Thymopentin
The five-amino-acid fragment of thymopoietin, sold as Timunox and tested in the 1980s and 1990s in eczema and rheumatoid arthritis
Thymopentin (TP-5) is a synthetic copy of residues 32 to 36 of thymopoietin, a hormone of the thymus. Sold as Timunox, it was tested by injection in the 1980s and 1990s in atopic dermatitis and rheumatoid arthritis, with modest benefits over placebo in small trials. It is not approved in the US, and its half-life in plasma is about 30 seconds.
What is it?
Thymopentin is a synthetic copy of the five amino acids at positions 32 to 36 of thymopoietin, a thymic hormone, developed as an immune modulator. In the 1980s and 1990s it was given by injection across a range of immune conditions, from rheumatoid arthritis and atopic dermatitis to immunodeficiency, sarcoidosis of the skin and Sézary syndrome.
The controlled trials were small. In rheumatoid arthritis, 41 patients given 50 mg by slow intravenous injection three times a week for three weeks improved more than on placebo in tenderness, swelling, pain on waking and disease activity, with a trend towards relapse four weeks after stopping. In atopic dermatitis, a 100-patient trial of daily injections for six weeks found a modest but significant fall in severity, and a 39-patient trial of 50 mg three times a week for 12 weeks found greater improvement than placebo.
A 1985 safety overview, which included patients treated for 12 to 24 months, found side effects no more frequent than on placebo. Its plasma half-life is only about 30 seconds. Thymopentin is not approved in the US; Drugs@FDA holds no application for it, and DailyMed lists no label.
Its recent clinical life is almost entirely Chinese, as an add-on: to tuberculosis drugs, where a meta-analysis of 23 trials found better sputum conversion; to haemodialysis, where inflammatory markers fell in a non-randomised comparison; to heart failure care in older patients; and to hepatitis B treatment, where HBsAg did not change overall. Most of these studies measure laboratory markers rather than hard outcomes, and their quality is mixed.
In China, a 2025 retrospective study linked it to fewer infections in peritoneal dialysis patients, an association rather than proof. Mouse studies continue to propose roles in cancer immunity and sepsis.
Mechanism of Action
Thymopentin is the active five-amino-acid fragment of thymopoietin, a thymus hormone involved in T-cell development.
T-cell support
Studies report rises in CD3+ and CD4+ T cells when it is added to standard treatment.
Inflammation
In haemodialysis and heart failure studies, inflammatory cytokines such as IL-6 and TNF-alpha fell.
Very short-lived
Plasma half-life is about 30 seconds, which has driven work on longer-acting formulations.
Published Research
These are the studies that describe thymopentin, read from their PubMed abstracts: three placebo-controlled trials and a safety overview, all from the 1980s and 1990s.
Atopic dermatitis: 100 patients, 6 weeks
Daily subcutaneous injections (48 patients) against placebo (52). Both groups improved, but severity fell more on thymopentin (p=0.04), including itch and redness. There were no serious adverse experiences in either group.
Severe atopic dermatitis: 39 patients, 12 weeks
50 mg by subcutaneous injection three times a week, alongside steroid creams and antihistamines, improved patients more than placebo after 12 weeks. No thymopentin-related adverse events occurred.
Active rheumatoid arthritis: 41 patients, 3 weeks
50 mg by slow intravenous injection three times a week improved tenderness, joint swelling, pain on waking and disease activity more than placebo. Improvement persisted four weeks later, with a trend to relapse; side effects were minor.
Safety overview
Across preclinical studies and patients treated for various conditions, some for 12 to 24 months, side effects were as frequent as on placebo, including when thymopentin was given with many other drugs.
Infection in peritoneal dialysis
In a retrospective Chinese study of peritoneal dialysis patients, thymopentin use was associated with fewer infections (0.73 against 1.00 per person-year; adjusted hazard ratio 0.54) and less peritonitis, without changes in T-cell counts. It was not randomised.
Older patients with heart failure
In 96 patients over 60 with chronic heart failure randomised to usual care with or without 2 mg thymopentin a day in three courses, ejection fraction, walking distance and T-cell counts rose and BNP and inflammatory markers fell more than on usual care alone.
Haemodialysis patients
In 112 patients on maintenance haemodialysis, allocated by convenience rather than at random, adding thymopentin lowered IL-6, IL-8 and TNF-alpha and raised CD3+ and CD4+ counts more than conventional therapy alone.
Add-on in chronic hepatitis B
In patients with HBeAg-positive hepatitis B after peginterferon and entecavir, 24 weeks of added thymopentin did not change mean HBsAg overall, though those with lower HBsAg fell further; no extra side effects were seen.
Colitis in mice
In mice with chemically induced colitis, thymopentin restored goblet cells, mucus and gut microbiota by triggering IL-22 from immune cells; blocking IL-22 abolished the protection.
Drug-resistant tuberculosis
Across 23 Chinese randomised trials and 2,031 cases, adding thymopentin to tuberculosis drugs raised sputum conversion (risk ratio 1.27 over the whole course) and T-cell counts; the trials' quality limits how far this can be taken.
Thymus and tumour immunity in mice
In mouse cancer models, thymopentin slowed tumour growth through T cells, restored the involuted thymus under immunosuppression and improved adoptive T-cell therapy.
Sepsis in mice
In septic mice, thymopentin restored the bacteria-clearing function of peritoneal macrophages, reduced inflammation and improved outcomes.
Dosing Data
There is no US-approved dose. Older trials gave 50 mg by injection three times a week; a Chinese heart failure study gave 2 mg a day in courses.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the trials and the safety overview.
Contraindications & Cautions
Thymopentin has no US label. These cautions follow from its record.
Legal Status
Thymopentin is not approved in the US.
Frequently Asked Questions
?What is thymopentin?
A synthetic five-amino-acid peptide, residues 32 to 36 of the thymic hormone thymopoietin, studied as an immune modulator and sold as Timunox.
?What was it tested for?
Mainly atopic dermatitis and rheumatoid arthritis, where small placebo-controlled trials found modest benefits, plus several immune conditions in smaller studies.
?Is thymopentin approved in the US?
No. Drugs@FDA holds no application for it, as of September 30, 2026.
?How long does it last in the body?
Its plasma half-life is about 30 seconds.
?What do the newer Chinese studies show?
Mostly changes in laboratory markers when thymopentin is added to standard treatment: more T cells and less inflammation in haemodialysis and heart failure patients, and better sputum conversion in tuberculosis across 23 small trials. Hard outcomes such as survival were rarely measured, and some studies were not randomised.
?Why does it have to be injected so often?
Its plasma half-life is only about 30 seconds, so the older trials gave it several times a week and Chinese regimens daily in courses. Much laboratory work since has tried to make longer-lasting or oral versions.
References
- [fda] FDA. Drugs@FDA (openFDA): no application for thymopentin. Read September 30, 2026.
- [pubmed] Leung DY, et al. "Thymopentin therapy reduces the clinical severity of atopic dermatitis." J Allergy Clin Immunol, 1990;85(5):927-33. PMID: 2185294.
- [pubmed] Stiller MJ, et al. "A double-blind, placebo-controlled clinical trial to evaluate the safety and efficacy of thymopentin as an adjunctive treatment in atopic dermatitis." J Am Acad Dermatol, 1994;30(4):597-602. PMID: 8157786.
- [pubmed] Malaise MG, et al. "Treatment of active rheumatoid arthritis with slow intravenous injections of thymopentin. A double-blind placebo-controlled randomised study." Lancet, 1985;1(8433):832-6. PMID: 2858708.
- [pubmed] Friedmann N. "Thymopentin: safety overview." Surv Immunol Res, 1985;4 Suppl 1:139-48. PMID: 3898287.
- [pubmed] Goldstein G, et al. "A synthetic pentapeptide with biological activity characteristic of the thymic hormone thymopoietin." Science, 1979;204(4399):1309-10. PMID: 451537.
- [pubmed] Zhang T, et al. "Thymopentin-loaded phospholipid-based phase separation gel with long-lasting immunomodulatory effects: in vitro and in vivo studies." Acta Pharmacol Sin, 2019;40(4):514-521. PMID: 30002492.
- [pubmed] Chen X, et al. "Effectiveness and safety of thymopentin for infection prophylaxis in peritoneal dialysis patients: a retrospective study." BMC Nephrol, 2025;26(1):538. PMID: 41023915.
- [pubmed] Xiaojing C, et al. "Thymopentin improves cardiac function in older patients with chronic heart failure." Anatol J Cardiol, 2017;17(1):24-30. PMID: 27564775.
- [pubmed] Zou Q, et al. "The effect of thymopentin on immune function and inflammatory levels in end-stage renal disease patients with maintenance hemodialysis." Am J Transl Res, 2022;14(1):414-420. PMID: 35173860.
- [pubmed] Ma Y, et al. "The effect of thymopentin add-on in hepatitis B e antigen positive chronic hepatitis B after virus suppression by peginterferon plus entecavir therapy." Cell Mol Biol (Noisy-le-grand), 2019;65(2):75-81. PMID: 30860474.
- [pubmed] Han YR, et al. "Clinical Efficacy of a Combination of Thymopentin and Antituberculosis Drugs in Treating Drug-Resistant Pulmonary Tuberculosis: Meta Analysis." Ther Clin Risk Manag, 2022;18:287-298. PMID: 35386182.
- [pubmed] Hossain MA, et al. "Thymopentin Enhances Antitumor Immunity Through Thymic Rejuvenation and T Cell Functional Reprogramming." Biomedicines, 2025;13(10). PMID: 41153776.
- [pubmed] Wen Z, et al. "Thymopentin plays a key role in restoring the function of macrophages to alleviate the sepsis process." Int Immunopharmacol, 2024;126:111295. PMID: 38048668.
- [pubmed] Cao Q, et al. "Thymopentin ameliorates dextran sulfate sodium-induced colitis by triggering the production of IL-22 in both innate and adaptive lymphocytes." Theranostics, 2019;9(25):7490-7505. PMID: 31695782.
Sources & Citations
Studies were read from their PubMed abstracts; no US label exists. Read October 7, 2026.
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