Educational reference only. Informational material drawn from peer-reviewed literature. Not medical advice and not a recommendation to use, dose, or modify any therapy. Decisions about hormone therapy should be made with a qualified healthcare provider.
Overview
Overview
TB-500 is a synthetic 7-amino acid peptide (sequence: Ac-LKKTETQ) that copies the central actin-binding region of thymosin beta-4 (Tβ4), a naturally occurring 43-amino acid protein found in nearly every cell in the human body. TB-500 is widely used in non-medical contexts (particularly in athletic recovery, injury rehabilitation, and biohacking communities), typically in combination with BPC-157 as the two most popular "research peptides" for tissue repair.
Like BPC-157, TB-500 has a substantial gap between its widespread use and its evidence base. The compound has no FDA approval, no completed Phase 2 or Phase 3 clinical trials for the injection-based use that dominates non-medical contexts, and is explicitly prohibited by WADA.
The closest legitimate clinical development has been for the full-length thymosin beta-4 protein in a topical eye drop formulation (RGN-259), a different compound, different formulation, different indication than the systemic injected TB-500 used in non-medical contexts. The conflation of these two is one of the most consistent misunderstandings in non-medical use of this compound class.
No human dose-response data for TB-500 has been published, so no validated clinical protocol exists for it.
Forms
Available forms & half-lives
| Form | Approximate half-life |
|---|---|
| Subcutaneous injection (estimated) | ~2–3 hours |
| Intramuscular injection (estimated) | ~3–4 hours |
What it does
Main effects
- Tendon and ligament repair: animal studies suggest accelerated healing (animal evidence only)
- Muscle injury recovery: accelerated regeneration in animal models
- Cardiac repair: full-length Tβ4 (RGN-352) reached Phase 2 for post-MI cardiac repair; TB-500 fragment effects extrapolated
- Wound and skin healing: full-length Tβ4 (RGN-137) investigated for epidermolysis bullosa and other wound conditions
- Corneal/eye surface healing: full-length Tβ4 topical eye drops (RGN-259) reached Phase 3 for dry eye and neurotrophic keratitis; NOT FDA-approved as of 2026
- Hair growth stimulation: Tβ4 has documented effects on hair follicle stem cells; some TB-500 users report increased hair growth
- Proposed mechanism: actin sequestration → cell migration, angiogenesis promotion, anti-inflammatory effects, stem cell modulation
- Veterinary use: used in racehorses for soft tissue and joint injury in some jurisdictions
- Combined use with BPC-157 has not been studied: no trial has characterized the two together, so neither added effect nor added risk is established
What to watch for
Common side effects
- No completed Phase 2 or Phase 3 trials of injectable TB-500 in humans: fundamental evidence gap; legitimate clinical research is on a different compound (full-length Tβ4) in different formulations (topical eye drops, topical wound healing)
- WADA-prohibited since 2011: section S2 (peptide hormones, growth factors); detection methodology well-validated; a Canadian athlete received a 4-year suspension; military and first-responder testing often aligns with WADA
- Theoretical cancer concerns: angiogenesis-promoting mechanism could theoretically promote tumor growth or activate dormant cancer cells; effects on tissue-resident stem cells uncharacterized
- Quality and purity concerns: research chemical supply varies in identity, concentration, sterility, and storage stability; veterinary-grade product is not approved for human use
- Infection risk: particularly with non-pharmaceutical-grade injectable products
- Injection site reactions: pain, swelling, redness reported anecdotally
- Fatigue, headache, lightheadedness: reported in non-medical use, particularly during loading phase
- Possible hypotension: anecdotal cardiovascular effects
- Fragment-vs-full-protein confusion: non-medical users frequently cite Phase 3 RGN-259 data as evidence for TB-500; these are scientifically distinct compounds with different formulations, routes, and indications
- Combination with BPC-157 compounds the unknowns: two unregulated products with overlapping angiogenic mechanisms; attribution of any effect (positive or adverse) is impossible
- No long-term human safety data: multi-year continuous use entirely uncharacterized
- Legal/regulatory uncertainty: research chemical sale exists in legal grey area; human consumption is outside any approved channel
Key facts
Key facts worth knowing
- TB-500 is a fragment, not the full peptide. The synthetic 7-amino acid sequence (Ac-LKKTETQ) corresponds to amino acids 17–23 of the parent 43-amino acid thymosin beta-4 protein. The fragment was selected because it contains the active actin-binding region of Tβ4, but it is not biochemically identical to the full-length protein and likely has different pharmacological properties.
- The full-length thymosin beta-4 protein has a more substantial clinical development history through the company RegeneRx Biopharmaceuticals. The compound RGN-259 (topical Tβ4 eye drops) has reached Phase 3 clinical trials for dry eye and neurotrophic keratitis. RGN-259 has NOT received FDA approval as of 2026, but represents the legitimate clinical development pathway for thymosin beta-4-based therapy.
- The distinction between full-length Tβ4 and TB-500 fragment is important and frequently confused. Non-medical use is overwhelmingly of injected TB-500 (the 7-amino acid fragment), while the legitimate clinical research is on topical full-length Tβ4. The two have different formulations, different routes, different indications, and likely different pharmacological behavior.
- WADA Prohibited Status: TB-500 has been on the WADA Prohibited List since 2011 under section S2 (peptide hormones, growth factors, related substances). It is banned both in and out of competition. A Canadian athlete received a four-year suspension for TB-500 use. Detection methodology has been refined for anti-doping testing.
- Veterinary use exists: TB-500 has been used in racehorses and other animals for soft tissue and joint injury treatment, particularly in Australian and other international racing contexts. This veterinary use has accelerated detection methodology development and predates widespread human use.
- The proposed mechanism involves actin regulation, cell migration, angiogenesis, and tissue repair. Thymosin beta-4 plays well-characterized roles in these biological processes; whether the TB-500 fragment recapitulates these effects in systemic injection contexts is less clear.
Legal status
Legal status
No FDA approval. Sale for human consumption is not legal. Sale for "research purposes" exists in legal grey area. Compounding through 503A pharmacies has been progressively restricted. Possession for personal use is in regulatory grey area but using for human consumption is outside any approved channel. WADA-prohibited since 2011.