Thymalin Research Guide: The Thymus Glu-Trp Dipeptide
By UK Peptide Lab Research Team•18 September 2026•8 min read
Key Takeaways
- Thymalin, as supplied here, is the dipeptide Glu-Trp (EW), molecular weight 333.34 g/mol and CAS 38101-59-6, identified within the calf-thymus polypeptide complex isolated by Morozov and Khavinson (Biokhimiya, 1981).
- The supporting data are a thymus-peptide immunology literature reporting T- and B-lymphocyte restoration in immunodepressed states (reviewed by Khavinson et al., Biol Bull Rev, 2021) and one dipeptide-specific rat study reporting slowed ageing and reduced spontaneous tumour incidence (Anisimov et al., Biogerontology, 2000).
- Thymalin is not thymulin: the latter is a distinct zinc-dependent nonapeptide characterised by Bach and colleagues (Nature, 1977). The two names are routinely confused.
- Supplied for in-vitro laboratory research only, with no dosing information, no human-use claims and no therapeutic promises.
What is Thymalin?
Thymalin, as supplied here, is the thymus-derived dipeptide L-glutamyl-L-tryptophan, written Glu-Trp, with the molecular formula C₁₆H₁₉N₃O₅, a molecular weight of 333.34 g/mol and CAS number 38101-59-6. In one-letter code the sequence is EW, the abbreviation used through much of the Russian literature, and the dipeptide is also referred to as timogen (thymogen). Chemically it is the minimal member of the thymus-peptide family: two residues joined by a single peptide bond, with a tryptophan indole ring at the C-terminus. That indole is the chemistry to design around, because it absorbs UV light strongly and oxidises readily in solution. UK Peptide Lab supplies Thymalin 10mg as research-grade lyophilised powder for in-vitro laboratory use only.
Origin: The Calf-Thymus Isolation Programme
The name Thymalin originally belonged to a polypeptide complex, not to this dipeptide. Morozov and Khavinson (Biokhimiya, 1981) reported the isolation, purification and identification of an immunomodulatory polypeptide preparation from the thymus of calves, an early product of the Soviet programme of organ-derived peptide bioregulators. The dipeptide came later, as the programme moved from extracts to defined molecules: Glu-Trp was separated from the thymalin complex by reversed-phase HPLC, then synthesised and taken forward as a discrete immunomodulator, a history set out in English by Morozov and Khavinson (Int J Immunopharmacol, 1997) and Khavinson and colleagues (Biol Bull Rev, 2021). The dipeptide is therefore not the extract itself but the defined component identified within it, and that is the sense in which the name Thymalin is used on this page.
Thymalin vs Thymulin: One Letter, Two Molecules
One letter of difference separates two unrelated compounds, and the confusion between them is common enough to warrant its own section. Thymulin, historically facteur thymique sérique, is a distinct nonapeptide with the sequence Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn whose biological activity and antigenicity depend on zinc coordination, first characterised by Bach and colleagues (Nature, 1977). Thymalin, as supplied here, is the two-residue synthetic dipeptide Glu-Trp. The two share a tissue of origin and an immunology-adjacent literature, and nothing else. Thymosin alpha-1, the 28-residue acetylated thymic peptide covered in its own guide, is a third molecule again. Checking the sequence before citing is the only reliable way through the naming thicket.
T-Cell Function and Immune Restoration in Aged Models
The literature that motivates research interest in thymalin concerns the restoration of immune function in ageing and immunodepressed states. Khavinson and colleagues (Biol Bull Rev, 2021) summarise the reported immunoprotective effects of the thymus peptides: restoration of the number and ratio of T and B lymphocytes and their subpopulations, an increase in their functional activity, and increased phagocytosis. Anisimov and Khavinson (Biogerontology, 2010) review the same programme's geroprotective claims across the thymus and pineal preparations, including reported immune restoration in aged animals. The proposed mechanism is set at gene-expression level, with the short peptides reported to modulate synthesis of cytokines, heat-shock proteins and other regulatory factors. These are reported effects within one research programme, and most of them concern the thymalin complex rather than the isolated dipeptide.
The Dipeptide's Own Data
The dipeptide-specific animal literature is smaller. The defining study is Anisimov, Khavinson and Morozov (Biogerontology, 2000), who treated outbred female rats with synthetic L-Glu-L-Trp and followed survival, lifespan and spontaneous tumour development. They reported a slowed ageing rate, increased survival and a roughly 1.5-fold decrease in the number of spontaneous tumours relative to controls. The paper is also where the thymogen brand name enters the English literature. It remains a single laboratory's long-term rat study with demographic endpoints, best read as the anchor of the dipeptide's own evidence base rather than settled pharmacology.
Research Applications
Laboratory use follows the two strands above: immunology work on T-cell function, lymphocyte subset recovery and phagocytosis in aged or immunodepressed models, and comparative work on short thymus-derived peptides, where the Glu-Trp dipeptide serves as the minimal defined sequence against which larger thymus peptides are benchmarked. Its two residues also make it a practical subject for analytical method development around a strongly UV-absorbing tryptophan chromophore. There is no established human-use application to describe, and none is implied.
Reading the Evidence Honestly
The honest caveats are structural and should be stated plainly. The primary data originate overwhelmingly from one affiliated research cluster, the St. Petersburg programme that designed these compounds; much of it is Russian-language; the human evidence is small, often uncontrolled by modern standards, and confined to the clinical tradition of the former Soviet Union. Thymalin holds no marketing authorisation in the UK, the EU or the United States, and no randomised controlled trial supports any therapeutic claim. The animal findings on immune restoration and lifespan are real but have seen sparse independent replication outside the originating group. This guide therefore carries no dosing information, no human-use claims and no outcome promises. The material is supplied for in-vitro laboratory research only.
Laboratory Handling and Storage
Store the lyophilised vial at -20°C, protected from light and moisture, for up to 24 months. Reconstitute by slowly injecting Bacteriostatic Water down the inner glass wall and swirling gently until dissolved; never shake or vortex. The tryptophan indole is the degradation target, so minimise headspace and stopper-open time, protect the reconstituted solution from light, keep it at 2-8°C and use within approximately 4 weeks. Prepare single-use aliquots for longer storage and avoid repeated freeze-thaw cycles. See the peptide storage guide for the general principles.
Sourcing Thymalin in the UK
UK Peptide Lab supplies research-grade Thymalin 10mg as lyophilised powder, supplier-tested, batch UKPL-9510 at 98.82% purity by HPLC, with the certificate of analysis published on the product page and independent third-party verification pending. Same-day UK dispatch on orders placed before 2pm GMT, free Royal Mail Tracked shipping over £45. For in-vitro laboratory research use only, not for human consumption.
Related Products
Disclaimer: This article is for research and educational purposes only. All information provided is not intended as medical advice. UK Peptide Lab products are not for human consumption and are sold strictly for laboratory research use only.
Frequently Asked Questions
What is Thymalin?
Thymalin, as supplied here, is the thymus-derived dipeptide L-glutamyl-L-tryptophan (Glu-Trp), with the molecular formula C₁₆H₁₉N₃O₅, a molecular weight of 333.34 g/mol and CAS number 38101-59-6. It is also referred to as timogen. The dipeptide was identified within the calf-thymus polypeptide complex isolated in the Soviet immunomodulator research programme (Morozov and Khavinson, Biokhimiya, 1981). It is supplied as lyophilised powder for in-vitro laboratory research only and holds no marketing authorisation in the UK, the EU or the United States.
Is Thymalin the same as Thymulin?
No. Thymulin, historically called facteur thymique sérique, is a distinct nonapeptide of sequence Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn whose biological activity depends on zinc coordination, first characterised by Bach and colleagues (Nature, 1977). Thymalin, as supplied here, is the two-residue dipeptide Glu-Trp. The two come from the same organ and share an immunology-adjacent literature, but they are chemically unrelated.
Is Thymalin legal to buy in the UK?
Thymalin is not a Controlled Drug, and it may lawfully be bought and held in the UK as a research chemical for in-vitro laboratory use. It is not a licensed medicine anywhere in the UK, the EU or the United States, and under the Human Medicines Regulations 2012 it cannot lawfully be sold or supplied for human consumption. Purchasers must be 18 or over and confirm research-only use at checkout.
How do I reconstitute Thymalin?
Allow the vial to reach room temperature, then inject bacteriostatic water slowly down the inner glass wall, never directly onto the powder, and swirl gently until dissolved. Do not shake or vortex. The tryptophan indole side chain is light- and oxidation-sensitive, so protect the solution from light, store it at 2-8°C and use within 4 weeks. Research use only.
References
- [1] Isolation, purification, and identification of an immunomodulatory polypeptide found in the thymus of calves and humans. Biokhimiya (1981). View →
- [2] Natural and synthetic thymic peptides as therapeutics for immune dysfunction. Int J Immunopharmacol (1997). View →
- [3] Immunomodulatory synthetic dipeptide L-Glu-L-Trp slows down aging and inhibits spontaneous carcinogenesis in rats. Biogerontology (2000). View →
- [4] Biochemical characterisation of a serum thymic factor. Nature (1977). View →
- [5] The Use of Thymalin for Immunocorrection and Molecular Aspects of Biological Activity. Biol Bull Rev (2021). View →