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Phase IIVendors pendingFacts verified · 2026-05-25

Thymosin Beta 4

Also known as tβ4, timbetasin, thymosin β4, tb4 · Wikipedia

Thymosin beta-4 (TB-4) is a 43-amino-acid naturally-occurring peptide and one of the most abundant intracellular proteins. It binds monomeric G-actin and regulates cytoskeletal dynamics, supporting cell migration, angiogenesis, and tissue repair. Research interest spans cardiac repair, wound healing, neuroprotection, and ocular-surface disease. RegeneRx has progressed RGN-259 (ophthalmic TB-4) through Phase III for neurotrophic keratopathy and Phase II for dry eye, and RGN-352 (IV TB-4) through early-phase trials for acute MI. No full regulatory approval exists in the US, EU, or major Western markets.

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Mechanism of action

Thymosin beta-4 is a 43-amino-acid G-actin-sequestering peptide that regulates cytoskeletal assembly by binding monomeric actin. This activity supports migration of endothelial cells, keratinocytes, fibroblasts, and cardiomyocyte progenitors.

Thymosin beta-4 is a 43-amino-acid G-actin-sequestering peptide that regulates cytoskeletal assembly by binding monomeric actin. This activity supports migration of endothelial cells, keratinocytes, fibroblasts, and cardiomyocyte progenitors. TB-4 also upregulates VEGF and laminin-5, suppresses NF-kB-driven inflammation, recruits epicardial progenitor cells in cardiac injury models, and accelerates re-epithelialization. Net biological effects are pro-angiogenic, pro-migratory, anti-inflammatory, and cardio- and neuro-protective in animal models, with corneal-healing efficacy demonstrated in human Phase II/III ophthalmic trials (Sosne et al., PMID 25826322; Sosne et al., PMID 36613994).

Pharmacokinetic properties

Half-life

approximately 2 hours plasma (RGN-352 IV human data); biological effects persist much longer

Routes

subcutaneous · intramuscular · intravenous · topical

Bioavailability

Not orally bioavailable. IV and SC formulations have been used in clinical trials. Topical ophthalmic formulation (RGN-259) reaches local ocular tissues.

Amino-acid sequence

Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln-Glu-Lys-Asn-Pro-Leu-Pro-Ser-Lys-Glu-Thr-Ile-Glu-Gln-Glu-Lys-Gln-Ala-Gly-Glu-Ser

Use & research dosing

RecoveryInjury RecoveryTissue RepairAnti-Inflammatory

Self-experimentation protocols commonly report 2-10 mg subcutaneous 2-3 times per week for 4-6 week loading cycles, followed by maintenance dosing at lower frequency. RegeneRx clinical programs used 0.1% RGN-259 ophthalmic drops 4-8 times daily for ocular indications, and RGN-352 IV infusion in early acute-MI studies. No FDA-approved systemic human dose exists, and compounded vendor products have variable peptide content. Research framing only.

Research-use framing only. SavePeptides sells nothing for human consumption. Doses above reflect reported research / self-experimentation ranges, not clinical recommendations.

Editorial perspective

Current state: TB-4 has the strongest preclinical credential of any wound-healing peptide, but human clinical development has stalled in financing rather than at efficacy. RegeneRx's ophthalmic program reached Phase III with positive signals in neurotrophic keratopathy; systemic indications (acute MI, stroke) remain early. No approved product on the US market. Compounded injectable TB-4 sold as a research chemical is unregulated and quality-variable.

— SavePeptides editorial desk · last updated 2026-05-25

Cautions & contraindications

Before researching this compound, note:

  • No full FDA approval; long-term systemic safety in humans not established
  • Theoretical concern for stimulating proliferation in malignancy — avoid with active cancer
  • Pro-angiogenic activity may have unknown effects in proliferative retinopathy or vascular tumors
  • Pregnancy and breastfeeding — no data
  • Injection-site reactions and mild headache reported in early-phase trials
  • Vendor-supplied compounded TB-4 has variable purity and verified peptide content
  • Most efficacy data are from animal models or small Phase II ophthalmic studies

Research foundation

The papers behind the page.

  1. [01]https://pubmed.ncbi.nlm.nih.gov/25826322/
  2. [02]https://pubmed.ncbi.nlm.nih.gov/36613994/

Facts verified

2026-05-25

Confidence

low

What this means

  • Phase II/III ophthalmic data only — no systemic approval
  • Systemic dosing protocols not validated in humans
  • Compounded vendor product quality not standardized

How we check →

Vendor data coming soon

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