An Unusual Regulatory History
Thymosin Alpha-1 (TĪ±1) is approved as a pharmaceutical product in more than 37 countries for immune modulation applications including hepatitis B, hepatitis C, and as an immune adjuvant in oncology. It is sold under the brand name Zadaxin in markets where it is approved. It is not FDA-approved in the United States but was included in the February 2026 Category 1 reclassification.
Mechanism of Action
Thymosin Alpha-1 is a naturally occurring peptide derived from the thymus gland. It modulates immune function primarily through T-cell regulation ā enhancing the immune response when it is suppressed and potentially moderating it when overactive. This bidirectional modulation is unusual and clinically interesting.
Research Applications
Clinical data from the 37 countries where it is approved covers immune support in chronic viral infections, immune enhancement in cancer patients receiving chemotherapy, and general immune senescence (age-related immune decline). This is a more developed human evidence base than most peptides discussed in longevity medicine.
Availability
Following the February 2026 reclassification, Thymosin Alpha-1 can be compounded by licensed 503A pharmacies with a physician prescription in the United States. Physicians specializing in immune function or longevity medicine are the most appropriate prescribers.