TB-500

Typical use cases

Dosing guidelines

Titration

Reported community pattern is a 4-6 week "loading" phase at a higher weekly total (often split into two doses), followed by a reduced once-weekly "maintenance" dose; this is anecdotal, not clinically validated.

Reconstitution

Supplied as a lyophilized powder; reconstituted with bacteriostatic water added slowly down the vial wall and swirled gently (not shaken) until dissolved. A common community ratio is ~2 mL bacteriostatic water per 5 mg vial.

Injection sites

Subcutaneous injection (commonly abdomen) is most often reported; intramuscular near an injury site is also described in community protocols

Storage & handling

Store lyophilized vials refrigerated (2-8 C) or frozen and protected from light; after reconstitution keep refrigerated at 2-8 C and typically use within ~28 days. Avoid freeze-thaw cycles of reconstituted solution.

Side effects

• Fatigue or lethargy Mild · Common
• Injection-site irritation, redness, or pain Mild · Common
• Headache Mild · Uncommon
• Transient flushing or head-rush sensation Mild · Uncommon
• Theoretical promotion of unwanted angiogenesis (e.g., tumor vascularization) Severe · Rare
• Unknown long-term effects (insufficient human safety data) Moderate · Uncommon

Research summary

The "TB-500" sold and discussed in community settings is most often the synthetic, N-terminally acetylated 17-23 fragment of thymosin beta-4 (Ac-LKKTETQ), which contains the seven-residue actin-binding motif believed to underlie much of the parent protein's activity; some products instead supply full-length 43-residue thymosin beta-4. The mechanistic rationale comes from thymosin beta-4 itself, the principal G-actin-sequestering peptide in cells, which regulates actin polymerization to drive cell migration, and which has shown accelerated wound healing in animal models (e.g., a rat full-thickness wound study reported ~42% greater reepithelialization at 4 days and up to 61% at 7 days versus saline, with increased collagen deposition and angiogenesis). Additional preclinical work documents pro-angiogenic, anti-inflammatory, and cardioprotective/neuroregenerative effects, and identifies the short actin-binding motif as essential for the angiogenic activity. Human clinical data, however, are almost entirely for full-length thymosin beta-4 in topical (RGN-137), ophthalmic (RGN-259, including a Phase 2 corneal-wound trial), or injectable (RGN-352) formulations rather than for the injectable 7-mer "TB-500" fragment, and several programs (including an acute-MI study) were withdrawn or terminated before completion. There are essentially no controlled human trials of the LKKTETQ fragment specifically, so claims about its injectable use rest on extrapolation from the parent peptide and anecdote. The fragment is on the anti-doping radar: analytical methods to detect Ac-LKKTETQ in plasma and urine were developed because of its suspected doping potential. Overall the evidence base is mechanistically plausible and rich in preclinical signals but weak in rigorous human data for the marketed fragment, and long-term safety is uncharacterized.

Key references

• https://pubmed.ncbi.nlm.nih.gov/10469335/
• https://pubmed.ncbi.nlm.nih.gov/30063849/
• https://pubmed.ncbi.nlm.nih.gov/22962027/
• https://pubmed.ncbi.nlm.nih.gov/14500546/
• https://clinicaltrials.gov/study/NCT01311518
• https://clinicaltrials.gov/study/NCT00598871

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