Thymalin vs Thymosin Alpha-1
Research Comparison

Research Overview

Thymalin vs thymosin alpha 1 compares a preparation with a molecule. Thymalin's developers isolated natural thymic peptides from calf thymus by mild acid extraction and put the pharmaceutical containing them into practice as thymalin (Morozov and Khavinson, 1997); a later review from the same group calls it a drug based on the thymus polypeptide complex (Khavinson et al., 2020). Thymosin alpha-1 is one sequence: a heat-stable, highly acidic peptide of 28 residues, isolated from calf thymus, sequenced in 1977 and described as one of several peptides in thymosin fraction 5 (Goldstein et al., 1977).

Both were first isolated from calf thymus, but through separate programs, and are defined differently: thymalin by how it is made, thymosin alpha-1 by its sequence. Disguised Alpha supplies Thymalin (10MG) and Thymosin Alpha-1 (listed in 5MG and 10MG) as lyophilized powders for laboratory research use only.

Composition and Class

Thymalin has no single sequence, formula or molecular weight, and its product page lists none. Its developers isolated one of its molecules, the dipeptide L-Glu-L-Trp, by reversed-phase HPLC and based the drug thymogen on the synthesized dipeptide, and they describe vilon, the dipeptide Lys-Glu (PubChem CID 7010502), as a novel dipeptide made by synthesis (Morozov and Khavinson, 1997).

A 2023 paper from the same group calls the KE (Lys-Glu) and EW (Glu-Trp) dipeptides active substances of thymalin (Linkova et al., 2023). Larger molecules have been reported too: an immunochemical study found a thymus protein antigen of about 12 kDa as a constant component of several thymus preparations, thymalin among them, at 1.6 to 3.2 percent (Falageeva and Kalashnikov, 1988).

A PubChem name search for thymalin returns CID 3085284, titled nonathymulin (C33H54N12O15, 858.9 g/mol). That record is the nonapeptide thymulin, a different substance covered in our thymulin research guide, so it gives no weight for this material.

Thymosin alpha-1 is residues 2 to 29 of prothymosin alpha (UniProt P06454, gene PTMA), with an acetylated N-terminal serine: Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN. Product page identity: C129H215N33O55, 3108.31 g/mol, matching PubChem CID 16130571, titled thymalfasin, its drug name.

In rat thymus, an antibody to the synthetic peptide mainly recognized prothymosin alpha, a polypeptide of about 112 residues with the same sequence at its N-terminus; it appears to be the native form from which thymosin alpha-1 and other fragments are generated during isolation of fraction 5 (Haritos et al., 1984). The drug form is a synthetic 28-amino acid peptide (Billich, 2002).

Side by Side

Research Context: Thymalin

The thymalin literature is mostly Russian-language and older. A PubMed search for thymalin, timalin or thymaline returned 300 records on 12 October 2026: 259 in Russian and 31 in English, 236 published from 1980 to 1999, and 101 with V. Kh. Khavinson or V. G. Morozov as an author. Its developers reported differences between the natural preparation and their synthetic dipeptides: only the natural peptides influenced the antioxidant response of thymocytes (Morozov and Khavinson, 1997).

In organ culture, thymalin at 5 ng/mL stimulated the development of thymus and spleen explants from 21-day-old rats, as did the synthetic dipeptides vilon (2 ng/mL) and thymogen (10 ng/mL), while vilon and thymogen inhibited thymus explants from 1-day-old rats (Chalisova et al., 1999). The 2023 paper paired docking of the KE and EW dipeptides to DNA with a cytokine assay in lipopolysaccharide-stimulated human blood mononuclear cells from four donors (Linkova et al., 2023). Models: rat explants and human blood cells.

Thymalin's developers list it as a medicine registered in Russia under registration number LS-000267, dated 26 February 2010, Ministry of Health of the Russian Federation (Khavinson et al., 2020). An openFDA search of Drugs@FDA on 12 October 2026 found no thymalin product, and ClinicalTrials.gov listed no thymalin study.

Research Context: Thymosin Alpha-1

Thymosin alpha-1's record is larger: a PubMed search for "thymosin alpha 1", "thymosin alpha1" or thymalfasin returned 965 records on 12 October 2026, 98 of them typed as clinical trials. In fungus-exposed dendritic cells, it induced functional maturation and interleukin-12 production through a p38 MAPK and NF-kappaB dependent pathway, signaling through MyD88 and distinct Toll-like receptors (Romani et al., 2004). Model: dendritic cell culture.

Its human research history includes a 22-center, double-blind, placebo-controlled phase 3 trial in 1106 adults with sepsis: 28-day all-cause mortality was 23.4% with thymosin alpha-1 and 24.1% with placebo, and no secondary or safety outcome differed significantly (Wu et al., 2025).

Its licensee, which held rights for regions excluding the United States and Europe from the early 1990s, reported approvals in more than 30 countries by 2007 (Tuthill, 2007). A 2002 drug profile listed launches in Argentina, China, Peru, the Philippines and Singapore and approvals in Thailand, Laos and Malta (March 2000), with HBV infection as the indication (Billich, 2002). Drugs@FDA lists no thymalfasin product (openFDA search, 12 October 2026), and an FDA page on bulk drug substances lists thymosin-alpha 1 (Ta1) among withdrawn nominations formerly in category 2, citing possible immunogenicity and peptide-related impurities.

Choosing Between Them for a Research Question

Thymosin alpha-1 is one sequence with a molecular weight, so arms can be planned in moles, about 0.32 µmol per milligram, and identity checked by mass. Thymalin is defined by its preparation, so plan on a mass basis, as the explant work did in ng/mL (Chalisova et al., 1999), and log each lot as its own material. An effect of thymalin cannot be pinned to one component without fractionation, which is how its developers found Glu-Trp (Morozov and Khavinson, 1997).

Check what an assay detects. Antibodies to thymosin alpha-1 mainly recognized prothymosin alpha in rat thymus extracts (Haritos et al., 1984), and one thymus protein antigen ran through several extracts (Falageeva and Kalashnikov, 1988). Head-to-head data are thin. A 1998 study in CBA mice and broiler chickens tested thymosin alpha-1, thymosin fraction 5 and thymalin beside amino acids and other peptides; these thymic preparations acted on the response to sheep red blood cells, a test antigen, only by the subcutaneous route (Belokrylov et al., 1998).

Handling and Storage

Both ship lyophilized, and both product pages list -20°C for the powder as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided. Let a sealed vial reach room temperature before opening, and split stock into single-use aliquots labeled with the lot number.

Thymosin alpha-1 is highly acidic (Goldstein et al., 1977), and on gel filtration both prothymosin alpha and synthetic thymosin alpha-1 ran at about three times their calculated mass, apparently as oligomers (Haritos et al., 1984), so size-based methods can mislead on identity. Thymalin's certificate summary (lot TY01) on its product page reports HPLC identity, purity and measured content but, like the page itself, no sequence or molecular weight. Use measured content from the COA portal, not label mass.

Questions Researchers Ask

Thymalin vs thymosin alpha 1: what is the difference?

Thymalin is a calf thymus polypeptide preparation with no single sequence (Morozov and Khavinson, 1997; Khavinson et al., 2020). Thymosin alpha-1 is one acetylated 28-residue peptide from thymosin fraction 5 (Goldstein et al., 1977), made by synthesis as the drug thymalfasin (Billich, 2002).

Thymosin alpha 1 vs thymalin: does thymalin contain thymosin alpha-1?

The sources we read do not report it. The peptides its developers name in thymalin are Glu-Trp, isolated from it (Morozov and Khavinson, 1997), and Lys-Glu, which a 2023 paper from the same group calls an active substance alongside Glu-Trp (Linkova et al., 2023). Thymosin alpha-1 came from thymosin fraction 5, a different calf thymus preparation (Goldstein et al., 1977).

Has any study tested both thymalin and thymosin alpha-1?

In a PubMed title and abstract search on 12 October 2026, one record named both: the 1998 study in CBA mice and broiler chickens described above (Belokrylov et al., 1998).

Are thymalin and thymosin alpha-1 approved drugs?

Thymalin is registered in Russia (LS-000267), as its developers state (Khavinson et al., 2020); thymalfasin's licensee, whose rights excluded the United States and Europe, reported approvals in more than 30 countries by 2007 (Tuthill, 2007). Drugs@FDA lists neither (openFDA search, October 2026). Our materials are research chemicals, not these medicines.