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TB-500

Thymosin fragment — not dispensed

TB-500 is not thymosin β4. Thymosin β4 is a 43–amino-acid protein with real human trial data; TB-500 is a seven–amino-acid fragment of its actin-binding region.

Recommended 8–6 for the 503A bulks list in July 2026; HHS has not acted. It is also on WADA’s prohibited list.

Preclinical only

Almost all published data is from animal or laboratory work. No completed human efficacy trial has been published.

43 vs 7

Amino acids in real thymosin β4 versus the fragment sold as TB-500

Structure
8–6

Advisory committee vote recommending it for the 503A bulks list

PCAC, 23–24 July 2026
None

Human trials of TB-500 itself, as distinct from thymosin β4

As of August 2026

What it is

TB-500 is sold as thymosin beta-4. It is not. Thymosin β4 is a 43–amino-acid protein that has been through human trials; TB-500 is a short synthetic fragment of its actin-binding region. Vendors cite the Tβ4 trials on TB-500 pages. Whealth does not dispense either.

How it works

Thymosin β4 sequesters actin and appears to promote cell migration, angiogenesis and wound closure. The fragment sold as TB-500 reproduces part of that binding region, on the assumption the rest of the molecule does not matter — an assumption nobody has tested head to head in people.

What the evidence actually says

  1. 2007

    A real human trial — of Tβ4

    A European prospective randomised study of thymosin β4 in venous ulcers. Genuine human data, on the full-length molecule, applied topically to a wound.

  2. 2012

    Class review

    A review of thymosin β4 as a regenerative peptide covering its basic properties and clinical applications, which remain mostly early phase.

  3. 2026

    PCAC vote

    Recommended 8–6 for the 503A bulks list on 23–24 July. Advisory; HHS has not acted.

What the first months look like

  • TodayNothing from us. Not on the 503A bulks list.
  • If HHS actsIt becomes compoundable. The fragment would still not be the molecule the human trials used.

Who this is not for

  • Anyone, from us, at present.
  • It is also on WADA's prohibited list. If you compete under any anti-doping code, this ends your season.
Sources
  1. Guarnera G et al. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study. Ann N Y Acad Sci 2007;1112:407–12. PMID 17495250.
  2. Goldstein AL et al. Thymosin β4: a multi-functional regenerative peptide. Expert Opin Biol Ther 2012;12(1):37–51. PMID 22074294.

Figures are quoted from the published trials and were last checked in August 2026. We update this page when the evidence changes.