What is TB-500 (thymosin beta-4 fragment LKKTETQ)?

The short answer

TB-500 is a short, lab-made piece of thymosin beta-4, a protein found in the body.

What it is
Actin-binding piece of thymosin beta-4, studied in tissue research.
What people look into
Muscle and exercise

8 sources
Status as of October 4, 2026
How we source
Ellum doesn't sell peptides.

By Ellum EditorialPublished October 6, 2026Updated October 11, 2026AI use

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What it is

Type: Thymosin beta-4 fragment (7-aa peptide)
Also known as: thymosin beta-4 fragment, lkktetq
How it works: Actin-binding piece of thymosin beta-4, studied in tissue research.

Regulatory status

Not FDA-approved · advisory vote July 2026 · no FDA decision How we label status

As of October 4, 2026, TB-500 (thymosin beta-4 fragment LKKTETQ) is not FDA-approved. On July 23, 2026, FDA's compounding advisory committee voted to recommend adding it to the 503A bulks list; FDA staff had recommended against it. FDA has not proposed that change.

See TB-500 (thymosin beta-4 fragment LKKTETQ) in the Index →

Federal (FDA): Not FDA-approved
503A compounding: No category since 2026-04-22 (nomination withdrawn); PCAC recommended 2026-07-23/24; no proposed rule as of 2026-10-04 (as of October 4, 2026)
PCAC history: 2026-07-23: recommended 8-6-1 (free base and acetate; use reviewed: wound healing; count as read into FDA's meeting recording; written minutes not posted as of 2026-10-04); FDA staff: against
WADA 2026: S2.3

Timeline

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Date	What happened	Source
April 16, 2026	Federal Register notice of an FDA Pharmacy Compounding Advisory Committee meeting lists TB-500 among bulk drug substances under consideration for the 503A bulks list.	Federal Register, event of April 16, 2026, on federalregister.gov
July 23, 2026	FDA presentations for the Pharmacy Compounding Advisory Committee meeting cover TB-500 as a bulk drug substance under consideration for the 503A bulks list.	FDA, event of July 23, 2026, on fda.gov

US enforcement actions

2 US enforcement actions since 2023.

Actions by US federal and state agencies whose documents name TB-500 (thymosin beta-4 fragment LKKTETQ). Each row links to the government's own document.

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Date	Agency	Action	Document
April 1, 2026	US Justice Department	Indictment	Justice Department document, indictment, April 1, 2026, on justice.gov
June 12, 2023	FDA	Warning letter	FDA document, warning letter, June 12, 2023, on fda.gov

References

Sources as of October 4, 2026