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TB-500 Side Effects: Withdrawal and Discontinuation Syndrome

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At a glance

  • Approval status / Not FDA-approved; no approved product contains it [1]
  • What it is / Synthetic 7-amino-acid fragment of thymosin beta-4, not the full protein [1]
  • Human data / None found; FDA found no study giving TB-500 to a person [1]
  • Withdrawal reports / None; FDA's adverse-event database search through March 26, 2025 retrieved no TB-500 reports of any kind [1]
  • Human half-life / Not established; FDA found no human pharmacokinetic data [1]
  • Main injectable concern / Immune reaction, possibly increased by peptide aggregation and impurities [1]
  • Sport status / Banned at all times by WADA [2]

Does TB-500 cause withdrawal?

There is no documented withdrawal syndrome, and that absence is not a finding that stopping is symptom-free. FDA found no human pharmacokinetic data for TB-500 by any route, so its human half-life, and therefore how long it stays in the body after the last injection, is unknown [1].

What is known about side effects?

FDA's main stated concern for injectable TB-500 is immunogenicity, an immune reaction, possibly amplified by peptide aggregation and impurities [1]. One adverse event involving a TB-500 product was described in FDA's BPC-157 review. A 40-year-old woman used a combined BPC-157 plus TB-500 injection and developed widespread skin hyperpigmentation and gum darkening within a week, and it recurred when she retried the product. Because the product held two peptides, FDA said it cannot tell whether either caused it [3].

Regulatory status

TB-500 is a common name, not an official drug name. FDA found several salts and derivatives, including different active moieties, sold under the same name [1]. What a given vial contains can therefore differ from product to product.

Frequently asked questions

Is TB-500 FDA-approved?
No. TB-500 is not an FDA-approved drug, and FDA found no approved product containing it [1]. WADA names thymosin beta-4 and its derivatives, including TB-500, as prohibited at all times [2].
What side effects have been linked to TB-500?
FDA's main concern for injectable TB-500 is immunogenicity, possibly amplified by peptide aggregation and impurities [1]. One case in FDA's BPC-157 review involved a combined BPC-157 and TB-500 product and skin and gum darkening; FDA said it cannot tell which peptide caused it [3].
What is TB-500?
TB-500 is a synthetic 7-amino-acid fragment of the 43-amino-acid protein thymosin beta-4; it is not full-length thymosin beta-4 [1].

References

  1. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  2. World Anti-Doping Agency. World Anti-Doping Agency
  3. U.S. Food and Drug Administration. U.S. Food and Drug Administration
Evidence overview for TB-500 Side Effects: Withdrawal and Discontinuation Syndrome