TB-500 questions, answered from the literature

Identity and basics

What is TB-500?

TB-500 is the synthetic, N-acetylated heptapeptide Ac-LKKTETQ corresponding to residues 17–23 — the actin-binding motif — of thymosin beta-4 ^[1]. It is a research and veterinary-context substance with no approved therapeutic indication. The name denotes the fragment; "Ac-LKKTETQ" denotes the sequence.

What does TB-500 stand for and what does TB stand for in TB-500?

TB refers to thymosin beta-4 (Tβ4), the parent protein. TB-500 is a research and veterinary designation for its synthetic actin-binding fragment, Ac-LKKTETQ ^[1]. It is a product designation rather than a chemical name, so it does not encode the sequence directly.

What is TB-500 used for in research?

In research models, thymosin beta-4 and its actin-binding region are studied for cell migration, wound healing, angiogenesis, cardiac and neurological repair, hair-follicle activation, and anti-inflammatory or anti-fibrotic effects ^[5]. These are study endpoints, not approved uses, and the strongest data are on the full-length protein.

How does TB-500 work?

TB-500 carries the LKKTETQ actin-binding motif of thymosin beta-4, the body's main G-actin sequestering peptide ^[1]. In injury models the parent protein drives cell migration, angiogenesis, anti-inflammatory and anti-apoptotic signaling, and reduced scarring ^[5]. Whether the isolated seven-mer reproduces these at research doses is not established in controlled human trials ^[5].

Steroid or peptide — is TB-500 a steroid?

No. TB-500 is a peptide fragment — the seven-amino-acid Ac-LKKTETQ sequence of thymosin beta-4 — not a steroid ^[1]. Steroids are lipid molecules built on a four-ring carbon skeleton; TB-500 is a chain of amino acids that works by binding actin, an entirely different mechanism and chemical class ^[5].

Safety and side effects

What are the side effects of TB-500?

Human safety data for the fragment are scarce. The main flagged concern is the tumor and angiogenesis signal associated with thymosin beta-4 ^[5]. In a Phase 1 IV study of full-length thymosin beta-4 to 1260 mg, only infrequent mild-to-moderate adverse events occurred, with no dose-limiting toxicities ^[6] — but that characterizes the parent protein, not the seven-mer, and not chronic use.

Does TB-500 cause cancer or promote tumor growth?

This is an open safety concern, not a settled finding. Thymosin beta-4 is overexpressed in several cancers and is implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression ^[5]. No human study establishes either harm or safety on this point for the fragment.

Is TB-500 safe for long-term use?

There are no long-term human safety data for the TB-500 fragment ^[5]. Given the tumor and angiogenesis signal and the absence of any completed controlled clinical trial of the seven-mer, long-term human safety is unestablished ^[5]. The available human tolerability data cover 14 days of IV dosing of the full-length protein only ^[6].

Comparisons and status

What is the difference between TB-500 and BPC-157?

TB-500 is the Ac-LKKTETQ actin-binding fragment of thymosin beta-4; BPC-157 is a separate synthetic pentadecapeptide ^[1]. They are distinct compounds studied for overlapping repair endpoints, not variants of one molecule. Both are listed among unapproved musculoskeletal peptides in a 2026 Sports Medicine review ^[10].

Is TB-500 banned by WADA and in competitive sports?

Yes. TB-500 and thymosin beta-4 fall under WADA-prohibited peptide, growth-factor, and tissue-repair categories and are banned in and out of competition ^[5]. They are detectable by LC-MS anti-doping assays, and a 2024 method specifically quantifies TB-500 and its metabolites for detection ^[15].

Is TB-500 FDA approved?

No. TB-500 is not approved by the FDA for human use and has no approved therapeutic indication ^[19]. FDA has placed the LKKTETQ thymosin beta-4 fragment, listed as "also known as TB-500," in 503A Category 2 for compounding ^[18]. It is a research-chemical and veterinary-context substance.

Is TB-500 legal?

TB-500 is sold by research suppliers for laboratory use and is not an FDA-approved drug ^[19]. FDA placed the LKKTETQ thymosin beta-4 fragment in 503A Category 2, so it is not within FDA's enforcement-discretion policy for routine 503A compounding ^[18]. It is also WADA-prohibited in sport ^[5]. This is general information, not legal advice.

Can you get TB-500 from a compounding pharmacy?

As a Category 2 substance, TB-500 is not eligible for routine 503A compounding while that status stands, because FDA flagged it for significant safety risks ^[18][19]. Legally compounded access in general runs through a licensed-prescriber evaluation, a valid patient-specific prescription, and a 503A pharmacy or 503B facility — but only for eligible ingredients ^[19].

What is the FDA 503A status of TB-500?

FDA lists the substance as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" and placed it in 503A Category 2 — bulk substances that may present significant safety risks — effective with the September 29, 2023 update, citing immunogenicity and a lack of safety information ^[18]. It is named on the July 23–24, 2026 PCAC agenda as under consideration, which is a scheduled discussion, not a decision ^[17].

Research findings and efficacy

Are there any human clinical trials on TB-500?

No completed controlled clinical trials of the TB-500 heptapeptide exist for any indication ^[5]. Human data are limited to full-length thymosin beta-4: a randomized Phase 1 IV safety and PK study ^[6] and topical ophthalmic (RGN-259) dry-eye trials ^[7]. An injectable acute-MI trial completed ^[8]; an early injectable stroke trial was withdrawn ^[9].

What is the latest research on TB-500 / thymosin beta-4?

Recent (2021–2026) work centers on engineered delivery and new repair endpoints: a 2025 thymosin beta-4-exosome wound hydrogel ^[12], a 2025 thymosin beta-4-plus-selenium diabetic-ulcer study ^[13], a 2025 engineered tandem corneal peptide ^[16], a 2024 anti-doping quantification method ^[15], and a 2026 Sports Medicine review of unapproved musculoskeletal peptides ^[10].

What is thymosin beta-4 as an exerkine and what does that mean for recovery?

A 2021 study characterized thymosin beta-4 as a human exerkine — a circulating factor released in response to exercise — and a growth factor ^[11]. That gives a contemporary framing for the athletic-recovery interest in TB-500, since the parent protein is part of the body's own response to exertion. It does not, by itself, prove the fragment improves recovery in people.

Does TB-500 work for muscle tears and recovery from exercise?

Animal data show thymosin beta-4 recruits myoblasts and aids connective-tissue healing, but in dystrophic (mdx) mice it increased regenerating fibers without improving muscle strength — a notable null functional result ^[5]. Human efficacy is unproven, and the exerkine framing ^[11] is a rationale, not an outcome.

How long does it take for TB-500 to work for injury healing?

No validated human timeline exists. In a rat wound model, full-length thymosin beta-4 increased re-epithelialization by 42% at 4 days and up to 61% at 7 days ^[3], but that is animal data on the protein and does not establish a human timeframe for the fragment. For TB-500 in people, the timing has not been measured.

Can TB-500 help with tendon injuries and ligament repair?

Thymosin beta-4 enhanced medial collateral ligament healing in a rat model — one of the few direct connective-tissue findings underpinning the athletic-recovery rationale ^[5]. Human tendon or ligament efficacy of the fragment is not established; the case rests on animal data plus the protein's general pro-migratory, anti-scarring mechanism ^[5].

Does TB-500 affect the heart?

In mice, thymosin beta-4 activated PINCH-ILK-Akt survival signaling, mobilized epicardial progenitors, and improved function after coronary ligation ^[2]. However, a porcine ischemia-reperfusion study found no benefit, and a human acute-MI trial of thymosin beta-4 was studied separately ^[8]. The rodent cardiac signal has not translated into an established human result for the fragment.

Does TB-500 have neuroprotective effects on the brain?

In a rat embolic-stroke dose-response study, intraperitoneal thymosin beta-4 improved neurological function at 2 and 12 mg/kg but not at 18 mg/kg — a non-monotonic result — with a modeled optimal near 3.75 mg/kg ^[4]. This is animal data on the parent protein; human neuroprotection by the TB-500 fragment is not established.

Does TB-500 help wound healing?

In animal and topical models, full-length thymosin beta-4 accelerated dermal and corneal re-epithelialization, increased collagen deposition and angiogenesis, and as little as 10 pg stimulated keratinocyte migration ^[3]. Recent delivery systems — exosome hydrogels ^[12] and engineered tandem peptides ^[16] — extend this work. Human wound-healing efficacy of the TB-500 fragment is not established ^[5].