Thymalin: what the Russian thymus extract is, what the studies show and where it is legal

Thymalin is a preparation of peptides extracted from calf thymus by mild acid extraction. Its developers, Vladimir Khavinson and Vyacheslav Morozov, describe it as the first of their thymic products, put into practice in the Soviet Union as an immunocorrector; a single immunomodulatory dipeptide, L-Glu-L-Trp, was later isolated from it by reversed-phase HPLC and became the synthetic drug thymogen, and a second synthetic dipeptide, Lys-Glu, was named vilon ^[1]. The thymalin-thymogen relationship is therefore that of an extract to a dipeptide derived from it. A 2023 paper from the same group calls Glu-Trp (EW) and Lys-Glu (KE) the active substances of the thymalin drug ^[4].

It is important to understand that thymalin is a mixture rather than a single molecule. A PubChem record exists under the name thymalin for a synthetic nonapeptide, but that is not the extract; no molecular formula or weight applies to the drug as sold. That distinguishes it from the defined thymic peptides sold by research suppliers such as thymosin alpha-1, a 28-amino-acid peptide with a licensed product (thymalfasin) in several countries, thymulin, a nine-amino-acid zinc-dependent hormone, and TB-500, a fragment of thymosin beta-4. Thymus extracts more broadly, including thymostimulin and tactivin, were reviewed by Russian immunologists in 1997 alongside thymalin ^[10].

Thymalin is the thymic half of the pair of organ extracts, thymalin and epithalamin, that started the Khavinson bioregulator programme. The pineal extract epithalamin gave rise to the synthetic tetrapeptide epitalon, and the same design approach later produced tissue-specific short peptides such as cortagen, pinealon, cardiogen and bronchogen ^[13]. Most of the published research on all of these comes from one group in St Petersburg and its collaborators, much of it in Russian journals, with English-language reports concentrated in the Bulletin of Experimental Biology and Medicine and a few open-access journals. That is the context for everything below.

The extract is made from calf thymus, the organ in which T lymphocytes mature. The developers report that thymalin and its synthetic derivatives activate T-cell differentiation and T-cell recognition of peptide-MHC complexes, change intracellular cyclic nucleotide levels and alter release of interleukin-2 and interferon by blood lymphocytes; the synthetic dipeptides also activated neutrophil chemotaxis and phagocytosis, while only the natural extract affected antioxidant responses in thymocytes ^[1].

A 2020 cell study reported that thymalin reduced expression of the stem-cell markers CD44 and CD117 by two to three times and increased the mature T-lymphocyte marker CD28 by 6.8 times in cultured human haematopoietic stem cells, which the authors interpreted as thymalin driving differentiation of stem cells into mature T lymphocytes ^[2]. In a 2022 study with Italian collaborators, thymalin, thymogen, vilon, epitalon and chonluten all increased tyrosine phosphorylation of mitogen-activated kinases in THP-1 monocytes and reduced the release of TNF and IL-6 after bacterial lipopolysaccharide, and reduced adhesion of the cells to activated endothelium; the authors described the peptides as inducers of TNF tolerance ^[9].

For the dipeptide components, the group has proposed an epigenetic mechanism in which EW and KE bind DNA and regulate genes; in the 2023 study, molecular docking pointed to AKT1, AKT2, ACE2, CYSLTR1 and CHUK as possible targets, and in an in vitro model thymalin, EW and KE reduced IL-1β, IL-6 and TNF-α synthesis by human blood mononuclear cells from four donors by 1.4 to 6 times ^[4]. Whether these laboratory effects explain any clinical effect has not been shown.

Interestingly, thymalin-like immunoreactivity has been detected outside the thymus. Immunohistochemical studies from Moscow found thymalin accumulating in young airway epithelial cells and diffusely in alveolar cells of the human fetus, alongside mature T cells, which the authors linked to local immune defence in the developing lung ^[15].

Thymalin benefits are usually described in three areas: immune function, ageing and longevity, and inflammatory or infectious disease. The strength of evidence differs in each.

Immune function: the immunomodulatory claims rest on the mechanistic work above and on decades of Russian clinical practice in conditions such as chronic bronchitis, burns and post-operative immunosuppression. A 2000 report described 32 patients with third- and fourth-degree burns treated with thymalin, in whom the authors observed resolution of disseminated intravascular coagulation, normalised fibrinolysis and changes in pro- and anti-inflammatory cytokines, with the first skin grafting brought forward by an average of five days and hospital stay shortened by 11 days ^[11]. The design of that study, as far as the abstract shows, was observational.

Ageing: the best-known thymalin study followed 266 elderly and older people for six to eight years, with thymalin, epithalamin or both given during the first two to three years. The authors reported a 2 to 2.4-fold fall in acute respiratory illness, fewer clinical manifestations of ischaemic heart disease, hypertension, osteoarthritis and osteoporosis, and a mortality rate 2 to 2.1 times lower in the thymalin group, 2.5 times lower with both peptides, and 4.1 times lower in a group given both annually for six years ^[5]. These are striking figures. They come from an open study run by the developers, published in a low-profile journal, without the randomisation, blinding or pre-registered outcomes that would be expected to support a claim of halved mortality, and they have not been replicated by an independent group. The same authors’ 2002 Russian-language report describes the same cohort ^[13].

Cancer: in rats with transplanted sarcoma 45, thymalin at lower-than-therapeutic doses given on an activation-therapy schedule produced tumour arrest or regression in more than half of animals and 78% growth suppression in the rest, with increased lymphoproliferative activity in the thymus ^[8]. The related dipeptide thymogen, given to rats five times a week for a year, did not change mean lifespan but extended the lifespan of the longest-lived 10% and reduced total tumour incidence 1.5-fold and blood cancers 3.4-fold ^[7]. These are animal findings from the developers and their collaborators.

Tissue repair: a 2024 Ukrainian study in 48 rats found that injecting thymalin into the soft tissue around a mandibular bone defect filled with a hydroxyapatite graft accelerated bone repair, with faster clearance of necrotic tissue, more macrophages and fibroblast-lineage cells, and more active mineralisation ^[12].

Thymalin has been used clinically in Russia since the 1980s, and PubMed lists dozens of Russian-language clinical reports from that era in conditions including pulmonary tuberculosis, chronic hepatitis B in children, multiple sclerosis, peritonitis and cervical cancer. Almost none of these are available in English beyond a title, and the abstracts that exist describe open or historically controlled studies. The 1997 Russian review of thymus preparations summarised the indications and dosages then in use ^[10].

Thymalin COVID-19 studies: during the pandemic the developers proposed thymalin as an adjunct treatment, on the basis that severe COVID-19 is marked by loss of CD28+, CD4+ and CD8+ T cells and that thymalin promotes T-cell differentiation ^[2]. A 2021 report described patients with COVID-19 given thymalin alongside standard treatment, in whom IL-6, C-reactive protein and D-dimer fell faster than in controls, which the authors linked to a lower risk of clotting ^[3]. A 2022 Russian-language study from Chita compared standard therapy, standard therapy plus tocilizumab and standard therapy plus thymalin in middle-aged and elderly patients with severe COVID-19, reporting hospital mortality of 40.9%, 28.4% and 20.6% respectively, with thymalin doubling lymphocyte and monocyte counts and lowering fibrinogen, lactate dehydrogenase and D-dimer ^[6]. Patients were allocated to groups, not randomised, and the study was not blinded, so the mortality difference cannot be attributed to thymalin with confidence.

Gynaecological infection: a 2015 study from Novosibirsk used thymalin and another immunomodulator in women with chronic salpingitis and oophoritis, and reported that timing the drug to a measurable lymphocyte enzyme response improved clinical and immunological outcomes ^[14]. Again, this is a small mechanistic clinical study rather than an efficacy trial.

In summary, as of September 2026 there is no double-blind, randomised, placebo-controlled trial of thymalin published in English, and no trial registered on ClinicalTrials.gov that we could find. The evidence base is large in volume but weak in design, and almost entirely from Russia and Ukraine.

In the COVID-19 cohorts, changes in inflammatory markers and blood counts were measured over the hospital stay ^{[3] [6]}. In the burns study, the benefit was described in days to grafting and length of stay ^[11]. The geroprotection study gave the extract in courses over the first two to three years and followed people for six to eight ^[5]. None of these studies gives a timescale that could be applied to a person taking a product bought online, and there is no evidence that thymalin does anything measurable in healthy people.

The following are doses from the literature, not recommendations. The registered Russian product is a powder for intramuscular injection, and Russian clinical studies since the 1980s have used short courses of daily injections; the 1997 review of thymus preparations discusses the dosages then in use ^[10]. The English abstracts of the 266-person study ^[5], the COVID-19 cohorts ^{[3] [6]} and the burns study ^[11] do not state the dose given. In rats with sarcoma, the effective doses were described as lower than the therapeutic doses used clinically, modulated over the course ^[8]. The dipeptide thymogen was given to rats at 5 µg per animal subcutaneously, five times a week for 12 months ^[7].

Research suppliers outside Russia sell thymalin as a freeze-dried powder, most often in 10 mg or 20 mg vials, and quote schedules that are copied from the Russian label or from other sellers rather than from trials. Because the product is an extract, milligrams of thymalin from one source are not necessarily equivalent to milligrams from another. If you are reconstituting a vial, the peptide calculator and its thymalin page will convert the contents to a concentration.

In Russia the thymalin injection is a licensed medicine, given intramuscularly. The animal studies used injection: subcutaneous for thymogen ^[7], local injection around a bone defect for thymalin ^[12]. We found no published study of oral thymalin, and as a mixture of peptides it would be expected to be digested. Products sold online as thymalin peptide capsules are not the same as the injectable medicine, and no evidence supports them.

Thymalin has been given to large numbers of patients in Russia over 40 years, and the published reports do not describe serious adverse effects; the 2022 COVID-19 study reported no safety signal in the thymalin group ^[6]. That is reassuring as far as it goes, but Russian-era clinical reports rarely used systematic adverse-event recording, and there is no pharmacovigilance data available in English. As an animal-tissue extract, thymalin carries theoretical risks that a synthetic peptide does not: allergic reactions to bovine proteins, and, for any bovine tissue product, the question of sourcing and prion safety, which the Russian manufacturer addresses under Russian rules that have not been assessed by the MHRA, FDA or EMA.

Because thymalin stimulates T-cell differentiation and cytokine changes, its use in people with autoimmune disease, organ transplants or lymphoid cancers is a specific concern that the literature does not address. Nothing is known about its effects in pregnancy or in children outside old Russian paediatric reports. As with every product on this site, none of the above means thymalin is safe; it means it has not been studied to modern standards.

For products bought from research suppliers the added risk is that the vial may not contain a genuine thymus extract at all. A certificate of analysis for a mixture cannot show a single molecular weight, so look for a supplier that states the source and the analytical method; our guides to reading a COA and third-party testing explain what to expect.

Thymalin is a registered medicine in Russia and in some other former Soviet countries, sold as an immunomodulator on prescription. It has never been submitted to or approved by the MHRA, FDA, EMA, Health Canada or the TGA, and material sold as a research product in those markets is not an approved medicine. Importing it for personal use may be restricted because it is an unlicensed medicine of animal origin. See our legal status overview and the pages for the UK, the US and Europe.

Thymalin is supplied as a freeze-dried powder that should be kept cold, dry and away from light, and reconstituted only when needed. Reconstituted solutions are refrigerated and used within a limited period. See how to store peptides and our guide to bacteriostatic water.

Compare thymalin prices across suppliers, including listings in the UK and the US. Because thymalin is an extract rather than a synthetic peptide, it is harder to test than most products on this site: a mass-spectrometry peak for a single peptide proves little, and the honest certificate is one that describes a peptide profile and the source tissue. Our lists of third-party tested suppliers and suppliers that publish COAs are a starting point, and our guide to spotting a fake supplier covers the warning signs. Some suppliers list thymogen or vilon as thymalin; they are single synthetic dipeptides derived from the extract, and their prices should be lower.