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Thymopentin (TP-5, thymopoietin 32-36)
A synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr) reproducing the active site of the thymic hormone thymopoietin. Unlike grey-market peptides, thymopentin was a genuinely registered immunomodulator drug — marketed as Timunox in Italy and widely used in China — so it has real Western randomized trials behind it, not just anecdote. The strongest data are small placebo-controlled RCTs in active rheumatoid arthritis from the 1980s (Lancet, German multicentre) showing short-lived symptomatic improvement, and a 352-patient double-blind HIV trial where it modestly delayed disease progression. But the evidence is old, heterogeneous, and short-duration; benefits faded weeks after stopping; it failed as a vaccine adjuvant in at least one trial; and it is NOT an FDA-approved drug or a dietary supplement. Modern meta-analyses of adjuvant-therapy trials (tuberculosis, lung cancer) report benefits, but the lung-cancer review rated its trials mostly at unclear risk of bias and moderate to very low quality, and the tuberculosis review's abstract reports no quality assessment. Treat this as a real but weakly-evidenced legacy immunomodulator, not a proven supplement.
Prescription medication — not a dietary supplement
Thymopentin is a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Thymopentin doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 1985–2022 with a typical study size of 1,925 participants.
Based on 38 studies · 5 meta-analyses · 30 RCTs · 9,552 total participants
Confidence
High confidenceBy outcome
A legacy immunomodulator drug with genuine Western placebo-controlled RCTs, but benefits were modest, transient and dated, and modern positive meta-analyses rest on trials of unclear or unreported quality.
28 randomised trials
93% were about Thymopentin in an audit of 28 of them
Every randomised or controlled trial of Thymopentin indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Sep 2026
1 trial ongoing or recruiting · 8 completed on ClinicalTrials.gov
Registered trials show research momentum for Thymopentin, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Nov 2026
Thymopentin (TP-5) is a synthetic pentapeptide with the sequence Arg-Lys-Asp-Val-Tyr, corresponding to residues 32-36 of thymopoietin, a polypeptide hormone produced by thymic epithelium.
The fragment reproduces the immunoregulatory ('biological') activity of the full hormone: it promotes T-lymphocyte differentiation and is reported to normalize T-cell subset ratios (CD4/CD8), nudging a dysregulated immune system back toward balance rather than simply stimulating it.
Because of this, thymopentin was developed as a pharmaceutical immunomodulator and was marketed under the brand Timunox (notably in Italy), with extensive subsequent use in China as an adjuvant in infectious disease and oncology.
That regulatory history matters: it means thymopentin has a body of real, PubMed-indexed human trials — including Western placebo-controlled RCTs — which is genuinely unusual for the peptides in this category.
The best-quality evidence comes from active rheumatoid arthritis: a 1985 Lancet double-blind placebo-controlled study (41 patients, slow IV TP-5 50 mg three times weekly for three weeks) found significant improvement over placebo in joint tenderness, swelling, pain and disease activity, with only minor side-effects — but the improvement faded over the four weeks after treatment stopped, and there were no changes in any laboratory or immunological markers.
A larger German multicentre placebo-controlled RCT (119 patients) reproduced the short-term symptomatic benefit.
In HIV, a 352-patient double-blind placebo-controlled trial in zidovudine-experienced asymptomatic patients reported that thymopentin delayed progression to ARC/AIDS/death, an effect magnified in higher-risk subgroups — a legitimate but historical signal from the pre-HAART era.
Modern systematic reviews and meta-analyses exist but must be read carefully: a 2022 meta-analysis of thymopentin as an adjuvant in drug-resistant pulmonary tuberculosis (23 RCTs, 2031 patients) reported higher sputum-conversion and focal-absorption rates and improved CD4 counts, and broader meta-analyses of synthetic thymic peptides in non-small-cell lung cancer report response-rate and quality-of-life gains — but the lung-cancer review pooled trials in China, mostly at unclear risk of bias with evidence of moderate to very low quality, the tuberculosis review's abstract reports no quality assessment, and the lung-cancer meta-analysis singles out thymosin-alpha-1 and gives no result for thymopentin specifically.
The honest counterweights are equally real: a meta-analysis of 11 trials found thymopentin did not overall improve the hepatitis-B-vaccine seroresponse in dialysis patients (only a higher-dose subgroup did); thymopentin failed as an influenza-vaccine immunoadjuvant in elderly patients in one controlled study; the Cochrane review of thymic peptides in cancer found no survival or tumour-response benefit for thymus extracts, only a nonsignificant trend for thymosin-alpha-1 and no separate result for thymopentin; and the Cochrane review of cold-sore prevention found only 'very few data' suggesting benefit.
The honest framing therefore is: thymopentin is a real approved/marketed immunomodulator drug outside the United States with genuine (if dated and heterogeneous) trial evidence, but its effects are typically modest, short-lived, and supported largely by old or low-quality studies; Western regulators have NOT approved it; long-term safety beyond the studied weeks-to-months is poorly characterized; and it is neither an FDA-approved medicine nor a lawful dietary supplement.
It should be used only under a clinician in jurisdictions where it is a registered drug.
Thymopentin reproduces the active site (residues 32-36) of the thymic hormone thymopoietin. It promotes maturation of T lymphocytes and is reported to normalize T-cell subset balance — shifting dysregulated CD4/CD8 ratios back toward normal in conditions such as rheumatoid arthritis, multiple sclerosis and HIV, rather than acting as a blunt immune stimulant.
Across trials, thymopentin is framed as an immunoregulator: in autoimmune synovitis it increased suppressor/naive T-cell populations, while in immunodeficiency states it supported CD4 counts. The proposed action is restoring immune homeostasis — but the molecular target downstream of the peptide is not fully characterized in humans.
How Thymopentin works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — safety in pregnancy and lactation is not established.
Only under specialist supervision — thymopentin modulates T-cell balance and its net effect in a given autoimmune condition is unpredictable.
Avoid unregulated sources — identity, purity and sterility are not guaranteed; a registered pharmaceutical product (where it exists) under clinical care is the only defensible route.
As an immunoregulatory agent, thymopentin could theoretically counteract or compound the effects of immunosuppressants or other immunomodulators. Combined use has not been systematically studied and should be clinician-supervised.
Thymopentin has been trialed as a vaccine adjuvant with inconsistent (including negative) results; it should not be assumed to improve vaccine response and any combined use should be clinician-directed.
Tip: Trials reported mostly minor side-effects from IV/SC dosing; administer per clinical protocol.
Tip: At least one RA RCT recorded a systemic allergic reaction; stop and seek care if hypersensitivity occurs.
Tip: Long-term and repeated-course safety is not well characterized; do not self-administer chronically.
The current evidence for Thymopentin is insufficient to assign an evidence score, based on 38 indexed studies, including 5 meta-analyses. A synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr) reproducing the active site of the thymic hormone thymopoietin. Unlike grey-market peptides, thymopentin was a genuinely registered immunomodulator drug — marketed as Timunox in Italy and widely used in China — so it has real Western randomized trials behind it, not just anecdote. The strongest data are small placebo-controlled RCTs in active rheumatoid arthritis from the 1980s (Lancet, German multicentre) showing short-lived symptomatic improvement, and a 352-patient double-blind HIV trial where it modestly delayed disease progression. But the evidence is old, heterogeneous, and short-duration; benefits faded weeks after stopping; it failed as a vaccine adjuvant in at least one trial; and it is NOT an FDA-approved drug or a dietary supplement. Modern meta-analyses of adjuvant-therapy trials (tuberculosis, lung cancer) report benefits, but the lung-cancer review rated its trials mostly at unclear risk of bias and moderate to very low quality, and the tuberculosis review's abstract reports no quality assessment. Treat this as a real but weakly-evidenced legacy immunomodulator, not a proven supplement. Representative study: PMID 26252373.
Dosing for Thymopentin: Thymopentin is a prescription/registered immunomodulator drug outside the US, NOT a dietary supplement — this library does not provide a self-administration protocol. The dose used in the active-RA RCTs was 50 mg given by slow intravenous injection three times weekly for three weeks; other regimens used subcutaneous dosing. Any use must be directed by a clinician in a jurisdiction where it is a registered drug. Individual needs vary, so check the right dose for you with a healthcare provider.
Timing is flexible for Thymopentin — consistent daily use matters more than the time of day. Thymopentin is injected (IV or subcutaneous) and its timing in trials was driven by the dosing schedule, not by food or circadian factors.
Thymopentin should be used with caution — talk to a healthcare provider before taking it. Reported side effects include systemic allergic / hypersensitivity reaction, unknown long-term effects, injection-related reactions. How often they occur is not established for all of them. Use caution if any of these apply to you: Not an FDA-approved drug or a regulated dietary supplement — approved/marketed as a prescription immunomodulator only in some countries; use only under a clinician; Known hypersensitivity to thymopentin (systemic allergic reactions have been reported); Pregnancy and breastfeeding (not established as safe).
Probiotics
Likely helpsLive microorganisms where strain selection determines outcome — Lactobacillus and Bifidobacterium strains best studied for gut, immune, and mood.
Andrographis
Likely helpsStudied for comfort and symptom duration during upper-respiratory infections when taken at onset — also supports liver health.
Lactoferrin
Too few graded studiesA multifunctional iron-binding glycoprotein from milk with broad antimicrobial, anti-inflammatory, and immune-modulating properties.
PT-141
Too few graded studiesA melanocortin-receptor (MC4R) agonist peptide for low sexual desire. Important honest framing: unlike most 'research peptides', bremelanotide is an FDA-APPROVED prescription drug — Vyleesi, approved 2019 — for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women, self-injected subcutaneously on-demand. It has real phase-3 RCTs (the RECONNECT program). The catch: the approved-trial benefit was statistically significant but small (a fraction of a point on desire scales), nausea is very common, and it transiently raises blood pressure. Grey-market 'PT-141' vials sold online are NOT the approved drug and are unregulated.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 38 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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