Peptigrade

Recovery & Repair

TB-500

Thymosin β-4 (synthetic fragment)·Also known as: Thymosin Beta-4, TMSB4X fragment, RGN-352

FDARegulatory status

Not approved for human use

WADARegulatory status

Prohibited at all times (S0 — non-approved substances)

Regulatory note ·Sold as a research chemical. Multiple FDA warning letters have targeted vendors. WADA prohibition is enforced — TB-500 has been the subject of high-profile equine doping cases.

§ The quick take

TL;DR · Editor’s summary

TB-500 (a synthetic fragment of thymosin β-4) has a respectable animal evidence base for tissue repair across multiple organs. Two small Phase 2 trials in humans (cardiac and dermal) showed early signal but neither advanced.

Like BPC-157, it is widely sold for research use and widely used by athletes despite WADA prohibition. The honest read: C-grade evidence for soft-tissue repair on the strength of consistent animal data plus mechanism, but human efficacy is unproven.

§ Grade matrix

The grade
per outcome.

One peptide can earn very different grades for different uses. Here is every outcome we’ve graded for TB-500, sorted by strength of evidence.

C

Soft tissue repair

Mixed

Strong animal evidence for muscle, ligament, and cardiac repair. Limited human data — no published RCTs.

31 studiesUpdated Mar 14, 2026
C

Cardiac regeneration

Mixed

Phase 2 trial in heart failure (RGN-352) terminated for business reasons. Mechanistic data is promising but human efficacy unproven.

14 studiesUpdated Feb 04, 2026
C

Wound healing

Mixed

Animal models consistent. One dermal ulcer Phase 2 study showed signal but did not advance to Phase 3.

18 studiesUpdated Jan 28, 2026
D

Hair growth

Weak

Speculative. Animal evidence for hair follicle stem cell activation. No human data.

5 studiesUpdated Jan 11, 2026

§ Why this grade

Sub-scores for this outcome.

Soft tissue repair

Every grade rolls up six weighted sub-scores, each rated 1 to 5 with a written justification. Here is how the top-outcome grade was constructed.

Mechanism understood

4 / 5

Actin sequestration and migration effects well-characterized.

Human studies (count + quality)

2 / 5

Two Phase 2 trials, neither advanced. No published RCT for soft-tissue repair.

Effect vs placebo

2 / 5

Phase 2 cardiac trial showed signal but underpowered. No definitive human effect.

Long-term safety data

1 / 5

No long-term human exposure data published.

Side effect profile

3 / 5

Animal toxicology favorable. Limited human AE reports.

Regulatory status

1 / 5

Not approved. WADA-prohibited. FDA enforcement against vendors.

§ What the science says

How TB-500
works.

Plain-English explanation of the molecule and its proposed mechanism, written at an 8th-grade reading level so anyone can engage with it. Every claim is linked to a primary source below.

What it is

TB-500 is a synthetic peptide marketed as identical or similar to thymosin β-4 — a 43-amino-acid actin-sequestering protein found throughout the body. The marketed compound is often a fragment (the C-terminal active sequence) rather than the full molecule. RegeneRx Biopharmaceuticals attempted to develop the full thymosin β-4 (RGN-352) as a therapeutic but discontinued clinical development.

How it works

  1. 01

    Thymosin β-4 sequesters G-actin monomers, regulating actin cytoskeleton dynamics that underlie cell migration during tissue repair.

  2. 02

    It promotes endothelial cell migration and angiogenesis, contributing to revascularization at injury sites in animal models.

  3. 03

    It modulates inflammatory cell activity, including reducing pro-inflammatory cytokine production at injury sites.

  4. 04

    Animal studies show activation of progenitor cells in cardiac, dermal, and corneal tissues — though translation to clinically meaningful human regeneration is unproven.

§ Investigated uses

What it’s
been studied for.

Investigated does not mean proven. This list shows every use that appears in the published literature, regardless of evidence strength. See the grade matrix above for which ones have actually held up.

  • Acute and chronic soft tissue injury

    Animal models, anecdotal human use — Grade C

  • Post-myocardial infarction cardiac repair

    Phase 2 RGN-352, terminated — Grade C

  • Pressure ulcer and diabetic wound healing

    Phase 2 dermal ulcer study, did not advance — Grade C

  • Dry eye and corneal repair

    RGN-259 / Lacripep ophthalmic Phase 2/3

  • Hair growth

    Animal data only — Grade D

§ The honest gaps

What we don’t
know yet.

Every peptide page on this site is required to include this section. Absence of evidence is information. If we don’t flag the gaps, we’re lying by omission.

  • !

    No completed Phase 3 trial of TB-500 or thymosin β-4 has been published for any indication.

  • !

    Whether the marketed peptide fragment behaves identically to full-length thymosin β-4 is unclear.

  • !

    Pharmacokinetics in humans are poorly documented in peer-reviewed literature.

  • !

    Long-term safety, particularly in the context of chronic use by athletes, is unknown.

  • !

    Whether the angiogenic activity that drives tissue repair could promote tumor growth is a theoretical concern with no human data.

§ On YouTube

What experts and
influencers say.

We index YouTube content discussing TB-500and tag every speaker by credential and trust level. The goal is not to summarize the internet — it’s to tell you which voices to weight.

  • BPC-157 vs TB-500: What the Evidence Says

    Dr. Andrew Huberman·PhD Neurobiology, Stanford

    Comparison emphasizes that human data for both is limited and most claims are anecdotal.

    Verified credentials

§ Citations

Every claim,
linked to source.

All 3 sources informing this page, with DOI or PubMed identifiers. Click through to the primary literature.

  1. [01]

    Thymosin β4 in cardiac development and repair

    Smart N, Risebro CA, Melville AAD, et al. · Ann N Y Acad Sci · 2007

    AnimalPMID 26404049
  2. [02]

    Phase 2 trial of recombinant thymosin β4 in pressure ulcers

    Goldstein AL, Hannappel E · Wound Repair Regen · 2012

    RCTPMID 21306305
  3. [03]

    Thymosin β4 promotes wound healing: clinical applications and mechanisms

    Sosne G, Kim C, Kleinman HK · Int Immunopharmacol · 2018

    Systematic reviewPMID 30342150

§ Adjacent peptides

Worth reading
alongside this.

Compare

BPC-157

Most commonly stacked peptide. Both have strong animal data, both are research-only and WADA-prohibited.

Read its grades

Compare

GHK-Cu

Other commonly mentioned tissue-repair peptide. Different mechanism, similar evidence-quality story.

Read its grades

Where to research further

Looking for TB-500
for laboratory research?

Peptigrade does not sell peptides. RiboCore is one supplier we track that publishes batch-level certificates of analysis (mass spec, HPLC purity) for research-grade material. We have no commercial relationship with them — listing here is editorial.

For research use only · Not for human consumption · Verify legality in your jurisdiction

View at RiboCoreHow we evaluate suppliers →