Immunomodulating peptide for immune system enhancement
Last reviewed: 2026-08-18
Also known as
Status: Research compound - Immune modulator
Full composition (formula, molecular weight, sequence) in Quick Facts →
Thymosin alpha-1 (thymalfasin; Zadaxin) is approved in more than 30 countries (not the US) for hepatitis B/C and as an immune adjuvant. The multicenter ETASS randomized controlled trial in 361 severe sepsis patients found 28-day mortality of 26.0% with Tα1 vs 35.0% in controls (relative risk 0.74, 95% CI 0.54-1.02; log-rank P=0.049) with improved monocyte HLA-DR expression. A propensity-score-matched analysis of 468 patients found adjuvant Tα1 improved recurrence-free and overall survival after curative resection of HBV-related hepatocellular carcinoma.
Tα1 enhances T-cell differentiation/function, NK activity, dendritic cell maturation and cytokine production in animal and immune models, restoring immune function in immunocompromised states.
Cell studies show Tα1 signals through Toll-like receptors (e.g., TLR9) and modulates both innate and adaptive immune responses without overstimulation.
US FDA approval is absent (Zadaxin never received US approval); evidence for sepsis and HCC is from single trials/observational analyses with mixed statistical significance, and benefits in healthy users (immune 'boosting') are not clinically established.
ETASS trial (361 severe sepsis patients): 28-day mortality was 26.0% with thymosin alpha-1 vs 35.0% in controls (RR 0.74; 95% CI 0.54-1.02; log-rank P=0.049), with significantly greater improvement in monocyte HLA-DR on days 3 and 7 and no serious drug-related adverse events.
In 468 patients with solitary HBV-related HCC after curative resection, propensity-score-matched analysis found Tα1 adjuvant therapy was associated with improved recurrence-free survival and overall survival (HR 0.381 and 0.308, respectively, on multivariate analysis).
Pharmacokinetics in healthy volunteers: thymosin alpha-1 is well absorbed after subcutaneous injection (tmax 1-2 h), with no accumulation between single- and 5-day multiple dosing.
Onset: During treatment
Management: Monitor LFTs; reflects immune activation
Reported values from research literature and community protocols. Educational reference only — not a dosing recommendation or medical advice.
1.6 mg 2x/week
Research protocols are for educational purposes only. Always consult qualified medical professionals.
No. Thymalfasin (Zadaxin) is approved in more than 30 countries for hepatitis B/C and as an immune adjuvant, but it is not FDA approved in the US.
The ETASS randomized trial in severe sepsis (28-day mortality 26% vs 35%, RR 0.74) and adjuvant-use analyses in hepatitis B-related hepatocellular carcinoma, plus decades of hepatitis B/C use in approved countries.
By subcutaneous injection; in the ETASS sepsis trial the regimen was approximately 1.6 mg twice daily for 5 days, and it is typically dosed 1.6 mg twice weekly in many clinical protocols.
Wei YT, Wang XR, Yan C, Huang F, Zhang Y, Liu X, Wen ZF, Sun XT, Zhang Y, Chen YQ, Gao R, Pan N, Wang LX (2022)
Ancell CD, Phipps J, Young L (2001)
Simonova MA, Ivanov I, Shoshina NS, Komyakova AM, Makarov DA, Baranovskii DS, Klabukov ID, Telepenina KP, Atiakshin DA, Shegay PV, Kaprin AD, Stepanenko VN (2025)
+ 46 more citations
Formula
C129H215N33O55
Molecular Weight
3108.28
Sequence
SDAAVDTSSEITTKDLKEKKEVVEEAEN
Mechanism
Immune system modulation and cellular repair
Used clinically in some countries. Research compound in others.
Wei YT, Wang XR, Yan C, Huang F, Zhang Y, Liu X, Wen ZF, Sun XT, Zhang Y, Chen YQ, Gao R, Pan N, Wang LX (2022)
Ancell CD, Phipps J, Young L (2001)
Simonova MA, Ivanov I, Shoshina NS, Komyakova AM, Makarov DA, Baranovskii DS, Klabukov ID, Telepenina KP, Atiakshin DA, Shegay PV, Kaprin AD, Stepanenko VN (2025)
+ 46 more citations