Thymosin Beta-4: What the Evidence Actually Shows

Thymosin beta-4 (Tβ4) is the full-length, 43-amino-acid protein whose name gets borrowed, in shortened and chemically altered form, by TB-500 — the small synthetic fragment this site already covers in its own dedicated evidence review. This article covers the real molecule, not the fragment: what full-length Tβ4 actually is, the two genuinely separate human drug-development programs built around it, and why — despite real, current, injectable clinical-trial data existing for it — this site does not carry a Tβ4 reconstitution calculator.

What it actually is, and how it differs from TB-500

Tβ4 is a naturally occurring 43-amino-acid protein, one of the most abundant intracellular actin-binding proteins in mammalian cells, with roles in cell migration, angiogenesis, and wound healing. TB-500 — the product actually sold in the peptide-research market under thymosin-beta-4-adjacent branding — is not this protein; it is a synthesized, acetylated 7-amino-acid fragment (Ac-LKKTETQ) drawn from one active region of it, confirmed by independent doping-control chemistry laboratories and detailed in this site's own TB-500 article. This article is about the real, full-length, 43-residue protein — the one with an actual pharmaceutical development history behind it.

RegeneRx's real U.S. trial program — and it's entirely topical

A live ClinicalTrials.gov query for "thymosin beta 4" returns a genuine, multi-decade U.S. human trial record sponsored by RegeneRx Biopharmaceuticals, and every product in it is topical, not injectable — confirmed directly from each trial's own intervention description rather than assumed from the drug class. The most advanced program is RGN-259, an ophthalmic solution for dry eye disease and neurotrophic keratopathy: three completed trials — ARISE-1, a combined Phase 2/3 study¹; ARISE-2² and ARISE-3³, both completed Phase 3 studies — and an actively recruiting fourth Phase 3 trial, SEER-2, testing a 0.1% ophthalmic solution specifically for neurotrophic keratopathy⁴. Separately, two completed Phase 2 trials tested Tβ4 as a topical gel: one in 72 patients with venous stasis ulcers, at three gel concentrations against placebo⁵, and one in 72 patients with pressure ulcers, using 0.01%, 0.02%, and 0.1% Tβ4 gel applied daily for up to 84 days⁶. Two more RegeneRx-associated trials in this same search were registered but never actually run: a Phase 2 injectable-Tβ4 trial for acute myocardial infarction was withdrawn before enrolling a single patient⁷, and a Phase 1 IV healthy-volunteer safety study was withdrawn the same way⁸ — both real, registered records, reported here precisely as withdrawn-before-enrollment rather than conflated with any completed study.

A genuinely separate, active Chinese IV drug program: NL005

Here is the finding this article adds that neither this site's own TB-500 article nor most marketing for either product mentions at all: a completely independent human clinical program exists for full-length, injectable Tβ4, sponsored by Beijing Northland Biotech in China, under the product name NL005 — "Recombinant Human Thymosin Beta 4 Injection." Two completed, randomized, double-blind, placebo-controlled Phase 2 trials in acute myocardial infarction, both fetched and read directly from ClinicalTrials.gov, give this program real, current substance: a 62-patient trial (2020-2021) tested low, medium, and high IV doses (0.25, 0.5, and 2.0 mcg/kg) given once 12 hours after PCI and then daily for six more days⁹; a follow-up 90-patient trial (2022-2023) tested 0.5 and 1.0 mcg/kg on the same schedule¹⁰. A third trial, an estimated 189-patient Phase IIc study, was registered as not-yet-recruiting as of this article's live check, with an estimated 2026-05-18 start date — its own intervention description confirms the real product form: "NL005 is a sterile solution of recombinant human thymosin beta 4 formulated for intravenous injection... supplied as a 1.5 mg (1 mL) vial¹¹." This is a genuine, current, injectable Tβ4 clinical-trial product — the RegeneRx program above never built one — but it is Chinese, investigational, has never filed for U.S. approval, and has no U.S. distribution channel this article could locate.

A live-confirmed naming trap, checked during the writing of this article

One more thing worth reporting directly, because it happened in real time while researching this piece: a live check of a U.S. peptide-research vendor's own product page, listed under the name "Thymosin Beta-4," found that page actually describing and redirecting to its own TB-500 product — the small synthetic fragment, not the full-length protein this article covers. That is a real, current instance of exactly the naming conflation this site's own TB-500 article already documented as a marketing pattern: sellers routinely use "thymosin beta-4" and "TB-500" interchangeably, even though the chemistry-identification literature and this site's own two separate articles treat them as different molecules with different evidence records. If you're shopping for either product by name, the label alone may not tell you which molecule is actually in the vial.

The regulatory picture

Full-length Tβ4 has a genuinely cleaner FDA posture than the fragment sold as TB-500. FDA's significant-safety-risks page, fetched live and read in full, carries an entry titled "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500¹²" — its own header makes clear that entry is about the fragment. A full-text search of that same page, and of FDA's current 503A Bulks List (May 14, 2026), for plain "thymosin beta-4" without the word "fragment" returns no separate match — full-length Tβ4 has never itself been flagged by FDA on either document. DailyMed's structured-product-label search¹³ and openFDA's Drugs@FDA database both return zero results for any form of "thymosin beta 4" — no FDA-approved U.S. human drug product exists for either the RegeneRx or the Northland Biotech product line. openFDA's FAERS database returns 3 total reports for "THYMOSIN BETA 4," live-queried for this article¹⁴.

What this means if you're considering it

None of the 31 providers this site's own reviews cover sell thymosin beta-4 — this site's own identity-layer research confirms it is not tagged to any reviewed seller. Full-length Tβ4 has a real, if genuinely mixed, pharmaceutical development history: a decades-long U.S. topical program (dry-eye drops, wound-care gel) with real completed and active Phase 2/3 human trials, and a separate, current, genuinely injectable Chinese Phase 2/IIc program for cardioprotection after heart attack — neither approved for U.S. marketing, and neither the same molecule as TB-500, the fragment actually sold in the U.S. peptide-research market, often under this exact name. This site does not carry a /calculator/thymosin-beta-4 reconstitution page for that reason: the real U.S. clinical product line is topical, not injectable; the one genuinely injectable clinical product (NL005) is a Chinese investigational drug with no U.S. retail form to check a calculator against; and a live vendor check during this article's research found "Thymosin Beta-4" branding redirecting to a TB-500 product rather than a distinct full-length-protein vial. If you're looking for the vial-to-syringe tool for the product actually sold under adjacent branding in this market, our TB-500 calculator does that arithmetic, alongside our TB-500 evidence review covering that fragment's own, much thinner, human evidence record directly.