TB-500

Name	What was studied
TB-500	The acetylated seven-amino-acid fragment Ac-LKKTETQ, as defined in the FDA review.60,61
Thymosin beta-4	The full-length, 43-amino-acid peptide. Timbetasin is its international nonproprietary name.62
NL005	A different recombinant thymosin beta-4 product studied by intravenous infusion in China. Its human results do not establish TB-500 results.63
LKKTETQ	The non-acetylated fragment used in older mouse wound research. It is chemically different from Ac-LKKTETQ.64,60

Vial labels

Analytical researchers identified Ac-LKKTETQ in one product sold as TB-500.⁶¹

Injury and healing research

The available findings leave large gaps between laboratory work and a treatment for people.

4 tendons per group

Thirty-two rats were assigned to four groups; four tendons per group were tested for strength and four for tissue changes. Material described as TB-500 improved strength versus control. Combining it with BPC-157 showed no added benefit. The paper did not report the peptide sequence or an independent identity assay.⁶⁵

Rat study limits

This was an early postoperative animal result, with one assessment time and no functional assessment.⁶⁵

The four knee-pain patients

In a retrospective report, four people received BPC-157 plus a product called TB4; three reported improvement. With no control group, two treatments and no confirmed fragment identity, the report cannot isolate a TB-500 effect.⁶⁶

The older mouse study

The 2003 paper tested non-acetylated LKKTETQ in aged mice. Its diabetic-mouse findings concerned full-length thymosin beta-4. Neither result is a human trial of Ac-LKKTETQ.⁶⁴

Cells and metabolism

A 2024 study examined breakdown in human serum, enzymes and rats. One breakdown product, Ac-LKKTE, increased fibroblast wound closure; the parent Ac-LKKTETQ did not in that assay. The human serum came from a laboratory experiment rather than treatment in people.⁶⁷

What about the human trials?

Some related products reached human trials. The findings apply only to those exact products.

Intravenous NL005

A phase 1 program studied 84 healthy Chinese adults. No serious adverse events or dose-limiting toxicity were reported during short follow-up. Its measured half-life belongs to intravenous NL005 and cannot supply a half-life for injected TB-500.⁶³

The heart-attack trial

A 96-person NL005 trial after treatment for a heart attack did not find a significant overall difference in infarct area. A subgroup of 43 people first treated within eight hours had a positive result. A subgroup result does not replace the main comparison.⁶⁸

Eye drops

In a 72-person dry-eye trial of full-length thymosin beta-4 drops, both primary outcomes were nonsignificant. SEER-1, a separate 18-person corneal-healing trial, also missed its primary outcome. Positive secondary findings do not change those results.^69,70

Later corneal-healing research

SEER-3 randomized 79 people and missed its primary healing outcome. The public report redacted numerical efficacy estimates. These topical eye-drop studies did not test TB-500 injections for injuries.⁷¹

The record that calls itself fictional

ClinicalTrials.gov entry NCT07487363 describes itself as a fictional example.⁷²

Safety and status

Information checked September 29, 2026. Country-specific gaps remain.

Human safety

FDA's assessment found no human clinical safety or pharmacokinetic studies for defined TB-500. It also identified concerns about peptide impurities and immune reactions. Safety findings for a related peptide or a short animal experiment cannot settle these questions.⁶⁰

US approval and compounding

TB-500 free base and acetate were not components of an FDA-approved drug in the FDA assessment. TB-500 was not found during the dated federal bulks-list check; an FDA-authored vote record remained unavailable.^60,73,74

Competitive sport

WADA lists thymosin beta-4 and derivatives such as TB-500 under S2.3, prohibited both in and out of competition. The published 2027 list retains this wording and takes effect January 1, 2027.^75,76

Common questions

This section covers the exact molecule and evidence described.

01 Is TB-500 the same as thymosin beta-4?

No. TB-500 usually means Ac-LKKTETQ, a 7-residue fragment; human thymosin beta-4 is a 43-residue protein. Unacetylated LKKTETQ and Ac-SDKP are also different molecules; NL005 is a separate recombinant formulation.^{77,78,79,61,63,60}

02 How do I know what a TB-500-labelled product contains?

The label alone does not settle the identity. In a WADA-funded project testing 12 seized or internet-sourced products with varied labels, one vial labelled TB-500 contained full thymosin beta-4. That mixed sample cannot estimate how often TB-500-labelled products are misidentified, and a vendor certificate is not independent proof.^80,81

03 Will TB-500 heal a tendon, ligament or muscle injury?

No controlled human injury-recovery study of exact Ac-LKKTETQ appears in the cited sources. A rat Achilles study of material described as TB-500 supports an animal hypothesis.^60,65

04 What about TB-500 with BPC-157?

The cited sources include no controlled human study of the pair. Four knee-pain patients received BPC-157 plus a product called TB4, with no control group or adequate product identification. In 32 rats, the combination did not add benefit over the individual treatment groups.^66,65

05 What dose or route has been tested in people?

None of the sources behind this chapter gives a human dose or route for exact Ac-LKKTETQ. Doses from topical full thymosin beta-4, intravenous full thymosin beta-4, intravenous NL005, horses or rats belong to different molecules, routes or species and cannot supply a human regimen.^{60,82,63,80,65}

06 How long until it works, and what happens after stopping?

The identified records do not establish a human onset, duration or post-use course for exact Ac-LKKTETQ. A cycle or maintenance schedule would therefore be an unsourced market protocol.⁶⁰

07 What did related thymosin products show in people?

Those human studies used related molecules rather than TB-500. A 72-person eye trial used topical full thymosin beta-4 and missed both primary endpoints; RGN-352 used intravenous full thymosin beta-4 in 40 healthy volunteers. NL005 is a separate recombinant thymosin beta-4 formulation that reached an intravenous 96-patient STEMI trial, where the overall infarct-size difference was not significant and a subgroup drove the signal.^83,82,63,68

08 Does exact TB-500 have direct preclinical evidence?

Yes, but the direct record is small and mixed. Exact Ac-LKKTETQ did not improve closure in an in-vitro scratch assay; one metabolite did. A rat Achilles study reported stronger repaired tendons using material described as TB-500, but the paper did not verify its sequence or acetylation.^67,65

09 What did the rat Achilles study find?

The study randomized 32 rats, eight per group, to daily intraperitoneal treatment for 30 days. Only four tendons per group entered strength testing and four entered histology; material described as TB-500 improved load to failure versus control, with adjusted p=0.0406, but no functional outcome or prospective power calculation was reported.⁶⁵

10 Does the mouse wound study test TB-500?

No. The diabetic-mouse arm used full thymosin beta-4; non-acetylated LKKTETQ was tested only in aged mice. Neither intervention is Ac-LKKTETQ.⁶⁴

11 What side effects are known?

A reliable human side-effect rate for exact Ac-LKKTETQ cannot be calculated from the identified records. FDA found no human exposure data and no toxicology study for the exact compound and flagged immunogenicity and product-related risks.⁶⁰

12 How should it be reconstituted or stored?

No approved label or validated human product protocol was identified for exact TB-500. Nothing in the sources supports any mixing or storage instructions for unverified market products. Their identity, sterility, endotoxin level and stability are open risks.^60,84

13 Is it safe with a condition, another drug, pregnancy or older age?

The cited sources do not provide an evidence-based answer for exact Ac-LKKTETQ. Results from other thymosin forms and routes do not establish interactions or safety in pregnancy, older adults or people with medical conditions.^60,82,63

14 Does TB-500 raise cancer risk?

No human risk estimate was identified. Angiogenesis and cell-migration findings measure mechanisms rather than a cancer outcome, and the missing toxicology package prevents a reassuring claim.⁶⁰

15 Is TB-500 FDA approved or lawfully compoundable after the July 2026 vote?

The sources behind this chapter show no FDA-approved TB-500 drug, and TB-500 was absent from the September 25, 2026 federal bulks list. A reported 8-6-1 committee vote recommended listing free base and acetate against FDA staff advice; that vote was advisory. No final FDA rulemaking outcome was found in the checked sources through September 29, 2026.^60,74,73,85

16 Is TB-500 banned in sport, and how long is it detectable?

Yes for athletes covered by the World Anti-Doping Code: the 2026 list names TB-500 under S2.3, and the published 2027 list keeps that wording. The 2 ng/mL figure specifies only a laboratory minimum performance level.^75,76,86

17 Is TB-500 approved or proven for dogs or horses?

No regulator-approved veterinary TB-500 product appears in the cited sources. The horse studies covered analysis and pharmacokinetics rather than controlled injury-treatment trials, and FEI lists synthetic thymosin fragments under the trade name TB500 as banned.^80,87

18 Does legal status change by country?

Yes, and one global label would be misleading. Health Canada warns about unauthorized injectable TB-500 products, while Australia lists TB-500 and thymosin beta-4 in Schedule 4 and Appendix D. These records do not answer every possession, prescribing or customs question.^84,88