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Explore  /  TB-500 (Thymosin Beta-4 fragment)

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TB-500 (Thymosin Beta-4 fragment)

C

best evidence

Peptide⚠ WADA-banned

also called — TB-500 · "Thymosin Beta-4 fragment" · often marketed (loosely) as Thymosin Beta-4 / Tβ4 / TB4

tissue repairwound healingangiogenesisanti-inflammatory (research context)

Research / reference — not for sale. No dosing, reconstitution, or administration is published (intentional). Neutral scientific reference only. Note the identity distinction below — "TB-500" and full-length Thymosin Beta-4 are related but not identical, and it matters for reading the evidence.

In brief

TB-500 is a synthetic actin-binding fragment related to Thymosin Beta-4, studied mainly in animal models for tissue repair, wound healing and inflammation. Importantly, the human clinical data belongs to full-length Tβ4 (mixed-result eye and cardiac trials, no approval), not to the TB-500 fragment — which has no completed human efficacy trials. It is not approved anywhere and is banned in sport.

Legal standing, by region

European Union

Not approved

Not approved for human use; not eligible for magistral/officinal compounding (no Ph. Eur. monograph). Sold only as a non-medicinal "research" chemical, which does not authorise human use.

United States · your region

Not FDA-approved (under review)

Removed from 503A Category 2 in April 2026; on the PCAC agenda for 23 July 2026 (with BPC-157) for possible 503A Bulks-List inclusion; FDA's pre-meeting briefing documents proposed not adding it. Advisory only; no Federal Register rule as of this writing. Full-length Tβ4 sits on a separate drug track (see below).

International

Approved nowhere

Approved nowhere.

⚠ WADA-prohibited in sportSport: WADA-prohibited at all times — Thymosin-β4 and its derivatives (e.g. TB-500) are named under Section S2 of the 2026 Prohibited List; detectable by LC-MS/MS. Athletes should treat it as banned.

Evidence, by outcome

An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.

OutcomeEvidence base · effectGrade

Musculoskeletal / tendon / muscle recovery (the marketed use)

Preclinical; no completed human efficacy trial for the fragment

Animal models only · Suggestive tissue repair

C

Wound healing / corneal repair

Data is on Tβ4, not TB-500; no FDA approval; orphan designation only (neurotrophic keratopathy)

Human trials of full-length Tβ4 — RGN-259 ophthalmic Phase 2/3 (ARISE-1/2); Philp 2003 corneal · Mixed; some benefit, primary endpoints not fully met

C

Cardiac repair

Full-length Tβ4; early-stage

Animal models + an early Tβ4 RCT · Suggestive

C

Marketed "recovery stack" (with BPC-157) for human injury/performance

No human RCT for the injuries the stack targets

None · Not demonstrated

F

Safety & long-term

WADA-banned; long-term/oncologic safety not established

Limited human data for the fragment; theoretical concern from pro-angiogenic activity · Unknown

—

Identity Thymosin Beta-4 (Tβ4) is the natural 43-amino-acid actin-sequestering peptide found in nearly every human cell. "TB-500" is a synthetic research/gray-market peptide reproducing Tβ4's actin-binding region (LKKTETQ) — the mechanistically active core. Sources disagree on its exact length (commonly described as a short acetylated fragment; some list ~17 aa), and many suppliers use "TB-500" and "Thymosin Beta-4" interchangeably even though they are not the same molecule. Both are < 43 aa → peptides. ## Development & history - Thymosin Beta-4 (Tβ4) was first characterised as a thymic peptide (Goldstein and colleagues) and later recognised as a ubiquitous actin-sequestering peptide involved in cell migration and repair.

The pharmaceutical development has been of full-length Tβ4, chiefly by RegeneRx Biopharmaceuticals (with partners such as ReGenTree / G-treeBNT) — the RGN-259 ophthalmic programme (dry eye, neurotrophic keratopathy; ARISE Phase 2/3, mixed results, orphan designation) and cardiac work — none of which reached approval.
"TB-500" emerged separately as a research/gray-market fragment, used in veterinary settings (notably racehorses) and by athletes for recovery; the fragment itself never had a formal clinical-development programme. It features in several sports-doping cases and is now in the 2026 FDA compounding review. ## Mechanism (as proposed) the LKKTETQ core binds/sequesters G-actin, promoting cell migration, angiogenesis, tissue repair and an anti-inflammatory milieu. Most mechanistic detail comes from full-length Tβ4 biology and animal studies; whether the fragment reproduces these effects in humans is unproven.

Sources — 5 cited

01Goldstein AL, Hannappel E, Kleinman HK. Thymosin β4: actin-sequestering protein moonlights to repair injured tissues. (Tβ4 biology review.)

02Philp D, et al. Thymosin β4 and corneal wound healing. 2003.

03RegeneRx / ReGenTree. RGN-259 (Tβ4) ophthalmic ARISE-1/ARISE-2 trials (NCT02597803, NCT02974907); acute MI trial (NCT01311518).

04Thymosin Beta-4 and TB-500 in tissue healing and musculoskeletal repair: a scoping review. Appl Sci. 2026.

05WADA. 2026 Prohibited List, Section S2.

Review status

Not yet reviewed

A credentialed reviewer (PharmD / PhD / MD) will be named before this entry is finalised. Until then, treat it as a working draft. Last updated July 2026 (US review status evolving — re-check the July PCAC outcome and any Federal Register rule).

Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.

Related compounds

Thymosin Alpha-1 (Thymalfasin / Zadaxin)B

Explore by goal

Tissue repair →Anti-inflammatory →

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TB-500 (Thymosin Beta-4 fragment) — evidence, uses & status · Vallydia