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All peptides

Immune · Investigational

Thymopentin (TP-5)

No lawful US pathway

Tell me if this changesRead the free 2026 Peptide Safety Checklist →
Written by Peptide Association Editorial TeamLast reviewed Editorial policy

01 · Overview

A synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr) corresponding to residues 32-36 of thymopoietin, a thymic hormone involved in T-cell differentiation (PMID 6365814). Thymopentin (TP-5) was developed as an immunomodulator intended to reproduce the T-cell differentiating activity of the parent hormone.

It is not FDA-approved, and most of its clinical studies date from the 1980s and 1990s.

02 · Research summary & key findings

In 26 patients with primary immunodeficiencies, TP-5 produced clinical and immunological improvement in some patients with DiGeorge syndrome or primary T-cell defects, but not in severe combined immunodeficiency, ataxia-telangiectasia, or hyper-IgE syndrome (PMID 6131256). In asymptomatic HIV infection, it helped maintain CD4 cell levels (PMID 1361746) and reduced disease progression in zidovudine-experienced patients, though not in those recently started on zidovudine (PMID 7859140). A randomized trial in 76 patients with rheumatoid arthritis found improved joint scores versus placebo (PMID 2650797), while a randomized trial in chronic hepatitis B found the regimen ineffective (PMID 7836705).

03 · Regulatory status

Thymopentin (TP-5) is in the investigational stage. While preclinical and early-phase data exist, it has not received regulatory approval for clinical use in the United States.

No lawful pathway today

Thymopentin (TP-5) is not FDA-approved and does not currently have a lawful prescription or compounding pathway in the United States, so we do not sell it and will not book a consultation for it. That can change: in 2026 FDA began reviewing several peptides for compounding.

See the 1 FDA-approved compound in Immune

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04 · Administration routes

  • Subcutaneous injection
  • Intramuscular injection

References

  1. [1]Maintenance of CD4+ cells by thymopentin in asymptomatic HIV-infected subjects: results of a double-blind, placebo-controlled study AIDS, 1992. PMID 1361746
  2. [2]Thymopentin (TP-5) in the treatment of rheumatoid arthritis Br J Rheumatol, 1989. PMID 2650797
  3. [3]Thymopoietin pentapeptide treatment of primary immunodeficiencies Lancet, 1983. PMID 6131256
  4. [4]Conformational properties of the pentapeptide fragment [32-36] of the thymic hormone thymopoietin Int J Pept Protein Res, 1984. PMID 6365814
  5. [5]A randomized controlled trial of thymopentin therapy in patients with chronic hepatitis B J Hepatol, 1994. PMID 7836705
  6. [6]Safety and efficacy of thymopentin in zidovudine (AZT)-treated asymptomatic HIV-infected subjects with 200-500 CD4 cells/mm3: a double-blind placebo-controlled trial J Acquir Immune Defic Syndr Hum Retrovirol, 1995. PMID 7859140

Primary literature

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Disclaimer: This information is provided for educational and research purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide therapy. The Peptide Association does not endorse or recommend any specific treatment protocol. See our editorial policy for how this content is produced and reviewed. Clinicians: join the network.