Immune & antimicrobial

Thymopentin

Also called TP-5, TP5, Timunox, Sintomodulina, ORF-15244, Thymopoietin 32-36

Thymopentin (TP-5) is a tiny five-amino-acid peptide copied from thymopoietin, a hormone made by the thymus gland. In the 1980s and 1990s it was tested as an immune 'regulator' in rheumatoid arthritis, eczema, HIV, hepatitis B and surgery, with mixed results. It is not FDA-approved, and no current approval in any other country could be confirmed from an official source.

Late-stage trialsTested in large human trials (phase 2b/3) but not yet approved in the US.

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All printable flashcards

Drawn from its published sequence: 5 residues, one bead each.

Overview

How it works

Proposed: thymopentin appears to reproduce the activities of the parent hormone thymopoietin, including effects on early T-cell development and immune regulation ¹. Early work linked its action on mature T cells to a rise in the messenger molecule cyclic GMP, and described it as 'immunonormalizing' in animal models, meaning it seemed to push both over- and under-active immune responses back toward normal ¹. A 1999 review still called its mode of action unknown ⁴. It is broken down very quickly in blood: a 2018 drug-delivery paper gives its plasma half-life as about 30 seconds ¹⁵.

What research shows

Rheumatoid arthritis (double-blind human RCT, n=41, Lancet 1985): 3 weeks of 50 mg IV three times weekly improved tenderness, swelling, morning pain and disease activity vs placebo; improvement was still present 4 weeks after stopping, with a trend toward relapse ⁵. A UK multicentre RCT (n=76) also found improvement in joint scores ⁶, and a German multicentre RCT (n=119, 107 evaluable) found improvement in 5 of 9 clinical measures that faded over 4 weeks after treatment ¹⁷.
HIV, before AIDS (double-blind human RCT, n=91, 1992): asymptomatic patients on thymopentin kept a higher CD4 cell percentage over the first 24 weeks; fewer progressed to symptoms (0 vs 2), but that difference was not statistically significant, and symptomatic patients showed no difference ⁷.
HIV with zidovudine (double-blind human RCT, n=352, 1995): fewer AIDS or deaths with thymopentin in people already on zidovudine for over 6 months (2 vs 10 events), but no benefit, and numerically more events (4 vs 0, not significant), in those with 6 months or less of zidovudine; CD4 counts did not differ ⁸.
Atopic dermatitis (double-blind human RCT, n=100, 1990): daily injections for 6 weeks reduced severity, itching and redness more than placebo (p=0.04) ⁹.
Chronic hepatitis B (human RCT, n=30, 1994): 6 months of thymopentin was not effective; viral clearance and liver enzyme normalization were no better than in controls ¹⁰.
Hepatitis B vaccine in dialysis patients (meta-analysis of 11 controlled studies, 272 patients, 2006): no overall improvement in vaccine response; a benefit appeared only in trials using higher doses, and the authors said numbers were too small for firm conclusions ¹¹.
Cancer surgery (human RCT, n=206, 1994): did not significantly reduce postoperative infections (17.5% vs 24.3%); infection severity was lower in elderly patients ¹².

Doses studied in people

Study or label	Dose used	Source
Double-blind RCT in rheumatoid arthritis (n=41)	50 mg slow IV injection three times weekly for 3 weeks, vs placebo	⁵
Multicentre RCT in rheumatoid arthritis (n=76)	50 mg slow IV injection three times weekly for 3 weeks, vs placebo	⁶
Double-blind multicentre RCT in rheumatoid arthritis (n=119)	50 mg IV over 10 minutes three times weekly for 3 weeks, vs placebo	¹⁷
Double-blind RCT in HIV infection (n=91)	50 mg subcutaneous three times weekly for 24 or 52 weeks, vs placebo	⁷
Double-blind RCT in zidovudine-treated HIV infection (n=352)	50 mg subcutaneous three times weekly for 48 weeks, vs placebo	⁸

Doses shown come from published 1980s-1990s trials only; they are reported, not recommended. Thymopentin has no FDA-approved dose.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Vial math

Many research vials hold 5 or 10 mg of powder. This table shows how much ends up in each mark on a U-100 insulin syringe for common amounts of added liquid. It is arithmetic only, not a dose.

Vial	Liquid added	Concentration	Per unit (0.01 mL)
5 mg	1 mL	5 mg/mL	50 mcg	Open in calculator
5 mg	2 mL	2.5 mg/mL	25 mcg	Open in calculator
5 mg	3 mL	1.67 mg/mL	16.7 mcg	Open in calculator
10 mg	1 mL	10 mg/mL	100 mcg	Open in calculator
10 mg	2 mL	5 mg/mL	50 mcg	Open in calculator
10 mg	3 mL	3.33 mg/mL	33.3 mcg	Open in calculator

More sizes: all vial sizes · How this works: Syringes and units · Reconstitution guide.

Safety

Trials generally reported few side effects: only minor side effects in the 1985 arthritis RCT ⁵, 'minimal' toxicity in the UK arthritis RCT ⁶, no serious side effects linked to the drug in HIV and eczema trials ⁷⁹, and no increase in adverse reactions vs placebo in the 352-person HIV trial ⁸.
A 1985 safety overview found side-effect rates similar to placebo groups, though at that time animal cancer studies were not yet complete ¹⁶.
One German RCT of 119 arthritis patients reported one systemic allergic reaction ¹⁷.
Most safety data are decades old and from small, short trials; long-term safety is not well established.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Legal status

FDA: Not FDA-approved; no FDA application for thymopentin was found in the sources reviewed.
Compounding: Not named on FDA's 503A nominated bulk drug substance category lists (Categories 1-3, updated May 14, 2026) ¹⁹.
Sports (WADA): Not named on the WADA 2026 Prohibited List. The S0 class bans substances with no current approval by any government health authority, so whether it applies depends on thymopentin's current approval status somewhere, which could not be confirmed; athletes should check with their anti-doping organisation ²⁰.
Other: Italy: several of the trials were run there ¹⁰¹², and PubChem lists Sintomodulina as a name for thymopentin ², but no official Italian authorisation record (AIFA or Gazzetta Ufficiale) could be found, and a search of AIFA's current medicines database on 2026-10-30 returned no thymopentin product ²¹. China: thymopentin injection appears in Chinese clinical use and trials, but its approval status was not confirmed from an official source.

Rules change often. See Legal status of peptides for how these categories work.

History

Thymopoietin was first isolated from cow thymus by researchers studying how thymus extracts affect nerve-muscle signaling, and was later found to act on T cells ³. Gideon Goldstein's group showed that the five-amino-acid fragment at positions 32-36, named thymopentin, carried the hormone's activity ¹. Through the 1980s and 1990s it was tested in many conditions in the US and Europe, sometimes under the name Timunox ⁹; Sintomodulina is another name listed for it in PubChem ². WHO assigns it the drug class code L03AX09 (other immunostimulants) ¹⁴.

Common questions

Is thymopentin FDA-approved?

No. No FDA application for thymopentin was found in the sources reviewed. No current approval elsewhere could be confirmed; AIFA's current Italian medicines database lists no thymopentin product ²¹.

What is thymopentin made from?

It is a lab-made copy of five amino acids (Arg-Lys-Asp-Val-Tyr) from thymopoietin, a thymus hormone, and appears to carry that hormone's activity ¹.

What does the human evidence show?

Small trials from the 1980s-1990s found benefits in rheumatoid arthritis and eczema ⁵⁶⁹, mixed results in HIV ⁷⁸, and no clear benefit in chronic hepatitis B, vaccine response or preventing surgical infections ¹⁰¹¹¹².

Is thymopentin safe?

Older trials reported few side effects, mostly minor, and one German trial reported a single systemic allergic reaction ⁵⁸⁹¹⁷. The data are old and from short studies, so long-term safety is not well known.

Is thymopentin banned in sport?

It is not named on WADA's 2026 list, but the list's S0 class covers drugs with no current approval anywhere, so athletes should check with their anti-doping organisation ²⁰.

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Sources

Wondering how to judge the claims made about compounds like this one? The Academy track Thinking clearly about peptide claims walks through it. You can try the Academy free first.

Last reviewed 2026-10-30 · How we research · Found an error? See our corrections policy.