Skin, Hair & Immune

Thymalin

Also known as Timalin, Thymalinum, Calf thymus polypeptide complex, Thymus peptide bioregulator

A polypeptide extract of calf thymus registered as a medicine in Russia since the 1980s, with a small randomised COVID-19 trial and a long tail of older Russian-language clinical reports behind it.

How it works

A thymic peptide that restores immune function by promoting T-cell development and thymic regeneration.

Performance edge

Studied for immune system rejuvenation; often stacked with Epithalon in longevity protocols.

Plain-English guide

Thymalin, without the jargon

What it is

Thymalin is not a single peptide. It is a mixture of short peptides extracted from the thymus glands of young calves, the thymus being the small organ behind the breastbone that trains the immune system's T cells and shrinks steadily from puberty onwards. It was developed in Leningrad, now St Petersburg, in the 1970s by Vladimir Khavinson and Vyacheslav Morozov, and it has been registered as a medicine by the Russian Ministry of Health since the 1980s, with the current registration number LS-000267. Researchers later identified short fragments inside the mixture, in particular the dipeptides KE (lysine-glutamic acid) and EW (glutamic acid-tryptophan), as carrying much of the activity. Almost the entire published literature on Thymalin comes from the same St Petersburg research network that created it, and it has no approval from the US Food and Drug Administration for any use.

What people use it for

Secondary immunodeficiency, meaning immune weakness caused by illness, surgery or treatment rather than inherited, which is what the Russian registration actually covers
Severe COVID-19 in older patients, where a randomised 80-patient hospital trial added it to standard care
Adjunct treatment alongside chemotherapy for destructive pulmonary tuberculosis, based on a 60-patient Russian report from 1990
Anti-ageing and longevity protocols, usually paired with Epithalon, based on a 266-subject Russian follow-up study of both preparations
General immune support in people who feel they pick up every infection going, which is an off-label use with no controlled trial behind it

How it works, simply

Think of the thymus as a training academy that graduates immune cells. In your twenties the academy is busy; by your sixties most of it has been replaced by fat and the intake has dwindled. Thymalin is a bag of chemical messages collected from a young calf's academy, and the idea is that giving them back tells your remaining immune stem cells to finish their training and report for duty. What has been measured is that immune cell counts go up during a ten-day course; whether the academy itself is rebuilt has not been shown in a person.

What to expect, and when

Day 1-3The trials gave one 10 mg intramuscular injection a day. Nothing is reported about how people feel in the first days; the measurements taken were blood counts, not symptoms.
Day 10This is where the trial data sits. At the end of a ten-day course in severe COVID-19, lymphocyte counts had roughly doubled, C-reactive protein and interleukin-6 had fallen faster than in the placebo group, and hospital mortality was 19.4 percent versus 40.9 percent.
Week 2-4No published study follows a Thymalin course past hospital discharge, so any claim about how long the immune changes last is an assumption rather than a measurement.
Month 3-6The twice-yearly course pattern sold in longevity protocols comes from the Russian geroprotection studies, which repeated courses over years. No dose-finding study has compared one course a year against two.
Year 6-8The only long-horizon human data is a 266-subject Russian follow-up over six to eight years reporting roughly halved mortality with Thymalin. It was not blinded and has never been repeated outside the originating institute.

Side effects and interactions

The randomised COVID-19 trial reported no adverse events, and the older Russian clinical reports likewise report none, which is not the same as none existing given that none of these studies were designed primarily to detect harm
Allergic reactions and individual intolerance are the adverse effects named on the Russian product information; this is an animal-derived protein preparation, so hypersensitivity is the foreseeable risk
Injection-site pain, redness and bruising follow from intramuscular injection of 2 mL and are not specifically characterised for this product
No published study reports genotoxicity, carcinogenicity, reproductive toxicity or drug interaction data for Thymalin in humans
Because it is an extract rather than a defined molecule, batch-to-batch variation is itself a source of unpredictable effects, and no independent analytical characterisation of vials sold outside Russia has been published

Who should avoid it

You are pregnant, trying to conceive, or breastfeeding; the Russian product information lists pregnancy and lactation as contraindications and no human reproductive data exists
You have a known allergy to bovine or other animal-derived protein preparations, since this is a calf tissue extract
You have an autoimmune condition or are taking immunosuppressant medication after a transplant or for an inflammatory disease; deliberately pushing T-cell activity is the opposite of the treatment goal and has not been studied in these groups
You have a lymphoid cancer such as lymphoma or leukaemia, or any active cancer; the one Russian report in chronic lymphocytic leukaemia is not a basis for self-treatment and the rodent tumour work is not a human result
You are under 18, or you are not working with a physician who knows you are taking it and can recognise an allergic reaction

Common mistakes

Treating it as a defined peptide. Thymalin is a bovine thymus extract, not a single synthesised sequence, so purity and potency claims on a vendor label mean something quite different from what they mean for a synthetic peptide.
Copying the trial dose without the trial route. Every human study used 10 mg in 2 mL of saline given intramuscularly; the insulin-syringe subcutaneous approach common in peptide protocols has not been studied for this preparation.
Assuming the Epithalon mortality figures apply here. Thymalin and Epithalamin were given together in the geroprotection studies, and the combined arm is where the largest numbers come from, so the individual contribution of Thymalin is not cleanly separable.
Reconstituting or storing it carelessly. Use bacteriostatic water, run it slowly down the vial wall rather than jetting it in, swirl instead of shaking, keep the powder cold and dark, and refrigerate once mixed.
Stacking it with immune-modifying drugs without telling a doctor. An immunostimulant taken alongside an immunosuppressant is a direct pharmacological conflict, and nobody has studied the combination.

Deep research

What the literature actually shows

Mechanism

Thymalin is a polypeptide complex isolated from the thymus glands of young calves, developed at the Kirov Military Medical Academy in Leningrad and registered as an immunomodulator by the Russian Ministry of Health. Chemically it is an extract, not a defined molecule, which is the single most important thing to hold in mind when reading its literature: what the studies administered is a mixture whose composition depends on the source tissue and the purification process, in the same way that Epithalamin is a pineal extract and Epithalon is the defined peptide derived from it.

The proposed mechanism has narrowed over time onto the short peptides inside the mixture. Work from the originating group attributes the immunoprotective action to the dipeptides KE (Lys-Glu) and EW (Glu-Trp) and the tripeptide EDP, and proposes that peptides this short enter cells, bind double-stranded DNA or histone proteins in a sequence-selective way, and change transcription of immune genes. A 2023 International Journal of Molecular Sciences paper combined molecular docking with a human peripheral blood mononuclear cell model and reported that Thymalin and the KE and EW dipeptides reduced synthesis of interleukin-1 beta, interleukin-6 and tumour necrosis factor alpha by 1.4- to 6.0-fold, with cluster analysis pointing to the AKT1 and AKT2 kinases as shared targets.

The cellular claim is that Thymalin pushes haematopoietic stem cells down the T-lymphocyte path. In a 2020 Bulletin of Experimental Biology and Medicine study, Thymalin reduced expression of the stem-cell markers CD44 and CD117 by two to three times while raising CD28, a co-stimulatory receptor carried by mature T cells, by 6.8-fold. That is a differentiation signature rather than direct evidence of thymic regrowth, and no published study has imaged or measured thymic tissue volume in a person given Thymalin.

Clinically the mechanism is framed as pre-empting the cytokine storm: restore lymphocyte numbers and T-cell subsets early, and the runaway inflammatory phase of a severe infection is less likely to develop. The randomised COVID-19 trial is consistent with that framing, reporting roughly doubled lymphocytes, a 6.5-fold fall in interleukin-6 and a 3.3-fold fall in C-reactive protein against placebo. Whether the immune changes caused the mortality difference or merely tracked recovery cannot be settled by a single trial of eighty patients.

Strength of evidence

Limited human dataEvery human study of Thymalin gave 10 mg intramuscularly, not by the subcutaneous route the insulin-unit figures in the cheatsheet above imply, so no human data exists for the way it is actually sold and used. The humans studied did receive Thymalin itself rather than a relative, in a randomised single-blind placebo-controlled trial of 80 older patients with severe COVID-19 reporting halved hospital mortality, a 266-subject multi-year geroprotection study, a 1990 tuberculosis series and a non-randomised tocilizumab comparison — but essentially all of it originates from the same St Petersburg and Chita research network with no independent replication, and the preparation is a bovine thymus extract rather than a defined molecule, so batches are not necessarily equivalent.

Key studies

Randomised controlled trial2021Advances in Gerontologyn = 80
Peptide Drug Thymalin Regulates Immune Status in Severe COVID-19 Older Patients
A prospective, randomised, single-blind, placebo-controlled trial at Chita State Medical Academy Hospital in Russia gave 36 older patients with severe COVID-19 Thymalin 10 mg in 2 mL of saline intramuscularly once daily for ten days on top of standard care, against 44 controls given saline injections. Hospital mortality was 19.4 percent with Thymalin against 40.9 percent with placebo. Blood lymphocytes rose about 92 percent from baseline, 66.6 percent of the treated group recovered from lymphopenia against 43.2 percent of controls, and interleukin-6, C-reactive protein and D-dimer fell faster. No adverse events were reported. This is the only randomised placebo-controlled trial of Thymalin located.
Human trial2021Stem Cell Reviews and Reports
Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19
Comparing standard COVID-19 therapy against standard therapy plus Thymalin, the authors reported that standard treatment alone lowered interleukin-6, C-reactive protein and D-dimer, and that adding Thymalin accelerated the decline of those markers and of T-cell system indicators, which they interpreted as a reduced thrombosis risk. The paper comes from the same Khavinson and Kuznik group as the randomised trial and largely reports the same clinical programme. It reports no participant counts or allocation method, and appears to describe the same Chita cohort as the randomised trial above rather than an independent one.
Human trial2022Advances in Gerontology
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
Severe COVID-19 patients were split into basic therapy, basic therapy plus tocilizumab, and basic therapy plus Thymalin. Hospital mortality was 40.9, 28.4 and 20.6 percent respectively. Thymalin roughly doubled lymphocytes and monocytes, cut the platelet-to-lymphocyte ratio 1.4-fold and reduced fibrinogen, lactate dehydrogenase and D-dimer, whereas tocilizumab raised the platelet-to-white-cell ratio. The comparison is not described as randomised and the arm sizes are not given in the abstract.
Human trial2003Neuro Endocrinology Lettersn = 266
Peptides of pineal gland and thymus prolong human life
266 elderly subjects were followed for six to eight years after courses of the thymic preparation Thymalin, the pineal preparation Epithalamin, or both. Mortality fell 2.0 to 2.1-fold with Thymalin, 1.6 to 1.8-fold with Epithalamin, 2.5-fold with the two combined, and 4.1-fold when the combination was repeated annually for six years, with acute respiratory disease incidence 2.0 to 2.4-fold lower. The study is indexed as a controlled clinical trial but was not blinded, and it comes from the institute that developed both preparations.
Human trial1990Problems of Tuberculosisn = 60
Effectiveness of administration of thymalin in the complex treatment of pulmonary tuberculosis
A clinical, radiological and immunological evaluation of 60 inpatients with destructive pulmonary tuberculosis concluded that adding Thymalin to chemotherapy, guided by immunological criteria, shortened hospital stay and increased treatment efficacy while normalising immune indices. The report is Russian-language, from 1990, and gives no blinding or randomisation details in the indexed abstract.
In vitro2020Bulletin of Experimental Biology and Medicine
Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells
In human haematopoietic stem cell cultures, Thymalin reduced expression of the stem-cell markers CD44 and CD117 by two to three times and increased CD28, a marker of mature T lymphocytes, by 6.8-fold. The authors read this as stimulation of stem cell differentiation into mature T cells and proposed it as the basis for using Thymalin in COVID-19, where CD28-positive, CD4-positive and CD8-positive T cells are depleted.
In vitro2023International Journal of Molecular Sciences
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
Molecular modelling, bioinformatics and a human peripheral blood mononuclear cell model were used to test the dipeptides KE and EW isolated from Thymalin. Docking identified preferred DNA binding sequences for each, cluster analysis pointed to the AKT1 and AKT2 kinases involved in cytokine storm, and in culture Thymalin and the two dipeptides reduced synthesis of interleukin-1 beta, interleukin-6 and tumour necrosis factor alpha by 1.4- to 6.0-fold.
Animal study2018Bulletin of Experimental Biology and Medicine
Effect of Thymalin on the Tumor and Thymus under Conditions of Activation Therapy In Vivo
In rats bearing transplanted sarcoma 45, Thymalin at doses below the therapeutic range produced an antitumour effect, with tumour regression in more than half the animals and roughly 78 percent growth suppression in the rest, alongside increased lymphoproliferative activity in thymic tissue. This is a rodent transplanted-tumour model and does not establish anything about cancer risk or benefit in people.

Safety data

The trials that exist report no adverse events. The randomised COVID-19 trial records none, and the older Russian clinical reports in tuberculosis and chronic lymphocytic leukaemia describe benefit without describing harm. None of these studies were designed or powered to detect uncommon adverse effects, and absence of reported events in small unblinded or single-blind studies from one research group is weak evidence of tolerability. The Russian product information for Thymalin names allergic reactions and individual intolerance as the adverse effects and lists pregnancy and lactation as contraindications.

The risks specific to this product follow from what it is. Thymalin is a protein preparation extracted from calf tissue, so hypersensitivity to bovine material is the foreseeable acute reaction, and any animal-tissue-derived biological carries a residual question about the source herd and the purification process that a synthetic peptide does not. Because it is an extract, the identity of the material in a vial bought outside the Russian regulated supply chain is unverifiable by the buyer, and no independent analytical study of such vials has been published.

The mechanistic risks are unstudied rather than excluded. Deliberately driving T-cell differentiation in someone with an autoimmune disease, a lymphoid malignancy, or a transplant on immunosuppression is a plausible way to do harm, and none of those groups appear in the published trials. Rodent work in transplanted sarcoma points towards tumour suppression rather than promotion, but that is a rat model and no human cancer safety data exists. There is no published genotoxicity, carcinogenicity, reproductive toxicity or drug-interaction dataset for Thymalin.

Regulatory status

FDA: As of 2026-09-19, Thymalin is not approved by the US Food and Drug Administration for any indication and does not appear on the agency's 503A bulk drug substances list, so it cannot lawfully be compounded for patients in the United States and is sold there only as a research chemical labelled not for human use.
WADA: As of 2026-09-19, Thymalin is not named anywhere on the World Anti-Doping Agency 2026 Prohibited List, and it is not a growth factor of the kind covered by section S2.3, which names thymosin-beta-4 but not thymic extracts. Because Thymalin does hold a current human therapeutic approval from the Russian Ministry of Health, the section S0 non-approved substances clause does not obviously capture it either, so its status is genuinely ambiguous and any competing athlete should get a written ruling from their anti-doping organisation before using it.
Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act

Open questions

Does the COVID-19 mortality result survive replication by a group unconnected to Khavinson and Kuznik? An 80-patient single-blind trial from the originating network is the strongest evidence this compound has, and it stands alone.
Does Thymalin actually regenerate thymic tissue, or only redistribute existing lymphocytes? No human study has measured thymic volume or thymic output markers such as T-cell receptor excision circles after a course.
How much of the geroprotection signal belongs to Thymalin rather than to Epithalamin or to the two together, given that the largest mortality reductions in the 266-subject study came from the combined arm?
What is actually in a vial? As a bovine tissue extract, Thymalin has no single molecular identity, and no published analysis compares batches or compares Russian pharmaceutical product with the material sold internationally.
Is an immunostimulant a good idea over decades in people who are well? Every human study treated sick or elderly patients, and nobody has followed healthy users of twice-yearly courses for autoimmune or malignant outcomes.