Thymalin

The original 'peptide bioregulator' from Khavinson and Morozov: a mixture of small protein fragments extracted from calf thymus, registered in Russia since 1982 as a prescription drug. The dipeptide Glu-Trp isolated from it later became the separate Russian drug Thymogen.

Not well defined. The developers propose that its short peptides restore low T-cell numbers and the CD4/CD8 ratio, promote maturation of blood-forming stem cells, calm inflammatory markers (IL-6, CRP) and normalize clotting. The gene-regulation model behind this is not independently established.

A single-center, open-label COVID-19 trial (42 vs 50 patients) found larger falls in IL-6, CRP and D-dimer and rises in lymphocytes with thymalin, but co-treatments differed and outcomes were lab markers. An elderly cohort (266 people) reported fewer respiratory infections and lower mortality, without group sizes or randomization details. Russian indications include infections, weakened immunity and suppressed immunity after chemotherapy or radiation. No blinded, placebo-controlled trial or independent replication exists.

The developers report essentially no side effects, but the label's adverse-reaction section could not be verified. As an animal-protein extract, allergic reactions (including anaphylaxis), batch variability and uncontrolled animal sourcing are the main concerns.

Not FDA-approved; approved in Russia since 1982 (current registration LS-000267). Not on any FDA compounding list, so not lawfully compoundable under 503A. Not named on the 2026 WADA List; because it is approved in Russia, S0 arguably does not apply.