Thymalin

Thymalin is a polypeptide preparation obtained from calf thymus, not a single defined molecule. Morozov and Khavinson developed it at the Military Medical Academy in Leningrad, now St Petersburg, and it is the extract predecessor of the synthetic short peptides later supplied as Vilon, Cartalax and Epitalon. It is made by acid extraction of thymus tissue, fractionation to a low molecular weight peptide fraction, and drying to a lyophilized (freeze-dried) solid. As a fraction it has no molecular formula, no single molecular weight and no one amino acid sequence.

The database position needs care. Public chemical databases hold no record for Thymalin as a preparation, so the CAS and PubChem lines above read “Not assigned in public databases”. PubChem CID 3085284 does carry Thymalin as a synonym, but that record indexes nonathymulin, also called thymulin: a defined nonapeptide, pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, CAS 63958-90-7. An extract and a purified nonapeptide are not the same material.

The two also differ in origin: thymulin is a serum thymic factor, Thymalin a tissue fraction. The conflation should be caught before a formula or mass is quoted. Thymalin is also registered as a medicine in the Russian Federation under this name, State Register of Medicines record LS-000267. It holds no approved indication in the United States, and the research-grade preparation listed here is not that registered product.

The work began in the 1970s with what its authors called cytomedins: low molecular weight peptide fractions isolated from animal organs and proposed to regulate the tissue they came from. Thymalin was the thymus member of that set and the starting point for the synthetic Khavinson peptides.

Early pharmacology described effects on immune and haemostatic parameters in animals (PubMed 6546722), and a Russian-language review sets out the geroprotective argument (PubMed 12577695). A 2020 report describes differentiation markers in cultured human hematopoietic stem cells (PubMed 33237528), and a 2023 study proposes that the dipeptides Lys-Glu and Glu-Trp account for part of its activity (PubMed 37686182).

The record is large but weak. PubMed indexes roughly 290 items mentioning thymalin, yet most are small Soviet-era Russian-language clinical reports across unrelated indications, uncontrolled and in English as abstracts only. Some later work comes from other laboratories (PubMed 29797130), but no active species has been characterised and the claims have not been reproduced independently.

The mechanism proposed for Thymalin is regulatory rather than receptor-specific. The cytomedin hypothesis holds that a peptide fraction from an organ acts preferentially on that organ’s own cell populations, shifting differentiation and gene expression rather than binding one target. The population named is the T-lymphocyte lineage, and in later work hematopoietic progenitors in culture (PubMed 33237528).

Three materials are routinely confused. Thymalin is a bovine thymus extract with no fixed composition. Thymosin Alpha-1 is a defined 28-residue synthetic peptide with its own CAS number and sequence. Thymulin is the nonapeptide named above. Only the defined peptides can be confirmed by mass spectrometry, and results for one do not transfer.

The methodology caveat follows from the material. When a mixture produces an effect the active species is inferred, not isolated, and composition can move with the source tissue and the batch. That is why the group turned to short synthetic peptides.

Sealed lyophilized Thymalin is held frozen at -20°C, shielded from light, in its original container. Lyophilized material is hygroscopic, so a container is allowed to reach ambient temperature before opening.

Repeated freeze-thaw cycles are avoided. Stability for a lot is documented on its Certificate of Analysis.

Reconstitution means returning a lyophilized compound to solution. No preparation procedure is given here: solvent and concentration belong to a study protocol. Thymalin is handled as aqueous-soluble polypeptide material.

Because the preparation is a mixture, one solubility figure describes it only approximately. Solubility and water-content data for a lot appear on its Certificate of Analysis.

An extract cannot be verified the way a single peptide can, and that is the central quality point here. There is no target mass and no sequence to match, so documentation shifts to process: source tissue, extraction route, peptide content, and a chromatographic profile reproducible between batches.

Verified purity and identity are documented per lot on the Certificate of Analysis. For a fraction, the useful specification is consistency across lots.

Thymalin heads a group of preparations and short peptides from one programme.

• Vilon.
  The dipeptide Lys-Glu, reported among Thymalin’s own components.
  
• Pinealon.
  The tripeptide Glu-Asp-Arg, developed on the same rationale.
  
• Cartalax.
  Indexed as the tripeptide Ala-Glu-Asp, from the same series.
  
• Epitalon.
  The tetrapeptide Ala-Glu-Asp-Gly, the most published member of the series.
  
• Thymosin Alpha-1.
  A defined 28-residue thymic peptide, often confused with Thymalin and chemically unrelated.
  

Kuznik BI, Budazhabon GB, et al. (1984). Thymalin as a modulator of immunogenesis and hemostasis. Farmakol Toksikol.
PubMed 6546722

Khavinson VKh, Morozov VG (2002). Geroprotective effect of thymalin and epithalamin. Adv Gerontol.
PubMed 12577695

Zhukova GV, Schikhlyarova AI, et al. (2018). Effect of Thymalin on the Tumor and Thymus under Conditions of Activation Therapy In Vivo. Bull Exp Biol Med.
PubMed 29797130

Khavinson VK, Linkova NS, et al. (2020). Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells. Bull Exp Biol Med.
PubMed 33237528

Linkova N, Khavinson V, et al. (2023). 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.
PubMed 37686182

Thymalin is stocked in one format: sealed lyophilized vials from two supplier brands, both listed at a 10mg fill. Vials are the only listed format, and per-vial strengths are product specifications only. Each lot is batch tested with a published Certificate of Analysis documenting verified purity and identity, the only identity reference available for a preparation.

• Browse all Thymalin research products
• Real Peptides Thymalin, 10mg lyophilized vial
• Verified Peptides Thymalin, 10mg lyophilized vial

These products are sold for Research Use Only and are not intended for human consumption.