Thymosin Beta-4

Thymosin Beta-4 (Tβ4) — Full-Length

Evidence & Status

  • Preliminary / Experimental
  • Moderate

At a Glance

The full-length, N-terminally acetylated 43-amino-acid precursor from which the TB-500 fragment is derived. Full-length Tβ4 has been studied in registered human clinical trials for dry eye disease, with mixed and largely inconclusive results — it has not been shown to be an approved or established therapy.

Plain English

Researchers study Thymosin Beta-4 because it is one of the body's own tissue-repair molecules, naturally concentrated where healing is needed. Scientists have tested a formulation of the full-length molecule (RGN-259) in registered human trials for dry eye disease, with mixed results — one trial did not meet its main goal, and a smaller one showed some improvement. Other registered trials exist without confirmed outcomes yet. TB-500, a shorter fragment sold in some communities for recovery goals, is chemically different from the full-length molecule described here and is discussed based on real-world/anecdotal use rather than established clinical evidence.

Overview

Thymosin Beta-4 (Tβ4) is the full-length, N-terminally acetylated 43-amino-acid peptide (Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES) naturally found in platelets, wound fluid, and many tissues. TB-500 (Ac-LKKTETQ, residues 17–23) is a chemically distinct fragment sold and discussed in some communities as a substitute for the full-length molecule; it is not equivalent to full-length Tβ4 and does not carry the same evidence base. Full-length Tβ4 (as RGN-259, an ophthalmic formulation) has been evaluated in registered human clinical trials for dry eye disease, with mixed results: a Phase II RCT (n=72) did not meet its prespecified primary endpoints (Sosne & Ousler, 2015), while a smaller Phase 2 trial (n=9) reported exploratory improvements (Sosne et al., 2015). A completed registry trial (ARISE-2, NCT02974907) and a separate registered trial (NCT05984134) exist, but no verified outcome data from either was identified in this review. These are registered investigational studies, not evidence of approved use or established efficacy. Products sold as TB-500 are discussed and used in some peptide and sports communities for recovery and tissue-repair goals. This reflects real-world/anecdotal use rather than established clinical efficacy, and TB-500 is chemically distinct from full-length Thymosin Beta-4.

Research Summary

Full-length Thymosin Beta-4 (Tβ4) has entered registered human clinical trials, distinguishing it from many purely preclinical research peptides. Two RGN-259 (topical Tβ4) dry-eye trials show a mixed picture: a 72-subject Phase II RCT did not meet its prespecified primary endpoints, though some secondary measures improved, while a separate 9-patient Phase 2 trial reported exploratory sign/symptom improvements. A registered trial (ARISE-2, NCT02974907) and a separate registered trial (NCT05984134) exist, but no verified outcome results were identified for either in this review — their existence establishes an active clinical-development program, not proven efficacy. Mechanistically, Tβ4 sequesters G-actin and promotes endothelial cell migration; this is well characterized preclinically. TB-500 (Ac-LKKTETQ, residues 17–23) is a distinct fragment retaining only part of full-length Tβ4's activity and is not supported by the same clinical evidence; its use is real-world/anecdotal rather than clinically established.

Research Areas

  • Wound healing
  • Cardiac repair
  • Corneal healing
  • Anti-inflammatory
  • Angiogenesis
  • Tissue regeneration

Safety & Risks

Serious Risks

  • Theoretical oncological risk via angiogenic promotion has been proposed but is not clinically confirmed in the human data reviewed here

Reported Side Effects

  • Injection site discomfort
  • Mild fatigue (anecdotal)
  • Theoretical promotion of existing neoplasia via angiogenesis
United States
Research use only; not approved for human use; FDA has identified as a peptide of concern in compounded products
United Kingdom
Research only; not licensed for human therapeutic use
Australia
Research only; TGA Schedule 4 — prescription required for compounded use
Canada
Research only; Health Canada has not approved for therapeutic use

Citations & Sources