Thymosin Beta-4: Complete Guide
Thymosin beta-4 (Tβ4) is a 43-amino-acid peptide that is one of the most abundant and highly conserved intracellular peptides in mammalian cells. It plays a central role in actin regulation, cell migration, wound healing, and tissue repair. Originally isolated from the thymus gland, thymosin beta-4 is now known to be present in virtually all nucleated cells. It is the parent molecule from which TB-500 (a synthetic fragment) is derived.
Last updated: 2026-01-28
Quick Facts
- Category
- therapeutic
- Also Known As
- TB4, Tβ4
- Related Goals
- healing, inflammation
Who Researches Thymosin Beta-4?
Thymosin beta-4 is researched by people interested in tissue repair and recovery — particularly those dealing with injuries, chronic wounds, or cardiac conditions. It's the full-length parent molecule of TB-500, with more formal clinical trial data behind it. If you're choosing between the two, thymosin beta-4 has the stronger research pedigree, while TB-500 is more widely available and affordable. Both are commonly paired with BPC-157 in healing-focused protocols. Athletes and active individuals recovering from musculoskeletal injuries are the primary research demographic.
Research Peptides
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What Is Thymosin Beta-4?
Thymosin beta-4 was originally isolated from the thymus gland by Allan Goldstein in the 1960s as part of research into thymic hormones and immune function. It was later discovered to be one of the most abundant peptides inside cells, where it serves as the primary regulator of the actin cytoskeleton — the structural framework that controls cell shape, movement, and division.
Unlike TB-500 (which is a synthetic fragment), thymosin beta-4 is the full-length, 43-amino-acid molecule. It has been the subject of clinical trials by RegeneRx Biopharmaceuticals for several indications including corneal wound healing (RGN-259 eye drops), cardiac repair after myocardial infarction, and pressure ulcer healing.
Mechanism of Action
- Actin sequestration: Tβ4 binds to G-actin (monomeric actin), maintaining a pool of unpolymerized actin for rapid deployment during cell migration and division
- Cell migration: Promotes endothelial cell, keratinocyte, and stem cell migration to injury sites
- Anti-inflammatory: Reduces inflammatory cytokine production and promotes anti-inflammatory pathways
- Angiogenesis: Stimulates new blood vessel formation
- Cardiac progenitor activation: Activates epicardial progenitor cells for cardiac repair
- Anti-fibrotic: Reduces excessive scar formation during tissue repair
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Dosage Overview
Clinical trial dosing has varied by indication:
- Corneal healing (RGN-259): 0.1% ophthalmic solution applied topically
- Cardiac repair (clinical trial): 1.2 mg/day intracoronary or IV
- Research subcutaneous: 750 mcg – 2 mg twice weekly
Use the peptide calculator for reconstitution.
Side Effects & Safety
- Generally well-tolerated across clinical trials
- Injection site reactions: Mild in reported studies
- Ocular formulation: Well-tolerated in eye drop trials with no significant ocular adverse events
- Theoretical tumor concern: Tβ4 is overexpressed in some cancers, though causality vs. correlation is unclear