Tissue Repair & RecoveryPreclinical / anecdotal

Thymosin Beta-4 fragment (Tβ4)

TB-500, Actin binding fragment

The synthetic actin binding fragment (LKKTETQ) of thymosin beta-4, studied for cell migration, angiogenesis, and systemic tissue repair in animal models.

Muscle repair Recovery Connective tissue Angiogenesis

Tβ4

Parent protein

Angiogenesis

Core mechanism

Large human trials

Mechanism of action

How TB-500 works

In animal studies, the actin binding fragment of thymosin β4 is thought to drive cell migration and new blood vessel growth, the basis for its tissue repair reputation.

TB-500

Tβ4 fragment

Actin binding

Cytoskeleton

Cell migration

+ angiogenesis

Tissue repair

Muscle and tendon

Also studied

Promotes endothelial cell migration and new vessel formation, a proposed driver of its wound- and tissue repair effects.

See related compounds

The full Tβ4 molecule (as RGN-137) reached human cardiac repair trials; preclinical work reports reduced injury and improved cardiac function.

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Full length Tβ4 reached Phase 2 dermal and corneal wound healing trials with a favorable safety profile.

See related compounds

Applications

Research applications

Musculoskeletal repair

Tendon, ligament & muscle

Animal (rodent) model

Rodent injury models

Cardiac repair

Infarct size & function

Human pilot data

Full Tβ4 Phase 2 (RGN-137)

Wound healing

Dermal & corneal

Human pilot data

Full Tβ4 Phase 2 trials

Angiogenesis

Endothelial migration

Animal (rodent) model

Preclinical

Bars indicate how far the evidence has progressed (in vitro to animal to human), not the size of any effect.

Compound data

Molecular profile

CAS number885340-08-9

Molecular formulaC39H67N9O13

Molecular weight877.99 g/mol

TypeAcetylated heptapeptide fragment

SequenceAc-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ)

AppearanceWhite lyophilized powder

Literature

Key studies

Review2010

Thymosin β4: structure, function, and biological properties supporting current and future clinical applications

Crockford D, Turjman N, Allan C, Angel J

Key finding

Reviews Tβ4 as the major G-actin sequestering molecule, promoting cell migration, angiogenesis, and survival, the rationale for dermal, corneal, and cardiac trials.

View on PubMed

Full profile

Evidence, safety & status

Claimed benefits & evidence

Marketed for tendon/joint/muscle healing and cardiac repair. The full Tβ4 molecule (as RGN-137) reached human trials for chronic skin wounds and cardiac repair with mixed results; Phase 2 data in hundreds of patients showed a favorable safety profile. There are no large randomized human trials of TB-500 itself for the musculoskeletal/athletic uses it is sold for.

Safety & dangers

The dominant concern is angiogenesis driven tumor support: Tβ4 is overexpressed in numerous cancers and correlates with metastatic potential in melanoma models (correlative, not proof exogenous dosing causes cancer). Pro angiogenic effects also raise concern in proliferative retinopathy.

Contraindications

Active/untreated cancer; proliferative retinopathy; pregnancy.

Regulatory status

Not FDA approved; Category 2 (2023) then removed April 2026 (grey zone); PCAC review July 23, 2026 (wound healing). WADA prohibited (S2, Tβ4 and derivatives explicitly named).

Administration

Subcutaneous/IM. Long tissue residence; systemic distribution.

Source: Fnx Performance Peptide Research Database, a synthesis of the scientific and regulatory literature, not medical advice. Anyone considering these compounds should consult a qualified physician.

For research use only

For Research Use Only. Not for human or animal consumption. Products are sold strictly for in vitro laboratory research, not for compounding or therapeutic application.