Thymosin Beta-4

Areas of active research — not promised effects

Each tag links to other compounds with research into that goal. Research use only: these are areas of study, not human-use claims.

Related by research scope · open each to compare

Full-length thymosin beta-4 is not an FDA-approved drug for any indication. The ophthalmic investigational drug RGN-259 (0.1% Tβ4 eye drops, developed by RegeneRx Biopharmaceuticals) has advanced to Phase 3 clinical trials for neurotrophic keratitis (NCT05555589) but has not received FDA approval or Breakthrough Therapy designation as of May 2026. The full-length Tβ4 protein does NOT appear on the FDA 503A Category 2 (significant safety risk) bulk drug substances list (fda19 flag: false in source data), meaning it is not subject to the same compounding prohibition as the TB-500 fragment. However, absence from Category 2 does not authorize compounding; it remains an unapproved drug subject to FDA oversight. Supply as a research-use-only material is permissible under applicable RUO regulations provided no therapeutic or human-use claims are made.

Transparent blend · bci-1.0 · never paid-placement

Primary name

Thymosin Beta-4

Origin

Thymosin beta-4 (Tβ4) is a naturally occurring 43-amino-acid polypeptide (MW ~4963 Da; C212H350N56O78S) found at high concentrations in virtually all nucleated mammalian cells and in plasma, platelets, and tears. It was originally isolated from thymic tissue as part of a family of actin-binding peptides but is now understood to be ubiquitously expressed and upregulated at sites of tissue injury. The recombinant or synthetic form used in research replicates the sequence of the endogenous human protein. Its principal active domain, the LKKT(X)E actin-binding motif (residues 17–23), is the basis for the related research fragment TB-500; however, the full-length protein possesses additional biological activities beyond actin sequestration.

Registry IDs

PubChem CID

45382195

InChIKey

UGPMCIBIHRSCBV-UHFFFAOYSA-N

Molecular formula

C212H350N56O78S

Molar mass

4963 g/mol

Monoisotopic

4960.4863169 Da

InChIKey

UGPMCIBIHRSCBV-UHFFFAOYSA-N

Appearance

White to off-white lyophilized powder

Solubility

Freely soluble in water and aqueous buffers; solutions at physiological pH (7.0–…

Sequence not available in current seed.

Stability: The full-length polypeptide is more susceptible to proteolytic degradation in solution than the shorter TB-500 fragment. Lyophilized form is stable; solutions s

Vial sizes

2 mg · 5 mg

Purity grades

research grade (>95% by HPLC) / research grade (>98% by HPLC)

Salt forms

Free base (primary)

• GHS hazard class on file
• PPE & spill response
• Disposal guidance
• Not-for-human-consumption posture

How much research exists, and of what maturity — never a verdict on whether it works.

Mechanism of action

• Thymosin beta-4 maintains a large intracellular pool of monomeric G-actin by forming a 1:1 sequestration complex, thereby modulating actin filament dynamics in a manner that facilitates lamellipodia formation, directed cell migration, and tissue remodeling at wound sites
• Beyond actin regulation, Tβ4 activates integrin-linked kinase (ILK), which drives downstream phosphorylation cascades promoting endothelial and keratinocyte motility, and upregulates pro-angiogenic mediators including vascular endothelial growth factor (VEGF), matrix metalloproteases, and laminin-332
• The peptide also exerts anti-inflammatory effects through inhibition of NF-κB signaling and direct suppression of pro-inflammatory cytokines, and has been associated with stem cell recruitment and differentiation in preclinical cardiac and neurological models
• In ocular tissue, Tβ4 promotes corneal epithelial cell migration and has demonstrated efficacy in human trials of neurotrophic keratitis (RGN-259 ophthalmic formulation, Phase 3)

Pharmacokinetics (ADME)

Half-life

Approximately 0.95–2.1 hours (plasma, intravenous; dose-dependent in human Phase 1 study; PMID 20536472)

Clearance

Presumed proteolytic degradation; terminal clearance was consistent across dose groups with no accumulation after repeated daily IV dosing in the human Phase 1 study

PK–PD note: A Phase 1 human IV study (published PMID 20536472, not in the gathered topPmids list) found dose-proportional increases in Cmax and AUC across 42–1260 mg single doses, with half-life increasing from ~…

Reading the evidence

• Evidence quality and gaps vary by application — see the cited grades above.
• Indexed-article counts span all evidence tiers, not only completed human trials.
• No first-party human-dosing, efficacy, or benefit claims are made here.

Key reviews & evidence-gap sources

• McGuire, Hughes, Maak & Cushman 2026 — PRISMA-ScR scoping review of Tβ4/TB-500 in tissue healing, regeneration & musculoskeletal repair (Applied Sciences 16(12):6202) — 80 included studies (33.8% mixed design, 28.8% in vitro, 23.8% human, 13.8% animal-only); the anchor for the era/design distribution used here.
• Xing, Ye, Zuo & Li 2021 — Progress on the Function and Application of Thymosin β4 (Front Endocrinol 12:767785) — Reviews PI3K/Akt/eNOS, Notch, TGFβ/Smad and Wnt involvement across cardiac, wound, fibrosis and hair-follicle contexts; also flags a preclinical caution — reducing Tβ4 shrank colorectal-cancer-stem-cell xenografts, a theoretical pro-tumor concern given the peptide's pro-angiogenic activity.
• Sosne et al. 2022 — 0.1% RGN-259 (Tβ4) Phase III RCT in neurotrophic keratopathy (Int J Mol Sci 24(1):554; PMID 36613994) — SEER-1 (NCT02600429): terminated early for a business decision after 18 of a planned 46 subjects (10 RGN-259 / 8 placebo). Reported finding: complete corneal epithelial healing at day 29 in 6/10 treated vs 1/8 placebo — the PRIMARY endpoint narrowly MISSED significance (p=0.0656); a day-43 secondary healing endpoint reached significance (p=0.0359). Attributed Layer-A finding for a specific ophthalmic formulation; RUO, not a first-party efficacy claim.
• Sosne, Dunn & Kim 2015 — Thymosin β4 in severe dry eye, phase 2 randomized trial (Cornea 34(5):491–6; PMID 25826322) — NCT01393132; small (9-patient) completed, published Phase 2 RCT. Significant vs vehicle at day 56 on total corneal fluorescein staining (59.1% reduction, P=0.0108) and ocular discomfort (35.1% reduction, P=0.0141); tear break-up time was a directional 'other improvement', NOT reported as significant. Registered primary endpoint was Safety. Ophthalmic formulation only; RUO.
• Sosne & Ousler 2015 — Tβ4 ophthalmic solution for dry eye, Phase II CAE-model RCT (Clin Ophthalmol 9:877–84; PMID 26056426) — NCT01387347; 72-subject, single-center, completed, published RCT using the controlled-adverse-environment model — distinct from the later multi-site ARISE dry-eye program. Ophthalmic formulation only; RUO.
• Guarnera, DeRosa, Camerini et al. 2010 — The effect of thymosin treatment of venous ulcers (Ann N Y Acad Sci 1194:207–12; PMID 20536470) — NCT00832091; 73-patient, 8-site (Italy/Poland) completed, published Phase 2 RCT. Authors state topical Tβ4 0.03% 'may have the potential to accelerate wound healing' and that complete healing within 3 months was reached in ~25% of treated patients — a hedged, exploratory dose-response signal, not established efficacy. RUO.

5 registered trials — 1 currently recruiting.

Phase 2
NCT00832091
Study of Thymosin Beta 4 in Patients With Venous Stasis Ulcers

COMPLETED

Phase 3
NCT05555589
Assessment of the Safety and Efficacy of 0.1% RGN-259 Ophthalmic Solution for the Treatment of NK: SEER-2

RECRUITING

Phase 2
NCT01311518
A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction

WITHDRAWN

Phase 2
NCT02597803
Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-1

COMPLETED

Phase 1
NCT00743769
A Phase 1 Safety Study of the Intravenous Administration of Thymosin Beta in Healthy Volunteers

WITHDRAWN

Summary (literature)

Full-length thymosin beta-4 has been evaluated in at least two Phase 1 human safety studies using intravenous administration. In the first (single and multiple ascending IV doses of 42–1260 mg), the compound was well tolerated with no dose-limiting toxicity identified; adverse ev…

WADA status

Prohibited at all times under WADA 2026 Prohibited List: Section S0 (Non-Approved Substances) and Section S2 (Peptide Hormones, Growth Factors, Related Substanc…

Dominant research route: Human clinical development concentrated on topical/local application (ocular — dry eye and neurotrophic keratopathy, the most advanced program, through Phase III; and dermal — chronic-wound gels, Phase 2) and on intravenous dosing. [Verification corrected: the first pass asserted 'no completed human IV trial exists for any disease indication' — REFUTED. RegeneRx's OWN IV program (RGN-352) never advanced (both NCT01311518 and NCT00743769 withdrawn without initiating), but a different sponsor, Beijing Northland Biotech, COMPLETED Phase 2 IV trials of recombinant Tβ4 in acute-MI patients (NCT05485818 n=62, NCT05984134 n=90) plus Phase 1 IV healthy-volunteer studies.] Preclinical efficacy work (cardioprotection, dermal wounds, hair growth) relied on intraperitoneal or topical dosing in rodents. Subcutaneous and intramuscular use is reported only in vendor/community material (usually under the 'TB-500' name), with no published human PK for either route.

Two completed Phase 1 human safety/PK programs in healthy volunteers: (1) a 2010 single/multiple-ascending-dose study of synthetic Tβ4 (42–1260 mg IV, Ruff et al. 2010, Ann NY Acad Sci); (2) Beijing Northland's recombinant Tβ4 (NL005) Phase 1a (NCT04555824, n=54) and Phase 1b (NCT04555850, n=30). Beyond safety/PK, Beijing Northland also COMPLETED Phase 2 IV trials in acute-myocardial-infarction patients (NCT05485818, NCT05984134). RegeneRx's own IV cardiac program (RGN-352, NCT01311518) and a matching Phase 1 (NCT00743769) were both WITHDRAWN without initiating (contract-manufacturing issues).

Bioavailability: 100% by definition (reference route). A secondary trial-registry aggregator (trial.medpath.com) summarizing Ruff et al. 2010 reports dose-proportional PK with plasma half-life rising with dose (~0.95 h at 42 mg to ~2.1 h at 1260 mg) — [UNVERIFIED against the primary paywalled paper this pass; human re-check before relying on these figures]. The NL005 PK numbers were published open-access (Wang et al. 2021, J Cell Mol Med 25(17):8222–8, PMID 34346165) even though numeric results were not posted to the registry.

Only healthy-volunteer safety/PK is answered for RegeneRx's IV work; completed disease-indication IV trials exist only from Beijing Northland (acute MI). Not a human dosing protocol.

No dedicated IM pharmacokinetic or clinical study was identified for full-length Thymosin Beta-4. Vendor/community sources describe IM as an alternative injection site alongside subcutaneous for research self-administration.

Bioavailability: No published IM pharmacokinetic or bioavailability data exists for this peptide.

Community/vendor material mentions IM alongside SC; absorption and kinetics are not established. No human dosing protocol implied.

No dedicated SC pharmacokinetic or clinical study was identified for full-length Thymosin Beta-4 — every completed human trial used IV (safety/PK) or topical (skin/eye) routes. SC is the route most commonly described in vendor/community material for self-administered research use, usually under the trade name 'TB-500.'

Bioavailability: No published SC pharmacokinetic/bioavailability data. SC absorption in humans is unquantified for this peptide.

Community forums and vendor sites often use 'TB-500' interchangeably with Thymosin Beta-4, but TB-500 as originally described is a distinct 7-amino-acid actin-binding fragment (Ac-LKKTETQ) of the 43-amino-acid full peptide — vendors do not always clarify which is sold. Absorption/kinetics not established for SC use of either form. No human dosing protocol implied.

A systemic route used in rodent efficacy models: full-thickness dermal wound healing in rats (Malinda et al. 1999, J Invest Dermatol, PMID 10469335) and post-MI cardioprotection in mice (systemic-dosing literature reviewed in Front Pharmacol 2013). Animal-only; not a route used in any completed human Tβ4 trial.

Bioavailability: No dedicated IP pharmacokinetic characterization; used as a systemic dosing route in efficacy studies rather than a PK study. In the rat dermal-wound model IP dosing performed comparably to topical application on re-epithelialization endpoints.

A laboratory-animal administration route, cited only to describe how preclinical efficacy work was conducted. No human dosing or efficacy claim implied.

Completed, randomized, placebo-controlled Phase 2 trials of daily topical gel (0.01–0.1%) in pressure ulcers (NCT00382174, 72 subjects) and venous stasis ulcers (NCT00832091, 72 subjects). A Phase 2 epidermolysis-bullosa trial (NCT00311766) was TERMINATED after 30 of a planned 36 subjects — an administrative halt (patient unavailability + study-drug expiration), NOT a safety/efficacy signal. Preclinically, topical gel accelerated full-thickness dermal wound closure in rats (Malinda et al. 1999) and topical Tβ4 with a hydrogel carrier induced hair growth in mice (Philp et al. 2004; replicated by Gao et al. 2015, PMC4470810).

Bioavailability: Local wound-bed gel application; the human trials measured local wound-closure endpoints, not systemic plasma levels — systemic skin absorption was not quantified. Venous-stasis-ulcer RCT (secondary endpoint, safety was primary): wound closure without drainage by day 84 in 12/55 (21.8%) treated vs 4/17 (23.5%) placebo — no benefit over placebo on that endpoint. Pressure-ulcer RCT registry reports only incidence of complete healing (8 across three Tβ4 doses vs 3 placebo, no analysis posted); a widely-cited '22 vs 57 days' median-time-to-healing figure is from the sponsor's press release (a mid-dose, healed-wounds-only subgroup) and was described as NOT statistically significant.

The dermal chronic-wound RCTs are completed but did not establish a significant efficacy benefit; hair-growth evidence is animal-only, with no completed human hair-growth trial. RUO; not systemic dosing.

The compound's most mature human-RCT program: completed Phase 2 trials of 0.1% Tβ4 (RGN-259) ophthalmic solution in severe dry eye (Sosne et al. 2015, n=9) and a controlled-adverse-environment dry-eye model (n=72); a small Phase III neurotrophic-keratopathy trial (SEER-1, NCT02600429, n=18) whose primary endpoint narrowly missed significance (p=0.0656) with a significant day-43 secondary healing endpoint (p=0.0359); and a US follow-on Phase III (SEER-2, NCT05555589) currently recruiting. A European Phase III (SEER-3) MISSED its primary endpoint vs placebo (Jun 2025). Preclinical rat/mouse corneal-injury models used topical eye drops.

Bioavailability: Direct ocular-surface instillation (drops); endpoints are local corneal/ocular-surface healing and symptom scores — no systemic bioavailability was measured in any ophthalmic trial.

The most mature human-RCT evidence for this compound, but every trial measures a LOCAL ocular-surface effect of a specific eye-drop formulation (RGN-259), not systemic Tβ4 as sold by research-peptide vendors; SEER-1's small n=18 and narrowly-missed primary endpoint should be weighed accordingly. RUO.

Animal & human figures are kept visibly separate so studied animal doses are never misread as human guidance.

Sorted A–Z by vendor — never by price

Weekly median $/mg from the live vendor crawl.

Researched storefront prices, bucketed

p25 $6.40 · median $9.00 · p75 $10.70 · 11 researched vendors

Legit, COA-backed band: $6.00–$10.70/mg.

Value rule: don't just buy the cheapest — a price under $3/mg is a red flag. Pair price with COA and independent-test grade.

Estimated cost of research (10 mg)

Vial (best researched price)

$30

Bacteriostatic water (generic estimate)

$6

Syringes / supplies (generic estimate)

$12

What each test proves — general guidance, plus this compound's researched purity data

Purity on the current market (researched)

Reputable US vendors advertise ≥98% HPLC purity with mass-spec identity confirmation at the expected ~4,963 Da mass for the full-length 43-residue protein (truncated ~2,000–4,000 Da byproducts are a known impurity on HPLC per a 2026 vendor buying guide). Independent aggregate testing of products sold under the dominant commercial name 'TB-500' (Finnrick Analytics, 19 samples / 3 vendors, 16 May–17 Dec 2025) found actual purity spanning 3.18%–99.89%, with vendor-level results varying sharply — illustrating the gap between advertised and delivered quality in the lower tiers. (Finnrick is an independent third-party testing aggregator — Layer B — not a regulatory action; figures are a point-in-time snapshot.)

Independent labs cited for this compound

No specific product recall (FDA Class I/II/III) of a Thymosin Beta-4 or TB-500 product was found (search window 2018–2026). As an unapproved drug sold outside the regulated supply chain, FDA/DOJ action takes the form of warning letters, 503A Category-2 listing/removal, import controls and criminal cases rather than formal recalls. Reported honestly as an empty recall result, not invented.

Buyer red-flag checklist

• Product sold as 'TB-500' or 'Thymosin Beta-4' with no mass-spec identity confirmation — the fragment and full-length protein have very different expected masses (~4,963 Da full-length vs a short synthetic fragment), and independent analysis has found TB500/TB1000-labeled products' content inconsistent with their label (Delcourt et al. 2023).
• No batch-specific COA provided on request, or the same COA reused across multiple lots.
• COA report/task ID does not resolve in the issuing lab's own public database (e.g. public.janoshik.com).
• Purity-only COA with no LC-MS identity confirmation — cannot rule out a wrong-compound substitution.
• No endotoxin (LAL) or sterility data for a product implied for injection.
• Price far below the market range for the mg size — Finnrick's TB-500 aggregate shows quantity can diverge up to ±100% from label, consistent with an underfilled vial.
• Human-dosing / benefit marketing on a site labeled 'research use only' — the pattern behind FDA warning letters in this market.

GMP vs research-grade: the chemistry (SPPS + HPLC + MS) is identical — the difference is the quality system.

Underdosing / mislabeling: No single peer-reviewed prevalence fraction specific to Thymosin Beta-4 / TB-500 was found — reported honestly as null. The best independent quantitative signal is Finnrick's TB-500 aggregate (19 samples / 3 vendors, 16 May–17 Dec 2025): measured quantity diverged by up to ±100% vs the advertised label and purity spanned 3.18%–99.89%. A widely-circulated '43% of research peptides failed label-purity claims (Janoshik, 2024)' figure recurs across vendor-guide blogs but could not be traced to a primary Janoshik publication — treated as UNVERIFIED (independently flagged unconfirmed in the BPC-157 overlay too).

• An RUO label is not an import exemption — CBP judges actual intended use.
• Lyophilized powder is ambient-stable in transit; temperature control needed for > 7-day transit.
• US-warehouse vendors dodge import scrutiny — they cost more but ship more reliably.

Every item dated & sourced

Prohibited AT ALL TIMES (in- and out-of-competition) under Section S2.3 (Growth Factors and Growth Factor Modulators) of the WADA Prohibited List — a non-Specified S2 substance. Thymosin-β4 and its derivatives (e.g. TB-500) were added as named examples on the 2018 Prohibited List (per the USADA 2018 Summary of Major Changes) and remain listed on the current List. No approved systemic human therapeutic use exists, so no Therapeutic Use Exemption pathway applies; default sanction up to 4 years. (Corrected from an initial 'S0 + S2' read — a substance named in S2.3 is not an S0 entry.)

No granted patents identified in current seed. Composition-of-matter coverage is limited given the peptide's synthetic origin.

• IACUC / IRB research context
• RUO buyer responsibilities & documentation
• Veterinary / alternative-use where lawful
• Jurisdiction-aware "who may lawfully obtain"

What people discuss

Reported concerns — discussion, not established effects

Reading caveats

• Concern data derives from a peptide-GENERAL Reddit study (Rosenberg et al. 2026, BPC-157-dominant), not a Tβ4/TB-500-specific analysis — do not read the mention-shares as compound-specific.
• Naming/product-identity conflation dominates the sample — most content indexed under 'thymosin beta-4' is actually about TB-500 (the 7-aa fragment), inflating apparent volume and blurring which molecule reported effects/concerns attach to.
• SEO / AI-generated vendor 'Reddit review' and 'best vendor source' roundups dominate search results and pollute any automated tone/theme read; some cite Reddit statistics not independently confirmable against a primary source.
• Affiliate incentive on vendor-authored 'best peptide source' content.
• Survivorship / positivity bias — recovery success stories over-shared vs. silent non-responders.
• Placebo / concurrent-substance confounding — self-reports are frequently stacked with BPC-157, MOTS-C and other peptides, muddying attribution.
• Thin primary-platform access this pass (native Reddit/X search not directly fetchable) — themes triangulated via secondary aggregators, a forum snapshot, and journalism rather than raw post sampling.

Manually researched from reddit, youtube— theme weights are research estimates, not live counts; aggregated & de-identified. No individual posts, quotes, or usernames are ever shown.

Relative research / market volume — populated once the activity stream is wired

Inline tooltips for lyophilized, RUO, EU/mg, SPPS, 503A and more.

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Endogenous 43-aa actin-sequestering peptide studied for wound repair, corneal healing, angiogenesis, and cardiac protection; ophthalmic form in Phase 3 trials. Approximately 1,020 articles are indexed (literature last scanned 2026-05-29). US regulatory status: Investigational; no approved drug; not on FDA-19 compounding restriction list; RGN-259 ophthalmic in Phase 3. Research use only.

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