Overview
TB-500 is a synthetic peptide marketed as a fragment of thymosin beta-4 (Tβ4), a 43-amino-acid actin-sequestering protein with documented roles in tissue repair, angiogenesis, and inflammation modulation in animal models. Confusingly, the term 'TB-500' is sometimes used for the full Tβ4 molecule and sometimes for a 7-amino-acid fragment containing the actin-binding region. Full Tβ4 has been investigated in early-stage human trials for wounds, dry eye, and post-MI cardiac repair, sponsored by RegeneRx; outcome data is mixed and trials are small. The 'TB-500' fragment marketed in self-experimenter channels has no published human RCTs.
Mechanism
Tβ4 binds and sequesters G-actin, modulating cell migration, angiogenesis, and stem-cell mobilization. The Tβ4 17-23 fragment retains the actin-binding region but lacks the full-length protein's other functional domains. Whether the fragment recapitulates Tβ4's clinical effects is not directly tested in humans.
Evidence by indication
We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.
Tissue / tendon repair
Animal models of tendon, ligament, and skin wound healing show consistent effects with full-length Tβ4 and (in fewer studies) the 17-23 fragment. No published human RCTs evaluate the fragment for musculoskeletal repair.
Cardiac repair after myocardial infarction
Early-phase human studies of full-length Tβ4 in post-MI populations have produced mixed results; trials are small and the fragment is not what was studied.
Athletic performance / recovery
No published primary literature evaluating the fragment for athletic recovery endpoints. Anti-doping agencies (WADA) prohibit Tβ4 in competitive sport regardless of evidence.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Studied dose ranges
The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.
Self-experimenter protocols typically use a 2–5 mg loading dose twice weekly for 4–6 weeks, then weekly for maintenance. These protocols are not validated by human RCTs.
Contraindications
- Active malignancy (Tβ4 promotes angiogenesis and cell migration in animal models)
- Pregnancy and breastfeeding
- Active competitive athletes — Tβ4 is on the WADA prohibited list
- Hypersensitivity to peptide formulations
Reported side effects
- Injection site reactions
- Headache
- Mild fatigue
- Theoretical concern: angiogenesis-promoting activity is not benign in the wrong context
- No long-term human safety data — flag explicitly
Reconstitution & storage
Lyophilized powder reconstituted with bacteriostatic water. A 5 mg vial in 2.5 mL BAC water = 2 mg/mL, putting a 2,000 mcg dose at 100 units (1.0 mL) on a U-100 syringe. The dose volume is significant — split between two injection sites if needed.
Storage. Lyophilized: refrigerate 2–8 °C. Reconstituted: refrigerate 2–8 °C, use within 30 days. Avoid agitation.
Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.
Editorial note
The 'TB-500 = TB4' equivalence is sloppy and pervasive. Be precise: the fragment marketed as TB-500 is not what was studied in human trials of full-length Tβ4. WADA prohibition is worth flagging up front for athletes.
Citations
- [1]Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applicationsGoldstein AL, Hannappel E, Sosne G, Kleinman HK · Expert Opinion on Biological Therapy · 2012 · PMID 23173600Comprehensive review of Tβ4 mechanisms and human pilot trials.View source