Thymosin Alpha-1 vs Thymalin

Thymosin Alpha-1

A 28-amino-acid thymic peptide marketed as Zadaxin. Approved in over 30 countries for hepatitis B and C; used off-label for chronic infection and immune resilience.

Best for

Best when you want the more clinically-validated thymic peptide, approved in several countries for immune modulation and certain infections.

Thymalin

A thymic peptide preparation developed in the Soviet bioregulator program. Used in Russia for decades as an immune support adjunct; Western trial data is sparse.

Best for

Best if you are exploring the older thymic-extract approach from the Russian literature, with much thinner Western data.

Thymosin Alpha-1

Zadaxin (Thymosin Alpha-1) is approved in over thirty countries — Italy, Spain, China, Brazil, Argentina, and others — for chronic hepatitis B and C. Clinical trial data in hepatitis is the most substantial and dates back to the 1990s. Adjunct use in sepsis, oncology, and immunocompromised states is supported by smaller but real RCT data. Not FDA-approved in the United States, which reflects regulatory history rather than a quality concern. Off-label use in healthy adults for general immune resilience is reasonable but not separately trial-validated.

Thymalin

Decades of Russian clinical use, with most peer-reviewed work from the Khavinson group at the St. Petersburg Institute of Bioregulation and Gerontology. Studies in elderly populations have reported improvements in immune markers and reductions in infection frequency over follow-up periods of months to years. The trial designs, sample sizes, and blinding standards rarely match Western RCT conventions, and independent replication outside the originating research network is limited.