Thymogen

Overview

Thymogen is a synthetic dipeptide — two amino acids, glutamic acid joined to tryptophan (Glu-Trp, single-letter E-W). The marketed substance is the monosodium salt; the corresponding free acid carries the international name oglufanide (CAS 38101-59-6, formula C16H19N3O5, molecular weight 333.34, PubChem CID 100094). It comes from the Russian Khavinson/Morozov "peptide bioregulator" school and is described as a short-peptide fragment derived from the thymic extract Thymalin.

Its evidence picture is genuinely mixed, which is why it is filed here as disputed rather than clearly established. On one side: a long-standing Russian registration as an immunomodulator, plus older, mostly preclinical mechanism papers. On the other: no completed Western approval, and mechanism claims that rest largely on animal and in-vitro work. The free-acid form (oglufanide) did progress into Western clinical development — it held US Investigational New Drug (IND) status and an FDA Orphan Drug designation for ovarian cancer (September 2001), and was studied for cancer and chronic hepatitis C — but no marketing approval resulted, and no robust positive Phase 3 outcome was located.

Chemistry and structure

The chemistry of the free acid is firmly established (PubChem). The salt form is less settled: the value CAS 122933-59-9 is listed by suppliers as both the monosodium and the disodium salt, so the exact stoichiometry — and therefore the exact salt molecular weight and formula — is reported inconsistently and was not independently re-verified in this pass. Only the free-acid oglufanide was confirmed.

Mechanism of action

All of the following are proposed mechanisms; note the evidence tier on each and that much of it is older, largely Russian, and preclinical.

• Immunomodulation — T-cell differentiation and recognition. Attributed activity includes activating T-cell differentiation and T-cell recognition of peptide-MHC complexes, altering intracellular cyclic-nucleotide balance, and stimulating neutrophil chemotaxis/phagocytosis. [Animal] — Khavinson-school work; mechanistic detail not independently confirmed at the human clinical level. (Source: DrugBank DB05779; Thymalin context, PMC8365293.)
• Cytokine and adhesion-molecule signalling. alpha-Glu-Trp reduced TNF-alpha-induced IL-1alpha, increased TNF-alpha-stimulated ICAM-1 on endothelial cells, and reduced TNF-alpha-induced IL-8 secretion. [In vitro] — cell-culture study (endothelial / mononuclear cells; THP-1 monocyte/macrophage line). (Source: Cell and Tissue Biology, 2023; PMC8999041.)
• Slows aging markers and inhibits spontaneous carcinogenesis. [Animal] — rat study (Anisimov / Khavinson school); preclinical only. (Source: Anisimov et al., ResearchGate.)
• Anti-angiogenic / inhibits VEGF activity — the stated basis for the ovarian-cancer orphan indication. [In vitro] — not established in humans. (Source: DrugBank DB05779.)
• Binds a specific AACG nucleotide motif in DNA to influence gene expression. [Hypothesis] — the Khavinson-school "peptide-DNA epigenetic regulation" idea; speculative, not a confirmed clinical mechanism. (Source: Khavinson-school reviews.)

Research and evidence

Human evidence. Limited and inconclusive in the Western literature. The free-acid form (oglufanide) held US IND status and an FDA Orphan Drug designation for ovarian cancer (Sept 2001), and was taken into trials for cancer and chronic hepatitis C (a US HCV trial was recruiting into roughly 2007 under Implicit Bioscience, which acquired the molecule in 2005). [Human] No trial documented here led to FDA or EMA marketing approval, and no robust positive Phase 3 outcome was found. In Russia, Thymogen has long been marketed/registered for immunocorrection, but the supporting clinical literature is older, mostly Russian-language, and methodologically limited — not equivalent to modern regulatory-grade efficacy evidence. Net: trials existed, but efficacy is not established to FDA/EMA standard.

Status and regulation

Orphan/IND status and a foreign (Russian) registration do not constitute FDA or EMA authorisation. The definitive current Russian registration number/status was not read from an official Russian registry in this pass (it is inferred from secondary sources), and the outcomes of the US oglufanide trials were not located — efficacy remains unestablished to FDA/EMA standard.

Safety

• Human safety/adverse-event profile: not characterised in the sources reviewed here.
• Reported activity is largely animal and in-vitro; a preclinical safety signal (or its absence) does not transfer to humans.
• Material sold outside Russia's regulated channel is not the registered medicine and may differ in identity, purity, and sterility.
• WADA status: not found. No source addressing prohibited-list classification was located; this does not mean "permitted," and non-approval must not be read as an automatic S0 classification.

Legal status

Outside its Russian registration, Thymogen / oglufanide is classified as a research reagent. That classification is not permission for human use: "no specific ban" is not affirmative authorisation, and a compound becomes an unauthorised medicine the moment it is intended for human use. WADA sport-prohibition is a separate axis from legality — and no WADA class code is asserted for this compound by any source found, so none is stated here. Regulatory status differs by country and changes over time. This is not legal advice — check your own jurisdiction. (Dated 2026-07-08.)

How it compares

• Thymalin is the parent extract: a heterogeneous calf-thymus polypeptide mixture from the same Russian school. Thymogen is one synthetic dipeptide (Glu-Trp) derived from it — a single defined molecule, not the extract.
• Thymosin alpha-1 is a fully defined 28-amino-acid thymic peptide with a substantial independent international literature and approval in several countries — a much stronger evidentiary standing than Thymogen's.
• Epitalon is another Khavinson bioregulator and shares Thymogen's pattern: bold claims resting largely on a single research school with limited independent replication.

Common misconceptions

• "Thymogen is FDA-approved because it had an Orphan Drug designation." No. An Orphan Drug designation (ovarian cancer, Sept 2001) and IND status mark a development pathway — they are not marketing approval, which never resulted.
• "Thymogen and Thymalin are the same thing." They are not. Thymalin is the multi-peptide thymus extract; Thymogen is a single synthetic dipeptide (Glu-Trp / oglufanide) derived from it.
• "It contains glutamine." No — it is glutamyl (glutamic acid) joined to tryptophan. Some secondary sources get this wrong.
• "Russian registration means it's approved in the US/EU." It does not. A national registration is a separate decision; the molecule is not FDA- or EMA-approved.
• "The anti-cancer and anti-aging effects are proven." They are not. Those findings are animal/in-vitro or hypothesis-level, and the Western clinical programme produced no documented approval or robust Phase 3 result.

Russian research

Much of the evidence for Thymogen (Glu-Trp, alpha-glutamyl-tryptophan) originates from one Russian network — Khavinson's St. Petersburg Institute of Bioregulation and Gerontology together with co-inventor V. Deigin — and is surfaced here for completeness, framed honestly for quality. Almost all of it is preclinical, small, single-group, and has not been independently replicated outside that school.

What is verifiable with a PMID/DOI:

• [Animal] In outbred female rats (n=76; 5 ug/rat given subcutaneously 5x/week for 12 months and followed to natural death), the dipeptide L-Glu-L-Trp was associated with longer maximum lifespan (1048 +/- 21.1 vs 949 +/- 16.1 days, P<0.001) and lower tumour incidence (total 1.5x lower, P<0.01; malignant 1.7x lower, P<0.01; haematopoietic malignancy 3.4x lower, P<0.02). This is a single-group study from one institute, of modest size, never independently replicated. Anisimov VN, Khavinson VKh, Morozov VG. Biogerontology. 2000;1(1):55-59. PMID 11707921; DOI 10.1023/a:1010042008969.

• [Animal] In mice (C57BL, CBA), the biological effect of Glu-Trp depended on amino-acid chirality and bond type: D-Glu variants inhibited bone-marrow colony-forming cells, one mixed isomer stimulated them, and — notably — the L-L form (the marketed Thymogen configuration) was inert on stem cells in this model. This is a useful counter-signal from the same developer group (Deigin) that the marketed isomer did nothing in this particular haematopoietic assay. Semina OV, Semenets TN, Zamulaeva IA, et al. Bulletin of Experimental Biology and Medicine. 2006;141(2):250-253. PMID 16984110; DOI 10.1007/s10517-006-0141-0.

• [In vitro] In an endothelial cell line (EA.hy926) plus mononuclear cells from healthy donors under a TNF-alpha inflammation model, alpha-Glu-Trp reduced TNF-alpha-induced IL-1alpha and IL-8 (suggested anti-inflammatory action) while increasing ICAM-1 adhesion-molecule expression. Small, single, mechanistic/preliminary; authors from St. Petersburg institutes including the Khavinson school; donor count not stated. Golovacheva EG, Starikova EA, Kudryavtseva TA, Apryatina VA. Cell and Tissue Biology. 2023;17(2):146-152. DOI 10.1134/S1990519X23020050; PMC10134718.

• [In vitro] In the human THP-1 monocyte/macrophage line, among five Khavinson peptides tested, Thymogen (Glu-Trp) was reported as most effective at attenuating IL-17 release from activated macrophages and appeared to reduce the percentage of adherent monocytes. Single cell-line study, Khavinson as co-author (not independent of the originating school), no dose-response or replication reported. Avolio F, Martinotti S, Khavinson VKh, et al. International Journal of Molecular Sciences. 2022;23(7):3607. PMID 35408963; DOI 10.3390/ijms23073607; PMC8999041.

• [Hypothesis / review] Two narrative reviews by the developers themselves restate clinical and mechanistic claims without new independent trial data. Deigin et al. frame Thymogen (L-L) and its enantiomer Thymodepressin (D-D) as a reciprocal up/down pair and confirm Thymogen's Russian registration certificate No. P N002408/01 (dated 10.06.2009). Deigin V, Linkova N, Vinogradova J, et al. International Journal of Molecular Sciences. 2024;25(9):5042. PMID 38732260; DOI 10.3390/ijms25095042; PMC11084461. Khavinson's own review cites an older registration string (90/250/1; manufacturer NPK Cytomed) and an author assertion of "more than 25 million" people treated over 30 years with no adverse reactions. Khavinson VKh. Klinicheskaya Meditsina (Clinical Medicine). 2020;98(3):165-177. DOI 10.30629/0023-2149-2020-98-3-165-177 (open text via CyberLeninka). Because these are reviews by the peptide's own inventors, they are citation sources for the registration and chirality framing, not independent efficacy proof.

What could not be verified. The "more than 25 million patients / zero adverse events over 30 years" figure is a single-author, unreferenced review assertion, not an epidemiological or pharmacovigilance study, and cannot be read as safety evidence. The exact current Russian registration number was not read directly from the official GRLS registry this pass; two different strings appear in the literature (P N002408/01 [2009] and 90/250/1) — consistent with a renewed entry, but reported-not-primary-verified. Mechanistic claims widely repeated in reviews (T-cell differentiation, neutrophil chemotaxis/phagocytosis, cyclic-nucleotide changes, and an "AACG DNA-motif / peptide epigenetic gene-regulation" idea) trace to older Russian-language papers for which no independently verifiable per-claim citation was found; Russian-language sources describe these activities, but no verifiable individual citation could be located here.

Quality. No independently verifiable randomised controlled human trial of Thymogen was located. The verified primary literature is one small rat study, one mouse isomer study (in which the marketed L-L form was inert), and two small in-vitro cell-line studies — all single-group and effectively from one Russian school, with no replication outside it. Thymogen is a registered medicine in Russia (alpha-glutamyl-tryptophan, MBNPK Cytomed, St. Petersburg), but that registration is a regulatory fact, not proof of efficacy, and it is not FDA or EMA approval. Being studied is not being proven.