TB-500
A synthetic peptide corresponding to the active actin-binding region of Thymosin Beta-4, sold for tissue repair, flexibility and recovery. Marketed heavily to athletes and in veterinary/equine circles, but human efficacy rests on animal models and anecdote. Not approved for human use; note that TB-500 and full-length Thymosin Beta-4 are related but not identical.
01 Overview
TB-500 refers to a fragment (often the Ac-LKKTETQ actin-binding sequence) of Thymosin Beta-4 (TB4), a naturally occurring peptide involved in cell migration and wound healing. Full-length TB4 has been studied clinically for dermal wounds, corneal injury and cardiac repair with mixed results; the research-chemical 'TB-500' sold to consumers is typically the shorter fragment and has not itself been through those trials.
Users take TB-500 for tendon and muscle recovery, joint mobility and hair regrowth. The rationale comes from TB4's documented roles in angiogenesis and cell migration in animal models. There are no controlled human trials of the fragment marketed as TB-500, no human pharmacokinetic data, and dosing is entirely convention-based. It is banned in sport by WADA.
02 Mechanism
Thymosin Beta-4 sequesters G-actin and promotes cell migration, angiogenesis and downregulation of inflammation, which in animal models accelerates wound and tissue healing. The TB-500 fragment is presumed to share the actin-binding activity; its behaviour in humans is unconfirmed.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Maintenance anecdotal | 2–2.5 mg/wk | SubQ | Reduced to a maintenance schedule (e.g. every 1-2 weeks) after loading, per user convention. |
| Loading anecdotal | 2–2.5 mg/wk | SubQ | Common self-reported loading dose split across the week for several weeks. No clinical basis. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Improved tissue recoveryThymosin Beta-4 accelerates wound, muscle and cardiac repair in animal models; the consumer fragment is untested in human trials. | Preclinical | ||
| Increased flexibility / reduced joint stiffnessFrequently reported by users; no controlled evidence. | Anecdotal | ||
| Angiogenesis and anti-inflammatory activityDocumented for full-length TB4 in vitro and in animals. | Preclinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site reactionsLocal redness, transient fatigue or head-rush reported after injection. | Mild | Common | Anecdotal | |
| Theoretical tumour-promotion riskBecause TB4 promotes angiogenesis and cell migration, there is a theoretical concern about supporting tumour growth or metastasis; unproven in either direction and no human safety data exists. | Moderate | Unquantified | Unconfirmed |