The TB-500 reading list
The identity papers, the repair experiments, the counter-results and the FDA documents.
Begin with the paper that answers the question
For the fragment's identity, the equine doping-control analysis is more direct than a general repair review. For the larger protein's actin interaction, the structural study is the useful starting point. They answer different questions, and I would put them beside each other before opening a benefits list.
The contrast I consider most instructive is between the rat wound-healing result and the mouse study without a significant strength gain. Both concern full-length thymosin beta-4. Together they make it harder to confuse a repair-related measurement with improved function.
The human intravenous safety study also tested the full-length protein. For regulatory wording, the FDA safety-risk page, PCAC meeting agenda and 503A framework are distinct records; none can substitute for the other.
The full citation list follows. A result that has been overstated deserves as much scrutiny as a citation that points to the wrong paper.
- Irobi E, Aguda AH, Larsson M, et al. Structural basis of actin sequestration by thymosin-beta4: implications for WH2 proteins. EMBO J. 2004;23(18):3599-3608. ↗
- Bock-Marquette I, Saxena A, White MD, et al. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004;432(7016):466-472. ↗
- Malinda KM, Sidhu GS, Mani H, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364-368. ↗
- Morris DC, Cui Y, Cheung WL, et al. A dose-response study of thymosin β4 for the treatment of acute stroke. J Neurol Sci. 2014;345(1-2):61-67. ↗
- Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert Opin Biol Ther. 2012;12(1):37-51. ↗
- Ruff D, Crockford D, Girardi G, Zhang Y. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin β4 in healthy volunteers. Ann N Y Acad Sci. 2010;1194:223-229. ↗
- Xiong Y, Mahmood A, Meng Y, et al. Neuroprotective and neurorestorative effects of thymosin β4 treatment following experimental traumatic brain injury. J Neurosurg. 2012;116(5):1081-1092. ↗
- Morris DC, Chopp M, Zhang L, et al. Thymosin beta4 improves functional neurological outcome in a rat model of embolic stroke. Neuroscience. 2010;169(2):674-682. ↗
- Sosne G, Rimmer D, Kleinman HK, Ousler G. 0.1% RGN-259 (Thymosin β4) Ophthalmic Solution Promotes Healing and Improves Corneal Integrity. Int J Mol Sci. 2022;24(1):554. ↗
- Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. 2026. ↗
- Su Y, Xu J, Zhu Z, et al. Thymosin β4 promotes zebrafish Mauthner axon regeneration by facilitating actin dynamics. BMC Biol. 2024;22(1):238. ↗
- Kim J, Hwang S, Lee S, et al. Targeted Deletion of Thymosin Beta 4 in Hepatic Stellate Cells Ameliorates Liver Fibrosis. Cells. 2023;12(12):1658. ↗
- Sosne G, Qiu P, Kurpakus-Wheater M, et al. Activation of pro-resolving pathways mediate the therapeutic effects of thymosin beta-4. Front Immunol. 2024;15:1458684. ↗
- Zhang Y, Li L, Wang J, et al. Tβ4-exosome-loaded hemostatic and antibacterial hydrogel to improve vascularized wound repair. Mater Today Bio. 2025;30:101585. ↗
- Wang L, Chen X, Liu Y, et al. Thymosin β4 improves the survival of cutaneous flaps of rat and activates Wnt/β-catenin signaling. Arch Med Sci. 2024. ↗
- U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks. (List entry: "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500," placed in 503A Category 2 effective with the September 29, 2023 nominated-substances update; the page, content current as of April 22, 2026, lists the entry under "Bulk drug substances nominated but withdrawn"; TB-500 is no longer in Category 2; page verified 2026-09-17.) ↗
- U.S. Food and Drug Administration. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. (Published agenda listing "TB-500 (free base)" / "TB-500 acetate," alongside BPC-157, KPV, and MOTs-C, as bulk drug substances being considered for inclusion on the 503A Bulks List; a scheduled discussion, not a decision; verified 2026-05-29.) ↗
- U.S. Food and Drug Administration. Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. (Definitions of 503A/503B and Category 1/Category 2; the bulks-list and nomination framework; the role of the Pharmacy Compounding Advisory Committee; verified 2026-05-29.) ↗
- Cha HJ, Jeong MJ, Kleinman HK. Role of thymosin beta4 in tumor metastasis and angiogenesis. J Natl Cancer Inst. 2003. ↗
- Zhang Y, et al. Thymosin beta 4 is overexpressed in human pancreatic cancer cells and stimulates proinflammatory cytokine secretion and JNK activation. Cancer Biol Ther. 2008. ↗
- Ho EN, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012. ↗
- Spurney CF, et al. Evaluation of skeletal and cardiac muscle function after chronic administration of thymosin beta-4 in the dystrophin deficient mouse. PLoS One. 2010. ↗
- Delcourt V, et al. TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023. ↗