied for tissue repair. Thymosin alpha-1 is studied for immune modulation.
What is the difference between thymosin alpha-1 and TB-500?
Thymosin alpha-1 is studied for T-cell and natural killer cell function. TB-500 is studied for cell migration, angiogenesis and tissue repair.
Is thymosin alpha-1 or TB-500 FDA-approved?
Neither is FDA-approved. Thymosin alpha-1 is reported to be approved in some other countries, and TB-500 is prohibited by the World Anti-Doping Agency.
Which has more human research, thymosin alpha-1 or TB-500?
Thymosin alpha-1 has randomized human trials, with mixed results. Human data on TB-500 is limited.
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