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TB-500 Unknown Long-Term Safety: When to Call the Doctor

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Published Updated Last reviewed
12 linked public sourcesEditorial, sourcing, and corrections policy

At a glance

  • Human studies of TB-500 / none found [2]
  • Reports in FDA's adverse-event database / zero through March 26, 2025 [2]
  • Reaction reported with a TB-500-containing product / skin and gum darkening in one woman using a BPC-157 and TB-500 blend [1]
  • FDA's stated concern for injectable TB-500 / immune reaction (immunogenicity) [2]
  • Toxicity and immunogenicity studies of TB-500 / none found [2]
  • Approval status / not FDA-approved in the US or in any other country FDA checked [2]
  • Sport status / prohibited at all times by WADA [3]

What is known about TB-500 safety?

FDA's July 2026 review searched PubMed, Embase, ClinicalTrials.gov and other sources and found no article in which TB-500 was given to a human for any condition, and no published case reports [2]. Its adverse-event database search through March 26, 2025 retrieved no TB-500 reports. Its food and supplement complaint system, searched from January 1, 2004 to March 10, 2025, returned two cases about a blended TB-500 and BPC-157 product, with no safety assessment [2].

The laboratory and animal work is thin. FDA found no in-vivo animal study of TB-500 for wound healing, no nonclinical toxicity studies, and no study of TB-500 immunogenicity or aggregation [2]. In an in-vitro scratch-wound test, TB-500 at 50 micrograms/mL did not induce wound closure in fibroblast cultures [2]. There is no approved dose and no human dosing study [2].

A reported reaction after a TB-500-containing blend

A 40-year-old woman injected a product labeled for research purposes only, containing 5 mg BPC-157 and 5 mg TB-500, under the skin twice daily [1]. Within a week she developed widespread skin hyperpigmentation and darkening of her gums [1]. The darkening returned when she tried the product again two weeks later [1]. Because the product held two peptides, FDA said it could not tell whether either one caused the reaction [1].

Other risks of injecting

Infections from unsafe injection practices. CDC says unsafe injection practices can spread hepatitis B, hepatitis C, bacterial and fungal infections, and possibly HIV when needles, syringes or vials are reused or shared [4]. TB-500 is sold online as research-use-only powder, and FDA found several salts and derivatives, including different active moieties, sold under the same name [2].

An immune reaction. FDA's stated concern for injectable TB-500 is immunogenicity, an immune reaction that peptide aggregation and peptide-related impurities could amplify [2].

Where TB-500 stands

TB-500 is not an FDA-approved drug and has no USP or National Formulary monograph [2]. It is in none of the three categories on FDA's lists of bulk substances for state-licensed pharmacies and physicians, or on FDA's list for outsourcing facilities [5][6][7]. In July 2026 an FDA advisory committee voted in favor of adding it to the compounding list, against FDA staff's recommendation; the vote is advice only and did not change its status [8][2]. A draft HHS enforcement-discretion policy filed in October 2026 names TB-500 but is not an approval and is not binding [9][10].

Frequently asked questions

Has TB-500 ever been tested in people?
FDA searched PubMed, Embase, ClinicalTrials.gov and other sources and found no article in which TB-500 was given to a human, and no published case reports [2].
Is TB-500 FDA-approved?
No. FDA found no approved drug containing TB-500 in the United States, no approved product in Canada, Australia, the UK or the European countries it checked, and no product authorized by the European Medicines Agency [2].
What is the main safety concern with injectable TB-500?
FDA named immunogenicity, an immune reaction that peptide aggregation and peptide-related impurities could amplify. FDA found no study of TB-500 immunogenicity or aggregation and no nonclinical toxicity studies [2].
Does TB-500 cause cancer?
This is unmeasured, since FDA found no study in which TB-500 was given to a person [2]. Lab work links overexpressed full-length thymosin beta-4 to increased invasion of colon carcinoma cells [11], but that work looked at the whole protein in cells, not at TB-500 given to a person.
Is TB-500 banned in sport?
Yes. WADA's Prohibited List names thymosin-beta4 and its derivatives, for example TB-500, in section S2.3, and prohibits them at all times, in and out of competition [3][12].

References

  1. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  2. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  3. World Anti-Doping Agency. World Anti-Doping Agency
  4. Safe Injection Practices and Your Health | Injection Safety | CDC. Safe Injection Practices and Your Health | Injection Safety | CDC
  5. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  6. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  7. Bulk Drug Substances Used in Compounding of the FD&C Act | FDA. Bulk Drug Substances Used in Compounding of the FD&C Act | FDA
  8. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  9. Official web page. Official web page
  10. Official web page. Official web page
  11. Wang WS, Chen PM, Hsiao HL, Wang HS, Liang WY, Su Y. Overexpression of the thymosin beta-4 gene is associated with increased invasion of SW480 colon carcinoma cells and the distant metastasis of human colorectal carcinoma. Oncogene. 2004;23(39):6666-71. Overexpression of the thymosin beta-4 gene is associated with increased invasion of SW480 colon carcinoma cells and the distant metastasis of human colorectal carcinoma
  12. World Anti-Doping Agency. World Anti-Doping Agency
Evidence overview for TB-500 Unknown Long-Term Safety: When to Call the Doctor