Thymosin Alpha-1

Overview

Thymosin Alpha-1 (Ta1) is a 28-amino-acid thymic peptide (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN) approved as Zadaxin in 35+ countries for chronic hepatitis B/C and as an immune adjuvant. It is NOT FDA-approved in the US.

Mechanism of Action

Thymosin Alpha-1 primes dendritic cells via TLR9-MyD88-IRF7 (driving IFN-alpha) and TLR2-MyD88-NF-kB (driving IL-12, TNF-alpha, IL-6). It promotes T-cell maturation and thymic output, enhances NK cytotoxicity, upregulates MHC class I antigen presentation, and induces IDO to balance inflammation with tolerance. It is a context-dependent immunomodulator that can both restore deficient responses and moderate overactive ones.

Research Summary

Approved in 35+ countries as Zadaxin (thymalfasin) for chronic HBV/HCV, immunodeficiency, and as a vaccine / chemotherapy adjuvant; adjunctive use in hepatocellular carcinoma and melanoma has been explored. A 2008 Yang et al. meta-analysis in Antiviral Research found HBV efficacy comparable to interferon-alpha. Multiple COVID-19 studies (Liu et al. 2020, Clin Infect Dis) reported reduced mortality in severe lymphopenic patients. A 2024 systematic review (Dinetz & Lee) covering 30+ trials and 11,000+ subjects found an excellent safety record. US FDA status: NOT approved; was on the 503A interim Category 1 list, moved to Category 2 in 2023, the nominator withdrew in September 2024, and on December 4, 2024 PCAC voted AGAINST inclusion on the 503A Bulks List — compounded US supply is now legally precarious.

Dosing Information

Reported Side Effects

• Injection site reactions (most common)
• Transient mild fatigue
• Rare low-grade fever (typically reflects immune activation)
• Transient lymphocyte subset shifts (generally asymptomatic)
• Excellent overall safety profile across 11,000+ trial subjects

Labs to monitor before & during your Thymosin Alpha-1 protocol

These biomarkers are commonly tracked to assess response and safety. Run baseline labs before starting, mid-cycle labs halfway through, and post-cycle labs 1–2 weeks after the final dose.

Commonly Stacked With

Research References

• Tuthill C, Rios I, McBeath R. Thymosin alpha 1: past clinical experience and future promise. Ann N Y Acad Sci. 2010;1194:130-135. (PMID 20536460)
• Romani L, et al. Thymosin alpha1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance. Blood. 2006;108(7):2265-2274. (PMID 16741252)
• Yang YF, et al. Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis. Antiviral Res. 2008;77(2):136-141. (PMID 18078676)
• Liu Y, et al. Thymosin Alpha 1 Reduces the Mortality of Severe COVID-19 by Restoration of Lymphocytopenia and Reversion of Exhausted T Cells. Clin Infect Dis. 2020;71(16):2150-2157. (PMID 32442287)
• Dinetz E, Lee E. Comprehensive Review of the Safety and Efficacy of Thymosin Alpha 1 in Human Clinical Trials. Altern Ther Health Med. 2024;30(1):6-12. (PMID 38308608)