PeptideGrids
Browse Database

Thymosin Beta-4

TB-500

Grade D: Preclinical or anecdotal only

TL;DR: Evidence is limited primarily to animal and preclinical studies; the evidence base for systemic injectable use in humans is early and incomplete. Thymosin Beta-4 (TB-4) is an endogenous actin-sequestering peptide with roles in cell migration, wound repair, and inflammation modulation, studied in animal models for cardiac, ocular, and tissue healing indications. A Phase I study in healthy volunteers established preliminary safety and pharmacokinetic data for recombinant human TB-4 given intravenously, and early-phase cardiovascular trials have been conducted, but no efficacy RCT has met its primary endpoint or supported regulatory approval in any indication. TB-500, a synthetic fragment of TB-4 used in the wellness market, has even less human evidence than the full-length recombinant protein.

Key Takeaways

  • Grade D: Preclinical or anecdotal only
  • Not FDA approved: Not FDA-approved; removed from Category 2 restriction April 2026, compounding pathway unresolved pending July 2026 PCAC advisory.
  • Compounding: The nomination to add Thymosin Beta-4 to the FDA 503A or 503B bulk-substances list was withdrawn; it is not on an active FDA bulks list and is not eligible for routine pharmacy compounding.
Thymosin Beta-4 chemical structure
Structure via PubChem CID 45382195

Mechanism

Thymosin Beta-4 sequesters G-actin monomers, modulating actin polymerization dynamics involved in cell migration, wound healing, and inflammatory signaling; this mechanism is established in vitro and in animal models.

Evidence

Evidence is limited primarily to animal and preclinical studies; the evidence base for systemic injectable use in humans is early and incomplete. Thymosin Beta-4 (TB-4) is an endogenous actin-sequestering peptide with roles in cell migration, wound repair, and inflammation modulation, studied in animal models for cardiac, ocular, and tissue healing indications. A Phase I study in healthy volunteers established preliminary safety and pharmacokinetic data for recombinant human TB-4 given intravenously, and early-phase cardiovascular trials have been conducted, but no efficacy RCT has met its primary endpoint or supported regulatory approval in any indication. TB-500, a synthetic fragment of TB-4 used in the wellness market, has even less human evidence than the full-length recombinant protein.

Safety and risks

Systemic injectable TB-4 has limited human safety data beyond early-phase studies. The Phase I data described mild and tolerable adverse events in healthy volunteers, but these studies were not designed to detect longer-term or population-specific harms. No human efficacy evidence exists for the indications most commonly marketed (tissue repair, recovery, anti-aging). Animal data include concerns about potential pro-fibrotic effects of TB-4 in hepatic stellate cells under certain conditions. The compound was placed on the FDA Category 2 restricted list before being removed in April 2026; like BPC-157, it is pending formal PCAC advisory review in July 2026. Compounded TB-500 formulations are not equivalent to the recombinant protein studied in clinical trials and have no specific safety data.

Interactions

Insufficient human data to characterize interactions; potential additive effects with other pro-angiogenic or anti-inflammatory agents are speculative.

Federal compounding status

Nomination withdrawn (was Category 2) as of 2026-06-02.

This substance was nominated for the FDA 503A or 503B bulk-substances list and previously sat in the Category 2 (significant safety risk) group; the nomination was later withdrawn, so it is not on an active FDA bulks list and is not eligible for routine pharmacy compounding. FDA source

Federal status only, from public FDA records. State pharmacy-board rules vary and are not covered here. This is regulatory reporting, not legal advice. All compounds.

Compounding legality

The nomination to add Thymosin Beta-4 to the FDA 503A or 503B bulk-substances list was withdrawn; it is not on an active FDA bulks list and is not eligible for routine pharmacy compounding.

Sources

  1. Thymosin beta-4 - A potential tool in healing middle ear lesions in adult mammals. (2023) other
  2. Thymosin beta-4 participate in antibacterial immunity and wound healing in black tiger shrimp, Penaeus monodon. (2023) other
  3. Thymosin beta 4: A potential novel adjunct treatment for bacterial keratitis. (2023) other
  4. Thymosin beta 4 and the eye: the journey from bench to bedside. (2018) review
  5. Thymosin Beta 4 Is a Potential Regulator of Hepatic Stellate Cells. (2016) review
  6. Thymosin beta-4 and the eye: I can see clearly now the pain is gone. (2007) review
  7. Thymosin beta 4 promotes corneal wound healing and decreases inflammation in vivo following alkali injury. (2002) other
  8. Thymosin beta(4) reduces lethality and down-regulates inflammatory mediators in endotoxin-induced septic shock. (2003) other
  9. Thymosin Beta-4 and Ciprofloxacin Adjunctive Therapy Improves Pseudomonas aeruginosa-Induced Keratitis. (2018) other
  10. Thymosin Beta 4: A Potential Novel Therapy for Neurotrophic Keratopathy, Dry Eye, and Ocular Surface Diseases. (2016) review
  11. In Vitro Study of Thymosin Beta 4 Promoting Transplanted Fat Survival by Regulating Adipose-Derived Stem Cells. (2024) other
  12. Thymosin beta 4 stimulates directional migration of human umbilical vein endothelial cells. (1997) other
  13. Recombinant Human Thymosin Beta-4 Protects against Mouse Coronavirus Infection. (2021) other
  14. Thymosin beta 4 induces hair growth via stem cell migration and differentiation. (2007) other
  15. Thymosin beta 4: A novel corneal wound healing and anti-inflammatory agent. (2007) other
  16. A novel dimeric thymosin beta 4 with enhanced activities accelerates the rate of wound healing. (2013) other
  17. Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. (2003) other
  18. Adjunctive Thymosin Beta-4 Treatment Influences PMN Effector Cell Function during Pseudomonas aeruginosa-Induced Corneal Infection. (2021) other
  19. Regenerative protein thymosin beta-4 is a novel regulator of purinergic signaling. (2011) other
  20. Thymosin Beta-4 Suppresses Osteoclastic Differentiation and Inflammatory Responses in Human Periodontal Ligament Cells. (2016) other
  21. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. (2007) rct
  22. Thymosin beta 4 and thymosin beta 10 expression in hepatocellular carcinoma. (2014) other
  23. Adjunctive Thymosin Beta-4 Treatment Influences MΦ Effector Cell Function to Improve Disease Outcome in Pseudomonas aeruginosa-Induced Keratitis. (2021) other
  24. Matrix metalloproteinase activity is necessary for thymosin beta 4 promotion of epithelial cell migration. (2007) other
  25. A thymosin beta-4 is involved in production of hemocytes and immune defense of Hong Kong oyster, Crassostrea hongkongensis. (2016) other

Thymosin Beta-4 is Not FDA approved. PeptideGrids presents evidence and regulatory status for informational purposes only. We do not sell, supply, source, or help anyone obtain this compound, and we provide no dosing or administration guidance. This is not medical advice; consult a licensed clinician. Full disclaimer.

Last reviewed June 1, 2026 by PeptideGrids editorial team (independently audited).