# TB-500 FAQ: Identity, Evidence, Safety, and Legal Status

> TB-500 FAQ: what TB-500 is, what TB stands for, how it differs from BPC-157, whether it is FDA approved or WADA-banned, and what the thymosin beta-4 research actually shows.

Direct answers to the most-asked TB-500 questions — definitional, mechanistic, safety, and regulatory — each cited where it states a number.

## What is TB-500 used for in research?

TB-500 is studied as a synthetic actin-binding peptide in tissue-repair, wound-healing, cardiac, neurological, and angiogenesis models. The parent protein thymosin beta-4 carries most of that evidence [5]. The fragment inherits the research interest; the demonstrated effects are largely the parent protein's.

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

No human timeline is established for the fragment. In a rat wound model, full-length thymosin beta-4 raised re-epithelialization by 42% at 4 days and up to 61% at 7 days [3] — an animal-model time course, not a human dosing schedule.

## Does TB-500 help wound healing?

In animal and topical models, thymosin beta-4 accelerated dermal and corneal re-epithelialization and increased contraction, collagen, and angiogenesis [3]. Human efficacy of the 7-mer is unproven; the strong wound-healing data are on the parent protein in rodents.

## Does TB-500 help corneal or eye healing?

Topical thymosin beta-4 promoted corneal wound healing and reduced inflammation in mice [7], and the clinical-grade formulation RGN-259 improved dry-eye signs in placebo-controlled trials. These results are on Tβ4-based formulations, not the TB-500 fragment as marketed.

## Can TB-500 be taken orally?

Studied routes are intraperitoneal, intravenous, and topical/ophthalmic [3][6]. As a peptide it is subject to gastrointestinal proteolysis, and no oral research dosing is validated. Oral administration is not a route the literature supports.

## What is TB-500?

TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ — residues 17 to 23, the actin-binding motif, of the 43-amino-acid protein thymosin beta-4 [1]. It is ~889 Da; the parent protein is ~4963 Da.

## What does TB-500 stand for?

"TB" refers to thymosin beta-4 (Tβ4). TB-500 is the commercial and veterinary designation for the synthetic Ac-LKKTETQ actin-binding fragment of that protein [1]. The name points at the parent; the substance is the fragment.

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

Injury-induced thymosin beta-4 recruits myoblasts, but a 6-month mdx-mouse study found more regenerating fibers without gains in strength or cardiac function — a notable null functional result. Mechanism did not translate into measured performance.

## Does TB-500 cause cancer or promote tumor growth?

Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis [5]. The same pro-migratory, pro-angiogenic properties that aid repair are a theoretical oncologic concern, and human safety data for the fragment are scarce.

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

Yes. TB-500 and thymosin beta-4 fall under WADA's prohibited peptide/growth-factor and tissue-repair categories, banned in and out of competition, and are detectable by LC-MS anti-doping assays in equine and human matrices.

## Is TB-500 FDA approved?

No. TB-500 has no approved therapeutic indication. FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 as a substance that may present significant safety risks [16], and it is sold for research and veterinary use only.

## Are there any human clinical trials on TB-500?

No controlled trials of the 7-mer exist. Human data are limited to full-length synthetic thymosin beta-4 — a randomized intravenous Phase 1 safety and PK study [6] and topical ophthalmic (RGN-259) dry-eye trials.

## How does TB-500 work?

Its LKKTETQ motif is the actin-binding core of thymosin beta-4, the body's main G-actin-sequestering peptide [1][5]. Full-length Tβ4 is linked to cell migration, angiogenesis, and anti-inflammatory and anti-fibrotic signaling.

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

One rat study found thymosin beta-4 enhanced medial collateral ligament healing — among the few direct connective-tissue findings. Broader tendon and ligament evidence in humans is lacking, and no controlled human trial supports the fragment here.

## Does TB-500 affect the heart?

In mice, thymosin beta-4 activated the PINCH–ILK–Akt survival pathway, improved cardiomyocyte survival, and improved cardiac function after coronary ligation [2]. A porcine ischemia-reperfusion study, however, showed no benefit — the cardiac picture is mixed.

## Does TB-500 promote angiogenesis and is that a safety concern?

Thymosin beta-4 drives endothelial migration and pro-angiogenic signaling, which aids repair but is also the basis of the tumor-angiogenesis safety concern [5]. The same mechanism cuts both ways.

## 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, with a modeled optimal near 3.75 mg/kg [4]. Higher was not better.

## Does TB-500 increase hair growth?

Nanomolar thymosin beta-4 stimulated hair growth in rodents by activating hair-follicle bulge stem cells [5]. This is animal data on the full-length protein, not human evidence for the fragment.

## Does TB-500 reduce inflammation?

In vitro, thymosin beta-4 suppressed TNF-α-induced NF-κB activation and IL-8 [5], and recent work links it to specialized pro-resolving inflammation pathways [13]. The findings are on the parent protein.

## What are the side effects of TB-500?

There is no human side-effect profile for the fragment. Intravenous full-length Tβ4 was well tolerated to 1260 mg in Phase 1 [6], but the tumor/angiogenesis signal [5] and unregulated material quality are the principal concerns.

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

TB-500 and BPC-157 are distinct peptides with different sequences and mechanisms. TB-500 is the actin-binding thymosin beta-4 fragment [1]; BPC-157 is a separate gastric-derived peptide. Both are unapproved, research-only compounds with limited human data, and neither is interchangeable with the other.

## TB-500 and BPC-157: How the Research Differs

TB-500 and BPC-157 are often discussed together, but their evidence bases differ. TB-500's case is dominated by full-length thymosin beta-4 data — actin sequestration [1], wound re-epithelialization [3], and a human Phase 1 of the parent protein [6] — with no completed controlled trial of the fragment itself. BPC-157's literature is its own separate body of gastric-peptide research with a different mechanism. The honest summary is that both are unapproved research compounds whose human evidence is thin, and this site makes no stacking or dosing claim about combining them.

## Is TB-500 safe for long-term use?

Long-term human safety is unknown. Chronic dosing has only been studied in animals, and the pro-angiogenic and tumor-overexpression signal [5] makes long-term human use an open safety question that clinical data cannot currently answer.

## Is TB-500 legal?

TB-500 is not an approved medicine. It is sold for research and veterinary use, classified as a prescription medicine in some jurisdictions, and is WADA-prohibited [16]. Legality depends on context; this is general information, not legal advice.

## Can you get TB-500 from a compounding pharmacy?

Access through compounding is constrained by FDA's review of peptide bulk drug substances under the 503A/503B framework. As a Category 2 substance, TB-500 is not eligible for routine 503A compounding while that status stands [16][19].

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

FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 — substances that may present significant safety risks — effective with its September 29, 2023 nominated-substances update [16]. As Category 2 it is outside FDA's enforcement-discretion policy for 503A compounding.

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A case review of the TB-500 evidence — every finding tagged for the molecule it is on, no clinic behind the file and nothing here for sale.