Thymalin
BioregulatorsResearch Use OnlyLast reviewed: September 28, 2026
Quick Facts
- What it is
- A multi-peptide complex extracted from the thymus of young animals — one of the original Khavinson bioregulator preparations, and the extract from which the synthetic Thymogen (EW dipeptide) was isolated.
- How it's taken
- Intramuscular in its Russian registration and in the published clinical work — not subcutaneous
- Half-life
- Not characterized — and not a single figure in principle, since this is a mixture rather than one molecule
- Typical research dose
- No validated general dose — the published regimens are protocol-specific to individual studies from one research programme
- Research status
- Registered as a medicine in Russia; not FDA- or EMA-approved — US research use only. Nearly all published work is from one programme.
On this page
Where to source Thymalin
Thymalin is not approved for human use in the US and is sold by specialty research peptide vendors for laboratory use only. Because it is an animal-tissue extract rather than a synthesised sequence, a Certificate of Analysis carries a different weight here than it does for a defined peptide: purity for a mixture is a harder claim to make and a harder one to verify.
Per-batch COAs
What is Thymalin?
Thymalin is a peptide complex extracted from the thymus glands of young animals — a mixture whose exact composition reflects its source tissue, not a single chemically defined sequence. It is one of the original preparations of the Khavinson bioregulator programme, developed at the St. Petersburg Institute of Bioregulation and Gerontology alongside Epithalamin from the pineal gland and Cortexin from the brain cortex. Its best-known descendant is Thymogen, the L-Glu-L-Trp dipeptide isolated from Thymalin by reversed-phase HPLC and identified as its principal active component. The bioregulator guide sets out how the extracts and the synthetics differ across the family.
Thymalin has the largest human dataset of any compound in this family, and it has the family's defining problem in the sharpest form. A 266-person controlled study followed older adults for 6-8 years and reported mortality reduced twofold or more; MEDLINE indexes it as a randomized controlled trial. It was published in 2003 by the institute that developed the compound, and in the twenty-plus years since, no independent group has replicated it. Both halves of that sentence are load-bearing, and this profile reports both. Compare it with Epitalon, the synthetic counterpart to the pineal preparation used in the same study. New to peptide research? Start with the basics
Reported in the cited studies: normalisation of cardiovascular, endocrine, immune and nervous-system indices, a 2.0-2.4-fold lower incidence of acute respiratory disease, and mortality reduced 2.0-2.1-fold against control over 6-8 years [1]; faster decline in IL-6, C-reactive protein and D-dimer when added to standard COVID-19 therapy [2]; activation of human hematopoietic stem cell differentiation in the laboratory [3]; and effects on gene expression traced to the KE and EW dipeptides the preparation contains [4].
How is Thymalin proposed to work?
Thymalin is an extract, so its mechanism is really several mechanisms attributed to several components. The programme's account is immunomodulatory — restoring thymic and T-cell function that declines with age — with a stem-cell differentiation claim added more recently.
- Thymic immune restoration. The general account across the programme is that Thymalin restores the immune-regulatory function of the thymus, which involutes with age, rather than stimulating immunity in one direction.
- Hematopoietic stem cell differentiation [3]. Thymalin is reported to activate differentiation of human hematopoietic stem cells (Khavinson et al. 2020) — the mechanistic basis later used to argue for its use in COVID-19 therapy.
- Gene expression via its component dipeptides [4]. Thymalin is described as containing the KE and EW dipeptides, whose effects on gene expression and protein synthesis were examined directly (Linkova et al. 2023). EW is the dipeptide sold separately as Thymogen.
- What an extract cannot specify. Because Thymalin is a multi-peptide mixture from animal tissue rather than a defined molecule, its composition depends on the source material and the preparation. Any mechanism attributed to "Thymalin" is attributed to whatever that particular preparation contained.
What is Thymalin researched for?
The research runs from a long controlled geroprotection study through clinical add-on work to laboratory studies of mechanism. Nearly all of it comes from one programme, and that pattern matters more here than the individual results, so it is stated with each entry rather than saved for the end.
- Geroprotection and mortality, 266 people over 6-8 years [1]. Reported normalisation of cardiovascular, endocrine, immune and nervous-system indices; a 2.0-2.4-fold fall in acute respiratory disease incidence; and mortality 2.0-2.1-fold lower in the Thymalin group than control, rising to 4.1-fold in a subgroup given Thymalin plus Epithalamin annually for six years (Khavinson and Morozov 2003). Indexed by MEDLINE as a randomized controlled trial. Never independently replicated, and from the institute that developed the compound.
- COVID-19 as an add-on to standard therapy [2]. Thymalin added to standard treatment was reported to accelerate the decline in IL-6, C-reactive protein and D-dimer and in T-cell indices, compared with standard treatment alone (Khavinson et al. 2021). Intermediate markers, not mortality or ventilation; no randomisation or blinding stated in the abstract.
- Human hematopoietic stem cells in the laboratory [3]. Activation of stem-cell differentiation (Khavinson et al. 2020). Mechanistic, cell-level.
- Component dipeptides and gene expression [4]. The KE and EW dipeptides within Thymalin, examined for effects on gene expression and protein synthesis (Linkova et al. 2023).
- Animal oncology work [5]. Effects on tumour and thymus under an activation-therapy protocol in vivo (Zhukova et al. 2018).
How is Thymalin dosed, and what is known about safety?
There is no FDA-approved dose for Thymalin, and the safety record is reported in this same section because both rest on the same body of work and carry the same limitation.
The only regulator-defined presentations are the Russian ones; Thymalin is registered as a medicine in the Russian Federation and not by the FDA or the EMA. The published studies each used a regimen specific to their own protocol: the 2003 geroprotection study administered the bioregulators during the first 2-3 years of a 6-8 year observation [1], and the COVID-19 work added Thymalin to a standard hospital treatment protocol [2]. Prof. Peptide does not reproduce any of those as a schedule, because a regimen inside a single programme's trial is not a general dose and presenting it as one would give it authority it has not earned. On safety, the honest position is that the 2003 study is the longest human exposure on record for this compound and reports improvements rather than harms across 6-8 years in 266 older people — but it is a single study from the developing institute, and an absence of reported adverse events in a paper whose conclusion advocates the compound's adoption is weak evidence of safety. No independent safety characterisation, no interaction data and no regulatory safety review outside Russia were located here. Thymalin is also an animal-tissue extract rather than a synthetic molecule, which raises a source-material question that a defined peptide does not have: composition and contaminant profile depend on the preparation. Research vendors sell it as material labelled for laboratory use only, and a Certificate of Analysis is the only check a buyer has.
What are the limitations of Thymalin research?
Nearly the entire literature comes from one research programme. Khavinson is an author on four of the five studies summarised here, and the fifth is from the same Russian institutional network. Several key papers are Russian-language with only an English abstract indexed. This is the pattern the whole bioregulator field shares, and it is the reason to treat even a well-designed study in it differently from one replicated across independent groups.
The mortality result is the specific thing to be careful with. A 2.0-2.1-fold reduction in mortality — 4.1-fold in a subgroup — is an extraordinary claim. Nothing in mainstream geroprotection research produces effects of that size, and no independent group has reproduced it in the twenty-plus years since publication. Prof. Peptide reports the finding because it is real and published; it is reported as what one group found, not as an established fact.
Thymalin is an extract, not a defined compound. Two vials from different preparations are not guaranteed to contain the same thing, and a study of one preparation is evidence about that preparation. Its best-characterised component, the EW dipeptide, is sold separately as Thymogen — whose own most rigorous test, a randomized double-blind placebo-controlled Phase III, was negative. That result belongs in view when reading positive reports about the mixture it came from.
The COVID-19 study measured intermediate markers, not clinical outcomes, and states no randomisation or blinding. Thymalin is not FDA- or EMA-approved and is research-use-only material in the US. See the bioregulator guide for the wider context this sits in.
Thymalin FAQ
What is Thymalin?
Thymalin is a peptide complex extracted from the thymus glands of young animals — a mixture, not a single defined molecule. It is one of the original preparations in the Khavinson bioregulator programme, alongside Epithalamin (pineal) and Cortexin (brain cortex). The synthetic Thymogen (L-Glu-L-Trp, the EW dipeptide) was isolated from Thymalin as its principal active component, which makes the two directly related: one is the extract, the other a single sequence taken out of it. The bioregulator guide explains that extract-versus-synthetic split across the whole family.
Is Thymalin FDA-approved?
No. Thymalin is not approved by the FDA or the EMA for any indication. It is registered and used as a medicine in the Russian Federation, and in the US it is sold as research-use-only material by specialty peptide vendors.
Did a study really report that Thymalin reduced mortality?
Yes, and the size of the reported effect is the reason to read it carefully rather than to repeat it. A 6-to-8-year controlled study in 266 elderly and older people, published in 2003 by the St. Petersburg Institute of Bioregulation and Gerontology with the Institute of Gerontology in Kiev, reported a 2.0-to-2.1-fold lower mortality rate in the Thymalin-treated group than in the control, and a 4.1-fold reduction in a subgroup given Thymalin plus Epithalamin annually for six years. MEDLINE indexes it as a randomized controlled trial. A mortality effect of that magnitude from a peptide has no parallel in the geroprotection literature, it has never been independently replicated, and the study comes from the institute that developed the compound.
How is Thymalin related to Thymogen?
Thymalin is the thymic extract; Thymogen (L-Glu-L-Trp) is the single dipeptide isolated from it by reversed-phase HPLC and identified as its principal active component. Later work from the same programme describes Thymalin as containing both the KE and EW dipeptides. The practical consequence is that Thymogen's evidence — which includes a negative randomized Phase III in AIDS-related Kaposi's sarcoma — is evidence about one component of this mixture, and is worth reading alongside this page.
Is there a standard Thymalin dose?
There is no FDA-approved dose. The Russian registration defines the presentations used there, and the published studies each used their own regimens in their own clinical settings. Prof. Peptide does not publish a milligram schedule for Thymalin: the regimens that exist sit inside specific trials run by one research programme, and reporting one as though it were a general schedule would misrepresent what it is.
References
- Khavinson VKh, Morozov VG. Peptides of pineal gland and thymus prolong human life. Neuro Endocrinol Lett. 2003;24(3-4):233-240. PMID 14523363. https://pubmed.ncbi.nlm.nih.gov/14523363/
- 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. doi:10.1007/s12015-020-10087-6. PMID 33575961. https://pubmed.ncbi.nlm.nih.gov/33575961/
- 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. doi:10.1007/s10517-020-05016-z. PMID 33237528. https://pubmed.ncbi.nlm.nih.gov/33237528/
- 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. Int J Mol Sci. 2023;24(17):13377. doi:10.3390/ijms241713377. PMID 37686182. https://pubmed.ncbi.nlm.nih.gov/37686182/
- Zhukova GV, Schikhlyarova AI, Barteneva TA, et al. Effect of Thymalin on the tumor and thymus under conditions of activation therapy in vivo. Bull Exp Biol Med. 2018;165(1):80-83. doi:10.1007/s10517-018-4104-z. PMID 29797130. https://pubmed.ncbi.nlm.nih.gov/29797130/
Published Studies
Plain-English summaries of the indexed studies behind the statements above. Click any title to read the source record. Khavinson is an author on four of the five, and the fifth is from the same institutional network.
Khavinson VKh, Morozov VG.
The strongest and the most problematic study on this page at the same time. 266 elderly and older people were followed for 6-8 years, with the bioregulators given during the first 2-3 years, by the St. Petersburg Institute of Bioregulation and Gerontology together with the Institute of Gerontology in Kiev. The paper reports normalisation of cardiovascular, endocrine, immune and nervous-system indices, a 2.0-2.4-fold fall in acute respiratory disease incidence, and mortality reduced 2.0-2.1-fold in the Thymalin group, 1.6-1.8-fold with Epithalamin, 2.5-fold with both, and 4.1-fold in a subgroup treated annually for six years. MEDLINE indexes the publication type as a randomized controlled trial. Three things belong beside those numbers: the effect sizes are far larger than anything established in human geroprotection, the study is from the institute that developed the compounds, and no independent group has replicated it in the twenty-plus years since.
Khavinson VK, Kuznik BI, Trofimova SV, et al.; Magen E.
Thymalin added to standard COVID-19 therapy, against a control group receiving standard treatment alone. The paper reports that adding Thymalin accelerated the decline in IL-6, C-reactive protein and D-dimer, and in T-cell system indices, relative to standard therapy alone. It is described as a comparison of treatment groups; no randomisation or blinding is stated in the abstract. Notable mainly as the first work here with a co-author outside the originating programme (Ben-Gurion University), and as an intermediate-marker study rather than an outcome study.
Khavinson VK, Linkova NS, Kvetnoy IM, et al.
Laboratory work on human hematopoietic stem cells, reporting that Thymalin activates their differentiation. This is the mechanistic claim the COVID-19 paper above builds its rationale on, and it is the kind of study that makes a rationale rather than an outcome. Cell-level evidence from the originating institute.
Linkova N, Khavinson V, Diatlova A, et al.
Useful for a structural reason rather than a clinical one: it treats Thymalin explicitly as a preparation containing the KE and EW dipeptides and examines their effects on gene expression and protein synthesis. EW is the dipeptide marketed separately as Thymogen. For anyone trying to work out what is actually in this extract and which of its components carries which activity, this is the paper that addresses the question directly.
Zhukova GV, Schikhlyarova AI, Barteneva TA, et al.
An animal study of Thymalin's effect on tumour growth and on the thymus itself under an activation-therapy protocol. Included here because it is one of the few indexed Thymalin papers that is a controlled animal experiment rather than a clinical report or a cell study, and because it sits in the same oncology-adjacent territory that Thymogen's trial record covers far more rigorously.
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