What it is
Thymosin alpha 1 is a 28-amino-acid acetylated peptide derived from prothymosin alpha and first isolated from thymic tissue. It is known in clinical literature as thymalfasin and is studied as an immune modulator. Published research covers sepsis, chronic hepatitis B and severe viral respiratory illness.
How it works
It is thought to act on dendritic cells and T lymphocytes, largely through Toll-like receptor signalling, promoting T-cell maturation and antigen-presenting function. Trials track that proposed mechanism through monocyte HLA-DR expression, T-cell counts and thymic output markers.
Regulatory status
- Cosmetic ingredient
- Research compound
- In clinical trials
- Approved medicine
Not approved as a medicine by the FDA or the EMA. Some are registered in individual countries. Supplied for laboratory research only.
What published research is studying
- 28-day all-cause mortality in adults with sepsis (phase 3 and earlier randomized trials)
- Immune restoration markers such as monocyte HLA-DR and CD4+ and CD8+ T-cell counts in critical illness
- Virological and biochemical response in chronic hepatitis B, compared with interferon alpha
- Outcomes and T-cell exhaustion markers in severe COVID-19 (retrospective cohorts)
Key findings
In a phase 3, double-blind, placebo-controlled trial across 22 centres in China, 1089 adults with sepsis were analysed. Mortality at 28 days was 23.4% with thymosin alpha 1 and 24.1% with placebo (hazard ratio 0.99, 95% CI 0.77 to 1.27).
Wu J et al., BMJ 2025 (TESTS)In an earlier multicentre randomized trial of 361 adults with severe sepsis, 28-day mortality was 26.0% versus 35.0% in controls (relative risk 0.74, 95% CI 0.54 to 1.02). Monocyte HLA-DR improved more on days 3 and 7.
Wu J et al., Crit Care 2013 (ETASS)A 2025 systematic review of 11 randomized trials in 1927 patients with sepsis found a pooled 28-day mortality odds ratio of 0.73 (95% CI 0.59 to 0.90). The high-quality and multicentre subgroups showed no significant difference.
Gu B et al., Front Cell Infect Microbiol 2025In a meta-analysis of 4 randomized trials in 199 patients with chronic hepatitis B, complete response favoured thymosin alpha 1 over interferon alpha. That comparison, 6 months after therapy ended, gave an odds ratio of 2.69 (95% CI 1.47 to 4.91).
Yang YF et al., Antiviral Res 2008
What the studies measured
Study durations
- Phase 3 sepsis trial: subcutaneous injection every 12 hours for 7 days, with the primary outcome assessed at 28 days (NCT02867267).
- ETASS sepsis trial: 28-day follow-up, with immune markers measured on days 0, 3 and 7 (NCT00711620).
- Chronic hepatitis B trials in the meta-analysis: 6 months of treatment, with response reassessed 6 months after treatment ended (Yang 2008).
Endpoints
- 28-day all-cause mortality
- Monocyte HLA-DR expression
- Sequential Organ Failure Assessment (SOFA) score
- CD4+ and CD8+ T-cell counts and T-cell exhaustion markers
- Virological, biochemical and complete response rates in hepatitis B
How strong is the evidence?
Human evidence is substantial but conflicting: a 1106-participant phase 3 trial found no mortality difference in sepsis, while smaller and earlier trials reported benefit.
Common questions
Is Thymosin alpha-1 an approved medicine?
Research compound. Not approved as a medicine by the FDA or the EMA. Some are registered in individual countries. Supplied for laboratory research only.
How much human research is there on Thymosin alpha-1?
Human evidence is substantial but conflicting: a 1106-participant phase 3 trial found no mortality difference in sepsis, while smaller and earlier trials reported benefit.
Does UU supply Thymosin alpha-1?
Yes, as premium-grade research material for laboratory use. Every batch is tested by an independent lab and the certificate of analysis is published.