TB-500

TB-500 is the common research designation for a synthetic peptide fragment of the endogenous thymosin beta-4 (Tβ4). TB-500 is NOT an approved drug: no FDA approval, no EMA approval, no completed controlled human trial of TB-500 itself. WADA lists it under Section S2 as a peptide hormone/growth factor mimetic.

The name "TB-500" is used inconsistently. Originally it referred to a synthetic 7-amino-acid fragment (Ac-LKKTETQ, positions 17-23) of the 43-aa Tβ4 - precisely the actin-binding domain. On the grey market, however, "TB-500" today frequently stands for the full Tβ4 sequence or for other fragment lengths. This terminological fuzziness makes the study landscape hard to compare.

How does TB-500 work?

The core mechanism is G-actin sequestration: TB-500 binds monomeric G-actin in a 1:1 ratio and thereby keeps a pool of actin monomers available that can rapidly polymerise to F-actin on demand. Because the actin cytoskeleton controls cell shape, migration and division, this drives several downstream effects:

• Angiogenesis: new blood vessels into under-perfused tissue (tendons, ligaments, muscle).
• Cell migration: faster fibroblast and keratinocyte recruitment into wounds.
• Anti-apoptotic and anti-inflammatory: reduces programmed cell death signals and dampens local inflammatory markers.

Recent preclinical work (2024) suggests that part of this wound-healing activity may come from the metabolite Ac-LKKTE rather than from the parent peptide - a detail that further complicates cross-study comparison.

What is TB-500 used for?

On the fitness, bodybuilding and horse-racing grey market, TB-500 is promoted mainly for:

• Tendon and ligament injuries
• Muscle strains and tears
• Skin wounds and post-surgical recovery
• Joint complaints and degenerative sports injuries

These claims derive mostly from preclinical rodent models and from equine sports studies. There is no controlled human study confirming any of these indications.

What does the evidence say?

Evidence level for TB-500 is 1 (preclinical). A 2025 scoping review (Applied Sciences) rates the musculoskeletal evidence for TB-500 as weak: of 1,506 screened records, only very few remained after full-text review, and the single direct TB-500 dataset was a metabolite-detection study plus an in vitro fibroblast scratch assay.

For full-length thymosin beta-4 (43 aa) there are clinical data, but they do not transfer directly to TB-500:

• RGN-259 (0.1 % Tβ4 eye drops): Phase 2 in dry eye significantly effective and well tolerated (Sosne et al., 2015); Phase 3 SEER-2 in neurotrophic keratopathy recruiting (NCT05555589).
• Cardiac Phase 1/2 after myocardial infarction: positive surrogate endpoints, but no registration-enabling study.

TB-500 as such has none of these data.

TB-500 vs. thymosin beta-4 vs. BPC-157

All three are often lumped together in regeneration marketing, but they are different:

• Thymosin beta-4 (Tβ4): endogenous 43-aa peptide, abundant in nearly all tissues; clinical data mainly ophthalmic (RGN-259).
• TB-500: synthetic fragment (or full-length product) of Tβ4; exclusively preclinical; included as a 10 mg component in the Glow Stack and Klow Stack.
• BPC-157: a completely different peptide (15-aa fragment of a gastric protection protein), different mechanism (angiogenesis via VEGFR2 and the NO system); separate evidence base.

Safety and regulatory status

• FDA: TB-500 is not approved for any indication. Grey-market products fall under the FDA warnings on unapproved peptides; BPC-157, TB-500, MOTS-C and KPV were removed from FDA Category 2 ("significant safety risks") in April 2026 and discussed before the Pharmacy Compounding Advisory Committee (PCAC) on 23-24 July 2026.
• WADA: explicitly listed under Section S2 ("Peptide Hormones, Growth Factors, Related Substances and Mimetics") in the Prohibited List 2026 - prohibited at all times, in and out of competition.
• Horse racing: TB-500 is also banned by IFHA and FEI; a population study showed that exogenous TB-500 measurably raises endogenous plasma Tβ4 in horses - a plausible detection method.
• Grey-market risk: independent analyses find mislabeling, under- or overdosing or microbial contamination in roughly 30 % of peptide samples from grey-market sources.

FAQ on TB-500

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

TB-500 is defined as a fragment of Tβ4 (originally the 7-aa actin-binding domain). In commerce, however, the name is often used synonymously for the full 43-aa sequence - a sourcing problem for any cross-study comparability.

Why is TB-500 on the WADA list?

WADA classifies TB-500/Tβ4 as a growth-factor mimetic that could theoretically support muscle, tendon and ligament regeneration. The listing is based on the postulated mechanism, not on controlled sports studies in humans.

Is TB-500 FDA-approved?

No - neither TB-500 nor full-length thymosin beta-4 has FDA approval. RGN-259 (Tβ4 eye drops) is in Phase 3 but is also not yet approved.

How is TB-500 typically reconstituted?

Lyophilised powder is dissolved in BAC water - a 5 mg vial in 2 mL BAC water yields 2.5 mg/mL. Store reconstituted at 2-8 °C. No dosing recommendation - information only, for proper handling as a research reagent.

No medical advice, no dosing or sourcing recommendation. Peptipedia informs - you decide together with your physician.