A hormone made only by the epithelial cells of the thymus. It is a chain of 9 amino acids that becomes active when a zinc ion binds to it, and it helps T cells mature. It was first called facteur thymique serique (FTS), and its international drug name is nonathymulin.

Research peptides

Thymulin: What the Thymus Peptide Is, the Research and Legal Status

Thymulin is a zinc-dependent thymus hormone. What the human and animal research shows, how it differs from Thymalin and Thymagen, and its US status.

Written bySebastian Hunter, Founder and EditorI'm a 42-year-old senior advisor and distance runner who came to peptides as a sceptic. I'm not a doctor: I read the research, run my own experiment and keep honest notes. Read full bio

Published October 3, 2026

The short version

Thymulin is a hormone made by the thymus: a chain of 9 amino acids that works only with zinc bound to it. Most of its research is in animals and cells. A few small human studies ran in the 1980s. Trials in rheumatoid arthritis reported a benefit at one dose, and a trial in multiple sclerosis found none. It is not FDA-approved and is sold as a research chemical. Thymalin, Thymagen and thymosin alpha-1 are different substances.

A few small human trials ran in the 1980s, with mixed results. The latest I found was published in 1989.
Its activity depends on zinc. Zinc-deficient people have low thymulin activity, and zinc restored it in small studies.
Not FDA-approved. FDA lists it among compounding nominations made without enough support to evaluate.
Thymalin is a calf-thymus extract and Thymagen is a 2-amino-acid peptide. Neither is thymulin, though some vials labelled Thymalin contain it.

Thymulin is a hormone made by the thymus gland: a chain of 9 amino acids that works only with a zinc ion bound to it. It was tested as an immune drug in a few small trials in the 1980s. It is not FDA-approved, and vendors sell it as a research chemical.

It is often mixed up with Thymalin, Thymagen and thymosin alpha-1, which are different substances. See how the names differ.

What is thymulin?

Thymulin was discovered in the early 1970s Reggiani 2009 - Reggiani PC, Morel GR, Cónsole GM et al. The thymus-neuroendocrine axis: physiology, molecular biology, and therapeutic potential of the thymic peptide thymulin. Ann N Y Acad Sci. 2009;1153:98-106., in the references below. Its first name was French: facteur thymique sérique (FTS), or serum thymic factor. In 1977 researchers isolated it from pig serum and worked out its sequence: pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn. A lab-made copy had the same activity as the natural peptide Pleau 1977 - Pleau JM, Dardenne M, Blouquit Y et al. Structural study of circulating thymic factor: a peptide isolated from pig serum. II. Amino acid sequence. J Biol Chem. 1977;252(22):8045-7., in the references below.

Zinc turns it on. In 1982 the same researchers found that FTS stripped of zinc lost its activity in a lab assay, and adding zinc back restored it. They named the active, zinc-bound form thymulin Dardenne 1982 - Dardenne M, Pléau JM, Nabarra B et al. Contribution of zinc and other metals to the biological activity of the serum thymic factor. Proc Natl Acad Sci U S A. 1982;79(17):5370-3., in the references below.

Only the epithelial cells of the thymus make it. It helps T cells mature, and the nervous and hormone systems influence how much the thymus releases Reggiani 2009 - Reggiani PC, Morel GR, Cónsole GM et al. The thymus-neuroendocrine axis: physiology, molecular biology, and therapeutic potential of the thymic peptide thymulin. Ann N Y Acad Sci. 2009;1153:98-106., in the references below. Its international drug name is nonathymulin, the name used in the 1987 and 1989 trials and in PubChem.

Limited human data

Small or uncontrolled human studies. Too little to settle the question either way. Five small human studies gave thymulin to people between 1982 and 1989: case reports in 3 children, a 4-patient study, two placebo-controlled trials in rheumatoid arthritis that reported a benefit at one dose, and a 40-patient placebo-controlled trial in multiple sclerosis that found none. Most other research is in animals and cells.

Thymulin benefits: what the research shows

Studies in people

These are the human studies I found that gave thymulin, as synthetic FTS or nonathymulin:

1982, 3 children with immune deficiency. Given synthetic FTS intravenously, they had fewer and milder infections and better immune test results. Two began making IgA antibodies they had lacked. In two, the gains faded when treatment paused and returned when it restarted Bordigoni 1982 - Bordigoni P, Faure G, Bene MC et al. Improvement of cellular immunity and IgA production in immunodeficient children after treatment with synthetic serum thymic factor (FTS). Lancet. 1982;2(8293):293-7., in the references below.
1983, 4 people with cancer. They got 10 micrograms per kilogram intravenously every 3 days. Natural killer (NK) cell activity rose in the 2 with low starting levels and fell in the 2 with normal or high levels Dokhelar 1983 - Dokhelar MC, Tursz T, Dardenne M et al. Effect of a synthetic thymic factor (facteur thymique serique) on natural killer cell activity in humans. Int J Immunopharmacol. 1983;5(4):277-82., in the references below.
1987, rheumatoid arthritis. Two double-blind, placebo-controlled trials compared 1, 5 and 10 mg a day. The 5 mg dose did best: 56% of patients improved on an overall assessment, against 17% on placebo. Side effects were minimal, and immune measures showed no clear change Amor 1987 - Amor B, Dougados M, Mery C et al. Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials. Ann Rheum Dis. 1987;46(7):549-54., in the references below. The abstract gives no patient numbers.
1989, multiple sclerosis. 40 patients had nonathymulin or a placebo injected under the skin for 6 months. Disability scores did not differ between the groups, and no significant side effects were recorded Roullet 1989 - Roullet E, Cesaro P, Simon-Lavoine N et al. Nonathymulin treatment of multiple sclerosis: double-blind pilot study. Acta Neurol Scand. 1989;80(6):575-8., in the references below.

Studies in animals and cells

Pain and inflammation, rats and mice. Tiny doses (20-150 nanograms) made rats more sensitive to pain and doubled an inflammatory signal, IL-1 beta, in the liver Safieh-Garabedian 1997 - Safieh-Garabedian B, Kanaan SA, Jalakhian RH et al. Hyperalgesia induced by low doses of thymulin injections: possible involvement of prostaglandin E2. J Neuroimmunol. 1997;73(1-2):162-8., in the references below. Higher doses reduced pain caused by endotoxin-induced inflammation in rats and mice Safieh-Garabedian 1996 - Safieh-Garabedian B, Jalakhian RH, Saadé NE et al. Thymulin reduces hyperalgesia induced by peripheral endotoxin injection in rats and mice. Brain Res. 1996;717(1-2):179-83., in the references below. A modified version, the peptide analogue of thymulin (PAT), reduced inflammatory pain without thymulin’s pain-sensitising effect Dardenne 2006 - Dardenne M, Saade N, Safieh-Garabedian B. Role of thymulin or its analogue as a new analgesic molecule. Ann N Y Acad Sci. 2006;1088:153-63., in the references below.
Ageing and cancer, mice, 2026. Thymulin declines with age. Older mice and people had more inflammatory immune cells of a type called myeloid cells, and thymulin damped their inflammatory signalling. In older mice with tumours, it improved tumour control and made the tumours respond to anti-PD-L1 immunotherapy. It did little in young mice Kanemaru 2026 - Kanemaru H, Luong S, Yamamoto Y et al. Thymulin restrains age-associated myeloid inflammation and enhances cancer immunotherapy. Nat Commun. 2026;17(1)., in the references below.
Gene therapy, mice. A gene for a thymulin analogue, given to newborn mice born without a thymus, prevented the ovarian failure these mice usually develop Reggiani 2012 - Reggiani PC, Barbeito CG, Zuccolilli GO et al. Neonatal thymulin gene therapy prevents ovarian dysgenesis and attenuates reproductive derangements in nude female mice. Endocrinology. 2012;153(8):3922-8., in the references below. Inhaled nanoparticles carrying a thymulin gene reversed the main features of allergic asthma in mice da 2020 - da Silva AL, de Oliveira GP, Kim N et al. Nanoparticle-based thymulin gene therapy therapeutically reverses key pathology of experimental allergic asthma. Sci Adv. 2020;6(24):eaay7973., in the references below.

Thymulin and zinc

Thymulin needs zinc to work, so zinc status shows up in thymulin levels. In people, the studies that raised thymulin did it by correcting a zinc deficiency.

Mice. On a mildly zinc-deficient diet, blood thymulin fell within 2 months. Adding zinc to the blood samples in the lab restored it. The thymus was most likely still releasing the peptide, just without its zinc Dardenne 1984 - Dardenne M, Savino W, Wade S et al. In vivo and in vitro studies of thymulin in marginally zinc-deficient mice. Eur J Immunol. 1984;14(5):454-8., in the references below.
Mild zinc deficiency in people. Thymulin activity fell in 2 volunteers made mildly zinc-deficient by diet. It was also low in 12 mildly deficient adults, half of them with sickle cell anaemia. Zinc corrected it Prasad 1988 - Prasad AS, Meftah S, Abdallah J et al. Serum thymulin in human zinc deficiency. J Clin Invest. 1988;82(4):1202-10., in the references below.
Crohn’s disease. In 27 patients with low zinc, 200 mg a day of zinc sulphate for 3 months restored thymulin. 60 mg a day and placebo did not Brignola 1993 - Brignola C, Belloli C, De Simone G et al. Zinc supplementation restores plasma concentrations of zinc and thymulin in patients with Crohn's disease. Aliment Pharmacol Ther. 1993;7(3):275-80., in the references below.
Older adults. In 44 people in care homes with low blood zinc, 20 mg of zinc a day for 16 weeks partly restored thymulin activity Boukaïba 1993 - Boukaïba N, Flament C, Acher S et al. A physiological amount of zinc supplementation: effects on nutritional, lipid, and thymic status in an elderly population. Am J Clin Nutr. 1993;57(4):566-72., in the references below.

Active thymulin is also lower in older people than in younger ones, and adding zinc to their blood in the lab revives less of it Licastro 1990 - Licastro F, Savorani G, Sarti G et al. Zinc and thymic hormone-dependent immunity in normal ageing and in patients with senile dementia of the Alzheimer type. J Neuroimmunol. 1990;27(2-3):201-8., in the references below. None of these studies shows that raising thymulin improves health.

Thymulin vs Thymalin, Thymagen and thymosin alpha-1

Name	What it is	US status
Thymulin (FTS, nonathymulin)	9-amino-acid peptide, active only with zinc bound	Not FDA-approved; sold as a research chemical
Thymalin	A mix of peptides extracted from calf thymus	Not FDA-approved; FDA warned a seller in 2024
Thymogen, sold as “Thymagen” (oglufanide, IM862)	2-amino-acid peptide, Glu-Trp	Not FDA-approved; no better than placebo in a phase III trial
Thymosin alpha-1 (thymalfasin)	28-amino-acid peptide	Not FDA-approved; licensed in some other countries

Thymulin vs Thymalin

Thymalin is a Russian preparation: a complex of peptides from calf thymus Anisimov 2000 - Anisimov VN, Khavinson VK, Morozov VG. Immunomodulatory synthetic dipeptide L-Glu-L-Trp slows down aging and inhibits spontaneous carcinogenesis in rats. Biogerontology. 2000;1(1):55-9., in the references below. Researchers at the St Petersburg Institute of Bioregulation and Gerontology call it an immune drug and report its use in lung disease and severe COVID-19 Linkova 2023 - 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. Int J Mol Sci. 2023;24(17)., in the references below. Thymulin is one defined molecule.

The two names are often swapped. PubChem lists “Thymalin” as a synonym on the nonathymulin record. One research vendor, Oath Research, says vials sold under either name in this market are the synthetic nonapeptide, and lists them as the same material. Power Peptides’ Thymalin page gives thymulin’s CAS number next to a 31-amino-acid sequence. The label on a vial doesn’t settle what is in it, so read the batch COA.

What vendors sell as Thymagen

“Thymagen” is a vendor spelling of Thymogen, the dipeptide Glu-Trp. BioEdge Research Labs’ product page gives the sequence Glu-Trp, says PubChem indexes it as Thymogen, mentions the synonym oglufanide, and files it under bioregulators. Russian researchers isolated Glu-Trp from Thymalin and made it into a drug branded Thymogen Anisimov 2000 - Anisimov VN, Khavinson VK, Morozov VG. Immunomodulatory synthetic dipeptide L-Glu-L-Trp slows down aging and inhibits spontaneous carcinogenesis in rats. Biogerontology. 2000;1(1):55-9., in the references below. The Khavinson group counts Thymogen among its peptide bioregulators Khavinson 2013 - Khavinson VKh, Kuznik BI, Ryzhak GA. [Peptide bioregulators: the new class of geroprotectors. Message 2. Clinical studies results]. Adv Gerontol. 2013;26(1):20-37., in the references below. It names Glu-Trp and Lys-Glu (sold as Vilon) as Thymalin’s active substances Linkova 2023 - 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. Int J Mol Sci. 2023;24(17)., in the references below.

Glu-Trp has more human data than thymulin. It was tested under the code name IM862, which PubChem lists as a synonym:

A phase II trial gave 44 people with AIDS-related Kaposi sarcoma 5 mg as nasal drops. Of them, 36% had a major response. Side effects were mild headache, fatigue, tingling and nausea Tulpule 2000 - Tulpule A, Scadden DT, Espina BM et al. Results of a randomized study of IM862 nasal solution in the treatment of AIDS-related Kaposi's sarcoma. J Clin Oncol. 2000;18(4):716-23., in the references below.
The phase III trial, in 202 people, found no benefit over placebo: 23% responded against 21%. Median time to progression was 16 weeks on IM862 against 35 on placebo. The authors suggest HIV treatment alone produced many of the responses and may have inflated the earlier result Noy 2005 - Noy A, Scadden DT, Lee J et al. Angiogenesis inhibitor IM862 is ineffective against AIDS-Kaposi's sarcoma in a phase III trial, but demonstrates sustained, potent effect of highly active antiretroviral therapy: from the AIDS Malignancy Consortium and IM862 Study Team. J Clin Oncol. 2005;23(5):990-8., in the references below.

Thymulin vs thymosin alpha-1

Thymosin alpha-1 is a 28-amino-acid peptide first isolated from a calf-thymus fraction in 1977. Its drug name is thymalfasin. FDA has approved no product containing it, though it is approved in some countries in Asia, Latin America, Eastern Europe and the Middle East. Its trial record in sepsis and hepatitis is far larger than thymulin’s.

Thymulin side effects

I found no long-term human safety data, so there is no reliable side-effect list. The studies report:

The 1987 rheumatoid arthritis trials reported minimal adverse effects at up to 10 mg a day Amor 1987 - Amor B, Dougados M, Mery C et al. Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials. Ann Rheum Dis. 1987;46(7):549-54., in the references below.
The 1989 multiple sclerosis trial recorded no significant side effects over 6 months of injections Roullet 1989 - Roullet E, Cesaro P, Simon-Lavoine N et al. Nonathymulin treatment of multiple sclerosis: double-blind pilot study. Acta Neurol Scand. 1989;80(6):575-8., in the references below.
In rats, very low doses increased sensitivity to pain Safieh-Garabedian 1997 - Safieh-Garabedian B, Kanaan SA, Jalakhian RH et al. Hyperalgesia induced by low doses of thymulin injections: possible involvement of prostaglandin E2. J Neuroimmunol. 1997;73(1-2):162-8., in the references below. I found no study of this in people.

No regulator checks research vials for identity, purity or sterility. For the general risks of injecting under the skin, see peptide injection-site reactions.

Thymulin dosage

No regulator has set a thymulin dose, and I found no trial since 1989. The 1987 rheumatoid arthritis trials compared 1, 5 and 10 mg a day Amor 1987 - Amor B, Dougados M, Mery C et al. Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials. Ann Rheum Dis. 1987;46(7):549-54., in the references below. The 1983 study gave 10 micrograms per kilogram intravenously every 3 days Dokhelar 1983 - Dokhelar MC, Tursz T, Dardenne M et al. Effect of a synthetic thymic factor (facteur thymique serique) on natural killer cell activity in humans. Int J Immunopharmacol. 1983;5(4):277-82., in the references below.

The 3 online dosing guides I checked disagree by more than a thousandfold: one gives micrograms a day, another milligrams. With that spread, this page gives no dose.

Is thymulin legal?

US legal status - Research use only

Sold for laboratory research use only. Not approved by the FDA for human use, and cannot be lawfully marketed as a supplement or a medicine. Products sold this way are not made to pharmaceutical quality standards, and their contents are not verified by anyone.

Thymulin is not an FDA-approved drug. I found no FDA approval under thymulin or nonathymulin in openFDA’s drug-approval data on 3 October 2026. Research vendors sell it labelled for laboratory use only, not for human use.

It isn’t on the 503A Bulks List that pharmacies compound from. FDA lists thymulin acetate in Category 3 of the substances nominated for that list: nominated without enough supporting information for FDA to evaluate. FDA’s interim policy, which tolerates compounding from some nominated substances while they are reviewed, covers only Category 1. See the 503A Bulks List explained.

A research-use label does not stop FDA treating a product as a drug. In February 2024 FDA warned US Chem Labs that its “Thymalin” product was an unapproved new drug, despite labels saying “research chemicals only” and “not for human consumption”. FDA said it was particularly concerned the product was marketed for children.

The one US drug label I found that names thymulin is a homeopathic pellet, Thymuline 9C. DailyMed lists it as an unapproved homeopathic product for immune support, not evaluated by FDA.

Regulatory changes for this compound and others, as they happen: US peptide regulation tracker.

Where to buy thymulin, and what it costs

Research vendors sell thymulin as a freeze-dried powder in vials, labelled for research use only. As of 3 October 2026, a 10 mg vial cost $45 at BioEdge Research Labs and $65 at Oath Research. Oath’s 5 mg vial, $45, was out of stock.

Both product pages give the formula of the peptide alone, without zinc, and neither says whether the vial contains zinc. That matters because the peptide is inactive in lab tests until zinc binds to it Dardenne 1982 - Dardenne M, Pléau JM, Nabarra B et al. Contribution of zinc and other metals to the biological activity of the serum thymic factor. Proc Natl Acad Sci U S A. 1982;79(17):5370-3., in the references below.

I have reviewed BioEdge Research Labs but not Oath Research. Check any seller against the vendor checklist before buying.

Common questions

Is thymulin the same as thymalin?

No. Thymulin is one defined 9-amino-acid peptide. Thymalin is a Russian preparation of peptides extracted from calf thymus. The names get mixed up online. PubChem lists Thymalin as a synonym on the thymulin record, and one research vendor says the vials sold under either name are the same synthetic nonapeptide. Check the certificate of analysis rather than the label.

What is thymulin good for?

No use has been established in people. In the 1980s it was tested in children with immune deficiency, in rheumatoid arthritis (where one dose beat placebo) and in multiple sclerosis (where it did not). Animal studies have looked at inflammation, pain, asthma, reproductive development and age-related inflammation. None of that has led to an approved medicine.

Has thymulin been tested in humans?

Yes, but only in a few small studies between 1982 and 1989. Two placebo-controlled trials in rheumatoid arthritis reported that 56% of patients improved on 5 mg a day, against 17% on placebo. A 40-patient placebo-controlled trial in multiple sclerosis found no benefit. I found no later trial that gave thymulin to people.

What are the side effects of thymulin?

I found no long-term human safety data, so there is no reliable list. The rheumatoid arthritis trials reported minimal adverse effects, and the multiple sclerosis trial recorded no significant side effects over 6 months. In rats, very low doses increased sensitivity to pain. No regulator checks what research vials contain.

Is thymulin legal in the US?

It is not an FDA-approved drug, and it is sold as a research chemical labelled not for human use. FDA lists thymulin acetate in Category 3 of substances nominated for pharmacy compounding, meaning the nomination lacked enough support for FDA to evaluate it. In a 2024 warning letter, FDA treated a Thymalin product labelled research chemicals only as an unapproved new drug.

How do you increase thymulin?

The human studies I found that raised thymulin did it with zinc, in people low in zinc. Thymulin activity fell in people with mild zinc deficiency and recovered with zinc supplements. Zinc also restored it in patients with Crohn's disease and partly restored it in older adults, all of whom were low in zinc. These studies measured the body's own thymulin. They did not show that raising it improves health.

What is Thymagen?

Thymagen is a vendor spelling of Thymogen, the dipeptide Glu-Trp, whose international drug name is oglufanide. It has 2 amino acids; thymulin has 9. Russian researchers isolated it from the calf-thymus extract Thymalin. Under the code name IM862 it was tested in Kaposi sarcoma, and a 202-patient phase III trial found it no better than placebo.

Is thymalin safe?

FDA has not evaluated its safety. In February 2024 FDA warned a US seller that its Thymalin product was an unapproved new drug, and said it was particularly concerned the product was marketed for children. Most published research on Thymalin is in Russian: 220 of the 256 PubMed records.

What is the usual thymulin dose?

No regulator has set one, and I found no trial since 1989. The 1987 rheumatoid arthritis trials compared 1, 5 and 10 mg a day. The online dosing guides I checked disagree by more than a thousandfold, so this page gives no dose.

Is thymulin the same as thymosin alpha-1?

No. Both come from the thymus, but thymosin alpha-1 is a 28-amino-acid peptide with a much larger clinical trial record. Thymulin has 9 amino acids and is active only with zinc bound.

Is there a thymulin supplement?

Thymulin is sold as a research chemical in vials, not as an approved product. The only US drug label I found that names it is a homeopathic pellet, Thymuline 9C, listed on DailyMed as an unapproved homeopathic product for immune support. A 9C preparation is diluted 100-fold nine times over.

References (42 sources)

Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.