Thymalin

01 · What it is

Thymalin is not a peptide. It is a polypeptide complex extracted from thymus tissue, and the two dipeptides its own developers identify as its active substances are sold separately as other compounds.

That first sentence has to lead because almost everything about how this compound is discussed depends on obscuring it. Thymalin is described in the primary literature as “a polypeptide complex isolated from the thymus and regulating the functions of the immune system” ⁹ and as “an immunomodulatory drug containing a polypeptide extract of thymus” ¹¹. It is a tissue preparation, in the same category as Epithalamin — which is the pineal equivalent from the same programme — and not in the same category as a defined synthetic peptide.

The active-substance claim is the most useful fact in this file. A 2023 paper from the developing group states plainly that “KE and EW dipeptides are active substances of Thymalin” ¹¹. KE is lysyl-glutamate — the dipeptide marketed under the name Vilon. EW is glutamyl-tryptophan. So the relationship runs: a thymic extract, containing among other things two dipeptides, one of which is itself sold as a separate compound.

Thymalin comes out of the same St Petersburg programme that produced Epitalon, Vilon and Pinealon, and it is the oldest and largest of them. PubMed indexes roughly 293 records under the name, the great majority from Soviet-era work in the 1970s and 1980s, much of it in Russian and much of it in journals whose contents are not retrievable at the standard this guide applies to citation.

The human claims are old, numerous and almost entirely uncontrolled. Thymalin was applied in the complex treatment of endometrial cancer patients as early as 1990 ¹. It is asserted in recent papers to have demonstrated efficacy in acute respiratory distress syndrome, chronic obstructive pulmonary disease and complex therapy of severe COVID-19 in middle-aged and elderly patients ¹¹ — but that assertion appears in the introduction of a bioinformatics and cell-culture paper, as background, with no trial cited in the abstract.

And it is half of the largest claim in this family. In a study of 266 elderly and older people followed six to eight years, with the bioregulators given during the first two to three years, investigators reported mortality lower by a factor of 2.0–2.1 in the Thymalin-treated group, 1.6–1.8 with Epithalamin, 2.5 with both, and 4.1 in a separate group given both annually for six years ^3,6. The abstract describes no randomisation, no blinding, and no account of how the control group was formed. It was published by the institutes that developed both preparations. No independent group has attempted to replicate it in more than twenty years.

Two recent studies do give the compound something it previously lacked: mechanism work in human cells, conducted with named methods and reported quantitatively ^9,11. Both are in vitro, both come from the same group, and both are described in Section 3.

02 · Evidence at a glance

Evidence grade

Early Clinical — indexed human clinical application exists ^1,6; no randomised controlled trial identified

What it is

A polypeptide complex extracted from thymus tissue, not a defined peptide ^9,11

Stated active substances

KE (Lys-Glu, marketed as Vilon) and EW (Glu-Trp) dipeptides ¹¹

Origin

St Petersburg Institute of Bioregulation and Gerontology programme

Indexed records

~293, the majority Soviet-era

Human clinical reports

Endometrial cancer, adjunctive ¹; 266-person geroprotection study ^3,6

Claimed indications, asserted in review text

ARDS, chronic obstructive pulmonary disease, severe COVID-19 ¹¹

Randomised controlled trials

None identified

Blinded studies

None identified

Mechanism work in human cells

Two studies, both in vitro, both from the developing group ^9,11

Quantified in vitro effects

CD28 expression ×6.8, CD44 and CD117 down 2–3× in haematopoietic stem cells ⁹; IL-1β, IL-6, TNF-α reduced 1.4–6.0× in stimulated PBMCs from four donors ¹¹

Approval status

Not approved in the US or EU; Russian registration status not verified for this guide

On the grade. The rubric places a compound at Early Clinical when at least one human study has been published, and several have ^1,3,6. None is randomised, none is blinded, and one carries an effect size no independent group has tested. The grade records that human studies exist. It does not record that they were well conducted.

03 · Mechanism of action

An extract, not a molecule

The first thing to say about Thymalin’s mechanism is that a mechanism is difficult to define for a tissue extract. A polypeptide complex isolated from thymus ⁹ contains many species, in proportions that depend on the source tissue and the extraction process. Batch-to-batch composition is not reported anywhere in the indexed literature, and the compound therefore has no molecular weight, no sequence and no structure to state.

The developing group’s response to this has been to name active components. In 2023 they identified the dipeptides KE and EW as the active substances ¹¹, which converts an undefined extract into a partly defined one — and raises the question, which the literature does not address, of why the extract would be used rather than the two dipeptides.

T lymphocyte differentiation

The most concrete cellular result concerns human haematopoietic stem cells. Thymalin reduced expression of CD44, a stem cell marker, and CD117, a marker of the intermediate stage of differentiation, by two- to three-fold, and increased expression of CD28, a marker of mature T lymphocytes, by 6.8-fold. The authors interpret this as stimulation of CD117-positive cells differentiating into mature CD28-positive T lymphocytes ⁹.

They connect it to COVID-19 by noting that CD28-positive, CD4-positive and CD8-positive T lymphocyte counts fall in severe disease, and propose that any antiviral effect would consist of compensatory stimulation of stem cell differentiation during immune suppression ⁹.

Quantified flow cytometry endpoints in human cells are a real advance on the descriptive Soviet-era literature. The COVID-19 connection is an inference the authors draw, not a result they report.

Cytokine suppression, and how it was established

The 2023 study combined molecular docking, bioinformatics and cell culture. Docking identified preferred double-stranded DNA sequences for each dipeptide — GGAG in classical B-form DNA for EW, GCGC in curved nucleosomal DNA for KE. Bioinformatic cluster analysis proposed AKT1 and AKT2 as shared targets, with ACE2 and CYSLTR1 specific to EW and CHUK specific to KE. The in vitro component used lipopolysaccharide-stimulated human peripheral blood mononuclear cells from four donors, with ELISA for IL-1β, IL-6 and TNF-α: Thymalin and both dipeptides reduced synthesis of all three by 1.4- to 6.0-fold ¹¹.

Four donors, ELISA repeated two to four times per cytokine. That is a small, carefully reported experiment, and the paper says so. The docking and pathway analysis around it are hypothesis generation, not evidence of what the compound does in a person.

Peptide effects in monocytes and macrophages

A separate 2022 study by an Italian group working with one of the original investigators examined peptides regulating proliferative activity and inflammatory pathways in the THP-1 monocyte and macrophage cell line ¹⁰.

Endogenous immunoreactive material

Two studies from the same era report “thymalin” as something detectable in human tissue rather than administered to it: age-related changes in thymalin content in human epidermis ⁴, and thymalin in the developing respiratory organs of the human fetus ⁵. These describe immunoreactive material identified with antibodies raised against the preparation, which is a different kind of claim from the pharmacological one and is presented here as such.

04 · Key research findings

The 266-person geroprotection study. Elderly and older people followed for six to eight years, with Thymalin and Epithalamin given during the first two to three years. Reported: improvement in cardiovascular, endocrine, immune and nervous system indices; acute respiratory disease incidence lower by a factor of 2.0–2.4; reduced clinical manifestations of ischaemic heart disease, hypertension, deforming osteoarthrosis and osteoporosis; and mortality lower by 2.0–2.1-fold in the Thymalin group, 2.5-fold with both preparations, and 4.1-fold in a group given both annually for six years ^3,6.

This is the single largest claimed effect on human mortality in the whole of this project. The abstract reports no randomisation, no blinding, and no description of the control group, and the study was conducted and published by the institutes that developed the preparations. Its size is a reason to want it replicated, not a reason to accept it.

Oncology, adjunctive. Thymic factor Thymalin was applied in the complex treatment of endometrial cancer patients in 1990 ¹. In 2018, Thymalin’s effect on tumour and thymus under conditions of activation therapy was examined in vivo ⁸.

Adjunctive use in cancer alongside conventional therapy is the oldest documented human application and the one furthest from how the compound is currently marketed.

Immune cell differentiation. Thymalin shifted human haematopoietic stem cells toward the mature T lymphocyte phenotype in vitro, with CD28 up 6.8-fold and the stem and intermediate markers down two to three-fold ⁹.

The clearest quantitative result in the file, and it is a cell-culture result.

Inflammatory cytokines. Thymalin and its two named dipeptides reduced IL-1β, IL-6 and TNF-α synthesis in stimulated human peripheral blood mononuclear cells by 1.4- to 6.0-fold, using cells from four donors ¹¹.

A consistent anti-inflammatory signal in primary human cells, at a scale — four donors — that the authors report transparently.

Radiation. A 2016 paper on cytogenetic effects of low-dose ionising radiation following the Chornobyl catastrophe and their modification includes Thymalin among the agents considered ⁷.

Radioprotection is a recurring theme across the Soviet-era literature for this class and is not supported by any controlled study retrievable at this guide’s citation standard.

Contemporary appraisal. A 2026 review of therapeutic peptides in gerontology surveys this class, including the St Petersburg bioregulators ¹², and the group’s own 2002 monograph-length supplement remains its foundational text ².

05 · Evidence overview

06 · Safety profile

Animal data. No formal toxicology programme is identified in the indexed record. The 2018 tumour and thymus study is the most recent in vivo work retrievable here ⁸.

Human data. Thymalin has been given to people since at least 1990 ¹ and to 266 older adults over several years in the geroprotection study ^3,6. Neither report describes systematic adverse event collection. Recent papers assert prior use in acute respiratory distress syndrome, chronic obstructive pulmonary disease and severe COVID-19 ¹¹ without citing the trials in which that use was studied.

The absence of reported harm across decades of use is worth noting and is worth very little as evidence, because none of the studies that generated it was designed to detect harm.

What is genuinely unknown. What is in the preparation. That is not a rhetorical point: a polypeptide extract of animal thymus ⁹ has a composition that varies with tissue source, animal health, extraction method and batch, and no paper in this literature reports a specification, an assay, or a lot-release standard. Downstream of that, everything: pharmacokinetics, which cannot be defined for an unspecified mixture; the identity of any species responsible for the reported effects beyond the two dipeptides now named ¹¹; immunogenicity, which is a live question for an animal-tissue-derived protein preparation and is unassessed anywhere in the indexed record; transmissible agent risk from bovine or porcine tissue sourcing, which no paper addresses; repeat-dose toxicology, genotoxicity, reproductive toxicology and carcinogenicity, none performed to a modern standard. And whether the cytokine suppression observed in vitro ¹¹ would be beneficial or harmful in a person with an active infection, which is the setting in which the compound is asserted to have been used ¹¹.

07 · US regulatory status

Current as of 6 September 2026. Thymalin is not approved as a drug in the United States or the European Union and is not a controlled substance in the United States.

Papers from the developing group describe Thymalin as a drug ^9,11, and the compound has a long history of use within the Soviet and later Russian medical systems. This guide does not state whether it currently holds a Russian marketing authorisation, because that could only be established from Russian regulatory records, which have not been consulted for this piece. That question is the top item in this guide’s verification queue, and it is the difference between an Early Clinical grade and an Approved Pharma one.

Under the World Anti-Doping Code, substances not approved for human therapeutic use by any governmental regulatory health authority fall within class S0, and peptide hormones and growth factors are prohibited at all times. Competitors should consult the current Prohibited List directly rather than rely on secondary summaries, including this one.

08 · Limitations of the evidence

1. It is an extract, and no composition is published. A polypeptide complex isolated from thymus ⁹ has no defined identity. Two dipeptides are named as active substances ¹¹; nothing states what fraction of the material they represent, what else is present, or how batches are controlled. Every downstream question about dose, pharmacokinetics and reproducibility is unanswerable for this reason alone.

1. The mortality claim is unreplicated and its method is not described. Up to 4.1-fold lower mortality ^3,6, from the institutes that developed the preparations, with no randomisation, blinding or control-group description in the abstract, and no independent attempt at replication in over twenty years.

1. No randomised controlled trial of Thymalin was identified in any indication.

1. Claims of efficacy in ARDS, COPD and COVID-19 appear as background assertions, not as cited trials. They are stated in the introduction of a bioinformatics and cell-culture paper ¹¹. This guide reports that they were asserted; it does not report them as established, because the studies behind them were not retrievable.

1. The bulk of the literature is not retrievable at this guide’s citation standard. Of roughly 293 indexed records, this guide cites twelve. The remainder are largely Soviet-era, Russian-language, and in journals whose abstracts are not indexed. A guide that cited them without reading them would be misrepresenting its own sourcing, and the shortfall in reference count here is a finding rather than an omission.

1. Research concentration is extreme. The great majority of the modern work carries authors from the St Petersburg institute ^2,3,4,6,9,11, including the two recent mechanistic studies that represent the strongest science in the file.

1. The mechanism work is in vitro and small. Flow cytometry on haematopoietic stem cells ⁹ and ELISA on mononuclear cells from four donors ¹¹. Both are honestly reported. Neither says what happens in a person.

1. Animal-tissue sourcing raises questions the literature does not address. Immunogenicity and transmissible agent risk are standard considerations for tissue-derived biologicals and are absent from this record entirely.

1. The relationship to Vilon is not addressed anywhere. If KE is an active substance of Thymalin ¹¹, then results attributed to Thymalin and results attributed to Vilon are not independent, and no paper in either literature discusses the overlap.

09 · References

1. 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 ↗

2. Khavinson VKh. Peptides and Ageing. Neuro Endocrinol Lett. 2002;23 Suppl 3:11–144.

   PMID 12374906 ↗

3. Khavinson VKh, Morozov VG. [Geroprotective effect of thymalin and epithalamin]. Adv Gerontol. 2002;10:74–84. Russian.

   PMID 12577695 ↗

4. Khlystova ZS, Kalinina II, Shmeleva SP, Ryabchikov OP, Khavinson VKh. Age-related changes of thymalin content in human epidermis. Bull Exp Biol Med. 2002 Jun;133(6):620–622.

   PMID 12447484 ↗

5. Khlystova ZS, Kalinina II, Shmeleva SP. Thymalin in developing respiratory organs of human fetus. Bull Exp Biol Med. 2003 Jun;135(6):600–602.

   PMID 12937685 ↗

6. Khavinson VKh, Morozov VG. Peptides of pineal gland and thymus prolong human life. Neuro Endocrinol Lett. 2003 Jun–Aug;24(3–4):233–240.

   PMID 14523363 ↗

7. Domina EA. Chornobyl catastrophe: cytogenetic effects of low dose ionizing radiation and their modification. Exp Oncol. 2016 Dec;38(4):219–223.

   PMID 28230819 ↗

8. 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 May;165(1):80–83.

   PMID 29797130 ↗

9. Khavinson VK, Polyakova VO, Drobintseva AO, Kvetnaia TV, Ivko OM, et al. Thymalin: activation of differentiation of human hematopoietic stem cells. Bull Exp Biol Med. 2020 Nov;170(1):118–122.

   PMID 33237528 ↗

10. Avolio F, Robuffo I, Bologna G, Simeone P, Lanuti P, Guarnieri S, Trofimova S, Procopio AD, Toniato E, et al. Peptides regulating proliferative activity and inflammatory pathways in the monocyte/macrophage THP-1 cell line. Int J Mol Sci. 2022 Mar 25;23(7):3607.

    PMID 35408963 ↗

11. Linkova N, Khavinson V, Diatlova A, Petukhov M, Vladimirova E, Sukhareva M, Ilina A. 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 Aug 29;24(17):13377.

    PMID 37686182 ↗

12. Mavrych V, Shypilova I, Bolgova O. Therapeutic peptides in gerontology: mechanisms and applications for healthy aging. Front Aging. 2026 Apr 7;7:1790247.

    PMID 42021992 ↗