Thymosin Alpha-1

A synthetic 28-amino-acid acetylated peptide identical to the naturally occurring thymic peptide first isolated by Allan Goldstein in 1977. Thymosin alpha-1 is the most clinically studied thymic peptide, with over 30 randomized controlled trials involving more than 11,000 human subjects across hepatitis B/C, sepsis, cancer immunotherapy, and vaccine adjuvant applications.

It is approved in 35+ countries (primarily in Asia, South America, and Eastern Europe) under the brand name Zadaxin, but has never received FDA or Health Canada marketing approval. Its mechanism of action involves dendritic cell maturation, T-cell differentiation, and toll-like receptor signaling modulation.

Thymosin alpha-1 has been studied in over 30 randomized controlled trials. In hepatitis B, four trials (195 patients) demonstrated HBV DNA clearance of approximately 41% vs. 9% for controls at 6 months. In hepatitis C, combination therapy with IFN-α2b produced 65% HCV RNA clearance vs. 29% with IFN alone. A 2015 meta-analysis of 12 sepsis trials (n=1,480) found a pooled relative risk of mortality of 0.68 (95% CI 0.59–0.78), though a large 2025 placebo-controlled trial found no clear mortality benefit.

Additional trials exist in melanoma, COVID-19, cystic fibrosis, drug-resistant tuberculosis, and vaccine adjuvant applications in immunocompromised populations. The standard clinical dose across trials is 1.6 mg SC twice weekly.