Thymalin - Study Reference

What it is

Thymalin is a polypeptide extract isolated from the thymus gland of calves, used in the former USSR and Russia since the 1970s as an injectable immunomodulator (an immune-system regulator). It is studied for restoring T-lymphocyte numbers and function in elderly people, in acute respiratory infections including severe COVID-19, and as a "geroprotector" (anti-ageing agent) intended to lower age-related illness and mortality.

How studies used it

Model: Human, hospitalised older adults with severe COVID-19 (mean age ~60-62 years)
Studied for: Severe COVID-19 pneumonia with lymphopenia and elevated inflammatory markers
Dose: 10 mg per day (absolute). Body weight was NOT reported in this trial, so a mg/kg figure cannot be derived from the trial's own data; for a typical ~75 kg adult this would be roughly 0.13 mg/kg/day, but that 75 kg is an external assumption, not a reported trial weight.
Dosing: Once daily, added on top of standard therapy
Route: Intramuscular
Duration: 5 days

Effects measured: Thymalin group (n=42) vs standard-therapy control (n=50): IL-6 fell 5.5-fold vs 1.41-fold in controls (p<=0.01); C-reactive protein fell 9.7-fold vs 1.7-fold; D-dimer fell 5.7-fold vs 2.1-fold; T lymphocytes rose 63.8% and total lymphocytes ~55% in the thymalin group. No deaths occurred in either group. Single-blind, randomised but small and single-centre (Chita/St Petersburg, Russia).

Side effects: No adverse events reported in this study

Sources: Khavinson VK, Kuznik BI, Trofimova SV, et al. Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19. Stem Cell Rev Rep. 2021;17(1):285-290.

Model: Human, 266 community/elderly persons over age 60 (controlled cohort, non-randomised)
Studied for: Age-related decline / geroprotection (cardiovascular, immune, endocrine, nervous-system function and mortality)
Dose: Per-dose amount is NOT stated in the published abstract; the documented standard clinical thymalin regimen is 10 mg per course-day (absolute). Body weight was not reported, so no validated mg/kg can be given; at an assumed ~70 kg this 10 mg would be about 0.14 mg/kg, but the trial reported neither the dose nor the weight in its abstract.
Dosing: Intermittent courses given only during the first 2-3 years of a 6-8 year follow-up; commonly cited as 10-day courses repeated roughly every 6 months
Route: Intramuscular (injectable thymic bioregulator)
Duration: 6-8 years of observation; peptide given in the first 2-3 years

Effects measured: Reported 2.0-2.4-fold lower acute respiratory disease incidence and reduced ischaemic heart disease, hypertension, osteoarthrosis and osteoporosis vs control. Mortality over the observation period was reported 2.0-2.1-fold lower in the thymalin-treated group, and 2.5-fold lower with thymalin+epithalamin combined; a subgroup given thymalin+epithalamin annually for 6 years had 4.1-fold lower mortality. These are open-label, single-group-author claims with no blinding or modern statistical reporting.

Side effects: No adverse events reported in this study

Sources: Khavinson VKh, Morozov VG. [Geroprotective effect of thymalin and epithalamin]. Adv Gerontol. 2002;10:74-84. [Russian]

Model: Rat (albino outbred males) with transplanted sarcoma 45
Studied for: Antitumour effect / thymus response under 'activation therapy' dosing
Dose: Reported only qualitatively as 'doses lower than the therapeutic dose,' modulated across the course. The exact mg/kg is NOT stated in the accessible record (full text paywalled), so no verified per-kg figure can be given.
Dosing: Repeated courses with dose modulation according to an 'activation therapy' schedule
Route: In vivo administration in rats (route not specified in the accessible abstract)
Duration: Treatment course (exact length not stated in abstract)

Effects measured: Tumour growth arrest and regression in more than half of the animals; in the remaining animals tumour growth was suppressed by 78%. Histology showed increased lymphoproliferative activity and more tissue basophils and plasmocytes in the thymus lobules. Small single-institution animal study; abstract gives no group sizes or statistics.

Side effects: No adverse events reported in this study

Sources: Zhukova GV, Schikhlyarova AI, Barteneva TA, et al. Effect of Thymalin on the Tumor and Thymus under Conditions of Activation Therapy In Vivo. Bull Exp Biol Med. 2018;165(1):80-83.

Model: Cell culture (in vitro), human haematopoietic stem cells (HSC)
Studied for: Mechanism study: whether thymalin drives HSC differentiation toward mature T lymphocytes
Dose: In vitro molar/mass concentration of thymalin was NOT recoverable from the accessible English record (Russian source paywalled), so the exposure concentration cannot be reported with confidence and should not be invented.
Dosing: Added to HSC culture (single in vitro exposure)
Route: In vitro (added to culture medium)
Duration: In vitro incubation (duration not stated in the accessible record)

Effects measured: Thymalin reduced the stem-cell marker CD44 and the intermediate marker CD117 by about 2-3 fold and increased the mature-T-lymphocyte marker CD28 about 6.8-fold, interpreted as thymalin pushing CD117+ cells toward mature CD28+ T cells. Mechanistic, indirect (marker expression only), no functional T-cell readout.

Side effects: No adverse events reported in this study

Sources: Khavinson VK, Linkova NS, Kvetnoy IM, et al. Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells. Bull Exp Biol Med. 2020;170(1):118-122.

How solid the evidence is

The evidence base for thymalin is weak, dated, and almost entirely Russian, dominated by one research group (Khavinson and colleagues at the St Petersburg Institute of Bioregulation and Gerontology) and their collaborators. Almost all of it would not meet modern Western trial standards. Human data: The strongest human study (PMID 33575961, COVID-19) is small (42 thymalin vs 50 controls), single-centre, only single-blind, and reports outcomes mostly as "fold changes" rather than absolute values with confidence intervals; importantly there were zero deaths in BOTH arms, so the much-quoted "halved mortality" claim comes from a separate, related, non-PubMed-indexed paper (Adv Gerontol 2021, PMC8654498) with different group sizes (36 vs 44) and a 10-day course, not from the PubMed-indexed paper cited here. The geroprotective cohort (PMID 12577695 and its companion PMID 14523363, the same 266-person cohort published twice) is non-randomised, open-label, decades old, authored by the developers, and reports no blinding, no per-protocol dose in the abstract, and no modern statistics; its dramatic 2- to 4-fold mortality reductions should be treated as low-confidence author claims, not established fact. Dose reliability: mg/kg cannot be honestly stated for the human studies because none reported patient body weight; the human dose is an absolute 10 mg/day IM and any per-kg figure here is flagged as an external assumption, not trial data. The animal (PMID 29797130) and in vitro (PMID 33237528) studies do not give a recoverable per-kg or molar concentration in accessible sources, so those dose fields are deliberately left as "not reported/not recoverable" rather than invented. Animal/in vitro: The rat sarcoma study and the HSC study are small, mechanistic, single-group, and from the same network of authors; the in vitro study measures only surface-marker expression, not actual immune function. No large, independent, multi-centre, double-blind randomised controlled trial of thymalin exists in the indexed Western literature. No formally negative/null trial was found, but the absence of independent replication and the publication-by-developers pattern are themselves major reliability concerns. Thymalin is not an approved drug in the EU/US; outcomes above are research findings, not therapeutic guarantees.