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Comparison

TB-500 vs Thymosin Alpha-1

TB-500 is healing & repair; Thymosin Alpha-1 is thymic & immune. They are compared here because they are frequently considered against each other, not because they act alike.

On published evidence alone, Thymosin Alpha-1 is the better documented of the two (clinical trials). That is a statement about the state of the literature, not a recommendation.

TB-500 Thymosin Alpha-1
Class Healing & repair Thymic & immune
Evidence Preliminary human Clinical trials
Human trials ~4 ~40
Half-life ~2-3 hours ~2 hours
Reported range 2-5 mg 1.6-3.2 mg
Frequency 2x weekly loading, then weekly 2x weekly
Routes Subcutaneous, Intramuscular Subcutaneous
FDA approved No No
Research use only Yes Yes
Banned in sport Yes No
Studied for Soft tissue repair research, Wound healing, Cardiac repair research Chronic hepatitis B and C, Immune modulation, Vaccine adjuvant research, Sepsis research
Reported side effects Injection-site reactions, Transient fatigue, Head rush, Mild nausea Injection-site erythema, Transient fatigue, Mild flu-like symptoms

TB-500

TB-500 is the synthetic form of thymosin beta-4, a 43-residue peptide whose principal activity is sequestering G-actin and regulating cytoskeletal assembly. That function underlies its reported effects on cell migration, angiogenesis and wound repair, with the LKKTETQ heptapeptide identified as the active binding region. Human data exists from small trials in dry eye and pressure ulcers; the musculoskeletal claims that drive its popularity rest on animal models.

Thymosin Alpha-1

Thymosin alpha-1 is a 28-residue peptide originally isolated from thymic tissue. It acts largely through Toll-like receptor signalling on dendritic cells, promoting maturation of T cells and enhancing Th1 responses, natural killer cell activity and antigen presentation. Unlike most compounds on this site it has a substantial approved clinical history outside the US, including as an adjuvant in hepatitis B and C and in sepsis research.

TB-500 vs Thymosin Alpha-1: common questions

What is the difference between TB-500 and Thymosin Alpha-1?

TB-500 is healing & repair and Thymosin Alpha-1 is thymic & immune, so they act on different pathways. TB-500: A synthetic version of thymosin beta-4, the actin-sequestering peptide most often paired with BPC-157. Thymosin Alpha-1: A thymic immunomodulatory peptide approved in more than 30 countries for hepatitis B and C, though not in the United States.

Which has stronger evidence, TB-500 or Thymosin Alpha-1?

Thymosin Alpha-1 has the stronger evidence base (clinical trials, about 40 human studies) compared with TB-500 (preliminary human).

Are TB-500 and Thymosin Alpha-1 FDA approved?

Neither is FDA approved for any indication.

References

Regulatory and primary sources

  1. PubChem compound record (CID 62707662) ↗ · structure, identifiers, synonyms
  2. WADA Prohibited List ↗ · current year
  3. FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
  4. CAS Registry Number 77591-33-4 ↗ · chemical identity
  5. PubChem compound record (CID 16130571) ↗ · structure, identifiers, synonyms
  6. CAS Registry Number 62304-98-7 ↗ · chemical identity

Published literature

  1. Sun HQ, Yin HL. The beta-thymosin enigma.Ann N Y Acad Sci 2007.PubMed 17495248 · doi:10.1196/annals.1415.021
  2. Hannappel E. beta-Thymosins.Ann N Y Acad Sci 2007.PubMed 17468232 · doi:10.1196/annals.1415.018
  3. Rahman OF, Lee SJ, Seeds WA. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.J Am Acad Orthop Surg Glob Res Rev 2026.PubMed 41490200 · doi:10.5435/JAAOSGlobal-D-25-00236
  4. Mayfield CK, Bolia IK, Feingold CL, et al.. Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians.Am J Sports Med 2026.PubMed 41476424 · doi:10.1177/03635465251357593
  5. Fox JE. The platelet cytoskeleton.Thromb Haemost 1993.PubMed 8165606
  6. Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance.Sports Med 2026.PubMed 41966639 · doi:10.1007/s40279-026-02437-0
  7. Gebran S, Romano E, Soyano A. [Biomolecules suppressing myelopoiesis].Acta Cient Venez 1992.PubMed 1343739
  8. Kleinman HK, Sosne G. Thymosin β4 Promotes Dermal Healing.Vitam Horm 2016.PubMed 27450738 · doi:10.1016/bs.vh.2016.04.005
  9. Ancell CD, Phipps J, Young L. Thymosin alpha-1.Am J Health Syst Pharm 2001.PubMed 11381492 · doi:10.1093/ajhp/58.10.886
  10. Hadden JW. T-cell adjuvants.Int J Immunopharmacol 1994.PubMed 7806429 · doi:10.1016/0192-0561(94)90090-6
  11. Hadden JW. Thymic endocrinology.Ann N Y Acad Sci 1998.PubMed 9629262 · doi:10.1111/j.1749-6632.1998.tb09574.x
  12. Rubin BK. Unmet needs in cystic fibrosis.Expert Opin Biol Ther 2018.PubMed 30063865 · doi:10.1080/14712598.2018.1484101
  13. Hoch K, Volk DE. Structures of Thymosin Proteins.Vitam Horm 2016.PubMed 27450728 · doi:10.1016/bs.vh.2016.04.009
  14. Gu B, Zhou Y, Nie Y, et al.. Efficacy of thymosin α1 for sepsis: a systematic review and meta-analysis of randomized controlled trials.Front Cell Infect Microbiol 2025.PubMed 40969554 · doi:10.3389/fcimb.2025.1673959
  15. Simonova MA, Ivanov I, Shoshina NS, et al.. Aging and Thymosin Alpha-1.Int J Mol Sci 2025.PubMed 41373628 · doi:10.3390/ijms262311470

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.

Read this first This page compares published reference data. It is not medical advice and not a recommendation to use either compound. Several compounds documented on this site are not approved for human use.