Thymopentin

TP-5, thymopentin, Timunox (historical, Italy); thymopoietin fragment (residues 32–36, Arg-Lys-Asp-Val-Tyr)

Immune & bioregulators

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Summary

Class: Synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr), corresponding to residues 32–36 of the thymic hormone thymopoietin
Mechanism: Reproduces the active site of thymopoietin, promoting maturation and regulation of T lymphocytes — a "two-way" immune modulator
Routes studied: Subcutaneous and intravenous injection
Dose range reported: Approved/clinical (prescription where marketed): commonly 1 mg or 10 mg per injection by schedules set by the local label (e.g. for injection preparations in China; historically 50 mg thrice weekly in Western trials). Prescriber-set
Half-life: Extremely short in plasma — on the order of seconds to a very few minutes (rapidly degraded); the biological effect outlasts the blood level
Storage: Lyophilised injection; refrigerate per product label
Regulatory status: Approved/marketed in some countries (notably China; historically Italy as Timunox). Not approved by FDA/EMA

Doses are as reported in studies or by the community — never recommendations.

1What it is

Thymopentin is a five-amino-acid peptide that copies the active region (residues 32–36) of thymopoietin, a hormone the thymus gland makes to help T cells — a key type of immune cell — mature and behave correctly. By reproducing just the business end of the larger hormone, thymopentin acts as a synthetic immune modulator. It is described as "two-way," meaning it is used to nudge an under-active immune system up without simply overstimulating.

It was first marketed in Italy in the 1980s (as Timunox) and is today manufactured and used mainly in China, where thymopentin-for-injection products are approved for immune-related conditions. It is not approved by the FDA or EMA, and there is little Western community self-use.

2How it's thought to work

Thymopentin mimics thymopoietin's effect on T-cell development: it is reported to promote differentiation of precursor cells into mature T lymphocytes, to help balance T-cell subsets, and to improve some measures of cell-mediated immunity. Despite a plasma measured in seconds, the downstream immune effect persists far longer, which is typical of signalling peptides that trigger a cascade rather than needing to stay in the blood. Some work links its activity to Toll-like receptor 2 signalling.

Proposed: five amino acids from the thymic hormone thymopoietin, intended to push immature T cells through a maturation step. Studied in HIV and eczema in the 1980s and 90s without a convincing result.Schematic — not to scale

3What the research shows

Immune reconstitution and immunodeficiency

Small human studies and clinical use (mainly where it is marketed) report improved T-cell measures and clinical benefit in primary and secondary T-cell deficiencies and as an adjuvant in chronic infections. Evidence quality is modest and much of it is older or regional.

Chronic hepatitis B

Thymopentin (and the related thymic peptides) has been used as an immunomodulatory adjunct in chronic hepatitis B, particularly in China, with mixed and generally small-trial evidence.

Rheumatoid arthritis and atopic dermatitis

Historical Western double-blind trials tested thymopentin (e.g. 50 mg subcutaneously thrice weekly) in rheumatoid arthritis and in atopic dermatitis, reporting some benefit on disease activity in small cohorts. These did not lead to major-regulator approval.

Graded B/C

HIV and cancer adjunct

Explored historically as an immune adjunct in HIV infection and alongside cancer treatment; results were not definitive and development in the West did not continue. Overall the literature is modest in size and quality, with the strongest practical footprint being regional approval and use rather than large modern .

4Reported side effects and interactions

Literature-reported

generally reported as well tolerated in the trials and in marketed use; injection-site reactions and occasional hypersensitivity are the main findings. Long-term, large-scale safety data from modern trials are limited.

Community-reported

Western community self-use is uncommon and poorly documented; where used it is as a prescription injectable in the countries that approve it. Do not infer a self-dosing practice.

Theoretical. as an immune modulator, a theoretical concern exists around use in autoimmune disease or transplant settings; not well quantified.

Interactions. none well established; caution is advised with immunosuppressants given the opposing actions.

Markers researchers commonly monitor

Reflecting its immune-modulating purpose:

Marker	Why it's watched
T-lymphocyte subsets (CD4/CD8, flow cytometry)	the direct readout of a T-cell-maturation agent and the usual efficacy measure in its trials.
Total lymphocyte count / CBC	general immune baseline.
Disease-specific markers	e.g. hepatitis B viral markers (HBV DNA, HBeAg) when used in hepatitis B; disease-activity scores in the autoimmune settings.
General safety panel (CMP)	baseline for any injectable.

Free for everyone. Safety information is never behind a paywall.

5Reconstitution and handling

Marketed as a peptide for injection (e.g. 1 mg and 10 mg presentations); and dosed per the local product label where it is approved. Because approved presentations and schedules exist, follow the label rather than a community protocol.

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6Commonly studied alongside

Thymosin alpha-1 and thymosin fraction (related thymic immune peptides), antiviral therapy for hepatitis B (as an adjunct), standard disease-modifying drugs in the autoimmune trials.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

Region	Status (checked —)
United States	Not FDA-approved
European Union	Not currently authorised (historically marketed in Italy as Timunox) †
United Kingdom	Not licensed
Australia	Not approved
South Africa	Not registered
Sport	Not specifically listed by WADA; as an immune peptide it is not a recognised performance substance †

8Open questions

Does thymopentin produce clinically meaningful benefit in modern, well-powered trials, or is its footprint mainly regional and historical?
What is its precise molecular target and the reason its effect outlasts its seconds-long blood level?
Is there a defensible role in chronic hepatitis B or immunodeficiency alongside current therapies?

9References

1Goldstein G et al. (1979). A synthetic pentapeptide (thymopentin) corresponding to the active site of thymopoietin. Science / Proc Natl Acad Sci. PubMed
2Sundal E, Bertelletti D (1994). Thymopentin treatment of rheumatoid arthritis (review of controlled trials). Arzneimittelforschung. PubMed
3Bianchi L et al. Thymopentin in atopic dermatitis: a controlled trial. Br J Dermatol. PubMed
4Fabrizi F et al. Thymopentin as an immunomodulatory adjunct (review). Int J Clin Pharmacol. PubMed

References are being resolved to PubMed/DOI identifiers; links search PubMed for the citation until then.

† Being confirmed by our reviewers against current sources.

10Community

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Self-reported side effects Phase 2

Not enough data yet. 0 of the 50 members needed have logged this compound for 4+ weeks. We don't show anything below 50, so no one can be identified.

11Page history

30 Oct 2026Profile published — awaiting medical review

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