Is TB-500 the same as thymosin β4?

Not exactly. Thymosin β4 (Tβ4) is a natural 43-amino-acid protein found in nearly all cells; TB-500 is a synthetic peptide marketed as its active actin-binding region. Most published research is on Tβ4 itself, so 'TB-500' data are usually extrapolated from Tβ4 studies rather than measured directly on the marketed fragment.

Are there human trials proving TB-500 works?

No published human randomized controlled trial has tested the injected TB-500 fragment for musculoskeletal or systemic healing. Thymosin β4 has reached Phase II trials in specific formulations — for example an ophthalmic solution for dry eye, which reported roughly a 35% reduction in ocular discomfort versus vehicle — but none of these has produced FDA approval.

Is TB-500 banned in sport?

Yes. Thymosin-β4 and its derivatives, including TB-500, are prohibited at all times under the World Anti-Doping Agency's S2 category (growth factors). Check the current WADA Prohibited List, as it is updated annually.

healing

TB-500

TB-500 is a synthetic peptide marketed as a version of thymosin β4 (Tβ4), a naturally occurring 43-amino-acid actin-sequestering protein involved in cell migration, angiogenesis, and tissue repair. Nearly all of the regenerative evidence comes from animal and cell-culture studies of Tβ4; the injectable TB-500 fragment sold in the research-chemical market has no published human randomized controlled trial. It is not FDA-approved, and thymosin-β4 and its derivatives are prohibited in sport by anti-doping authorities.

By LetsTalkPeps Staff2 min read● Preclinical / animal

Also known as: Thymosin Beta-4 fragment, TB4 fragment, LKKTETQ

Educational content only — this is not medical advice. This page describes what the research does and does not show. It is not a recommendation to obtain or use TB-500.

What it is

TB-500 is a synthetic peptide sold as a healing and recovery compound. It is marketed as the biologically active fragment of thymosin β4 (Tβ4), a naturally occurring 43-amino-acid protein present in nearly every human cell. Tβ4's core molecular job is G-actin sequestration — it binds monomeric actin and helps regulate the actin cytoskeleton — and that role underlies its broader reported activities in cell migration, angiogenesis, and anti-inflammatory signaling.

An important distinction that most marketing blurs: the peer-reviewed literature is overwhelmingly about Tβ4, the full protein. The "TB-500" fragment you can buy is assumed to reproduce Tβ4's actin-binding activity, but it is not the molecule most studies actually tested.

What the evidence shows

The evidence is preclinical. In a classic rat full-thickness wound model, Tβ4 increased re-epithelialization by 42% at day 4 and by as much as 61% at day 7 versus saline, alongside increased collagen deposition and angiogenesis, and it stimulated keratinocyte migration 2–3 fold in cell culture. A later study of an engineered dimeric Tβ4 in rats reported roughly 50% wound closure a few days faster than control hydrogel. Across the literature, the strongest signals are in wound healing, soft-tissue and corneal repair, and cardiac tissue.

For humans, the picture is much thinner. A 2021 review notes that Tβ4 has reached Phase I and Phase II trials in specific formulations — for acute myocardial infarction, dry eye, and wound healing — with a dry-eye trial showing about a 35% reduction in ocular discomfort versus vehicle. But there is no FDA approval, and critically, no published human randomized controlled trial of the injected TB-500 fragment for the muscle/tendon "recovery" uses it is sold for. That is why this page is tagged preclinical: the underlying study types are animal and cell-culture work, plus a handful of early-phase trials of Tβ4 in unrelated indications.

Risks & unknowns

Because there is no completed human RCT of the TB-500 fragment, its efficacy and its safety in people are both not established. Animal and early-phase Tβ4 work has not flagged acute toxicity, but that tells you little about chronic, self-administered injectable use of an unregulated research chemical. Real-world risks include unknown purity, mislabeling, and contamination of product sold outside any pharmaceutical quality system.

Legal / regulatory status

TB-500 is not an approved drug. Thymosin β4 has no FDA approval for any indication, and the thymosin-β4 fragment (LKKTETQ) was added in 2023 to the FDA's Category 2 list of bulk drug substances that may present significant safety risks in compounding. In sport, thymosin-β4 and its derivatives — TB-500 explicitly among them — are prohibited at all times under WADA's S2 (growth factors) category. Material sold as a "research chemical" is not authorized for human use.

FAQ

Is TB-500 the same as thymosin β4?: Not exactly. Thymosin β4 (Tβ4) is a natural 43-amino-acid protein found in nearly all cells; TB-500 is a synthetic peptide marketed as its active actin-binding region. Most published research is on Tβ4 itself, so 'TB-500' data are usually extrapolated from Tβ4 studies rather than measured directly on the marketed fragment.
Are there human trials proving TB-500 works?: No published human randomized controlled trial has tested the injected TB-500 fragment for musculoskeletal or systemic healing. Thymosin β4 has reached Phase II trials in specific formulations — for example an ophthalmic solution for dry eye, which reported roughly a 35% reduction in ocular discomfort versus vehicle — but none of these has produced FDA approval.
Is TB-500 banned in sport?: Yes. Thymosin-β4 and its derivatives, including TB-500, are prohibited at all times under the World Anti-Doping Agency's S2 category (growth factors). Check the current WADA Prohibited List, as it is updated annually.

References

Progress on the Function and Application of Thymosin β4 (Frontiers in Endocrinology, 2021) — review (preclinical + early clinical)
Thymosin beta4 accelerates wound healing (Journal of Investigative Dermatology, 1999) — preclinical (animal)
A novel dimeric thymosin beta 4 with enhanced activities accelerates the rate of wound healing (Drug Design, Development and Therapy, 2013) — preclinical (animal)