Thymalin Is Calf Thymus Extract, and Its Clinical Record Is Being Lent Forward to Two Other Peptides
The registered active substance is the words thymus extract, 10 mg from the glands of calves and cattle under one year. Khavinson's group now says the active substances are the dipeptides KE and EW, sold separately as Vilon and Thymogen. In the geroprotection paper everyone cites, 24 people received Thymalin on its own.
10 sections
- Top of article
- What it is
- Three different products sell under this name
- What the human record actually shows
- The COVID-19 papers, and which number belongs to which hospital
- Whose evidence it is, and where it is going
- Where the 10 mg came from
- What the regulators have on file
- What could go wrong
- What we do not know
- What this adds up to
What it is
Open the Russian marketing authorisation and read the composition line. The active substance is тимуса экстракт, thymus extract, 10 mg. The only other ingredient is 20 mg of glycine, and a footnote says where the extract comes from: the thymus glands of calves and young cattle up to one year old. That is the registered identity of a licensed medicine, printed on the label that two independent Russian drug references transcribe.
The product is Тималин, marketing authorisation ЛП-№(005867)-(РГ-RU) dated 21 June 2024, held by Samson-Med LLC of St Petersburg, a freeze dried powder for a solution injected into a muscle. Cerebrolysin at least prints a mass for its fraction, 215.2 mg of enzyme chopped pig brain protein per millilitre. Thymalin's label prints 10 mg of a noun.
Khavinson's group says the same in English, describing it in 2021 as a complex of peptides isolated from calf thymus with none heavier than 10 kilodaltons, the unit molecules are weighed in, and in 2023 as an immunomodulatory drug containing a polypeptide extract of thymus (PMID 37686182).
Three different products sell under this name
Peptide Warehouse says thymalin has no single defined molecular formula or weight because of its composite nature, then, lower down, that purity is confirmed by chromatography. A percentage needs a reference standard to be a percentage of. American Peptides claims at least 99 percent purity and calls its thymalin synthesized, and a synthesised calf thymus extract cannot exist. Bio Longevity Labs sells thymulin under the name outright, printing a nine residue sequence and a molecular weight of 858.86.
The databases carry the collision too. Ask PubChem for substances called thymalin and four deposits come back, none with a structure. Ask it for a compound and it hands over thymulin, fully drawn, with the word Thymalin in that record's own synonym list.
What the human record actually shows
I searched PubMed for thymalin on 7 August 2026 and got 293 records, of which 254 are indexed Russian and 30 English, leaving 9 in neither language. Half the file was in print by 1990 and seven in ten by 1995, so it is overwhelmingly Soviet era hospital reporting. Being written in Russian is a fact about my access, not a verdict on the work. Thirteen records carry the Clinical Trial publication type, two match a randomised filter, and a search for retraction notices returned none.
Go to PubMed and pull up 14523363, Khavinson and Morozov 2003. The full text is a free PDF on Khavinson's own site, and the methods change the number everybody quotes. The headline 266 is three groups added together: 94 women aged 66 to 94 at a St Petersburg war veterans home, split four ways by stratification randomisation into placebo, Thymalin, Epithalamin or both, everything injected into a muscle at 10 mg daily for 10 days, double blind; a separate twenty on both agents annually; and 152 people in Kiev split three ways. Twenty four people received Thymalin on its own.
The mortality everyone cites comes from the 114 person St Petersburg set and is quoted in folds, which hide the denominators. In counts, over six years: 18 of 22 died on placebo, 10 of 24 on Thymalin, 11 of 24 on Epithalamin, 8 of 24 on both for two years, 4 of 20 on both every year.
The other randomised record is a 154 patient Russian tuberculosis study in four groups of 38, 39, 38 and 39, reporting clinical cure after chemotherapy of 61.1, 76.3, 72.2 and 94.7 percent across them, at a p value the abstract reports as below 0.05 (PMID 18038603). Thymalin is not named anywhere in that abstract. It matched because glutoxim and thymalin are both indexed to the record, and nothing says which group got which.
The COVID-19 papers, and which number belongs to which hospital
The St Petersburg study is the earlier of the two that are readable in full (PMC7877506): open label, randomised by the envelope method, at City General Hospital No. 2 in 2020. Forty two patients got standard care plus 10 mg of thymalin into a muscle once daily for 5 days and 50 got standard care alone, with no dummy injection. The first line of its results says there were no deaths in any of the groups, and the paper does not designate mortality as an endpoint.
The two arms were not on matched background treatment, which cuts against the result. Off label antiviral therapy went to 27 of 42 in the thymalin arm against 35 of 50 in the control, and lopinavir with ritonavir to 17 of 42 against 28 of 50.
The Chita trial is the source of the sentence sellers repeat (PMC8654498). Eighty critically ill older patients at Chita State Medical Academy Hospital, 6,000 km east of St Petersburg, allocated by an independent statistician with the treating doctors kept unaware: 36 on 10 mg of thymalin into a muscle daily for 10 days, 44 on standard care plus a saline injection. Hospital mortality was 7 of 36 against 18 of 44, at a p value of 0.039, meaning a gap that size or bigger would come up by chance about four times in a hundred if the drug did nothing.
Read what that endpoint was. Mortality was a secondary one, meaning it was not the question the trial was built to answer. Of the three primary endpoints one was met, more patients improving clinically on thymalin, 29 of 36 against 26 of 44, and two were not: the treated group took longer to get there, 8.63 days against 7.61, and the day 14 lung scan improvement was 11 of 36 against 10 of 44. Neither of those two reached statistical significance, the time difference at p 0.41 and the scan difference at p 0.43.
A 2022 paper comparing three regimens gives hospital mortality of 40.9 percent on standard therapy, 28.4 percent with tocilizumab and 20.6 percent with thymalin in its English abstract, and 40.9, 28.8 and 16.2 percent in the Russian abstract on the same PubMed record (PMID 36169363). Four figures circulate, then, and zero deaths in St Petersburg does not contradict 19.4 percent in Chita: St Petersburg enrolled moderate to severe patients, Chita critical ones.
Whose evidence it is, and where it is going
On Epithalon the borrowing ran backwards: a synthetic four amino acid chain inherited the clinical record of Epithalamin, the cow pineal extract it was designed from. Thymalin is the opposite case. The extract is what was registered, what was studied and what is sold, and nothing took its record.
It is being lent forward instead. The 2021 Advances in Gerontology paper says the mechanism of Thymalin's immunoprotective action is due to the short peptides KE, EW and EDP in its composition, which bind to DNA or to histones, the spools DNA winds around. The 2023 paper is blunter: KE and EW dipeptides are active substances of Thymalin. KE is Lys-Glu, sold as Vilon; EW is Glu-Trp, sold as Thymogen, which a 2020 paper from the same group calls a dipeptide isolated from thymalin with similar effects. Both can be weighed and confirmed on a certificate, which the extract cannot. That is the trade on offer: an argument built out of calf glands, attached to a molecule a buyer can verify.
One note on how carefully that claim is being handled. The cell experiment under it is Khavinson's own: thymalin raised CD28, a marker of mature T cells, on human blood forming stem cells by 6.8 times, in an abstract that gives no concentration, no donor count and no duration (PMID 33237528). The Chita paper cites that exact reference and writes that thymalin reduced CD28 by 6.9 fold. Wrong direction, wrong figure, same senior author, both papers free to read.
Where the 10 mg came from
Unlike most entries here, the answer is not nowhere. It is the label and the vial.
The registered label gives adults 5 to 20 mg daily into a muscle over 3 to 10 days, 30 to 100 mg per course, a repeat after 1 to 6 months, and the powder dissolved in 1 to 2 mL of saline. That is what a licensed label says, not a recommendation from me. Its own numbers do not close, either: 5 mg for 3 days is 15 mg, under its 30 mg course floor, and 20 mg for 10 days is 200 mg, double its 100 mg ceiling. That is the label's arithmetic, not mine.
What circulates, reported as convention and not as advice, is 10 mg a day for 5 to 10 days with courses repeated every 6 to 12 months. One dosage guide credits Khavinson clinical protocols and then says its dosing comes from those protocols and community experience, not from approved pharmaceutical labeling. There is approved labeling, and the number is on it. Ten milligrams a day sits inside the label's 5 to 20 mg range and below its midpoint of 12.5 mg, is one whole vial, and is the dose in all five published human uses I could open, from the geroprotection cohort of the 1990s to the Chita ward in 2020. The course arithmetic lands inside the label too: 10 mg for 5 days is 50 mg and for 10 days is 100 mg, both within its 30 to 100 mg range. Nothing drifted on quantity.
The drift is route. The label lists injection into a muscle and no other, and every human dose I found in a paper went that way. The same guide offers injection under the skin at the same 10 mg as an easier way to self administer. I searched PubMed for thymalin and subcutaneous and got 8 records; one, a 1998 paper, gives thymalin under the skin to CBA mice and broiler chickens and reports it stimulated the immune response only at the injection site. The rest are the synthetic dipeptide Glu-Trp, a parasite study in mice, or Russian animal and clinical work. I found no published human study giving thymalin under the skin.
A second page prints a number and gets it wrong: 30 units once daily under the skin, which it calls approximately 30 mcg. Thirty units is 0.3 mL, and a 10 mg vial made up in the 1 to 2 mL the label specifies holds 3 mg or 1.5 mg in that volume, so the figure is out by a factor of 50 to 100. Its own next line gives it away, saying a vial lasts about 7 injections. It cites no study.
What the regulators have on file
In Russia this is a registered medicine, classified L03AX, other immunostimulants. Pharmacy listings also show an older number, ЛС-000267, which I could not confirm against the register; two of Khavinson's papers give it with a date of 26 February 2010 and a third says the Ministry of Health approved thymalin in 1982. Those are journal statements, not register entries.
Outside Russia I found nothing: no FDA approval, no FDA bulk drug substance listing, no European Medicines Agency authorisation. ClinicalTrials.gov, the United States government's trial registry, returned 0 studies for it, and the EU register no match.
The indications section, as both Russian drug references transcribe it, covers immunodeficiency states with depressed cellular immunity: septic processes with bone destruction, infection, suppressed immunity after chemotherapy. The selling is thymic rejuvenation and longevity in healthy adults. Only one of those has a document behind it.
What could go wrong
The label's entire adverse effects entry, on both Russian drug references I could open, is two words: allergic reactions. Contraindications are hypersensitivity, pregnancy and breastfeeding. That is the whole safety text.
My searches did not fill it in. Thymalin with toxicity, safety, adverse or side effect returns 21 records, and reading the titles I found no repeat dose toxicology, carcinogenicity, genotoxicity or pharmacokinetic study among them. For an extract with no defined molecule there is no single analyte to measure anyway, the problem Cerebrolysin's label states about itself.
It is also a tissue extract from cattle, and I found no statement in either label transcription about source herd status or about transmissible spongiform encephalopathy, the family that includes BSE. A gap in what I could read, not a finding.
The animal work that might fill the gap does not print the numbers to do it with. A 2018 Russian study reports a pronounced antitumour effect in albino outbred male rats carrying transplanted sarcoma 45, growth arrest or regression in more than half of them, at doses the abstract calls lower than the therapeutic ones and never states, and it gives no route, no group size and no duration either (PMID 29797130). A 2024 study put 48 WAG rats into four groups of 12, a jaw defect alone, a defect with a bone graft, a defect with thymalin injected into the soft tissue around it, and a defect with both, so 24 of the 48 got thymalin. The faster clearance of dead tissue is reported for the group that got the graft and the thymalin together, and no dose is printed anywhere. I have not established a milligram per kilogram figure in any species from a source I opened.
What we do not know
Whether it does anything to a thymus. The pitch is thymic rejuvenation, and I found no measurement of thymic output in a person given thymalin, by the blood test that counts newly made T cells or by imaging.
What a dose under the skin delivers. I found no human study by that route and no pharmacokinetic study by any route in any species.
Which mortality figure is right. Four circulate for COVID-19, and one paper's own two abstracts disagree about the treated group.
What is in a vial sold outside Russia. A certificate of analysis has nothing to settle it against, because a mixture has no reference standard to be a percentage of.
What this adds up to
Thymalin has the cleanest dose derivation on this site and the murkiest identity. The 10 mg traces to a licensed label, to one vial's contents and to five published human uses across 25 years, and none of that tells you what is in the vial you bought.
The Russian literature does not deserve to be waved away, and where the arithmetic could be checked it closed: every fold in the 2003 abstract reproduces from the counts in its own table. The seller's sentence is a different matter. Thymalin halved hospital mortality comes from a secondary endpoint in a trial that met one of its three primary endpoints and missed the other two, and whose treated group took longer to improve. And 266 is not a trial. It is three cohorts added together, and 24 people got Thymalin by itself.
The lending forward is the part to watch. If KE and EW really are the active substances, Vilon and Thymogen inherit an argument built out of calf glands, and two amino acids made in a factory do not come with 293 papers.
If you have bought Thymalin, read the composition line the seller printed. Does it say thymus extract, or does it give you a sequence and a molecular weight? Those are two different products, and one of them is thymulin.
Frequently asked
Is Thymalin an approved medicine?
In Russia, yes. Тималин is a registered prescription medicine, marketing authorisation ЛП-№(005867)-(РГ-RU) dated 21 June 2024, held by Samson-Med LLC of St Petersburg, supplied as a freeze dried powder for a solution injected into a muscle and classified L03AX, other immunostimulants. Its licensed indications are immunodeficiency states with depressed cellular immunity, not longevity. I found no FDA approval, no FDA bulk drug substance listing and no European Medicines Agency authorisation, and ClinicalTrials.gov returned no studies for it by term or by intervention.
What is Thymalin actually made of?
Calf thymus. The Russian label names the active substance as тимуса экстракт, thymus extract, 10 mg per vial, with a footnote saying it comes from the thymus glands of calves and young cattle up to one year old, and 20 mg of glycine as the only other ingredient. Because it is an extract rather than a single molecule there is no sequence and no molecular weight for a certificate of analysis to confirm, so a lab report has no reference standard to measure a vial against, and cannot show you that two vials hold the same material.
Did Thymalin really extend life in 266 people?
The paper is real and 266 is not a trial. Khavinson and Morozov reported three cohorts at two institutions added together: 94 women at a St Petersburg war veterans home randomised four ways, a separate 20 given two agents annually for six years, and 152 people in Kiev randomised three ways on a different schedule. Twenty four received Thymalin on its own, and in that arm 10 of 24 died over six years against 18 of 22 in the placebo arm. The St Petersburg women were aged 66 to 94 and all lived in the same home.
Did Thymalin halve COVID-19 hospital mortality?
That sentence comes from one trial in Chita, Russia, and mortality was a secondary endpoint in it. Eighty critically ill older patients were randomised, 36 to thymalin into a muscle on top of standard care and 44 to standard care plus a saline placebo injection, and hospital mortality was 7 of 36 against 18 of 44. Of the three primary endpoints, one was met, more patients improving clinically on thymalin, and two were not: the treated group took slightly longer to improve, and the day 14 lung scan difference did not reach significance. A separate open label study of 92 patients in St Petersburg recorded no deaths in either arm.
What doses were used, and what do people take?
The registered Russian label, which is a licensed dosing table and not a recommendation from this site, gives adults 5 to 20 mg daily into a muscle over 3 to 10 days, 30 to 100 mg per course, with a repeat course after 1 to 6 months, and smaller amounts for children by age band. What circulates outside a clinic, reported here as convention rather than advice, is 10 mg a day for 5 to 10 days with courses repeated every 6 to 12 months. That sits inside the label range and matches the trial dose: 10 mg into a muscle daily was what patients received in the geroprotection study, in both COVID-19 studies and in the published case report.
Has injecting Thymalin under the skin been studied?
Not in people, as far as I could find. The Russian label lists a solution for injection into a muscle and no other route, and every human dose I found in a paper went into a muscle. I searched PubMed for thymalin and subcutaneous and got 8 records: one 1998 paper does give thymalin under the skin, to CBA mice and broiler chickens, and reports it stimulated the immune response only at the injection site, while the rest concern a synthetic dipeptide, a parasite study in mice, or Russian animal and clinical work. I also found no pharmacokinetic study of thymalin by any route, so there is no established way to say what a dose under the skin delivers.
Is Thymalin the same as thymulin or thymosin alpha-1?
They are three different substances and their evidence does not transfer. Thymalin is a calf thymus extract with no defined structure. Thymulin is a nine amino acid hormone, CAS 63958-90-7, with its own literature, and at least one vendor page and one chemical database record treat the two names as interchangeable, which they are not. Thymosin alpha-1 is a defined 28 amino acid peptide with separate trials and a separate regulatory history. Khavinson's group also now describes two dipeptides, KE and EW, sold as Vilon and Thymogen, as the active substances of Thymalin, which is an argument about mechanism rather than a transfer of the clinical record.
This content is for educational and informational purposes only and is not medical advice. Peptides discussed are research compounds and may not be approved for human use. Nothing here should be used to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before starting any peptide, supplement, or protocol. Individual responses vary. Do not self-administer compounds without proper medical supervision.
Get the next one in your inbox
Free. One email a week at most. Unsubscribe in one click.
Double opt-in · No spam · Unsubscribe anytime
More in Immune and thymic
- ARA-290 Has Real Randomised Trials, and Their Main Endpoint Was a Photograph of an EyeIts sequence does not appear in erythropoietin at all, which is the interesting part. Across a 1 mg to 8 mg range the response did not rise with the dose, the skin biopsy that diagnoses the disease did not move, and I found no trial registered anywhere after the 2017 announcement of progress.
- LL-37 Has a Human Dosing Record. I Found None of It Under the SkinThree randomised trials I found put it on a wound and one injected it into tumours. The largest missed its primary endpoint, its sponsor went into liquidation in October 2023, and the dose response ran backwards twice, the second time in a different molecule.
- Thymosin Alpha-1: The Approval and the Evidence Are for Different ThingsThe only European registration I could verify is Italian, and its indication section is one sentence about influenza vaccination in immunocompromised patients. The two largest placebo controlled trials I found, in sepsis and in hepatitis C, both came back null.