Thymosin Alpha-1

Educational overview

Thymosin Alpha-1 is listed in the ezGLP knowledgebase under Immune. Evidence and regulatory status can vary by formulation, route, and jurisdiction.

Thymosin alpha-1 (Tα1), also called thymalfasin, is a 28-amino-acid peptide first isolated from thymic tissue. It is classed as an immunomodulator rather than a tissue-repair or metabolic peptide. Its described actions include promoting T-cell maturation, increasing cytotoxic and helper T-cell activity, stimulating dendritic cell function through Toll-like receptor signaling, and shifting cytokine output toward a Th1 pattern. Endogenous Tα1 is cleaved from the precursor prothymosin alpha, and the synthetic form used in medicine is chemically identical to the natural sequence. Its terminal half-life in plasma is reported at roughly two hours, which is short compared with many other injected peptides in this category.

Thymosin alpha-1 has a substantial human evidence base compared with most compounded peptides. Randomized and controlled trials have studied it in chronic hepatitis B and C, often alongside interferon; in severe sepsis, including a multicenter randomized trial across six Chinese teaching hospitals; as a vaccine adjuvant in older adults and hemodialysis patients; and as an adjunct in several cancers. A 2023 meta-analysis of COVID-19 studies reported lower mortality among moderate-to-critical patients, although the underlying studies were heterogeneous and largely non-randomized. Much of the trial literature comes from China and Italy, and independent replication of several findings remains limited.

Thymalfasin is marketed under the brand Zadaxin and is approved in more than 35 countries, including Italy and China, primarily for chronic hepatitis B and as an immune adjunct. It has never been approved by the FDA in the United States, and in 2023 the agency placed thymosin alpha-1 on its list of bulk drug substances that may present significant safety risks when compounded, citing immunogenicity concerns and inadequate safety information. Products encountered in the United States are therefore compounded or research-grade material rather than an approved medicine. The approved product is given by subcutaneous injection; other routes are not part of any authorization.

Thymosin alpha-1 is typically supplied as a lyophilized powder in a vial that is reconstituted before injection. Because storage and beyond-use dating differ between an approved product, a compounded preparation, and research-grade material, the dispensed label is the controlling reference for temperature and in-use time. A dose log for this peptide commonly records the vial lot, reconstitution date, concentration, injection site, and any local reaction, which are the details later needed to interpret a response or to report an adverse event. An inventory record that tracks vials by lot number also helps reconcile what was received against what was administered.

Category

Immune

Routes represented

Subcutaneous (SubQ)

Approximate library half-life

2 hours; formulation-dependent and not dosing guidance

Storage context

Follow the dispensed product or pharmacy label; storage and beyond-use time vary by formulation.