Overview

Thymosin alpha-1 (Tα1) is a 28-amino-acid peptide with an N-terminal acetyl group, originally isolated from calf-thymus extract and now produced by chemical synthesis. It is derived post-translationally from the larger prothymosin alpha precursor. Tα1 has been approved in more than 30 countries (marketed as Zadaxin/thymalfasin) for indications related to chronic hepatitis B, hepatitis C adjunct therapy, and as a vaccine adjuvant in specific populations.

Mechanism (as reported in the literature)

  • Toll-like receptor signalling. Research characterises Tα1 as a TLR2 and TLR9 agonist that shifts dendritic-cell maturation toward a T-helper-1 profile.
  • T-cell maturation and activity. Studies indicate increases in CD4 and CD8 T-cell counts, enhanced NK-cell cytotoxicity, and improved antigen-specific T-cell responses in models of immune suppression.
  • Regulatory-cell modulation. Animal studies report modulation of regulatory T-cell activity that may contribute to the “immune-restorative” framing used across the Tα1 literature.

Research findings

  • Chronic hepatitis B trials. Multiple randomised trials of Tα1 monotherapy and combination regimens reported HBeAg seroconversion and viral-load reductions relative to controls (Andreone et al., 2001; Sherman et al., 2001).
  • Sepsis trials. A Chinese multicentre randomised trial in severe sepsis reported reduced 28-day mortality in the Tα1 arm versus placebo (Wu et al., 2013, Critical Care; PMID 24004807).
  • COVID-19 observational studies. Retrospective cohorts during 2020–2021 reported reduced mortality among older patients treated with Tα1 (Liu et al., 2020).
  • Vaccine-adjuvant studies. Trials in older adults with influenza vaccination and in dialysis patients with hepatitis B vaccination reported improved seroconversion rates.

Common dosing (from published research protocols)

The reference clinical dose across most trials is 1.6 mg subcutaneously, twice weekly, for durations of six months to one year depending on indication. Sepsis-trial protocols used higher and more frequent dosing early in the course.

Reconstitution

A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields a 2,500 mcg/mL solution.

  • 1,600 mcg = 0.64 mL = 64 units on a U-100 syringe
  • 800 mcg = 0.32 mL = 32 units

Storage

Lyophilised Tα1 is described as stable at 2–8 °C for long-term storage. Reconstituted solutions are refrigerated and used within approximately 14 days.

  • BPC-157 — a distinct peptide occasionally discussed in the same immune-modulation research context.
  • KPV — a shorter anti-inflammatory tripeptide from the melanocortin family.

References

  • Sherman, K. E., et al. (2001). “Combination of thymosin alpha 1 and interferon alfa in the treatment of chronic hepatitis C.” Journal of Hepatology, 35(6). PMID 11738111.
  • Andreone, P., et al. (2001). “A randomized controlled trial of thymosin alpha 1 versus interferon alfa treatment in patients with hepatitis B e antigen antibody-negative and HBV DNA-positive chronic hepatitis B.” Hepatology, 34(4). PMID 11584387.
  • Wu, J., et al. (2013). “The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial.” Critical Care, 17(1). PMID 24004807.
  • Goldstein, A. L., Hannappel, E., Kleinman, H. K. (2005). “Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues.” Trends in Molecular Medicine, 11(9). PMID 16095970.