Thymalin (Russian: Тималин) is an injectable mixture of peptides extracted from the thymus glands of calves. It was developed by Vladimir Morozov and Vladimir Khavinson of the Institute of Bioregulation and Gerontology in St. Petersburg (Morozov and Khavinson, Int J Immunopharmacol 1997). In Russia it is a registered prescription drug, classed as an immunostimulant, and is labeled for immune deficiency linked to infections, thymus damage and cancer treatment (Vidal: Thymalin).

Thymalin is not a single molecule, and it is not an anabolic agent. It is also a different product from thymulin, thymosin alpha-1 and TB-500, despite the similar names. It is sometimes described as an “anti-aging” peptide. Most of that claim traces to a single study from the developers’ own institute, and nearly all of the clinical data are small Russian-language reports.

This page summarizes what the Russian product information, clinical studies and lab research report. It is for education only and is not medical advice.

Property	Detail
Drug class	Animal-derived thymus peptide extract; classed in Russia as an immunostimulant (ATC code L03AX, other immunostimulants)
Brand / holder	Thymalin (Тималин), Samson-Med LLC, Russia; registration ЛП-№(005867)-(РГ-RU), June 21, 2024
Composition	10 mg of thymus extract per vial, from the thymus glands of calves and cattle under one year old, with 20 mg glycine, as a freeze-dried powder
Route	Intramuscular injection
Labeled adult dose	5–20 mg once daily for 3–10 days (30–100 mg per course)
Half-life	Not established: no human pharmacokinetic data are published, and the product information gives none
Mechanism	Not established; the label describes effects on T and B lymphocytes and phagocytosis
US status	We found no FDA or EMA approval; not named as a controlled substance
WADA status	Not named on the 2026 Prohibited List

What it is

The Russian product information lists one active ingredient, “thymus extract,” made from the thymus glands of calves and young cattle up to one year old. Each vial holds 10 mg of extract and 20 mg of glycine (Vidal: Thymalin). The developers describe it as a complex of natural peptides obtained from calf thymus by mild acid extraction (Morozov and Khavinson 1997). No published analysis lists every peptide in the mixture.

The same group later reported that short peptides in thymalin carry much of its activity:

Glu-Trp (EW). A dipeptide of glutamic acid and tryptophan, isolated from thymalin by high-performance liquid chromatography. It was then made synthetically and sold as a separate drug, Thymogen (Morozov and Khavinson 1997). The library covers it as Thymagen.
Lys-Glu (KE). A 2023 paper from the developers’ institute called KE and EW the “active substances” of thymalin. Its evidence came from computer modeling and cell culture (Linkova et al., Int J Mol Sci 2023).

Thymalin belongs to a family of organ extracts from the same group, each made from a different cattle tissue, such as epithalamin from the pineal gland. Synthetic short peptides were later designed from these extracts, including Epitalon from epithalamin (Khavinson, Neuro Endocrinol Lett 2002). A comparison study lists Cortexin, from the brain cortex, among the calf-tissue polypeptide products alongside thymalin (Ryzhak et al., Adv Gerontol 2015).

How it differs from other thymus peptides

Several unrelated products are named after the thymus. They differ in what they are and in their evidence, and results for one cannot be applied to another:

Product	What it is	Library page
Thymalin	A natural mixture of peptides extracted from calf thymus; registered in Russia	This page
Thymagen (Thymogen)	A single synthetic dipeptide (Glu-Trp) first isolated from thymalin	Thymagen
Thymulin	A single defined thymic peptide hormone (serum thymic factor)	Thymulin
Thymosin alpha-1 (thymalfasin)	A single defined synthetic peptide	Thymosin Alpha-1
Thymosin beta-4 / TB-500	A different thymus-derived peptide and a short synthetic fragment of it	TB-500 (Thymosin Beta-4)
Epitalon	A synthetic peptide designed from the pineal extract epithalamin, not from the thymus	Epitalon

How it works in the body

The Russian product information states that thymalin restores impaired immune reactivity. It describes the drug as regulating the number and ratio of T and B lymphocytes, stimulating cell-mediated immunity and enhancing phagocytosis (the engulfing of microbes by immune cells). It also claims that thymalin stimulates tissue repair and blood-cell formation when these are suppressed (Vidal: Thymalin).

Mechanistic studies come almost entirely from the developers’ institute and are lab-based:

Stem cells, in cell culture. Thymalin lowered markers of immature blood stem cells (CD44 and CD117) 2–3-fold and raised CD28, a marker of mature T cells, 6.8-fold. The authors read this as a push toward T-cell maturation (Khavinson et al., Bull Exp Biol Med 2020).
Inflammation, in cell culture. In blood immune cells from four donors stimulated with bacterial endotoxin, thymalin and its KE and EW dipeptides reduced the inflammatory signals IL-1β, IL-6 and TNF-α by 1.4–6.0-fold (Linkova et al. 2023).
Monocyte cell line. In a joint Italian–Russian study, thymalin and four related peptide products reduced endotoxin-driven TNF and IL-6 in a human monocyte cell line (Avolio et al., Int J Mol Sci 2022).

These are cell-culture results. They do not show what happens after an injection in people.

No human pharmacokinetic study of thymalin has been published, so its absorption, half-life and breakdown are unknown. As a mixture of many peptides, it has no single half-life to measure in the usual way.

Approved medical use in Russia

The Russian product information lists immune deficiency in adults and in children from 6 months to 14 years, in the following settings (Vidal: Thymalin):

infections with pus formation or sepsis;
lasting loss of thymus function, for example after radiation sickness, thymus tumors or surgical removal of the thymus;
acute and chronic viral and bacterial infections;
impaired tissue repair;
suppressed immunity and blood-cell formation after chemotherapy or radiotherapy for cancer.

It is given by intramuscular injection once daily:

Patient group	Daily dose	Course
Adults (treatment)	5–20 mg	3–10 days; 30–100 mg per course
Children 6–12 months	1 mg	3–10 days
Children 1–3 years	1.5–2 mg	3–10 days
Children 4–6 years	2–3 mg	3–10 days
Children 7–14 years	3–5 mg	3–10 days
Prevention, adults	5–10 mg	3–5 days
Prevention, children	1–5 mg	3–5 days

The course length depends on how severe the immune impairment is, and the label allows a repeat course after 1–6 months. It states that no dosing data exist for people with kidney or liver disease or for older adults. Thymalin is a prescription drug in Russia.

What the research shows

There are no controlled trials of thymalin for muscle, strength, body composition or athletic performance, and we found no studies of these outcomes.

Aging and lifespan

The main source of thymalin’s “longevity” reputation is a study by its developers. They reported on 266 older people followed for 6–8 years, who received thymalin, epithalamin or both during the first 2–3 years (Khavinson and Morozov, Neuro Endocrinol Lett 2003):

Group	Reported mortality vs control
Thymalin	2.0–2.1-fold lower
Epithalamin	1.6–1.8-fold lower
Thymalin plus epithalamin	2.5-fold lower
Thymalin plus epithalamin, given every year for 6 years	4.1-fold lower

The authors also reported 2.0–2.4-fold fewer acute respiratory infections and less heart disease, high blood pressure, osteoarthritis and osteoporosis.

The abstract does not state how people were assigned to groups, whether anyone was blinded, how large each group was, what doses were used, or how deaths were analyzed. The authors developed both products. We found no independent study that has repeated these results. A mortality difference this large, from small groups without described randomization, should be treated as unconfirmed.

COVID-19

Thymalin was tested as an add-on in hospitalized COVID-19 patients in Russia in 2020. In a single-center, open-label randomized trial, 92 adults with moderate or severe disease, pneumonia and low lymphocyte counts received standard care with or without thymalin 10 mg intramuscularly once daily for 5 days (Khavinson et al., Stem Cell Rev Rep 2021). Both groups also received anticoagulants and nearly all received antibiotics; many received off-label antivirals and some received dexamethasone.

Outcome	Standard care (n = 50)	Standard care + thymalin (n = 42)
Deaths	None	None
Worsening on chest CT	5 patients	2 patients
Fall in C-reactive protein (inflammation marker)	1.7-fold	9.7-fold
Fall in D-dimer (clotting marker)	2.1-fold	5.7-fold
Fall in IL-6	1.41-fold	5.5-fold
T-cell measures	No improvement reported	Lymphocytes +55%; T cells +63.8%

The outcomes were laboratory markers, not survival or recovery. The trial was not blinded, the groups received somewhat different mixes of other drugs, and thymalin’s developer was among the authors.

A second Russian study compared standard care, standard care plus tocilizumab (an IL-6 blocking antibody) and standard care plus thymalin in severe COVID-19 in middle-aged and older patients (Kuznik et al., Adv Gerontol 2022). The English abstract reports hospital mortality of 40.9%, 28.4% and 20.6% in the three groups. The Russian abstract of the same paper gives 40.9%, 28.8% and 16.2%. Neither abstract gives group sizes or says whether patients were randomized, so these figures cannot be weighed.

Cancer and other conditions

Many small Russian and Ukrainian reports from the 1980s to the 2000s describe thymalin added to treatment for cancer, tuberculosis, pancreatitis, chronic lymphocytic leukemia, Parkinson disease and dental conditions. Most were small, not blinded and often not randomized. For example, one report compared 38 women with advanced cervical cancer who received radiotherapy plus thymalin with 58 who received radiotherapy alone (Vishnevskaia et al., Vopr Onkol 1991). A Parkinson disease report had 15 patients and no control group (Musienko, Lik Sprava 1999).

Independent reviews have not assessed thymalin itself. The closest is a 2011 Cochrane review of thymus extracts in cancer, which pooled 26 randomized trials with 2,736 patients (Wolf et al., Cochrane 2011). Its extract trials used thymostimulin or thymosin fraction 5, not thymalin. Adding these extracts to cancer treatment did not improve survival (RR 1.00, 95% CI 0.79–1.25) or tumor response. It did lower the risk of severe infections (RR 0.54, 95% CI 0.38–0.78), but most trials had at least a moderate risk of bias. Because thymalin is a different extract, these results cannot be applied to it directly.

Side effects and risks

Reported side effects

The Russian product information lists only possible allergic reactions as side effects (Vidal: Thymalin). Published studies are small and short and rarely report adverse events in a systematic way, so uncommon or long-term risks are not known.

Who should not use it

According to the product information:

Contraindicated: known allergy to the extract or to glycine; pregnancy; breastfeeding.
Use with caution: people with a history of allergies.
Relative contraindications for bovine thymus peptide products: the days around menstruation, and some endocrine conditions such as pituitary adenoma and acromegaly. Side effects may be more frequent in people with severe endocrine disorders and in women in the second half of the menstrual cycle.
Alcohol is not recommended during treatment.

Interactions

The product information states that thymus extract can be combined with isoniazid, rifampicin, glucocorticoids, pain relievers and other immunostimulants. It advises against combining drugs with a similar mechanism. It also notes possible synergy with growth hormone, LH and estrogens. It describes thymalin’s effects on lymphoid tissue and bone marrow as opposite to those of progestins, androgens and adrenal hormones (Vidal: Thymalin).

Animal origin

Thymalin is made from cattle tissue, and each batch is a natural mixture rather than a defined chemical. The published product information does not describe how batches are standardized beyond their 10 mg content.

Legal status and use outside medicine

Russia. A registered prescription drug, held by Samson-Med (Vidal: Thymalin).
US and EU. We found no FDA or EMA approval. Thymalin is not named among the US controlled substances in Schedule III (21 CFR 1308.13).
Sport. Thymalin is not named on the 2026 WADA Prohibited List. Class S0 bans any substance not covered elsewhere on the list “with no current approval by any governmental regulatory health authority for human therapeutic use” (WADA 2026 Prohibited List). Thymalin holds a Russian registration, and we found no specific WADA ruling on it.

Key takeaways

A calf thymus extract, not a single peptide. Thymalin is a mixture of peptides from the thymus glands of young cattle, registered in Russia as an immunostimulant.
Not thymulin, thymosin alpha-1, TB-500 or epitalon. These are separate substances with separate evidence. Thymagen is a single synthetic dipeptide first isolated from thymalin.
Labeled for immune deficiency in Russia. The adult dose is 5–20 mg intramuscularly once daily for 3–10 days. No human pharmacokinetic data, including a half-life, are published.
The longevity claim is unconfirmed. The reported 2-fold lower mortality comes from one study by the developers that does not describe randomization, blinding or group sizes, and no independent study has repeated it.
Small, mostly Russian trials. The best-reported trial, in 92 COVID-19 patients, was open-label and measured lab markers rather than survival. No studies exist for muscle or performance.
Few documented side effects, little safety data. The label lists allergic reactions and rules out use in pregnancy and breastfeeding. Long-term risks have not been studied.

Sources

Vidal Russia. Thymalin (Тималин), lyophilisate for solution for intramuscular injection 10 mg: drug description (in Russian). Updated March 25, 2025. Vidal.
Morozov VG, Khavinson VK. Natural and synthetic thymic peptides as therapeutics for immune dysfunction. Int J Immunopharmacol. 1997;19(9-10):501–505. PubMed.
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):13377. PubMed.
Khavinson VK, Linkova NS, Kvetnoy IM, et al. Thymalin: activation of differentiation of human hematopoietic stem cells. Bull Exp Biol Med. 2020;170(1):118–122. PubMed.
Avolio F, Martinotti S, Khavinson VK, et al. Peptides regulating proliferative activity and inflammatory pathways in the monocyte/macrophage THP-1 cell line. Int J Mol Sci. 2022;23(7):3607. PubMed.
Khavinson VKh, Morozov VG. Peptides of pineal gland and thymus prolong human life. Neuro Endocrinol Lett. 2003;24(3-4):233–240. PubMed.
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 Rev Rep. 2021;17(1):285–290. PubMed.
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 (in Russian). Adv Gerontol. 2022;35(3):368–374. PubMed.
Vishnevskaia EE, Khavinson VKh, Nikolaeva DV. The use of thymalin in the combined treatment of patients with disseminated cancer of the cervix uteri (in Russian). Vopr Onkol. 1991;37(1):86–90. PubMed.
Musienko GV. Thymalin in the combined treatment of parkinsonism patients (in Russian). Lik Sprava. 1999;(1):119–122. PubMed.
Wolf E, Milazzo S, Boehm K, Zwahlen M, Horneber M. Thymic peptides for treatment of cancer patients. Cochrane Database Syst Rev. 2011;(2):CD003993. PubMed.
World Anti-Doping Agency. The 2026 Prohibited List. In effect January 1, 2026. WADA 2026 Prohibited List.
US Code of Federal Regulations. 21 CFR 1308.13, Schedule III. 21 CFR 1308.13.
Khavinson VKh. Peptides and ageing. Neuro Endocrinol Lett. 2002;23(Suppl 3):11–144. PubMed.
Ryzhak AP, Chalisova NI, Lin’kova NS, et al. Polypeptides influence on tissue cell cultures regeneration of various age rats (in Russian). Adv Gerontol. 2015;28(1):97–103. PubMed.

Thymalin