Thymosin β4 — Canada Research Brief

Origin and biological role

Thymosin β4 was originally isolated from bovine thymus tissue by Low and Goldstein in the 1980s, but it is now known to be expressed in almost all mammalian cells. Its principal molecular role is to sequester G-actin monomers and thereby regulate the pool available for F-actin filament assembly. At typical cellular concentrations, Tβ4 binds roughly half of the unpolymerised actin in a cell.

Clinical trial history

Unlike most research peptides, thymosin β4 has a real clinical trial record:

• Epidermolysis bullosa (RGN-137) — topical Tβ4 tested in dystrophic EB for accelerated wound closure; did not meet primary endpoint in phase-3.
• Dry eye disease (RGN-259) — phase-3 trials showed modest benefit on corneal staining and symptom scores; no approval as of publication.
• Post-myocardial infarction cardiac repair — early-phase trials building on Bock-Marquette et al. (Nature 2004); no approved indication.

This clinical history is why Tβ4 is sometimes referred to as "the peptide that didn't make it" — real trials, real endpoints, and results that didn't quite cross the approval threshold.

Comparisons

• TB-500 vs thymosin β4 — full-length parent versus short synthetic fragment.

Storage

Store lyophilised thymosin β4 at −20°C. Reconstituted material is stable refrigerated at 2–8°C for 2–4 weeks.