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Thymalin

Also known as Timalin, thymus polypeptide extract, Thymalinum

Bovine thymus extract from the Russian bioregulator programme, with mortality claims the evidence cannot carry.

early-clinical Immune & longevity approved drug

At a glance

Category
Immune & longevity
Status
approved drug
Made from
animal-derived Acid or heat extract of the thymus of calves and young cattle under one year old, supplied as a lyophilised polypeptide mixture.
Route
intramuscular according to the Russian product information; also subcutaneous in user protocols
Half-life
No published pharmacokinetics in humans or animals. For a mixture of unprotected polypeptides, plasma survival is presumably short; any circulating half-life figure is extrapolation without a primary source.
Onset
No validated onset time. Protocols assess immunological parameters after a course of 5-10 days, but there is no controlled research into the time course of any effect.
Molecular weight
No single value can be given: this is not a defined molecule but a mixture of polypeptides, usually specified as fractions below approximately 10 kDa. The ratio between those fractions is not standardised.

Thymalin holds a pharmaceutical registration in Russia, and previously in the Soviet Union, as an immunomodulator, including for secondary immunodeficiency in infection, burns and after radiotherapy or chemotherapy. That registration rests on the Soviet and Russian approval procedure and not on a dossier assessed by the EMA or the FDA; outside Russia and a few neighbouring countries it is not authorised anywhere. The label 'registered medicine' therefore says something about a national procedure, not about the quality of the underlying efficacy evidence. What is sold online as 'thymalin' is moreover not a Russian pharmaceutical product but a research chemical of unknown origin.

Doping status: Not listed by name on the WADA list

Checked against the WADA 2026 Prohibited List. For a specific product and country, Global DRO is the lookup athletes are expected to use — the List names substances, not brand names.

The registered Russian product uses controlled veterinary sourcing; material bought on the grey market carries the same foreign-animal-protein exposure with no traceable animal origin at all.

Mechanism of action

Thymalin is not a defined molecule but an acid or heat extract of calf thymus tissue, containing a mixture of polypeptides of varying length. That makes it fundamentally different from synthetic thymus peptides such as thymosin alpha-1, whose exact structure is known and whose effect can be attributed to a single molecule. With an extract that is by definition impossible: there is no identifiable active substance whose action can be tested, and the composition may differ between batches.

The presumed action is that of the thymus itself: promoting the maturation and differentiation of T lymphocytes, normalising the ratio between T helper and T suppressor cells, and restoring cellular immunity in an involuting thymus. The Russian literature additionally describes effects on phagocytosis and on tissue regeneration. For none of these effects has an independently confirmed molecular target been identified.

Thymalin belongs to the same programme as Epitalon and Pinealon: the doctrine of the 'peptide bioregulators' of Khavinson and the St Petersburg Institute of Bioregulation and Gerontology. That doctrine holds that short peptides derived from an organ selectively restore the function of that same organ by binding to DNA and directing gene expression. This tissue specificity is the central and least substantiated assumption of the entire programme: there is no accepted mechanism by which short peptides, chemically indistinguishable from ordinary proteolytic breakdown material present throughout the body, would selectively navigate to an organ and bind there to promoter DNA in a sequence-specific manner.

For Thymalin there is a further objection that does not apply to the synthetic members of the series: it is an animal extract, so even the identity of the presumed bioregulator is unknown. This should be labelled a hypothesis, not a mechanism.

What the research shows

Thymalin has a long history of use in Russian clinical practice and an extensive Russian-language publication record, but that record rarely meets the methodological standards against which an efficacy claim is tested. The best-known finding - a substantial reduction in mortality among older people - comes from a single research group, from a study in which randomisation and blinding were not described, and has not been independently replicated in over twenty years. Moreover, the group with the largest reported effect did not receive Thymalin as the only agent 1. There is no basis for stating that Thymalin extends lifespan or slows immune ageing in humans.

Research in humans

The most cited human claim is Khavinson and Morozov (2003): 266 people over 60 years of age, followed for 6 to 8 years, treated with Thymalin and/or Epithalamine, a bovine pineal extract 1. A mortality reduction of 1.6 to 2.1-fold was reported for the individual agents and of 4.1-fold for the combination of Thymalin and Epithalamine with six years of annual administration 1. That largest effect is therefore by definition not attributable to Thymalin alone: the contribution of each agent separately cannot be disentangled from this design, and the same publication also puts the same mortality figures forward as evidence for Epithalamine. Quite apart from that, the numbers as such are not credible - a 4.1-fold mortality reduction in an elderly cohort exceeds anything medicine has ever achieved, more than statins, antihypertensives and smoking cessation combined. Beyond this there are Russian clinical series in burns, tuberculosis, sepsis and postoperative immunosuppression; these are predominantly uncontrolled and small. Where the work does reach internationally indexed journals it is through the same group and remains open-label - a 1997 paper describing Thymalin as an immunocorrector 3, a 2013 review in which the developers summarise their own long-term clinical results across several bioregulators including Thymalin 4, and a 2021 study that added Thymalin to standard COVID-19 treatment as combination therapy 5. None is an independent, blinded, placebo-controlled trial, and there is not a single Western randomised trial of Thymalin.

Animal and lab research

Mouse and rat studies from the same research tradition report extension of mean lifespan, restoration of T cell counts and delayed tumour development; a 1993 study, for instance, reported that Thymalin - alongside other thymic and tracheal peptides - raised resistance to influenza A and B in chick embryos and mice 2. Virtually all of this work comes from the Khavinson group or affiliated Russian laboratories; independent replication outside that circle is absent. Here too, a non-standardised extract may differ between batches, which hampers reproduction even within the programme.

Caveats. The human studies are structurally impossible to assess: the randomisation method, allocation concealment and blinding cannot be verified; treated participants received annual courses of injections and with them repeated clinical contact that the control group did not get, which on its own can produce large apparent differences in mortality; nothing is reported about dropout over six to eight years of follow-up, while differential dropout manufactures mortality differences; there is no registered protocol and no pre-specified primary endpoint across a wide range of reported outcomes. Everything comes from a single research group, published in journals with limited external scrutiny, largely in Russian and therefore hard to assess independently, and in over twenty years without independent replication. The strongest reported effect moreover concerns combined administration with Epithalamine, which means it cannot be assigned to Thymalin. On top of that comes the nature of the product: an animal tissue extract with a non-standardised composition is inherently poorly reproducible, and grey-market products have an unknown composition and an untraceable origin for the animal starting material.

What it is used for

  • Secondary immunodeficiency in infection, burns and after radiotherapy or chemotherapy - the registered Russian indications
  • Adjunctive use in chronic inflammatory disease and tuberculosis in Russian clinical practice, on the basis of uncontrolled series
  • Presented as a geroprotector and a means of 'immune restoration' in older people - a claim resting on a single unreplicated study from one research group, in which the largest reported effect belonged to Thymalin combined with Epithalamine rather than to Thymalin alone 1
  • Outside Russia it is self-administered in courses on the grey market, without a validated indication or a dose supported by controlled evidence

Dosing

Dose
Russian product information: 5-20 mg per day intramuscularly, depending on the indication. Khavinson's geroprotection protocol uses 10 mg per day.
Frequency
once daily
Route
intramuscular according to the Russian product information; also subcutaneous in user protocols
Duration
Courses of 5-10 days; repeated annually or every six months in the geroprotection protocol
  • The course structure (10 days, then months off) comes directly from the Russian product information and from Khavinson's research 1, not from independent randomised trials.
  • In the published geroprotection research Thymalin was in part combined with Epithalamine, and the largest reported mortality effect - 4.1-fold, over six years of annual courses - belongs to that combination 1; the doses from that research therefore belong to the combination and not to Thymalin as a standalone treatment.
  • There is no dose-finding research, no maximum tolerated dose, no human pharmacokinetics and no dose-response curve.
  • Because Thymalin is an extract and not a defined molecule, a dose in milligrams is not a reliable measure of biological activity: the same 10 mg may have a different composition between batches and suppliers.
  • Doses are described here solely because they circulate in the product information and in protocols, not because they are supported by controlled evidence.

These figures describe what the literature and published protocols report. They are not advice and not a dosing instruction.

Protocols

Annual geroprotection course (Khavinson protocol)

user protocol — not validated

Source: Khavinson's geroprotection research and the user protocols derived from it

This is not a validated schedule. It is a pattern that circulates among users and sellers, reproduced because it is what people actually follow — not because it has been tested. No trial established these doses, this interval or this duration, and nobody is checking what is in the vial. Treat every number below as an assertion, not a finding.

Days 1-1010 mg per day by intramuscular injection
Repeatannually, or every six months in some protocols

This course structure comes from a single research group, published outside indexed journals and never independently replicated; it is not a trial schedule. In that research Thymalin was partly co-administered with Epithalamine, so the reported outcomes do not belong to Thymalin alone. The Russian product information covers different indications at 5-20 mg per day intramuscularly over 5-10 days. Thymalin is an extract, so 10 mg is a mass of powder rather than a defined quantity of active substance.

Schedules are reproduced as their source states them. Units, IU and milligrams explains why the figures are not interchangeable between products.

Reconstitution

Vial sizes
10 mg, 20 mg (lyophilised powder)
Solvent
0.9% sodium chloride or procaine solution according to the Russian product information; bacteriostatic water in user protocols
Storage
Keep the powder dry and protected from light. The Russian product information prescribes using the solution immediately after preparation; solutions made with bacteriostatic water are in practice kept at 2-8 °C.

Worked example

10 mg vial + 2 ml diluent = 5 mg/ml. 10 mg is then the entire contents, that is 2 ml.

Let the water run slowly down the wall of the vial, swirl and do not shake; do not use if cloudy. With an animal extract the chance of protein residues triggering an allergic reaction is greater than with a synthetic peptide. Grey-market products are regularly mislabelled or contaminated; certificates of analysis drawn up by the sellers themselves cannot be independently verified, and with animal starting material the origin cannot be traced.

Work it out for Thymalin

Safety

Side effects

  • Allergic reactions, including anaphylaxis in theory - this is foreign animal protein; it is the most important predictable risk
  • Pain and redness at the injection site
  • Transient fever or a flu-like feeling
  • The Russian reports mention few side effects, but that reflects the absence of systematic safety monitoring in uncontrolled series and is not evidence of safety
  • No internationally verifiable toxicology, carcinogenicity or reproductive toxicity programme has been carried out

Do not use if

  • Hypersensitivity to animal proteins
  • Autoimmune disease - immune stimulation could theoretically worsen the condition; not studied
  • Immunosuppression after organ transplantation
  • Pregnancy and breastfeeding - no data
  • Lymphoproliferative disorders - no safety data

Interactions

Not studied. Opposition to immunosuppressants is plausible but has not been demonstrated. There are no published pharmacokinetic interaction studies, and with an extract whose active constituents are unknown such a study would also be difficult to carry out.

Sources