TB-500 (Thymosin B4)

Thymosin beta-4 is one of the most abundant proteins inside cells and is absent only from red blood cells. Its main job is to hold actin building blocks (G-actin) in reserve, thereby governing how cells remodel their scaffold and move. TB-500 is the synthetic reproduction of the active region of that protein.

Profile of the molecule:

• 43 amino acids, molecular mass 4982 daltons
• an acetylated N-terminus, without which function is lost
• binding to G-actin as the central molecular target

The effects described in studies build on that actin binding: stem and progenitor cells travel in greater numbers to injured tissue, new blood vessels sprout (angiogenesis), and inflammatory signals are dampened. This has been examined in skin, cornea, heart tissue and the nervous system. Mouse models with diabetes or advanced age receive particular attention: there, wounds closed faster under thymosin beta-4, which makes the peptide of interest for questions about impaired regeneration.

On the regulatory side, the US agency FDA is currently reviewing whether TB-500 should be added to the 503A Bulk Drug Substances list. In regeneration research it is frequently considered together with BPC-157, since the two peptides cover different phases of tissue repair. Read into the field and you will rarely meet one without the other.

Preclinical data spanning several decades describe a mild profile without notable toxicity in the models examined. Long-term human studies are lacking; the assessment rests on animal work and short periods of experience.

• Injection site: redness, a feeling of pressure or a brief irritation with subcutaneous administration, the most frequent observation.
• Circulation: occasional tiredness, slight dizziness or a sensation of warmth shortly after administration.
• New vessel growth: because TB-500 stimulates angiogenesis in studies, the literature debates a theoretical risk that pre-existing abnormal tissue might also gain better supply. This is unproven but remains an open question.

This summary is no substitute for medical advice.

• Thymosin beta 4 promotes corneal wound healing and decreases inflammation in vivo following alkali injury - mouse model of corneal alkali burn: under topical thymosin β4 the epithelium closed faster, fewer inflammatory cells moved in, and mRNA of inflammatory messengers fell.
• Thymosin β4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair - faster wound closure in diabetic and aged mice.
• Progress on the Function and Application of Thymosin β4 - recent review of function and state of research.
• Thymosin β4 increases hair growth by activation of hair follicle stem cells - activation of stem cells in the hair follicle.