subcutaneous

Thymosin Beta-4

Thymosin Beta-4 (Tβ4 / Timbetasin)

Thymosin Beta-4 at a glance

Not on either FDA list

How studies gave it

Injected into the fat under the skin

Evidence on this page

3 peer-reviewed papers, published 2010 to 2021

FDA compounding lists

It appears on neither of the two FDA compounding tables.

What it is

The full-length 43-amino-acid endogenous polypeptide encoded by the TMSB4X gene. Thymosin Beta-4 is the most abundant G-actin-sequestering protein in mammalian cells and has been studied in Phase 1–3 human trials for wound healing, corneal repair, and cardiac recovery. It contains multiple functional domains — including the central LKKTETQ actin-binding motif (the basis for the TB-500 fragment, which is a separate database entry) and the N-terminal Ac-SDKP anti-fibrotic tetrapeptide.

Unlike TB-500, the full-length protein retains all known bioactive regions. RegeneRx/ReGenTree's ophthalmic formulation (RGN-259) holds FDA orphan drug designation for neurotrophic keratitis.

Published research

Thymosin Beta-4 has one of the most advanced clinical programs among tissue-repair peptides. A Phase 1 safety study in 40 healthy volunteers (Ruff et al., 2010) demonstrated tolerability of IV doses up to 1,260 mg with dose-proportional pharmacokinetics. A separate Phase 1 in 84 Chinese volunteers (Wang et al., 2021) confirmed safety of recombinant Tβ4 at 0.05–25 µg/kg.

Phase 2 trials in venous stasis ulcers showed accelerated wound closure with topical 0.03% Tβ4 gel. The RGN-259 ophthalmic formulation has completed Phase 2 and entered Phase 3 for dry eye and neurotrophic keratitis. A cardiac STEMI pilot study suggested improved left ventricular function. Preclinical data spans wound healing, cardioprotection, neuroprotection, hair follicle activation, and anti-fibrotic effects via the Ac-SDKP domain. Community dosing protocols are extrapolated from these clinical trials and animal data.

What the terms on this page mean9 terms

endogenous: Made by the body itself, rather than given from outside.
Phase 1: The first test in people, usually a small group, looking mainly at safety rather than at whether it works.
neurotrophic: Supporting the growth, repair or survival of nerve cells.
peptide: A short chain of amino acids, the building blocks of proteins.
pharmacokinetics: How fast the body absorbs a substance, where it goes, and how it clears it out.
Phase 2: A mid-size trial testing whether the substance does anything useful.
Phase 3: A large trial, the kind regulators read before approving a drug.
preclinical: Laboratory and animal work done before any testing in people.
clinical trial: A study that tests something in people under a written plan, with results recorded.

Compounding status

Not on either FDA list

FDA listing: Thymosin Beta-4 appears on neither FDA's category 2 table nor its table of withdrawn nominations.
What that means: Absence from both lists is not permission to compound. Section 503A allows a bulk drug substance only where a USP or NF monograph exists, or the substance is a component of an FDA-approved drug product, or it appears on the 503A bulks list.
Note: FDA lists the thymosin beta-4 fragment LKKTETQ (TB-500) among withdrawn nominations. It does not list full-length thymosin beta-4.

Source: Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks, FDA. Content current as of 2026-04-22; read 2026-09-05. This describes what a compounding pharmacy may supply. It is not advice about your own use.

Reading up on Thymosin Beta-4 is the easy part

Keeping the schedule straight is the hard part. PepKit is the app for that.

Does the reconstitution math for you
Logs each dose and reminds you when the next is due
Counts down every vial's expiration

Where this came from3 references

Each one was resolved at PubMed and confirmed to be the work this page cites. Author, title, journal and year come from the PubMed record, not from the page text.

A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers
Ruff D, et al.. Annals of the New York Academy of Sciences (2010). PMID 20536472.
Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications
Goldstein AL, et al.. Expert opinion on biological therapy (2012). PMID 22074294.
A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers
Wang X, et al.. Journal of cellular and molecular medicine (2021). PMID 34346165.

About this page

Reviewed 2026-08-11. This page reports what published studies and FDA documents say. It carries no dose, cycle length or stack, and it does not tell you whether a substance is appropriate for you. Side-effect reports circulating on forums are self-reported rather than measured, so they are not republished here.

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