Immune & antimicrobial

Thymalin

Also called Thymaline, Timalin, Тималин, Calf thymus polypeptide extract

Thymalin is a mix of small protein pieces (peptides) taken from the thymus gland of young calves. It has been a prescription immune drug in Russia since the Soviet era, given as an injection into muscle ¹⁵. Most published studies on it are small and come from the group that developed it ²⁵. It is not an FDA-approved drug in the United States ⁹¹⁰.

Early human dataSome small human studies exist; evidence is limited.

New · under editorial review. Added October 28, 2026 by our automated research, with every claim sourced. A person has not checked this page yet; treat it with extra care. How we research

All printable flashcards

Illustrative chain. The exact sequence has not been published in a source we could verify.

At a glance

Type: Peptide
Size: Mixture of short peptides, not a single defined molecule. Its developers report that processing keeps peptides under 10 kDa [3], and that short peptides of up to about ten amino acids, including the dipeptides KE and EW and the tripeptide EDP, have been identified in it [2].
Origin: Thymalin is a polypeptide extract (complex) rather than a single synthetic peptide. The Russian product information describes each vial as 10 mg of thymus extract from calves and young cattle under one year old, with glycine as an added ingredient [1]. Because it is a natural mixture, it has no single sequence, formula or molecular weight. Some identified components were later made as separate synthetic drugs, such as the EW dipeptide (thymogen) and the KE dipeptide (vilon) [2].
Evidence: Early human data
US FDA status: Not FDA-approved. Not named on the FDA page of bulk substances that may pose significant safety risks in compounding (Category 2), as retrieved (page dated April 22, 2026) ¹⁰.

Overview

How it works

Described in the Russian product information (based mainly on developer studies): thymalin is presented as an immune modulator that helps restore disturbed immune responses, affects the numbers and balance of T and B white blood cells, supports cell-based immunity and boosts phagocytosis (the process where immune cells swallow germs) ¹. Proposed (lab and computer studies only): researchers suggest its short peptides, such as KE and EW, may bind DNA and change which genes are switched on; this comes from computer modeling ⁷. In human immune cells grown in a dish, thymalin lowered the inflammatory signals TNF-alpha and IL-1 beta after a bacterial-toxin challenge, and the KE and EW dipeptides lowered TNF-alpha ⁷. In blood stem cell cultures, thymalin was linked to signs that stem cells were maturing toward T cells ⁸. These ideas have not been confirmed by independent researchers.

What research shows

Randomized, single-blind trial (human, n=80, one hospital in Chita, Russia): adults with severe COVID-19 got thymalin plus standard care (n=36) or saline plus standard care (n=44). Hospital deaths were 19.4% with thymalin vs 40.9% without, and lymphocyte counts recovered more often. The study was small, and some co-authors are thymalin's developers ⁴.
Long-term studies in older adults (human, two small trials in St. Petersburg and Kiev, run by the developers): the authors reported fewer deaths and fewer respiratory infections over 6 to 8 years in people given courses of thymalin. Groups were small (for example, 24 thymalin vs 22 placebo in the St. Petersburg trial; 58 thymalin vs 48 control in Kiev). The authors describe the trials as placebo-controlled, but the methods are only briefly reported ³.
Developer review of clinical studies (human, mostly older Soviet-era studies): reports use in skin and bone infections, pneumonia and asthma in children, and immune support during cancer chemotherapy and radiation. Reported group sizes range from about 20 to several hundred patients, and many study summaries do not describe how controls were chosen or whether patients were randomized ⁵.
Cell study (human immune cells in a dish, cells from 4 donors): thymalin and its KE and EW dipeptides lowered some inflammatory signals after a bacterial-toxin challenge. Computer modeling suggested these dipeptides could bind DNA ⁷.
Cell study (human blood stem cells in a dish): thymalin lowered levels of two stem-cell markers by about 2 to 3 times and raised CD28, a marker of mature T cells, about 6.8 times ⁸.
Animal studies (guinea pigs, rats, mice): the developers report effects on immune cells and the thymus, blood clotting, and recovery after radiation ⁶.
The reviews summarizing thymalin research were written by Khavinson and colleagues and mostly cite their own group's work; many papers are in Russian-language journals, and independent replication was not found ²⁵.

Doses studied in people

Study or label	Dose used	Source
Russian official product information, adults, treatment of immune deficiency	5–20 mg intramuscularly once daily, 30–100 mg total per course	¹
Russian official product information, adults, prevention	5–10 mg intramuscularly once daily for 3–5 days	¹
Randomized trial in adults with severe COVID-19 (n=80)	10 mg intramuscularly once daily for 10 days, added to standard care	⁴
Long-term study in older women, St. Petersburg	10 mg intramuscularly once daily for 10 days per course (100 mg per course)	³
Long-term study in older adults, Kiev	10 mg intramuscularly per injection, 50 mg per course	³

These doses come only from the Russian product information and published human studies; they are listed for reference and are not a recommendation ¹³⁴.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Vial math

Many research vials hold 5 or 10 mg of powder. This table shows how much ends up in each mark on a U-100 insulin syringe for common amounts of added liquid. It is arithmetic only, not a dose.

Vial	Liquid added	Concentration	Per unit (0.01 mL)
5 mg	1 mL	5 mg/mL	50 mcg	Open in calculator
5 mg	2 mL	2.5 mg/mL	25 mcg	Open in calculator
5 mg	3 mL	1.67 mg/mL	16.7 mcg	Open in calculator
10 mg	1 mL	10 mg/mL	100 mcg	Open in calculator
10 mg	2 mL	5 mg/mL	50 mcg	Open in calculator
10 mg	3 mL	3.33 mg/mL	33.3 mcg	Open in calculator

More sizes: all vial sizes · How this works: Syringes and units · Reconstitution guide.

Safety

The Russian product information lists allergic reactions as the possible side effect. It says the drug should not be used by people allergic to its ingredients or during pregnancy and breastfeeding, and should be used with caution in people with a history of allergies ¹.
The developers report no side effects, but their papers do not include detailed, systematic safety data ³⁵.
No large independent long-term safety studies were found.
No independent data were found on the content, purity or sterility of thymalin products sold outside regulated pharmacies.
Thymalin is not an FDA-approved drug and was not found on the FDA compounding lists checked ⁹¹⁰.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Legal status

FDA: Not FDA-approved. Not named on the FDA page of bulk substances that may pose significant safety risks in compounding (Category 2), as retrieved (page dated April 22, 2026) ¹⁰.
Compounding: Not found on the FDA list of bulk drug substances nominated for 503A compounding, as retrieved (updated May 14, 2026). The list does include thymulin acetate, a different thymus-related substance ⁹.
Sports (WADA): Not named on the 2026 WADA Prohibited List ¹¹. The list's S0 class covers substances with no current approval by any government health authority; thymalin is registered in Russia ¹, but athletes should confirm its status with their anti-doping organization.
Other: According to the Vidal drug reference, thymalin is registered in Russia as a prescription drug (lyophilisate for intramuscular injection, 10 mg per vial) under registration certificate ЛП-№(005867)-(РГ-RU) dated 21 June 2024, held by SAMSON-MED ¹. Developer papers state it was first approved by the USSR Ministry of Health in November 1982 ³⁵.

Rules change often. See Legal status of peptides for how these categories work.

History

According to a review by its developers, V. G. Morozov and V. Kh. Khavinson developed a method in 1974 to isolate low-molecular-weight peptides from calf thymus, which led to thymalin, the first drug in what they call the peptide bioregulator class ⁶. The same review says this work built on experimental studies carried out at the Kirov Military Medical Academy since 1973 ⁶. Developer papers state that the USSR Ministry of Health approved thymalin for medical use on 10 November 1982 ³⁵. These two papers give different order numbers for the approval. According to the Vidal drug reference, thymalin remains registered in Russia as a prescription injectable product, with a registration certificate dated 21 June 2024 ¹.

Common questions

Is thymalin a single peptide?

No. It is a mixture of many small peptides extracted from calf thymus, so it has no single sequence or formula ¹². A few of its components, such as the KE and EW dipeptides, have been identified and studied on their own ²⁷.

Is thymalin an approved medicine?

It is a registered prescription drug in Russia ¹, and developer papers say it was first approved in the USSR in 1982 ³⁵. It is not an FDA-approved drug and was not found on FDA's 503A compounding nominations list as retrieved ⁹.

How strong is the evidence?

There is one small randomized trial in severe COVID-19 with 80 patients ⁴, plus older and smaller studies in many conditions ³⁵. Most of this work comes from the developers' group, and large independent trials were not found ²⁵.

Is thymalin the same as thymosin alpha-1 or thymulin?

No. Thymalin is a natural extract mixture ¹, while thymosin alpha-1 and thymulin are separate substances. The FDA compounding nominations list includes thymulin acetate but not thymalin ⁹.

What side effects are known?

The Russian product information lists allergic reactions as possible and advises against use in pregnancy and breastfeeding ¹. The developers report no side effects, but detailed independent long-term safety data were not found ³⁵.

Is thymalin banned in sports?

It is not named on the 2026 WADA Prohibited List ¹¹. Athletes should check its status with their anti-doping organization.

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Cortagen

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LL-37

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LL-37 is the only cathelicidin-type germ-fighting peptide made by the human body.

Sources

Last reviewed 2026-10-28 · How we research · Found an error? See our corrections policy.