Thymogen

Thymogen is a dipeptide of just two amino acids, L-glutamic acid and L-tryptophan (Glu-Trp). It comes out of the Russian Khavinson program: the group around Morozov and Khavinson took the calf thymus extract Thymalin apart by chromatography, found this dipeptide to be the most active of its tryptophan-containing components and then made it synthetically (Morozov, 1997; Deigin, 2024). In that sense Thymogen is one of the defined single substances behind the multi-component mixture Thymalin.

Unlike most Khavinson peptides, Thymogen is an approved medicine: in Russia it is registered as an immunomodulator (ATC code L03AX), as an injection solution of 100 mcg per millilitre for intramuscular use, as a metered nasal spray, as a cream and as a powder for an oral gel. Under the name IM862 or oglufanide the same substance went through clinical trials in the USA and the UK up to phase III, there given intranasally against Kaposi's sarcoma. That makes the evidence unusual for a bioregulator peptide: there are randomised human trials, including a placebo-controlled phase III, even though they asked a very different question.

This information is for research and educational purposes only. No medical advice.

Thymogen is regarded as a thymus mimetic: it is meant to imitate what the thymus signals to immune cells through its own peptides. In the originating group's work it promotes T-cell differentiation, improves recognition of peptide-MHC complexes, shifts cyclic nucleotides (cAMP, cGMP) in lymphocytes and prompts release of IL-2 and interferon. On top of that it activates neutrophils, with increased chemotaxis and phagocytosis (Morozov, 1997). The Russian prescribing information sums this up as Thymogen normalising the number of helper and cytotoxic T cells and their ratio in people with immune deficits.

CD4 and CD8 receptors on T lymphocytes are named as the target. There is also a hypothesis that in stem cell cultures the dipeptide binds promoter regions of DNA and opens silent heterochromatin for transcription (Deigin, 2024). That is the classic Khavinson explanation for all short bioregulators and so far more model than proof.

Independently, a US group showed in a mouse model that the antitumour effect of Glu-Trp does not run through direct toxicity to tumour cells but needs NK cells and their perforin; without IL-12 it dropped sharply, while interferon-gamma was not required (Smith, 2003). So Thymogen nudges the cellular immune response rather than fighting anything itself. In a cell culture study using a human monocyte cell line, Thymogen and related Khavinson peptides also dampened the LPS-driven production of TNF and IL-6, which points more towards immune balance than pure stimulation.

Pharmacokinetics: according to the prescribing information, Thymogen reaches the bloodstream quickly after injection and is split there by peptidases into glutamic acid and tryptophan, which the body simply reuses. No human half-life has been published; for a free dipeptide, minutes are the realistic expectation. Swallowed, according to the prescribing information of the Russian oral gel it acts mainly locally on the stomach lining. Only a small fraction reaches the bloodstream.

• The Thymogen vial with 20 mg of lyophilised powder.
• Bacteriostatic water, 2 ml for this vial.
• U-100 insulin syringes, ideally 0.3 ml (30 units) with a fine scale, plus alcohol swabs.

A note on the size: 20 mg is 200 times the registered daily dose of 100 mcg. The vial is sized for the community's mg range, not for the medicine's dose. The daily dose is therefore a very small volume. A small syringe with clearly readable single-unit marks makes measuring it much easier.

Use the calculator above. A 20 mg vial with 2 ml of water gives 10 mg per ml. The registered dose of 0.1 mg is then exactly 1 unit on a U-100 syringe, 0.2 mg is 2 units and 0.5 mg is 5 units. That puts every step on a full mark; with 3 ml the standard dose would be an awkward 1.5 units.

Just add the water to the vial, the dipeptide dissolves quickly and clear. Swirl or shake, both are fine. With only one unit per day it pays to read the syringe at eye level and tap out air bubbles first, otherwise the dose can easily be off by half.

The medicine in Russia is injected intramuscularly. Studies from the originating program also used subcutaneous and nasal dosing. In the research context, subcutaneous injection into the fat under the skin has become the norm. Disinfect the site, pinch a skin fold, rotate sites.

Because the volume is tiny, the injection is barely noticeable. If you notice a slight sting, warm the filled syringe in your hand for a moment first, cold solution tends to sting more. If redness lasts longer than a day or keeps spreading, that is a reason to stop the course.

The founding work: Morozov and Khavinson described in 1997 how Glu-Trp was isolated from Thymalin and synthesised as Thymogen, with the effects on T-cell differentiation, cytokines and neutrophils mentioned above. They also reported its use in people with chronic disease and immune dysfunction, though without the detail you would expect from a trial today (Morozov, 1997). A recent review by the Russian developers summarises that in patients with lymphoproliferative disease Thymogen sped up the recovery of leukocytes and granulocytes after chemotherapy, with mean leukocyte counts twice as high as under standard care (Deigin, 2024). The Russian clinical data are plentiful but almost always small, open-label and without a placebo group.

Lifespan and tumours: in a study of 76 female rats, 44 animals received 5 mcg Glu-Trp subcutaneously five times a week for a year. Mean lifespan was unchanged, but the longest-lived 10 percent lived 1048 instead of 949 days. The Gompertz aging rate was 0.0041 instead of 0.0071 per day. Tumours were 1.5 times less frequent, malignant ones 1.7 times and leukaemias and lymphomas 3.4 times less frequent (Anisimov, 2000). A rat is not a human. This study did not look at the mechanism, but as a hint the result is still remarkable.

The Western trials under the name IM862: a randomised study in 44 patients with AIDS-related Kaposi's sarcoma compared two dosing schedules of 5 mg as nasal drops and saw a response in 36 percent, including five complete remissions, with mild and transient side effects; nearly all participants were also taking protease inhibitors (Tulpule, 2000). The subsequent double-blind phase III with 202 patients could not confirm this: 23 percent response on IM862 versus 21 percent on placebo. Time to progression was actually shorter on IM862 (16 versus 35 weeks). The authors consider it likely that concurrent antiretroviral therapy accounts for part of the earlier response rates; slightly more patients in the placebo group were on such therapy (96 versus 88 percent) (Noy, 2005). For immunology this is still valuable: it is one of the few placebo-controlled human trials of a Khavinson peptide. It shows that an immune stimulant can also push in the wrong direction in an active tumour disease.

Mechanistically, a US group showed in a mouse model that Glu-Trp inhibits tumour growth without direct cytotoxicity and needs working NK cells with perforin to do so (Smith, 2003). That fits the picture of a peptide that nudges the cellular immune response. Honest read: for the uses the community mostly has in mind, susceptibility to infections, recovery after illness or immune aging, there are no controlled data beyond the Russian short reports.

• The Russian prescribing information lists only allergic reactions and hypersensitivity to the active substance for the injection, with no frequency given. Contraindications are hypersensitivity and age under 6 months; in pregnancy and breastfeeding only after weighing benefit against risk.
• In the IM862 trials with 5 mg intranasally, side effects were mild and transient: headache, fatigue, tingling, nausea, no changes in blood counts (Tulpule, 2000). Even 20 mg three times daily intranasally for eight weeks caused no relevant toxicity in a British phase II study in renal cell carcinoma.
• The most important signal: in the phase III trial in Kaposi's sarcoma, time to progression was shorter on IM862 than on placebo (Noy, 2005). With an active tumour disease Thymogen is therefore not something for self-experiments. The Russian prescribing information for the oral gel explicitly excludes cancer.
• As an immune stimulant it calls for caution in autoimmune disease. There are no data on this, but the risk is plausible.
• Local: redness or mild burning at the injection site, as with any peptide.
• Long-term data on self-use in the mg range are completely missing.

Before mixing the powder is robust, normal room temperature (around 20 to 25 degrees) is fine, ideally kept in the dark. After mixing, keep in the fridge (2 to 8 degrees), do not freeze. It stays good there for several months with barely any loss of potency. Swirl or shake to mix, both are fine.

With Thymogen the arithmetic matters: a 20 mg vial holds 200 daily doses of 0.1 mg, enough material for 20 to 60 courses. With courses of 3 to 10 days and breaks in between, you will not come close to using up a mixed vial within its shelf life. So keep the powder dry in the cupboard until you actually start the first course. Expect some to be left over.