Compound record · Tissue repair
TB-500
Also Thymosin beta-4 fragment · Tβ4 17–23 · LKKTETQ · Ac-LKKTETQ · TB500 · Thymosin beta 4 (TB-500)
Synthetic thymosin β4 fragment (residues 17–23)
Thymosin β4 fragment sold for healing; no human trials of the fragment
Record reviewed 1 September 2026 · 6 references
In the AERVYN range
4 pens carry TB-500
Single-compound pen
TB-500
Peptide pen · 10 mg / 3 mL
£180 · In stock
Blend pen
Wolverine
BPC-157 + TB-500 · 40 mg / 3 mL
TB-500 with BPC-157
£235 · In stock
Blend pen
Klow
GHK-Cu + BPC-157 + TB-500 + KPV · 80 mg / 3 mL
TB-500 with GHK-Cu, BPC-157 and KPV
£340 · In stock
Blend pen
Glow
GHK-Cu + BPC-157 + TB-500 · 70 mg / 3 mL
TB-500 with GHK-Cu and BPC-157
£295 · In stock
- Class
- Synthetic 7-amino-acid fragment of thymosin β4
- Human trials
- None for the fragment; parent protein trialled as eye drops (mixed results)
- Regulatory status
- Not authorised anywhere; US compounding review ongoing
- Anti-doping
- Prohibited at all times (WADA S2.3 growth factors)
- Typical sale form
- Unregulated injectable vials (2 mg / 5 mg / 10 mg)
01 Overview
What TB-500 is
Summary
TB-500 is a short synthetic peptide (Ac-LKKTETQ) copying the actin-binding region of thymosin beta-4, a 43-amino-acid protein involved in cell migration and wound repair. Full-length thymosin beta-4 has been tested in human trials as eye drops and skin gel with mixed results, but the TB-500 fragment sold online has never been studied in people. It is not authorised anywhere and is prohibited in sport as a growth-factor derivative.
Mechanism
Thymosin β4 binds actin and regulates its assembly, which in laboratory and animal models promotes cell migration, new blood-vessel formation, reduced inflammation and scar-free wound healing. The 17–23 fragment retains the actin-binding sequence; whether it reproduces the parent protein's effects in humans has not been tested.
02 Evidence by goal
What has been shown, for which goal
Grades follow one scale across the site. Insufficient overall means: no reliable human evidence for this use — animal or laboratory data only.
Injury & recovery support
InsufficientAnimal studies of full-length thymosin β4 show faster wound closure and improved cardiac and corneal repair. No human study of the TB-500 fragment exists for any injury; the parent protein's human trials are in eye and skin wounds, not musculoskeletal injury.
Muscle & recovery
InsufficientRodent and horse data suggest thymosin β4 influences muscle repair; there are no human recovery, soreness or strength studies of TB-500.
Athletic performance
InsufficientNo performance data in humans. TB-500 has a history of illicit use in horse racing, which is why doping-control laboratories developed tests for it.
Hair
InsufficientHair-growth claims rest on mouse studies in which thymosin β4 accelerated follicle development; nothing has been published in humans.
03 Regulatory status
Where it is authorised, and for what
Status is recorded per jurisdiction from regulator sources and reviewed by hand. It is never inferred from another region's decision.
United Kingdom
Not authorisedNo marketing authorisation; sold online as a 'research chemical'.
No MHRA-licensed medicine contains TB-500 or thymosin β4. Products labelled 'for research use only' fall outside medicines quality controls.
04 Dosing research
What the evidence says about exposure
Published human studies and the doses, routes and durations they used — reported as research information, not a recommendation.
Research information — not a recommendation. These are the exposures used in published human studies, reported so you can see what has been tested. They are not dosing instructions and do not apply to any individual.
Study 01
Full-length thymosin β4 (RGN-259 0.1% eye drops), NOT the TB-500 fragment — SEER-1 in neurotrophic keratopathy
Sosne G et al., Int J Mol Sci 2023;24(1):554 · Source
- Design
- Randomised, double-masked, placebo-controlled
- Population
- Adults with stage 2–3 neurotrophic keratopathy (persistent corneal epithelial defects)
- Participants
- n = 18
- Duration
- 4 weeks of treatment, follow-up to day 43
- Route
- Topical
- Doses studied
- 0.1% timbetasin (thymosin β4) ophthalmic solution, one drop five times daily — a topical eye medicine, not an injected peptide
- Outcome at this exposure
- Complete corneal healing at 4 weeks in 6 of 10 treated versus 1 of 8 placebo eyes (p = 0.0656, not statistically significant); the later European SEER-3 trial missed its primary endpoint and the US SEER-2 trial reads out in late 2026.
- Adverse events observed
- No significant adverse effects were observed; the three phase 3 dry-eye trials (ARISE) also reported a benign safety profile in over 1,600 participants.
The study above used the full 43-amino-acid thymosin β4 protein as eye drops and is included only to show what human research on the parent molecule looks like. The TB-500 fragment that is sold for injection has no human pharmacokinetic, dose-finding, safety or efficacy studies of any kind — the FDA stated in 2023 that it had identified no human exposure data. Vendor 'loading and maintenance' schedules (commonly 2–5 mg per week) are extrapolated from veterinary and animal use and are not evidence.
05 Safety
Adverse effects and contraindications
Common effects seen in trials or reports, serious effects that warrant urgent review, and conditions under which use is not appropriate or needs assessment.
Common adverse effects
- Not systematically studied in humans
- Injection-site pain, redness or bruising (user reports)
- Headache or lethargy shortly after injection (user reports)
- Transient nausea or 'head rush' (user reports)
Serious adverse effects
- Unknown — no human safety data for the fragment
- Theoretical promotion of tumour growth or spread (angiogenic and pro-migratory activity)
- Immune reactions to the peptide, aggregates or impurities (FDA-identified risk)
- Infection from non-sterile injectable products
- Unpredictable effects from mislabelled or contaminated vials
Contraindications
- CancerCaution
Thymosin β4 is over-expressed in several tumour types and promotes angiogenesis and cell migration in cancer models; the effect of exogenous peptide on an existing or previous cancer is unknown.
- Blood-clotting disorderCaution
Thymosin β4 is abundant in platelets and influences clot structure in laboratory studies; there are no human data on bleeding or thrombosis risk.
- Autoimmune conditionCaution
The FDA has flagged immunogenicity and aggregation risk for the injected fragment; effects in autoimmune disease or alongside immune-modifying therapy are unknown.
Do not use = should not be used · Caution = needs assessment
06 Interactions
Medicine classes that need review
Grouped by how seriously the combination should be taken. Class labels match the medicines questionnaire in the assessment.
- Major
- Moderate
- Minor
Moderate
Monitoring or dose review is usually advised.
Anticoagulant (blood thinner)
Warfarin, apixaban, rivaroxaban
Interactions are unstudied in humans. Given thymosin β4's role in platelet and actin biology, combination with a blood thinner should not be assumed safe.
Cancer treatment
Chemotherapy, hormone therapy, immunotherapy
A pro-angiogenic, pro-migratory peptide could in theory oppose anti-angiogenic or anti-metastatic cancer treatment; this has not been tested. Disclose to the treating oncologist.
Minor
Generally compatible; awareness is sufficient.
Immunosuppressant / biologic
Methotrexate, tacrolimus, adalimumab
Thymosin β4 has anti-inflammatory and immune-modulating actions in animals; no human data on combined use with immunosuppressants.
07 Pregnancy & breastfeeding
Status in pregnancy
No human or reproductive-toxicity data exist for the fragment. An unlicensed injectable of unknown purity is not something to use while pregnant, trying to conceive or breastfeeding.
08 Monitoring
What is usually monitored
Parameters that trials and product information track. A clinician decides what applies to an individual.
- 01Injection sites for infection or persistent reactions
- 02Any new lump, changing mole or unexplained symptom, given the angiogenic mechanism
- 03Bleeding or bruising if combined with any blood thinner
- 04Whether the underlying injury has been properly diagnosed and imaged
- 05Anti-doping status if you compete in tested sport (prohibited at all times under S2.3)
09 Combinations
What is known about combining it
Notes on pairing with other compounds in the directory: whether the combination has been studied in people, and where mechanisms overlap.
BPC-157
No human studies
Overlap · Both are marketed as tissue-repair peptides acting through angiogenesis and cell migration.
The most commonly co-marketed 'healing stack'. Neither peptide has human efficacy data alone; there are no data on the combination, and both are WADA-prohibited.
CJC-1295
No human studies
No human studies of TB-500 combined with growth-hormone secretagogues; both are WADA-prohibited.
Ipamorelin
No human studies
No human studies of TB-500 combined with growth-hormone secretagogues; both are WADA-prohibited.
IGF-1 LR3
No human studies
Overlap · Both sit in WADA's S2.3 growth-factor category and both drive cell growth and migration.
No human data; combining two growth-factor-type agents of unknown purity multiplies theoretical tumour-promotion concerns.
Thymosin alpha-1
No human studies
Overlap · Similar names, different peptides: thymosin α1 is an immune-modulating peptide, thymosin β4 an actin-binding repair protein.
The two are often confused or sold together; there are no human data on combined use.
GHK-Cu
No human studies
No human data. Both are promoted for repair and both show angiogenic activity in laboratory models.
KPV
No human studies
Blended together in the Klow pen. No human data on the combination; TB-500 has no human data at all and KPV has none by any route.
Discuss any proposed combination with a qualified healthcare professional.
10 Source considerations
Supply, quality and legitimacy
How the compound reaches people in practice, and what that means for product quality.
- 01No authorised, pharmaceutical-grade TB-500 exists anywhere; all products come from unregulated suppliers with no GMP assurance.
- 02Identity is a specific problem: vials sold as 'TB-500' may contain the fragment, full-length thymosin β4, a different peptide or nothing active — independent analyses of grey-market peptides have found all of these.
- 03The FDA's 2023 safety listing cited aggregation, peptide-related impurities and immunogenicity — risks that are greatest for poorly manufactured injectables.
- 04Regulators in the UK, Australia and Canada have acted against online sellers of unapproved injectable peptides; a seller's certificate of analysis is not independent verification.
11 Questions for your clinician
Take these to your appointment
Specific to this compound. The personal assessment adds questions drawn from your own history and medicines.
- 01Has my injury been properly diagnosed, and what does the evidence-based rehabilitation pathway look like?
- 02Do I understand that the human trials I have read about used full-length thymosin β4 as eye drops, not the injectable fragment?
- 03Does my history — any cancer, clotting or autoimmune condition — make an angiogenic peptide a particular concern?
- 04If I have already used TB-500, are there any checks you would recommend?
- 05Are there authorised treatments or supplements with actual human evidence for my goal?
The personal assessment tailors this list to your responses.
12 Alternatives
Compounds with stronger evidence or firmer regulatory footing
Listed for overlapping goals. Whether any is appropriate depends on your history — the assessment maps that for you.
13 References
Sources behind this record
Regulator documents and peer-reviewed publications used to derive every grade and statement above.
- 01WADA Prohibited List 2025 — S2.3 growth factors: 'thymosin-β4 and its derivatives e.g. TB-500'
- 02FDA — Certain bulk drug substances for use in compounding that may present significant safety risks (thymosin β4 fragment entry)
- 03Sosne G et al. 0.1% RGN-259 (thymosin β4) ophthalmic solution in neurotrophic keratopathy — phase 3 (SEER-1). Int J Mol Sci 2023
- 04Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide. Expert Opin Biol Ther 2012;12:37–51
- 05Ho ENM et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma. J Chromatogr A 2012;1265:57–69
- 06RegeneRx — RGN-259 development programme (neurotrophic keratopathy and dry eye)
The Peptide Checkup provides educational information and a structured summary of published research and regulatory status. It is not medical advice, does not diagnose or treat any condition, and does not replace a consultation with a qualified healthcare professional.
Personal assessment
Check TB-500 against your history
Seven minutes of structured questions about your goal, history and medicines, mapped against this record by a deterministic, clinician-reviewable rules engine. The report tells you when not to buy.