Thymosins
Small peptides originally isolated from the thymus gland involved in immune development. Thymosin alpha-1 (immune modulation) and thymosin beta-4 (tissue repair) are the most studied members. Both are widely discussed research peptides; thymosin alpha-1 is approved in some countries outside the US and EU.
Technical Context
Thymosin alpha-1 (Tα1, thymalfasin): 28 amino acid N-terminally acetylated peptide, produced commercially by SPPS. Mechanism: activates toll-like receptors (TLR2, TLR9) on dendritic cells, promotes T-cell maturation and differentiation (especially CD4+ and CD8+ T cells), enhances NK cell activity, and modulates cytokine production (increasing IL-2, IFN-α/γ). Approved in approximately 35 countries (China, Italy, South Korea, among others) for: hepatitis B/C treatment (as adjunct to interferon), immunodeficiency, and cancer immunotherapy adjunct. Not approved in US/EU/UK (where regulatory standards require larger, more rigorously designed clinical trials). Thymosin beta-4 (Tβ4): 43 amino acid peptide, primary intracellular function is actin sequestration (binds G-actin monomers, regulating actin polymerisation and cell motility). TB-500 is a synthetic fragment of Tβ4 commonly used in research peptide settings.