TB-500
Published research and evidence base
Thymosin beta-4 (Tb4) is a 43-amino-acid endogenous actin-sequestering peptide with a large preclinical literature on tissue repair, angiogenesis, anti-fibrotic activity and inflammation resolution. TB-500 is the synthetic Ac-LKKTETQ fragment marketed as a Tb4 analogue; almost all published biology concerns full-length Tb4 rather than the fragment, and the two are frequently conflated. Human evidence is more developed than for most peptides in this category, including completed phase 1 safety studies, a phase 2 dry eye trial and a 2025 study reporting outcomes in both mice and STEMI patients, but no product is approved for musculoskeletal recovery.
- Studies cited
- 15
- Published 2023+
- 8
- Newest paper
- 2026
- Last reviewed
- Aug 2026
Recurring themes in the literature
- actin sequestration and cell migration
- angiogenesis and endothelial migration
- cardiac repair and epicardial activation
- anti-fibrotic activity
- corneal and dermal wound healing
- inflammation resolution
- TB-500 fragment pharmacology and doping detection
Compound identifiers
- CAS
- 885340-08-9
- PubChem
- 62707662
Recommended by an FDA advisory committee.
On 23–24 July 2026 the FDA’s Pharmacy Compounding Advisory Committee considered TB-500 for the 503A Bulks List and recommended its addition on a reported vote of 8–6 with one abstention. Heard as TB-500 free base and TB-500 acetate, and recommended on a divided vote.
This is not an approval. The committee advises; it does not decide. The recommendation is not binding, the FDA has not completed the rulemaking that would formally change anything, and inclusion on the 503A Bulks List is not equivalent to FDA approval of a drug. The list also governs pharmacy compounding for patients, which is a separate activity from research-use-only supply.
What the July 2026 advisory vote actually did sets out the process, the other compounds heard, and the four things the vote is routinely misreported as meaning.
What TB-500 is, chemically.
- Molecular formula
- C38H68N10O14
- Molecular weight
- 889.0 g/mol
- CAS number
- 885340-08-9
- PubChem CID
- 62707662
TB500
These figures come from the PubChem record for this compound and describe the free base. Lyophilised peptide is normally supplied as an acetate or trifluoroacetate salt and carries residual water, so the mass of powder in a vial is not the same quantity as the molecular weight above would suggest. Chromatographic purity on a certificate of analysis does not resolve that difference either — how to read a certificate of analysis explains why.
15 published studies.
Ordered by strength of study design, then by recency. Every entry links to its source record so the finding can be checked against the paper rather than taken on our word.
- 01Human clinical2025
Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion
Zhang Y, et al. · Cardiovasc Res · murine myocardial ischemia/reperfusion models plus subjects with acute ST-segment elevation myocardial infarction after primary percutaneous coronary intervention
Recombinant human thymosin beta 4 was evaluated for its effect on chronic cardiac functional recovery after ischemia/reperfusion in mice and in STEMI patients following reperfusion. This is the most substantial human cardiac dataset for the peptide to date.
- 02Human clinical2021
A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin beta4 in healthy Chinese volunteers
Wang X, et al. · J Cell Mol Med · phase 1 randomised double-blind study; 54 healthy subjects across 7 single-dose cohorts (0.05 to 25.0 ug/kg intravenous) and 30 subjects in 3 multiple-dose cohorts
The trial evaluated safety, tolerability, pharmacokinetics and anti-drug antibody formation for recombinant human Tb4 (NL005) after single and multiple intravenous doses in healthy volunteers.
- 03Human clinical2015
Thymosin beta4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial
Sosne G, et al. · Cornea · multicentre, randomised, double-masked, placebo-controlled 56-day phase 2 trial at 2 US sites; 9 patients with severe dry eye, RGN-259 0.1% or vehicle 6 times daily for 28 days with 28-day follow-up
Tb4 eye drops improved signs and symptoms of severe dry eye compared with vehicle in this small phase 2 trial, which included patients with graft-versus-host-associated disease.
- 04Human clinical2010
A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers
Ruff D, et al. · Ann N Y Acad Sci · 4 cohorts of 10 healthy subjects; single intravenous placebo or synthetic Tb4 at 42, 140, 420 or 1260 mg, then the same dose daily for 14 days
Adverse events were infrequent and mild across the ascending single and 14-day repeat intravenous dose ranges, with pharmacokinetic parameters characterised. This remains the primary human safety dataset for systemic Tb4.
- 05Human clinical2010
The effect of thymosin treatment of venous ulcers
Guarnera G, et al. · Ann N Y Acad Sci · multicentre randomised controlled phase 2 study of topical synthetic Tb4 in patients with chronic venous ulcers of the lower limbs
The trial assessed safety, tolerability and healing effect of topical Tb4 added to standard care in venous leg ulcers.
- 06Animal in vivo2026
Recombinant human Thymosin beta4 ameliorates experimental colitis and intestinal fibrosis through suppression of mineralocorticoid receptor signaling
Zhao TR, et al. · Mol Biomed · murine experimental colitis and intestinal fibrosis models, with TMSB4X expression profiling in colonic tissue from inflammatory bowel disease patients
TMSB4X, the gene encoding Tb4, was downregulated in colonic tissue from IBD patients, and recombinant human Tb4 reduced colitis severity and intestinal fibrosis in mice via suppression of mineralocorticoid receptor signalling.
- 07Animal in vivo2026
Thymosin beta4 alleviates sepsis-associated acute kidney injury by suppressing MAPK signaling pathway
Ouyang X, et al. · Clin Sci (Lond) · in vivo and in vitro lipopolysaccharide-induced models of sepsis-associated acute kidney injury; Tb4 given 30 minutes after LPS exposure
Tb4 administration after LPS exposure attenuated markers of sepsis-associated acute kidney injury, with the protective effect linked to suppression of MAPK signalling.
- 08Animal in vivo2026
Reparative Outcomes in Corneal Infection: Linking Adjunctive Tbeta4 Treatment to Nerve Regeneration and Visual Function
Ebrahim AS, et al. · Invest Ophthalmol Vis Sci · bacterial keratitis induced in C57BL/6 mice by inoculating wounded corneas; adjunctive Tb4 with ciprofloxacin
The study evaluated whether adjunctive Tb4 supports corneal nerve regeneration and restores visual function after infection, extending earlier findings that the combination reduces keratitis severity and enhances wound repair.
- 09Animal in vivo2026
Decidualization-empowered ECM hydrogel integrating sustained Tbeta4 release drives endometrial regeneration in intrauterine adhesions
Liang Y, et al. · Nat Commun · murine intrauterine adhesion model treated with a decidualized-endometrium extracellular matrix hydrogel providing sustained Tb4 release
A single application of the Tb4-releasing hydrogel shifted the uterine injury response away from fibrotic scarring and toward endometrial regeneration in mice.
- 10Animal in vivo2025
Tbeta4-Engineered ADSC Extracellular Vesicles Rescue Cell Senescence Through Separable Microneedle Patches for Diabetic Wound Healing
Ding Y, et al. · Adv Sci (Weinh) · separable microneedle patches loaded with extracellular vesicles from Tb4-overexpressing adipose-derived stem cells, applied to aged diabetic wound models
Tb4-modified extracellular vesicles delivered by microneedle patch reversed markers of cellular senescence and improved healing in chronic diabetic wounds aggravated by senescence.
- 11Animal in vivo2025
Inhaled exogenous thymosin beta 4 suppresses bleomycin-induced pulmonary fibrosis in mice via TGF-beta1 signalling pathway
Yu R, et al. · J Pharm Pharmacol · bleomycin-induced pulmonary fibrosis in mice; nebulised recombinant human Tb4 given under three dosing strategies
Nebulised recombinant human Tb4 suppressed bleomycin-induced pulmonary fibrosis in mice, with the anti-fibrotic effect associated with TGF-beta1 signalling.
- 12Animal in vivo2013
Thymosin beta4-sulfoxide attenuates inflammatory cell infiltration and promotes cardiac wound healing
Evans MA, et al. · Nat Commun · zebrafish wounding model and mammalian cardiac injury
Thymosin beta4-sulfoxide was identified downstream of wound-derived hydrogen peroxide as a resolution signal that depletes inflammatory macrophages and promotes cardiac wound healing. This established an inflammation-resolution mechanism distinct from actin binding.
- 13Animal in vivo2011
De novo cardiomyocytes from within the activated adult heart after injury
Smart N, et al. · Nature · adult mouse heart, epicardial progenitor population primed with thymosin beta4 prior to myocardial infarction
Priming with thymosin beta4 mobilised a resident adult epicardial progenitor population that contributed structurally and functionally to new myocardium after infarction. This is the landmark cardiac-regeneration result for the peptide.
- 14Animal in vivo1999
Thymosin beta4 accelerates wound healing
Malinda KM, et al. · J Invest Dermatol · rat full-thickness dermal wound model; topical or intraperitoneal Tb4
Tb4 increased re-epithelialisation by 42 percent at 4 days and up to 61 percent at 7 days versus saline controls, with at least 11 percent greater wound contraction by day 7 and increased collagen deposition and angiogenesis. This is the foundational wound-healing paper.
- 15In vitro2024
Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro
Rahaman KA, et al. · J Chromatogr B Analyt Technol Biomed Life Sci · in vitro metabolic incubations and rat administration, with synthesised authentic standards; scratch wound healing assays for the metabolites
This is one of the few papers addressing TB-500 (Ac-LKKTETQ) itself rather than full-length Tb4. It established simultaneous quantification of TB-500 and its metabolites and screened them for wound healing activity in vitro.
What this evidence does not establish.
No human trial has tested Tb4 or TB-500 for tendon, ligament or muscle injury, which is the marketed use; the completed human trials cover dry eye, venous ulcers, cardiac ischemia and healthy-volunteer safety. The specific TB-500 fragment (Ac-LKKTETQ) has almost no independent pharmacology of its own, and its equivalence to full-length Tb4 is assumed rather than demonstrated. Tb4 is also prohibited in sport and in equine competition, and several of the recent papers are doping-detection methods rather than efficacy studies.
Common questions about the research.
- What is TB-500?
TB-500 is the research designation for synthetic thymosin beta-4 chemistry supplied for laboratory work. Thymosin beta-4 is a naturally occurring 43-amino-acid peptide and the main actin-sequestering molecule in mammalian cells; it is studied for its role in cell migration, angiogenesis, and tissue repair.
- How does TB-500 differ from BPC-157?
They are unrelated molecules studied in overlapping models. TB-500 derives from thymosin beta-4 and is investigated for actin regulation, cell migration, and angiogenesis; BPC-157 is a gastric-juice-derived pentadecapeptide studied in tendon, ligament, and gastrointestinal models. The two are frequently co-studied, which is why combined vials are offered.
- Why do some papers describe a short fragment instead?
Much of the activity attributed to thymosin beta-4 maps to its central actin-binding motif (LKKTETQ), so some studies work with the full 43-amino-acid peptide and others with shorter fragments. Comparing protocols across papers requires checking which preparation was used.
Available from our catalog
For research purposes only. Not for human consumption, diagnosis, treatment, or prevention of any condition. Nothing on this page is medical advice, and no study summarised here should be read as a recommendation.