Thymosin β4 (full length)

Thymosin β4 has genuine clinical trial evidence, and it is by routes almost nobody uses it by. The Phase 3 data is an ophthalmic solution for neurotrophic keratopathy; the Phase 2 cardiac data is intravenous and its results were never posted. The systemic subcutaneous injection people actually do has no trial support at all. Read this record alongside TB-500: FDA defines TB-500 as the acetylated seven-amino-acid fragment Ac-LKKTETQ, thymosin β4 is the full 43-amino-acid peptide, and the classic aged-mouse wound-healing study everyone cites used full-length thymosin β4 and the non-acetylated heptapeptide, neither of which is the compound being sold.

Thymosin β4 is the full-length 43-amino-acid peptide. TB-500 is a seven-amino-acid acetylated fragment of it, and they are not interchangeable. FDA says so explicitly. Thymosin β4 has genuine Phase 3 data, in an eye drop for neurotrophic keratopathy, and Phase 2 data by intravenous infusion after a heart attack. It has no trial support at all for the systemic subcutaneous injection people actually do.

Thymosin β4 is the most abundant actin-sequestering protein in most cells: it binds monomeric actin and controls how quickly the cytoskeleton can be assembled and disassembled. That sounds abstract until you consider what wound healing physically is: cells crawling into a gap, which requires exactly that kind of controlled cytoskeletal remodelling. Downstream of it, thymosin β4 promotes cell migration, angiogenesis and survival signalling, and reduces inflammation. Note that the fragment sold as TB-500 covers residues 17 to 23, the actin-binding region, with an acetyl group added at the N-terminal leucine. FDA’s position is that acetylation irreversibly alters charge, hydrophobicity and size, so the pharmacology of the non-acetylated heptapeptide cannot be extrapolated to the acetylated one, and neither can be assumed to reproduce the full protein.

• Neurotrophic keratopathy (Phase 3, RGN-259)0.1 %

  Ophthalmic solution, as used in the randomised trial

  The SEER-2 Phase 3 (NCT05555589) dosed 0.1% RGN-259 five times daily for 28 days. This is an eye drop, not an injection.

• Acute myocardial infarction (Phase 2)0.25–2 mcg/kg

  × body weight in kg

  Daily on days 1–7 after PCI

  NCT05485818, recombinant human thymosin β4 intravenously at 0.25, 0.5 and 2.0 mcg/kg, 62 participants, completed September 2021. Results have never been posted, so the outcome is unknown.

Not established in available literature. Use the calculator with the figures printed on your own vial.
Open the calculator

1. 1
   Week 4 (neurotrophic keratopathy, Phase 3)

   Complete corneal healing in 6 of 10 patients on 0.1% RGN-259 against 1 of 8 on placebo, with significant improvements in ocular discomfort, foreign-body sensation and dryness, and no significant adverse effects reported.

2. 2
   Day 43 (same trial)

   The single healed placebo patient had recurred; the RGN-259 healings held. Small numbers, but the direction is consistent.

Absence from this list does NOT mean safety. It means lack of research.

Storage

Our sources do not publish a vial and diluent pairing or a beyond-use window for thymosin β4. The two evidenced formulations are a manufactured eye drop and an intravenous infusion prepared in a hospital, neither of which is a home reconstitution.

Cost

Not established in available literature

1. 1
   FDA · TB-500 briefing document for the Pharmacy Compounding Advisory Committee

   Source
2. 2
   Int J Mol Sci, January 2023 · Phase 3 RGN-259 in neurotrophic keratopathy

   Source
3. 3
   NCT05555589 · SEER-2, Phase 3, 0.1% RGN-259 for persistent epithelial defect

   Source
4. 4
   NCT05485818 · Phase 2, intravenous recombinant human thymosin β4 after PCI, results not posted

   Source