‹ Library

TB-500

Research compound · not FDA-approvedChecked Oct 2026

Also called Ac-LKKTETQ, N-acetylated thymosin beta-4 fragment 17-23, Thymosin beta-4, fragment (LKKTETQ), TB-500 acetate

Research and education only. Not medical advice. Talk to a doctor.

FDANot approvedNot in any approved drug
HUMAN TRIALSNone foundNo genuine human trial
SPORTBannedWADA S2.3, at all times

In 30 seconds

FDA describes it as a lab-made copy of a 7-amino-acid piece of thymosin beta-4, not the whole protein.[1]

Research is mostly lab, horse and rat work; FDA found no published reports of it being given to people.[1]

Not FDA-approved, and banned in tested sport.[1][8]

How far has the research gotten?

FDA approved
Large human trials
Small human studies
Animal studiesMOST HERE
Lab cells

Much of the published work is about detecting it in doping tests.[1]

The molecule

LeuLysLysThrGluThrGln
NeutralNegative chargePositive charge

Acetylated at the start (Ac-LKKTETQ), as FDA describes it.

7amino acids

Research over time

Papers on PubMed each year that mention TB-500.0520102015202020253 papers in 2025
Same name, different things

Some sellers and papers call TB-500 "synthetic thymosin beta-4". FDA says the two aren't the same substance.[1][5]

What studies used

What each paper reports. A record of published research, not a recommendation.
Lab analysisWhat's in a product

Identifying the active ingredient of a product sold as TB-500 and building a test to detect it in plasma and urine.

Drug Test Anal · 2012 · PubMed 22962027
What the paper reports
Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential.

not stated in abstract

Who: none (chemical analysis of a commercial product)
HorsesDoping test

A lab method for detecting TB-500 and its breakdown products in horse urine and blood, to control its misuse in equine sports.

J Chromatogr A · 2012 · PubMed 23084823
What the paper reports
Doping control analysis of TB-500, a synthetic version of an active region of thymosin β₄, in equine urine and plasma by liquid chromatography-mass spectrometry.

Single dose of TB-500 containing 10 mg of N-acetylated LKKTETQ (route not stated in abstract)

Who: horse
Rats & cellsBreakdown products

How TB-500 is broken down and whether TB-500 or its breakdown products affected wound closure in cultured cells; only one breakdown product (Ac-LKKTE) did.

J Chromatogr B Analyt Technol Biomed Life Sci · 2024 · PubMed 38382158
What the paper reports
Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro.

not stated in abstract

Who: rat, plus human serum and fibroblast cell experiments
Rats · 32Tendon healing

Tendon strength and tissue structure after Achilles tendon repair in rats given TB-500, BPC-157, both, or no treatment.

Jt Dis Relat Surg · 2026 · PubMed 42542926
What the paper reports
Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study.

TB-500 60 µg/kg/day intraperitoneally for four weeks (BPC-157 10 µg/kg/day; also a combination group)

Who: rat (32 male Sprague-Dawley)
What's "Category 2"?

FDA's list of bulk substances it says may raise significant safety risks if pharmacies compound them. TB-500 was on it until its nomination was withdrawn.[6]

What it is, in full 4

FDA describes TB-500 as a lab-made copy of a seven-amino-acid stretch (positions 17-23, LKKTETQ) of the natural protein thymosin beta-4, with an acetyl group added at one end, rather than the whole protein[1].

Anti-doping chemists who analyzed a commercial product sold as TB-500 identified this acetylated fragment in it[2].

Thymosin beta-4 itself was first isolated from calf thymus and is found in many cell types and body fluids, and the TB-500 sequence contains the protein's actin-binding region[1].

Research on TB-500 itself is mostly lab, horse and rodent work, often aimed at doping detection, and FDA's 2026 review found no published reports of TB-500 being given to humans[1].

What the name means. FDA's 2026 review describes TB-500 as a synthetic seven-amino-acid fragment of thymosin beta-4 (amino acids 17-23, LKKTETQ, acetylated at the N-terminus), not the full 43-amino-acid protein. It notes that many websites call TB-500 a synthetic version of thymosin beta-4 and use the names interchangeably, but says the two are not the same substance[1]. Anti-doping analysis of a TB-500 product identified this acetylated fragment in it[2]. Some published papers disagree in wording and still describe TB-500 as 'synthetic thymosin beta-4'[5]. FDA also says products with different salts and even different active molecules are sold under the TB-500 name, so what a given product contains cannot be assumed[1].

Regulatory details 5
FDANot FDA-approved

FDA's May 2026 briefing document states that neither TB-500 (free base) nor TB-500 acetate is a component of an FDA-approved drug and that there is no USP or NF monograph for either.[1]

Checked 2026-10-06
FDA COMPOUNDINGFormerly in 503A Category 2; nomination withdrawn

FDA's safety-risk page (content current as of 04/22/2026) lists 'Thymosin beta-4, fragment (LKKTETQ), also known as TB-500' among substances previously in Category 2 whose nominations were withdrawn, noting immunogenicity concerns and that FDA found no human exposure data.[6]

Checked 2026-10-06
FDA COMPOUNDINGNot in any current 503A category

TB-500 does not appear in Categories 1, 2 or 3 of FDA's 503A nominated-substances list updated May 14, 2026.[7]

Checked 2026-10-06
FDA COMPOUNDINGFDA proposed not adding it to the 503A Bulks List

For the July 23, 2026 Pharmacy Compounding Advisory Committee meeting, FDA reviewed TB-500 (free base and acetate) for wound healing on its own initiative and proposed not adding either form to the 503A Bulks List; no committee vote or final FDA decision was found.[1]

Checked 2026-10-06
WADAProhibited at all times (S2.3)

The 2026 Prohibited List names 'Thymosin-ß4 and its derivatives e.g. TB-500' under S2.3 growth factors, which are banned both in and out of competition.[8]

Checked 2026-10-06
Human trials on ClinicalTrials.gov

ClinicalTrials.gov returns one record for TB-500 (NCT07487363), and its own summary calls it a fictional example record, so no genuine registered human trial of TB-500 was found; of the 18 records returned for 'thymosin beta-4', that same record is the only one naming TB-500, and the other 17 list interventions such as thymosin beta 4, recombinant human thymosin beta 4 (NL005) and RGN-259[9][10].

All sources 11
  1. FDA Briefing Document, PCAC July 23-24, 2026: Evaluation of TB-500-Related Bulk Drug SubstancesU.S. FDA
  2. Esposito S et al. N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500. Drug Test Anal 2012PubMed (NLM)
  3. Ho EN et al. Doping control analysis of TB-500 in equine urine and plasma. J Chromatogr A 2012PubMed (NLM)
  4. Rahaman KA et al. TB-500 and its metabolites in vitro and in rats. J Chromatogr B 2024PubMed (NLM)
  5. Biçer O et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats. Jt Dis Relat Surg 2026PubMed (NLM)
  6. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2 page)U.S. FDA
  7. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A (updated May 14, 2026)U.S. FDA
  8. World Anti-Doping Code International Standard: Prohibited List 2026World Anti-Doping Agency
  9. ClinicalTrials.gov search: TB-500ClinicalTrials.gov (NLM)
  10. ClinicalTrials.gov search: thymosin beta-4ClinicalTrials.gov (NLM)
  11. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory CommitteeU.S. FDA
Tip

Tap any purple number to open the source it came from.

CalculatorDiscuss in Community

Written from the sources above and checked on the date shown. Sources can be incomplete or out of date, and summaries can contain mistakes: read the source. See the terms.