Thymalin: research, side effects and doses used in studies

In short

Thymalin is a mixture of peptides extracted from calf thymus [5]D, studied almost only in Russia, the Soviet Union and Ukraine. There are many human studies, but they are small and none we found had a placebo group. Thymalin has no marketing authorisation in any EU or EEA country [1]regulator.

• Thymalin is not one molecule but a peptide mixture isolated from the thymus. A few short peptides have been reported as its active components [5]D [6]A.
• The best human evidence is one open-label randomised trial in 92 COVID-19 patients. In the thymalin group blood lymphocytes rose and inflammation markers fell more than in the controls, but no patient died in either group, so mortality could not be compared [6]A.
• The claim of longer life rests on one study of 266 older people by the developers' group [8]A, and we found no replication elsewhere. An independent Cochrane review of other thymus extracts found no survival benefit in cancer patients [11]A.
• In Finland thymalin is not named in Fimea's medicines list, but the list is not exhaustive [2]regulator. The WADA Prohibited List does not name it [3]regulator.

What is thymalin?

Thymalin is a mixture of natural peptides isolated from calf thymus by mild acid extraction [5]D. According to the researchers, the peptides in the mixture have a molecular weight of up to 10 kilodaltons [6]A.

Two dipeptides, Glu-Trp (EW) and Lys-Glu (KE), and a tripeptide, Glu-Asp-Pro, have been reported as its active components [6]A [19]D. The Glu-Trp dipeptide isolated from thymalin was the basis of a synthetic product, Thymogen (thymogen) [5]D.

Thymalin is one of the tissue extracts developed in St Petersburg, along with the pineal extract epithalamin. The synthetic epitalon was designed on the basis of epithalamin [10]. Thymalin is not the same substance as thymosin alpha 1, which is a single synthetic thymic peptide [11]A.

According to the researchers, the Russian Ministry of Health approved thymalin for medical use as an immunomodulator in 1982 [6]A. In EU and EEA countries thymalin has no marketing authorisation [1]regulator. All substances: Peptides A-Z.

Evidence at a glance

Each cell gives the kind of study and its source. The letter is the evidence level, not the result.

"-" = no such study is known.

What is thymalin studied for?

In humans thymalin has been studied mainly as an add-on alongside other treatment [4]B [6]A [12, 13]B. None of these is an approved use in the EU [1]regulator.

• COVID-19: hospital patients in St Petersburg and Chita [6]A [7]B.
• Ageing: a long follow-up study of older people [8]A.
• Cancer treatment: endometrial and cervical cancer, added to hormone therapy, surgery or radiotherapy [12, 13]B.
• Severe inflammation and surgery: peritonitis in children [4]B and acute pancreatitis [16]B.
• Other: Parkinson's disease [14]B, treatment-resistant schizophrenia [15]B and ulcerative colitis [17]B.

Most of the studies were published in Russian- or Ukrainian-language journals [7, 14, 16]B. No registered clinical trials of thymalin are known (as of October 2026).

How does thymalin work?

The exact mechanism is not known. The developers' own papers state that the molecular mechanism needs further study [18]D and that the mechanism of thymalin's immune effect remains unclear [19]D.

According to the developers' review, thymalin's most prominent effect is stimulation of the immune system [10]. In laboratory experiments, natural and synthetic thymic peptides increased T-cell differentiation and affected cytokine release by white blood cells [5]D.

• Stem cells: in cultures of human blood-forming stem cells, thymalin lowered stem cell markers 2-3-fold and raised the mature T-cell marker CD28 6.8-fold [18]D.
• Inflammation: in human white blood cell cultures, thymalin and its dipeptides KE and EW lowered production of the inflammatory signalling molecules IL-1β, IL-6 and TNF-α 1.4-6.0-fold. Blood samples came from four donors [19]D.
• Macrophages: in an Italian-Russian cell study, thymalin and four other peptides from the same developer lowered TNF and IL-6 production in macrophages derived from a leukaemia cell line [20]D.

These are cell experiments. They do not show what an injected peptide mixture does in the human body.

Has thymalin been studied in humans?

Yes, but the studies are small and mostly old, and almost all were published in Russia, the Soviet Union or Ukraine. The newest and best reported is an open-label randomised COVID-19 trial from 2021 [6]A. We found no Western clinical trials.

COVID-19

• Randomised trial, St Petersburg 2020. 92 hospital patients with moderate or severe COVID-19, pneumonia and low lymphocyte counts were assigned to two groups by the envelope method. 42 received thymalin into a muscle for five days on top of standard care, 50 received standard care only. The trial was open-label, without a placebo. In the thymalin group lymphocytes rose by 55%, helper T cells (CD4) by 88.9% and IL-6 fell 5.5-fold, while in the controls IL-6 fell 1.41-fold. CRP fell 9.7-fold in the thymalin group and 1.7-fold in the controls [6]A.
• Deaths and lungs in the same trial. No one died in either group. On computed tomography, lung changes progressed in five controls and in two patients given thymalin [6]A.
• Three-group comparison, Chita. Middle-aged and older people with severe COVID-19 received basic therapy, basic therapy plus tocilizumab, or basic therapy plus thymalin. According to the English abstract, hospital mortality was 40.9%, 28.4% and 20.6%. The abstract does not give group sizes or say whether patients were randomised [7]B.

Ageing

The gerontology institutes of St Petersburg and Kyiv followed 266 older people for 6-8 years. Some received thymalin, some the pineal extract epithalamin and some both during the first 2-3 years. According to the abstract, mortality in the thymalin group was 2.0-2.1 times lower than in the controls, and the treated people had 2.0-2.4 times fewer acute respiratory illnesses [8]A.

The abstract does not describe randomisation, blinding, group sizes or doses [8]A. The same figures were published a year earlier in a Russian-language journal [9]. Both are publications by thymalin's developers.

Cancer and other diseases

• Endometrial cancer. Of 111 patients, 35 received thymalin on top of hormone therapy and surgery. The researchers reported positive effects on cell-mediated immunity values [12]B.
• Cervical cancer. 38 patients received thymalin with radiotherapy and 58 controls radiotherapy alone. According to the researchers, more could undergo surgery and treatment results were better [13]B.
• Parkinson's disease. 15 patients were examined before and after thymalin treatment. Symptoms eased, and EEG mapping showed a change the author interpreted as an improvement. No control group is mentioned [14]B.
• Schizophrenia. 36 treatment-resistant patients received thymalin on top of psychiatric drugs. According to the researchers, symptoms eased, and improvement went together with normalisation of immune values [15]B.
• Pancreatitis. 18 patients with acute necrotic pancreatitis received thymalin as part of their treatment. All survived, and four had surgery. The abstract mentions no control group [16]B.
• Peritonitis in children. The surgical treatment of 21 children included, among other steps, local treatment of the wound edges with a thymalin solution. There were fewer complications than in the controls, but thymalin was only one part of the treatment package [4]B.

In these studies thymalin was always given on top of other treatment, and none of the abstracts mentions a placebo group. So the result cannot be separated from the effect of the other treatment [4, 12, 13, 14, 15, 16]B.

Promising, but only in animals so far

These findings look interesting, but they have not been studied in humans with the same measure. Results from animal experiments cannot be transferred directly to humans.

• Tumour growth no human studies

  In mice, thymalin strengthened the effect of cytostatic drugs: tumours grew and spread less, the animals lived longer and the drug-induced weakening of the immune system was milder [22]C. In rats with transplanted sarcoma, tumour growth stopped or the tumour shrank in more than half of the animals, and in the rest growth was suppressed by 78% [21]C.

  If it held in humans: thymalin might strengthen cancer drug treatment or slow tumour growth.

  Why it might not translate: the tumours were transplanted into rodents, which does not match human cancer. The human studies measured mainly immune values and the chance of surgery, not tumour shrinkage [12, 13]B. In an independent review, other thymus extracts did not improve survival or treatment response in cancer patients [11]A.

  Evidence now: two animal studies, from 1987 and 2018, by Russian groups [21, 22]C. No registered human study is known (as of October 2026).

• Melatonin and the pineal gland no human studies

  In adult mice, a single thymalin injection raised blood melatonin after three hours and lowered it after 24 hours. The effect depended on the season. In old mice, no stimulating effect on the pineal gland's melatonin production was seen [23]C.

  If it held in humans: thymalin might affect melatonin, which regulates sleep and the daily rhythm.

  Why it might not translate: the experiment used mice and a single injection, and the effect was missing in exactly the old animals that ageing claims are about [23]C.

  Evidence now: one mouse study [23]C. We found no human study.

Who studies thymalin?

Thymalin goes back to V. G. Morozov and V. Kh. Khavinson [5, 20]D, and most research has been done at the St Petersburg Institute of Bioregulation and Gerontology or its network [8]A [18, 19]D. The COVID-19 studies involved a St Petersburg hospital and Chita State Medical Academy [6]A [7]B.

Other groups have published, for example, in Ukrainian journals [14, 16]B and from Rostov [21]C. The only Western group we found is an Italian group that did a cell study with Khavinson among the authors [20]D. We found no independent human studies from outside Russia and the former Soviet Union.

Who wrote this page: the editorial team

This page was written by the Molecular Recovery editorial team. The draft was produced with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.

What are the side effects of thymalin?

There are no systematic research data on thymalin's side effects. The abstracts we read do not report side effects, and the full text of the randomised COVID-19 trial contains no reporting of adverse events [6]A.

What is known

In an independent Cochrane review, other thymus extracts and synthetic thymic peptides were well tolerated by cancer patients [11]A. Thymalin was not among the studies in the review, so the result cannot be applied to it as such [11]A.

What has not been studied

There is no safety research on long-term use, repeated treatment courses or use by healthy people. The abstract of the long follow-up study of older people says nothing about side effects [8]A. On peptide side effects in general: side effects in studies.

Interactions and who has no data

There are no studies of drug interactions. In the COVID-19 trial thymalin was given together with an anticoagulant, antibiotics and, in some patients, antiviral drugs and a glucocorticoid (dexamethasone), but interactions were not assessed separately [6]A.

There are no data on pregnancy or breastfeeding. In children, thymalin has been used locally in a surgical wound in one study [4]B.

Evidence against and what is unknown

The biggest weakness is that almost all the evidence comes from the developers' group or its circle, and we found no placebo-controlled study.

Evidence against

• Thymus extracts in cancer treatment. A Cochrane review pooled 26 randomised trials with 2,736 patients. Purified thymus extracts added to cancer treatment did not improve survival (risk ratio 1.00), disease-free survival or treatment response. Severe infections were possibly less common (risk ratio 0.54). The extracts were thymostimulin and thymosin fraction 5, not thymalin [11]A.
• Corticosteroids worked better in severe bowel inflammation. In a comparison of 50 patients, corticosteroids worked better when inflammation had damaged the mucosa. The researchers preferred thymalin only in mild inflammation [17]B.
• Skin sarcoidosis. In a treatment comparison of 28 patients, immunostimulating therapy, which included thymalin among other agents, failed [24]B.
• Inconsistent figures. In the abstract of the Chita COVID-19 study, hospital mortality in the thymalin group is 20.6% in English and 16.2% in Russian [7]B.
• Limits of the COVID-19 trial. The trial was open-label and single-centre. The results are laboratory values, there were no deaths in either group, and other treatment differed between groups: for example, 40.5% of the thymalin group and 56% of the controls received lopinavir and ritonavir [6]A.

What the evidence does not support

• "Thymalin extends life": the claim rests on one study by the developers' group whose abstract does not describe randomisation or doses [8]A. We found no replication by another group.
• "Thymalin helps against cancer": tumour shrinkage has been seen only in rodents [21, 22]C, and other thymus extracts did not improve survival [11]A.
• "Thymalin is an approved medicine": it has no marketing authorisation in EU and EEA countries [1]regulator. The Russian approval is the researchers' statement [6]A.
• "Thymalin is one peptide": it is a peptide mixture extracted from the thymus [5]D.

What is not known

• How long thymalin's peptides stay in the body. We found no human study of its pharmacokinetics.
• Whether thymalin is safe in long-term or repeated use [6]A [8]A.
• Whether the results hold up in a placebo-controlled study by a group other than the developers.

Thymalin doses used in studies

Thymalin has no approved dosing in the EU, because it has no marketing authorisation [1]regulator. Below are the doses used in human studies as the sources report them. They are not recommendations.

What the numbers cannot tell you. The COVID-19 trial dose is from the full text, and it was given in hospital during a serious infection alongside other treatment [6]A. It does not indicate a suitable or safe dose for a healthy person. More detail: thymalin doses used in studies. The calculator has no thymalin preset: thymalin calculator.

Thymalin vs thymosin alpha 1: what is the difference?

Thymalin and thymosin alpha 1 are both linked to the thymus, but they are different substances. Thymalin is a peptide mixture extracted from calf thymus [5]D, thymosin alpha 1 a single synthetic thymic peptide [11]A.

• Composition: thymalin contains many peptides, of which a few short peptides have been reported as active [5]D [6]A. Thymosin alpha 1 is one synthetic peptide [11]A.
• Evidence: thymalin has been studied in small Russian studies [6]A [12, 13]B. Thymosin alpha 1 was included in the randomised cancer trials of the Cochrane review, where the risk of death showed a trend towards being lower, but the difference was not statistically significant [11]A.
• In Finland: thymalin is not named in Fimea's medicines list. The list does include another synthetic thymic peptide, thymopentin [2]regulator.

Thymalin and epithalamin: combinations

Thymalin has been studied in humans together with the pineal extract epithalamin. In the developers' follow-up study, mortality among people given thymalin and epithalamin together was 2.5 times lower than in the controls. In a group given both every year for six years, mortality was 4.1 times lower [8]A.

The figures come from the same study, whose abstract does not describe randomisation, group sizes or doses [8]A. The synthetic epitalon, designed on the basis of epithalamin, is a different substance from epithalamin [10]. We found no studies of blends containing thymalin.

Is thymalin legal in Finland?

Thymalin has no marketing authorisation in Finland or in any other EU or EEA country [1]regulator. Fimea's medicines list does not name it, but according to the list, a substance that meets the definition of a medicine is a medicine even if it is not listed [2]regulator.

• Marketing authorisation. EMA's Article 57 database, to which all human medicines authorised in EU and EEA countries must be reported, contained no thymalin product on 9 Oct 2026 [1]regulator.
• Medicines list. Fimea's medicines list (230/2025) does not include thymalin in annex 1 or annex 1 A. Annex 1 includes another thymic peptide, thymopentin. According to the decision, the list is not exhaustive, and where needed Fimea decides whether a substance is to be considered a medicine [2]regulator.
• Russia. According to the researchers, thymalin has been approved for medical use in Russia since 1982 [6]A. That does not make it an approved medicine in Finland.
• Import. Ordering medicines from outside the EU is covered on the page Peptides and the law in Finland. Bringing them back from a trip: Travelling with peptides.

This is not legal advice. Disclaimer.

Is thymalin a doping substance?

The WADA 2026 Prohibited List does not name thymalin [3]regulator. Class S0 prohibits at all times pharmacological substances that no other section covers and that have no current approval by any governmental regulatory health authority for human therapeutic use [3]regulator. Thymalin has no authorisation in EU or EEA countries [1]regulator, and the Russian approval is only the researchers' statement [6]A. Athletes should check with the Finnish Center for Integrity in Sports (SUEK).

How to judge the quality of a thymalin product

There is no certainty about the content of a thymalin product without analysis. Thymalin is a peptide mixture extracted from animal tissue, not one molecule [5]D, so a single purity percentage on a certificate of analysis (COA) does not describe the mixture's composition the way it would for a single peptide.

If a product is claimed to contain thymalin's dipeptides Glu-Trp and Lys-Glu [19]D, check on the certificate which peptides were identified and by which method, for example HPLC or mass spectrometry. The synthetic Glu-Trp dipeptide is a different product from thymalin [5]D, so read the label carefully. How to read one: how to read a COA.

FAQ

Read the research yourself: sources

Every source opens the original publication or the regulator's page. The level shows what the source itself reports.

1. European Medicines Agency. Article 57 product data (EMA/518502/2018 Rev.90, data as present in the Article 57 database on 9 Oct 2026): no product with thymalin in any EU/EEA country. EMA regulator
2. Finland. Lääkeluettelo (Fimea medicines list), 230/2025, section 1 and annexes 1 and 1 A: thymalin is not listed; thymopentin is in annex 1; the list is not exhaustive. Finlex regulator
3. World Anti-Doping Agency. The 2026 Prohibited List (in effect from 1 Jan 2026): thymalin is not named; class S0 Non-approved substances. WADA regulator
4. Bushmelev VA, Pozdeev VV, Nikolaev MV. Prevention of postoperative complications in diffuse purulent peritonitis in children. Khirurgiia (Mosk). 1994;(8):56-59. (In Russian.) PMID 7990325 B
5. Morozov VG, Khavinson VK. Natural and synthetic thymic peptides as therapeutics for immune dysfunction. Int J Immunopharmacol. 1997;19(9-10):501-505. PMID 9637345 D
6. Khavinson VK, Kuznik BI, Trofimova SV, et al. Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19. Stem Cell Rev Rep. 2021;17(1):285-290. Full text read. PMID 33575961 A
7. Kuznik BI, Shapovalov KG, Smolyakov YN, et al. Morphological compound and indicators of the blood clotting system in severe COVID-19 patients of middle aged and elderly during treatment of Tocilizumab and Thymalin. Adv Gerontol. 2022;35(3):368-374. (In Russian.) PMID 36169363 B
8. Khavinson VKh, Morozov VG. Peptides of pineal gland and thymus prolong human life. Neuro Endocrinol Lett. 2003;24(3-4):233-240. PMID 14523363 A
9. Khavinson VKh, Morozov VG. Geroprotective effect of thymalin and epithalamin. Adv Gerontol. 2002;10:74-84. (In Russian.) PMID 12577695 (review)
10. Khavinson VKh. Peptides and Ageing. Neuro Endocrinol Lett. 2002;23 Suppl 3:11-144. PMID 12374906 (review)
11. Wolf E, Milazzo S, Boehm K, Zwahlen M, Horneber M. Thymic peptides for treatment of cancer patients. Cochrane Database Syst Rev. 2011;(2):CD003993. PMID 21328265 A
12. Bakhidze EV, Bokhman JaV. Application of thymic factor "Thymalin" in complex treatment of endometrial cancer patients. Eur J Gynaecol Oncol. 1990;11(4):251-256. PMID 2245808 B
13. Vishnevskaia EE, Khavinson VKh, Nikolaeva DV. The use of thymalin in the combined treatment of patients with disseminated cancer of the cervix uteri. Vopr Onkol. 1991;37(1):86-90. (In Russian.) PMID 2014686 B
14. Musienko GV. Thymalin in the combined treatment of parkinsonism patients. Lik Sprava. 1999;(1):119-122. (In Russian.) PMID 10424021 B
15. Govorin NV, Stupina OP. Use of thymic peptide thymalin in the complex treatment of therapy-resistant schizophrenia. Zh Nevropatol Psikhiatr Im S S Korsakova. 1990;90(3):100-103. (In Russian.) PMID 2163147 B
16. Kopchak VM, Khomiak IV, Stasenko AA, Todurov IM, Kopchak KV. The application efficacy of immunomodulators in complex of treatment of an acute necrotic pancreatitis. Klin Khir. 2004;(9):5-7. (In Ukrainian.) PMID 15560588 B
17. Tkach SM, Bychkova NG, Fomina AA, Perederii VG. Differentiated immunocorrective therapy in nonspecific ulcerative colitis. Lik Sprava. 1992;(4):34-36. (In Russian.) PMID 1441366 B
18. Khavinson VK, Linkova NS, Kvetnoy IM, et al. Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells. Bull Exp Biol Med. 2020;170(1):118-122. PMID 33237528 D
19. Linkova N, Khavinson V, Diatlova A, et al. The Influence of KE and EW Dipeptides in the Composition of the Thymalin Drug on Gene Expression and Protein Synthesis Involved in the Pathogenesis of COVID-19. Int J Mol Sci. 2023;24(17):13377. PMID 37686182 D
20. Avolio F, Martinotti S, Khavinson VK, et al. Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Line. Int J Mol Sci. 2022;23(7):3607. PMID 35408963 D
21. Zhukova GV, Schikhlyarova AI, Barteneva TA, Shevchenko AN, Zakharyuta FM. Effect of Thymalin on the Tumor and Thymus under Conditions of Activation Therapy In Vivo. Bull Exp Biol Med. 2018;165(1):80-83. PMID 29797130 C
22. Amosova EN, Iaremenko KV, Cherdyntseva NV, Nikolin VP, Ogreba VI. The immunomodulator thymalin in the experimental chemotherapy of tumors. Vopr Onkol. 1987;33(10):68-72. (In Russian.) PMID 3686911 C
23. Labunets IF. Thymic factors influence on melatonin-producing pineal function in mice of different age: the possible mechanisms. Adv Gerontol. 2007;20(1):86-91. (In Russian.) PMID 17969591 C
24. Samtsov AV. A comparative evaluation of the efficacy of different therapeutic methods in sarcoidosis of the skin. Vestn Dermatol Venerol. 1990;(4):52-54. (In Russian.) PMID 2389612 B

PubMed records fetched and abstracts read on 15 Oct 2026; the full text of source 6 read in Europe PMC. EMA Article 57 data (as of 9 Oct 2026), Fimea's medicines list 230/2025 and the WADA 2026 Prohibited List checked on 15 Oct 2026. Many sources are in Russian, and only their English abstracts were read.

Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.

Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.