Peptide Medicine
TB-500: Evidence, Safety and Regulatory Status
Evidence checked by HealthRX.com Editorial Team · Last evidence check
What is TB-500, and is it thymosin beta-4?
TB-500 is the N-terminally acetylated 17-23 fragment of thymosin beta-4, not the complete naturally occurring protein. The fragment contains seven amino acids, while full-length thymosin beta-4 contains 43. Results from studies of the complete protein cannot be assumed to establish the fragment's efficacy, safety, pharmacology or dose. [1][2]
The names are often used interchangeably in marketing, but FDA evaluates TB-500 free base and acetate as distinct bulk drug substances. FDA also documented inconsistencies in a prior nomination package about which form was actually being proposed. [2]
Does TB-500 heal tendons, muscles or wounds?
There is no reliable human evidence that TB-500 heals tendons, ligaments, muscle injuries or surgical wounds. Laboratory work on thymosin beta-4 biology supports hypotheses involving actin binding, cell migration and blood-vessel formation, but those findings do not establish a clinical benefit for injected TB-500 in people. [3]
Small human studies have evaluated full-length thymosin beta-4 formulations in settings such as venous ulcers and dry eye. Those products and routes are not TB-500, so their results should not be presented as clinical trials of this fragment. [4][5]
Has TB-500 been tested in humans?
FDA states that it has not identified human exposure data for drug products containing the TB-500 fragment. That means there is no established clinical dose, no validated treatment schedule, no reliable adverse-event rate and no evidence-based monitoring protocol for the uses commonly promoted online. [2][6]
- No FDA-approved indication
- No established human efficacy dose
- No validated injection or cycling protocol
- No adequate long-term safety data
- No basis for transferring full-length thymosin beta-4 trial results to TB-500
What are the safety concerns with TB-500?
TB-500's human safety profile is unknown. FDA identifies potential immunogenicity from peptide aggregation and peptide-related impurities and says it lacks information needed to determine whether the fragment would cause harm in humans. Sterility, identity and concentration add further risk when injectable products come from unverified sellers. [6]
Absence of reported harm is not evidence of safety when controlled exposure data and adverse-event denominators do not exist. Anyone with an injury needs a diagnosis and an evidence-based rehabilitation plan rather than an unvalidated peptide protocol.
Is TB-500 FDA approved or permitted for compounding?
TB-500 is not FDA approved. Its earlier 503A nomination was withdrawn, removing it from interim Category 2 in April 2026. On July 23, 2026, an FDA advisory committee recommended the free base and acetate forms for the 503A bulks list by an 8 to 6 vote, but that recommendation is non-binding and is not a final FDA decision. [2][7]
A substance identifier, a nomination or an advisory vote does not make a product FDA approved. FDA's general 503A rules also require a lawful bulk-substance basis, a valid certificate of analysis and an FDA-registered bulk manufacturer. [8]
How does TB-500 compare with other peptides?
| TB-500 | Thymosin beta-4 | |
|---|---|---|
| Structure | Acetylated 7-amino-acid fragment | 43-amino-acid natural peptide |
| Human drug exposure data | FDA identified none | Limited formulation-specific trials |
| Injury-healing efficacy | Not established | Not established for routine injury treatment |
| FDA approved | No | No |
How to get TB-500 online
TB-500 is available through HealthRX.com after an online visit with a licensed provider, who reviews your history and, when appropriate, issues a prescription that a licensed US pharmacy dispenses and ships to you.
Because TB-500 is a investigational synthetic peptide fragment and prescription-only, it cannot be bought over the counter. What you pay depends on the dose and quantity your provider recommends. You can begin the online visit in a few minutes and are only prescribed if a provider determines it is appropriate.
Frequently asked questions
Is TB-500 the same as thymosin beta-4?
No. TB-500 is an acetylated seven-amino-acid fragment related to the 43-amino-acid thymosin beta-4 protein. Evidence from a full-length thymosin beta-4 formulation cannot automatically be applied to TB-500.
Is TB-500 FDA approved?
No. TB-500 is not FDA approved. A July 2026 advisory committee recommendation about the 503A bulks list was non-binding and did not approve a drug or create a final FDA compounding decision.
What is TB-500 used for?
It is marketed for wound, tendon, ligament and muscle recovery, but those uses are not supported by adequate human clinical trials of TB-500 itself.
What is a safe TB-500 dose?
No evidence-based human dose or schedule has been established. Online injection, cycling and stacking protocols are not validated clinical guidance.
What are the risks of TB-500?
The human risk profile is unknown. FDA highlights possible immunogenicity and peptide-impurity concerns and says it lacks the exposure data needed to determine whether TB-500 would harm humans.
Citations
- Esposito S, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500. Drug Test Anal. 2012;4(9):733-738.
- FDA. Briefing Document for TB-500-Related Bulk Drug Substances. Pharmacy Compounding Advisory Committee, July 23, 2026.
- Philp D, et al. The actin binding site on thymosin beta4 promotes angiogenesis. FASEB J. 2003;17(14):2103-2105.
- Malinda KM, et al. Thymosin beta4 and venous ulcers: a prospective randomized study. Ann N Y Acad Sci. 2007.
- Sosne G, et al. Thymosin beta 4 ophthalmic solution for dry eye: a randomized Phase II trial. Clin Ophthalmol. 2015.
- FDA. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks.
- FDA. July 23-24, 2026 Pharmacy Compounding Advisory Committee meeting materials.
- FDA. Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act.
This guide is educational and is not a substitute for individualized medical advice. TB-500 is prescription-only and requires evaluation by a licensed provider.