Thymalin Research, Specifications & Scientific Information

Introduction

Thymalin is a thymus extract, and almost every difficulty in reading its literature follows from that one fact. It is a polypeptide complex isolated from thymus tissue, described as regulating immune function and registered in the Russian Federation as an immunomodulatory preparation ^[1]. It has no sequence, no molecular formula and no entry in any structural register.

That places it in a different evidentiary category from the defined thymic peptides it is usually listed beside. Thymosin alpha-1 is 28 residues with a known structure; Thymulin is nine residues and a zinc ion. A result obtained with either can in principle be reproduced anywhere from the structure. A result obtained with this preparation can only be reproduced with material from the same source tissue and the same process.

The second difficulty is provenance. The great majority of the primary literature comes from a small number of Russian institutions, much of it published in Russian with English abstracts, and none of it is registered on an international trials register. Reports from that network during the COVID-19 pandemic include mortality figures that would be remarkable if produced under the conditions the rest of the field expects ^[3]. They were not produced under those conditions, and this page says so where it reports them.

What Is Thymalin?

Thymalin — also transliterated Timalin — is a polypeptide complex isolated from thymus tissue and administered by injection. The accounts of it in the indexed literature describe it as regulating the functions of the immune system and as increasing the functional activity of T lymphocytes, with reported clinical use in acute respiratory syndrome, chronic obstructive bronchitis and other immunopathology ^{[1, 4]}.

It belongs, by programme rather than by chemistry, to the group of preparations developed at the St Petersburg Institute of Bioregulation and Gerontology — the same programme that produced the short synthetic peptides Epitalon and Pinealon. Those are defined molecules designed from the composition of an extract. This is the extract.

A recent development in that programme is worth noting precisely, because it is easy to misread. Papers from 2023 name two dipeptides, Lys-Glu (KE) and Glu-Trp (EW), as the active substances of the preparation and analyse them separately ^[4]. Those dipeptides are defined molecules with their own identifiers. Naming them as active components of a mixture is a hypothesis about the mixture; it does not make the mixture a defined substance, and it does not make results obtained with the dipeptides results about the preparation, or the reverse.

It has not been approved by the U.S. Food and Drug Administration for any indication, no marketing application for it is on record in the United States, and no study of it is registered on ClinicalTrials.gov.

Thymalin Specifications

Thymalin has no sequence, no molecular formula and no molecular mass, because it is a polypeptide complex isolated from thymus tissue rather than a single molecule. No PubChem compound identifier, CAS registry number or FDA/NCATS UNII code resolves for it, and those fields are therefore published as unknown rather than filled with values belonging to a related substance. Papers from the originating programme name two dipeptides, Lys-Glu and Glu-Trp, as active substances of the preparation; those are defined molecules with their own identifiers and are not the same substance as the complex that contains them. Identity here rests on the source tissue and the manufacturing process, which means a preparation made by a different process is a different substance however similar its description.

Values that a public register does not carry are shown as not publicly characterised rather than estimated. Identifiers are reference values; the certificate of analysis supplied with a laboratory order is the record for a given lot.

How Does Thymalin Work?

Not established, and the originating group says so in print: the targeted molecular mechanism of its biological activity requires further study ^[1].

What exists is a descriptive account at the level of cell populations. The preparation is said to raise the functional activity of T lymphocytes, and the mechanistic proposal built on that is a compensatory one — that it pushes haematopoietic precursors toward mature T-lymphocyte phenotypes at a stage when immunity is suppressed ^[1].

The 2023 work approaches the same question differently, by treating the mixture as the sum of two named dipeptides and analysing those. For Lys-Glu the account is stimulation of cellular immunity and non-specific resistance, with activating effects on macrophages, lymphocytes, thymocytes and neutrophils. For Glu-Trp it is reduced angiotensin-induced vasoconstriction and preserved endothelium-dependent vascular relaxation through inhibition of ACE2 ^[4]. That second claim is of a different order from the first — it names a specific protein target — and it rests in that paper on molecular docking and bioinformatic pathway analysis rather than on a binding measurement.

No pharmacokinetic data of any kind are published. For a polypeptide complex quantified by mass of extract rather than of an identified active substance, a conventional pharmacokinetic profile cannot be constructed even in principle.

Thymalin Mechanism of Action

In vitro research

Haematopoietic stem cell surface markers. In cultured human haematopoietic stem cells, the preparation reduced expression of CD44, a stem-cell marker, and of CD117, a marker of an intermediate differentiation stage, by two to three times, and increased expression of CD28. The authors read this as stimulated differentiation of CD117-positive cells into mature CD28-positive T lymphocytes, and connect it to the observation that CD28-positive, CD4-positive and CD8-positive lymphocyte counts fall in severe COVID-19 ^[1].

Cytokine release from stimulated mononuclear cells. In a lipopolysaccharide-induced inflammation model using human peripheral blood mononuclear cells, the preparation and both named dipeptides reduced measured IL-1 beta, IL-6 and TNF-alpha by 1.4- to 6.0-fold. Blood came from four donors, with each cytokine assayed between two and four times ^[4].

Computational target identification. Molecular docking indicated preferred double-stranded DNA sequences for each dipeptide, and cluster analysis of promoter and pathway databases nominated AKT1 and AKT2 as shared potential targets, with ACE2 and CYSLTR1 specific to Glu-Trp and CHUK specific to Lys-Glu ^[4]. Docking and database analysis generate hypotheses. They do not demonstrate binding, and the paper presents them as the first half of its argument rather than as its conclusion.

Two cautions apply across this section. The cell-culture work is small in scale — four blood donors in the cytokine experiment — and it comes from the programme that developed the preparation. And the causal chain runs from a mixture whose composition is defined by process to endpoints measured in cells; no step in it isolates what is responsible.

Findings in this section were obtained in cell culture and by computation. Nothing in them establishes anything about intact animals or about humans.

What Is Thymalin Being Researched For?

• Immunomodulation and T-lymphocyte function — the central claim of the preparation and the subject of the stem-cell work ^[1].
• Severe COVID-19, as an addition to standard therapy — reported in two Russian clinical series with inflammatory, coagulation and mortality outcomes ^{[2, 3]}.
• Inflammatory cytokine regulation — through the two named component dipeptides ^[4].
• Geroprotection — the six-to-eight-year observational report of thymic and pineal preparations in older adults that is shared with the pineal side of the programme ^[6].
• Experimental oncology in rodents — a transplanted sarcoma model ^[5].

Each of those is research conducted with a preparation registered as a medicine in one jurisdiction. None of it is research into, or evidence about, research-grade material supplied for laboratory use.

Human Research on Thymalin

Human clinical research

Results from pharmaceutical clinical trials describe the investigational material and populations used in those studies and should not be interpreted as establishing the effects of research-grade materials offered for laboratory use.

COVID-19, added to standard therapy, 2021

Design. A report of standard and complex treatment in patients with COVID-19, with the preparation added to standard therapy in one group, and inflammatory and coagulation markers as the measured outcomes ^[2].

Result as reported. Standard treatment alone was followed by declines in interleukin-6, C-reactive protein and D-dimer. Adding the preparation accelerated the decline in those markers and in indicators of the T-cell system ^[2].

Limitations. The report is descriptive and does not present as a randomised, blinded, placebo-controlled trial. No participant numbers, allocation method or statistical analysis plan is stated in the indexed abstract. The endpoints are laboratory markers that move with the natural course of the illness, which is precisely the situation in which an unrandomised comparison is least informative.

Severe COVID-19 against tocilizumab, 2022

Design. Middle-aged and elderly patients with severe COVID-19 in three groups — basic therapy alone, basic therapy with tocilizumab, and basic therapy with the preparation — compared on blood morphology and coagulation indices. Published in Russian in Advances in Gerontology ^[3].

Result as reported. Hospital mortality was 40.9% with standard therapy, 28.4% with tocilizumab and 20.6% with the preparation. The preparation was reported to double lymphocyte and monocyte counts, raise leukocytes by 1.3 times and platelets by 1.5 times, lower the platelet-to-lymphocyte ratio by 1.4 times and the neutrophil-to-lymphocyte ratio by 2 times, and reduce fibrinogen, lactate dehydrogenase and D-dimer by 1.2-, 1.8- and 1.7-fold respectively ^[3].

Limitations, and they are decisive. A mortality difference of roughly twenty percentage points against standard care, and roughly eight against an established biologic, is an extraordinary claim. The report describes group allocation by treatment received rather than by randomisation, states no allocation concealment or blinding, provides no confidence intervals or adjustment for baseline severity, and is published in a gerontology journal in Russian. Groups in a severe-COVID-19 cohort that differ in what they received differ in why they received it, and nothing in the available record excludes that explanation. This page reports the figures because they are in the indexed literature; it does not present them as an estimate of effect.

Long-term observation of thymic and pineal preparations, 2003

Design and result as reported. A geroprotective assessment in older people over six to eight years, with preparations applied only during the first two to three years. Reported mortality reductions were 2.0- to 2.1-fold for the thymic preparation, 1.6- to 1.8-fold for the pineal preparation, 2.5-fold for the combination, and 4.1-fold in a group given the combination annually for six years ^[6].

Limitations. The investigators are the compounds' originators; the reductions reported are far larger than established medicine achieves in comparable populations; and the work has not been replicated by an independent group, registered as a trial, or published outside the small set of journals that carries this programme's output. The same report is discussed on the Epitalon entry, where it is equally central and equally limited.

Preclinical Research on Thymalin

Animal research

Transplanted sarcoma in rats, 2018

Design. Outbred albino male rats carrying transplanted sarcoma 45, given the preparation at amounts below the therapeutic range, with modulation of those amounts across the course according to an activation-therapy regime. Tumour growth and thymic microstructure were assessed ^[5].

Result as reported. Growth arrest and regression of the tumour in more than half of the animals, and suppression of growth by 78% in the remainder. Thymic lobules showed significantly increased lymphoproliferative activity and higher content of tissue basophils and plasmocytes. Tumour regression was accompanied by what the authors describe as stable antistress adaptation reactions ^[5].

Limitations. A single report from one laboratory in a transplanted-tumour model, with an effect size — regression in the majority of treated animals — far above what is typical for an immunomodulatory preparation in such a model. The design deliberately varied the amount administered across the course rather than holding it fixed, which is the study's own stated explanation for the result and also makes the comparison harder to interpret. No group sizes appear in the indexed abstract.

Findings described in this section were observed in rats. Nothing in them establishes anything about humans.

Current Research Status

Status as of September 22, 2026. This block is rendered from maintained fields, not from prose, so it cannot go stale in one place and stay current in another.

Thymalin vs Related Compounds

Against defined thymic peptides

Thymulin is a nine-residue peptide requiring bound zinc, with a sequence and a PubChem record. Thymosin alpha-1 is a defined 28-residue peptide with an approval history in several countries. This preparation is an extract. The distinction decides what can be said about reproducibility, purity and batch identity, and it is not a matter of degree.

Against the short synthetic bioregulators

Epitalon and Pinealon came out of the same programme, but in the opposite direction — they are defined short peptides designed from the composition of extracts like this one. The 2023 identification of Lys-Glu and Glu-Trp as active substances of this preparation ^[4] is that same move applied here.

Against Cerebrolysin

Cerebrolysin is the other animal-tissue peptide preparation in this library, and the comparison is instructive in one respect only: it has been subjected to Cochrane review and to large registered randomised trials, and this preparation has not. Nothing else transfers between them.

The dipeptide question

If the activity of this preparation really does reside in two dipeptides, then the dipeptides can be made synthetically, characterised, and tested against it. That experiment would settle a great deal, and it has not been published.

No comparison of effect between these compounds is made on this page.

Chemical & Molecular Characteristics

This section records structure. For this entry it records the absence of one, and what follows.

There is no molecule. The preparation is a polypeptide complex isolated from thymus tissue ^[1]. No PubChem compound identifier, CAS registry number or FDA/NCATS UNII code resolves for it. Sequence, molecular formula and molecular mass are published as not publicly characterised because those fields have no value for a mixture.

Identity is defined by process, not by structure. Source tissue, extraction conditions and fractionation determine what is in a given lot. Two preparations described identically but made differently are different substances, and there is no structural test that would establish otherwise.

Purity has no determinate meaning here. A percentage purity presupposes one intended species and a set of impurities. Mass spectrometry on this material confirms that many species are present, not that a particular one is. A certificate reporting a purity figure for a tissue extract is reporting the output of a method, and the method is the claim.

The named dipeptides are separate substances. Lys-Glu and Glu-Trp are defined molecules — two residues each, with unambiguous masses and their own register entries — and the 2023 work treats them as the active components of this complex ^[4]. A vial of either dipeptide is not a vial of this preparation, and a vial of this preparation is not a defined quantity of either.

The source is animal tissue. Material derived from mammalian thymus carries source, viral-safety and transmissible-agent considerations that a synthetic peptide does not. Those controls belong to the licensed product in the jurisdiction that licensed it, and nothing about them transfers to material offered elsewhere under the same name.

Frequently Asked Questions

Scientific References

1. Khavinson VK, Linkova NS, Kvetnoy IM, et al.. Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells Bulletin of experimental biology and medicine; 2020. PMID 33237528 doi:10.1007/s10517-020-05016-z
2. 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 reviews and reports; 2021. PMID 33575961 doi:10.1007/s12015-020-10087-6
3. 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.] Advances in gerontology = Uspekhi gerontologii; 2022. PMID 36169363
4. 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 International journal of molecular sciences; 2023. PMID 37686182 doi:10.3390/ijms241713377
5. Zhukova GV, Schikhlyarova AI, Barteneva TA, et al.. Effect of Thymalin on the Tumor and Thymus under Conditions of Activation Therapy In Vivo Bulletin of experimental biology and medicine; 2018. PMID 29797130 doi:10.1007/s10517-018-4104-z
6. Khavinson VKh, Morozov VG. Peptides of pineal gland and thymus prolong human life Neuro endocrinology letters; 2003. PMID 14523363

Every identifier above is resolved against PubMed, Crossref or ClinicalTrials.gov at build time, and the title returned by the register is compared with the title stored here. A page does not publish if a reference fails to resolve.

Research-Use Information

For in vitro research use only. This material is a laboratory reagent. It is not a drug, food, dietary supplement, or cosmetic and is not for human or veterinary use, including ingestion, injection, or any other administration. No information on this page describes or implies any effect in humans or animals. Sold only to researchers under our Terms of Sale.