Thymalin 10mg Peptide

Thymalin is not a molecule. It is a polypeptide fraction extracted from calf thymus tissue, and every other fact about it follows from that. There is no sequence, no molecular formula, no CAS number and no single molecular weight, because the material is a mixture of peptides recovered from an organ rather than a defined compound assembled on a synthesiser. Published characterisations describe it as a complex of peptides of molecular weight up to roughly 10 kDa, within which three short components have been named: the dipeptides Lys-Glu and Glu-Trp and the tripeptide Glu-Asp-Pro.

It came out of Soviet military medicine. Khavinson and Morozov reported the experimental and clinical work on it in Voenno-Meditsinskiy Zhurnal in 1982, and the preparation entered Soviet medical use that year. It remains a registered medicine in Russia, carrying Ministry of Health registration number LS-000267 dated 26 February 2010, and it is the parent of a whole family of organ-derived peptide preparations that Khavinson's St Petersburg group went on to develop. Almost the entire clinical record sits in Russian-language journals, and none of it is registered on ClinicalTrials.gov: a query of the registry for thymalin returns zero studies.

Two naming collisions cause most of the confusion around this compound, and both are worth clearing up before anything else. Thymalin is not Thymosin Alpha-1, which is a defined 28-residue synthetic peptide sold in this catalogue as thymosin-alpha-1-10mg. It is also not thymulin, a zinc-dependent nonapeptide from a different research lineage. PubChem's own synonym index conflates the second pair: a name lookup for thymalin resolves to CID 3085284, nonathymulin, C33H54N12O15, 858.9 g/mol, CAS 63958-90-7. That record describes thymulin. It has nothing to do with a calf thymus fraction, and it is the source of the specification tables that circulate across the research peptide market attached to the wrong name.

A fraction cannot have a receptor mechanism in the way a single ligand can, and the literature does not claim one. What exists instead is a hypothesis about the short peptide components plus a set of cell-population readouts. The hypothesis is Khavinson's peptide bioregulation model: that di- and tripeptides small enough to reach the nucleus can dock into the grooves of double-stranded DNA at specific base sequences and shift transcription. Molecular modelling of the two named dipeptides put Glu-Trp preferentially at a GGAG site in classical B-form DNA with an ICM score of -32.6 kcal/mol via minor-groove hydrogen bonding, and Lys-Glu at a GCGC site in the curved nucleosomal form at -30.7, with an earlier calculation placing it at TCGA in B-form at -35.8 (Linkova et al., International Journal of Molecular Sciences 2023). These are docking scores from an in silico study, not measured binding constants.

The most concrete cellular observation is on progenitor differentiation. In cultured human hematopoietic stem cells, exposure to Thymalin lowered expression of CD44 and CD117, the stem and intermediate-stage markers, by two to three fold, while raising CD28, a marker of mature T lymphocytes, by 6.8 fold (Khavinson et al., Bulletin of Experimental Biology and Medicine 2020). The direction of that shift is the mechanistic claim the Russian group makes for the whole preparation: it pushes progenitors along the T-lineage rather than acting on mature T cells directly.

The second reproducible readout is cytokine damping under bacterial stimulus, and here the fraction and its isolated components behave differently. In lipopolysaccharide-stimulated human peripheral blood mononuclear cells at 1 mg/mL, Thymalin brought tumour necrosis factor alpha down to 44.9% of the stimulated control, interleukin-1 beta to 37.5%, and interleukin-6 to 80.0%. The isolated Lys-Glu dipeptide was sharper on tumour necrosis factor alpha, cutting it to 16.8% of control, and Glu-Trp reached 19.7%. In the monocyte and macrophage line THP-1, the same family of peptides raised tyrosine phosphorylation of mitogen-activated kinases, suppressed tumour necrosis factor and interleukin-6 output after endotoxin, and reduced monocyte adhesion to endothelial monolayers, which the authors framed as induction of endotoxin tolerance rather than immune stimulation (Avolio et al., International Journal of Molecular Sciences 2022).

Those two strands do not obviously belong to the same mechanism, and the literature has not reconciled them. A preparation that accelerates T-lineage differentiation is an immune activator; a preparation that blunts monocyte cytokine output after endotoxin is an immune brake. The clinical work in severe respiratory illness leans on both at once, arguing that the useful case is a depleted immune system with an over-active innate compartment. That is a plausible reading of the data. It is not a demonstrated mechanism, and no target has been isolated from the fraction and shown to account for either effect.

Most compounds in a research catalogue are defined by a sequence and confirmed by mass. Thymalin is defined by a process. The starting material is calf thymus, the process is extraction and fractionation to peptides below roughly 10 kDa, and the product is whatever that process yields from that tissue. Two lots made to the same specification are similar in the way two batches of a botanical extract are similar, not in the way two syntheses of a 28-residue peptide are identical.

This has a direct consequence for what a certificate of analysis can honestly say. A purity figure by reverse-phase HPLC answers the question 'what fraction of the material is the intended single species', and for a mixture that question has no answer. A meaningful characterisation of a peptide fraction looks different: total peptide content by a nitrogen or Lowry-type assay, a molecular weight distribution by size exclusion chromatography, an amino acid composition after hydrolysis, a reproducible reverse-phase fingerprint compared against a retained reference lot, and, because the source is animal tissue, species verification plus endotoxin and bioburden limits.

None of that appears on the specification sheets circulating for this compound in the research market, where a single purity percentage is the norm. It is the sort of detail that only matters until a study fails to replicate, at which point it becomes the first thing anyone asks about.

These two are the most frequently confused compounds in the thymic peptide category, and they sit next to each other in this catalogue, so the distinction is worth stating precisely. Thymosin Alpha-1 is a synthetic 28-residue acetylated peptide corresponding to the N-terminal fragment of prothymosin alpha, with a defined formula, a CAS number, an international non-proprietary name (thymalfasin), marketing authorisations in more than 30 countries, and dozens of registered clinical trials. Its activity has been traced to Toll-like receptor 2 and Toll-like receptor 9 agonism on dendritic cells through MyD88.

Thymalin shares the source tissue and roughly the functional territory and nothing else. It has no defined structure, no receptor, no international non-proprietary name, and no registered trials. What it has instead is four decades of clinical use inside one national health system and a set of Russian-language cohort reports.

The practical result of the confusion is that the two get sold as a package. At least one supplier in this market lists a product combining the names, and its specification table carries the CAS number and formula of Thymosin Alpha-1 alongside a second CAS number and formula that belong to thymulin, not to Thymalin at all. Anyone comparing that sheet against a real Thymalin fraction is comparing three different substances.

The short peptides identified inside Thymalin did not stay inside it. Each was synthesised and developed as a separate preparation once the extraction work had pointed at it. Glu-Trp became Thymogen, Lys-Glu became Vilon, and Glu-Asp-Pro was carried forward as a third short bioregulator. The logic was that if a dipeptide accounts for the activity, a synthetic dipeptide removes the lot-to-lot variability, the animal source and the extraction cost in one step.

That logic has a Western test case, and it did not go well. The same L-glutamyl-L-tryptophan dipeptide was developed outside Russia as oglufanide, also known as IM862, on an antiangiogenic rationale. An early randomised study of intranasal IM862 in 44 patients with AIDS-related Kaposi sarcoma reported major responses in 36%, with five complete and 11 partial remissions. A Phase 2 trial in 25 patients with metastatic renal cell carcinoma then found no significant objective responses, with eight cases of stable disease, and the authors concluded it should not be pursued further as a single agent (Deplanque et al., British Journal of Cancer 2004).

So the best-characterised single component of Thymalin has been through Western randomised oncology testing and failed it. That does not settle the question of what the whole fraction does in immune models, since the components were not tested in an immune indication and the fraction is more than the sum of the three named peptides. It does mean the strongest available Western evidence on any part of this preparation is negative, which is a fact the marketing copy for the compound never mentions.

Thymalin entered Soviet medical use in 1982, the year Khavinson and Morozov published the experimental and clinical work on it in the military medical journal. It has stayed on the register since: the current Russian Ministry of Health registration number is LS-000267, dated 26 February 2010, and the preparation is manufactured in St Petersburg. Registered indications in that system cover acute and chronic viral and bacterial infection, purulent and septic processes, impaired regeneration, and suppression of immunity and haematopoiesis following chemotherapy or radiotherapy.

The published clinical use spans a much wider range than the registration does, which is characteristic of the Soviet and post-Soviet literature on this class. Indexed reports include lymphocyte subset correction in 120 patients with duodenal ulcer, immunocorrection in 96 patients with chronic purulent otitis media, immunological correction in 154 patients with progressive pulmonary tuberculosis, acute lung abscess, thyroid disease before and after surgery, and a 15-patient series in idiopathic parkinsonism. Almost all of these are open-label, single-centre, and published in Russian.

Two independent research groups outside Russia have worked with the preparation recently. A Ukrainian and Polish collaboration produced the rat mandibular regeneration studies published in 2024, and an Italian group at Chieti-Pescara ran the THP-1 monocyte work with Khavinson as a co-author. Both are laboratory studies. Neither is a clinical trial.

The single most-cited claim about Thymalin comes from a follow-up of 266 elderly and senile subjects in St Petersburg, reported by Khavinson and Morozov over six to eight years. Subjects given repeated courses of Thymalin were reported to have 2.0 to 2.1 fold lower mortality than untreated controls; subjects given Thymalin together with epithalamin, the pineal fraction from the same programme, were reported at 4.1 fold lower mortality over six years of annual treatment. Acute respiratory disease incidence fell 2.0 to 2.4 fold in the treated groups.

An effect of that magnitude on all-cause mortality would be larger than anything achieved by any registered geroprotective intervention, which is precisely the reason to look hard at the design. The cohort was single-centre, run by the group that developed the preparation, and reported in Russian-language and translated summary journals without the trial documentation a modern reader would expect: no registration, no published protocol, no allocation procedure, no blinding, and no independent adjudication of cause of death. It has never been replicated by another group, and it never will be in that form.

None of that makes the result false. It makes it uninterpretable at the level of confidence the number implies. The honest position is that the study is the largest and longest human dataset on this compound and that its design cannot support the causal claim usually attached to it.

The most recent human data came out of Russian hospitals during the pandemic, and it is the closest this compound has to a controlled result. An 80-patient study in older inpatients with severe COVID-19 compared 36 given Thymalin at 10 mg intramuscularly on each of ten consecutive days against 44 given saline. Lymphocyte counts rose from 0.61 to 1.17 times ten to the ninth per litre in the treated arm against 0.89 to 0.96 in controls; CD4-positive cells rose 2.2 fold and CD8-positive 2.2 fold; interleukin-6 fell from 155 to 24.2 pg/mL. Clinical improvement was reported in 80.5% against 59% (p=0.039) and mortality at 19.4% against 40.9%.

A second 92-patient study, 42 treated and 50 control, reported C-reactive protein falling from 13.11 to 1.35 mg/dL and D-dimer from 1820 to 319 ng/mL in the treated arm, with no deaths in either group. A third report compared standard care, tocilizumab and Thymalin in severe COVID-19 in middle-aged and elderly patients, with in-hospital mortality of 40.9%, 28.4% and 20.6% respectively, and lymphocyte and monocyte counts doubling in the Thymalin group.

These are the strongest human numbers the compound has, and they still sit well below the bar a Western regulator applies. All three came from the same national research network during a period when standard care was changing week to week, none was preregistered, and the allocation and blinding procedures are not described in enough detail to assess. The registry position is unambiguous: a search of ClinicalTrials.gov for thymalin returns no studies at all, in any phase, in any country. There is no Western randomised trial of this preparation and there is no protocol on file for one.

Supplied as a lyophilised powder, the dry material is the stable form and should be kept cold, dark and dry, with long-term holding at minus 20 degrees Celsius or below and short excursions to room temperature tolerated during shipping. Once taken into aqueous solution the material is a mixture of small peptides in water, and small peptides in water are substrates for any residual protease and for simple hydrolysis, so solutions are held at 2 to 8 degrees Celsius and used within a short window rather than stored.

Two handling considerations are specific to a fraction rather than a synthetic peptide. Repeated freeze and thaw cycles matter more, because the components differ in stability and cycling changes the composition of what remains, not just the total concentration. And because the source is bovine tissue, a research record should note the manufacturing origin and the endotoxin figure alongside the peptide content, since neither is inferable from a purity percentage.

For the same reason, results from different lots are not automatically comparable. Any study design that spans more than one lot should record the lot identifier against each experimental block, which is routine practice for tissue extracts and rarely done for research peptides.