Thymosin Alpha-1 and Immune Support: What Has Been Studied

What the research covers

Thymosin alpha-1 has been tested in trials in chronic hepatitis B and in sepsis. A 2026 Cochrane review rated the hepatitis B evidence as very low certainty for all but one outcome.

The authors of a large sepsis trial call it an immune-modulating drug. A PubMed search found no trial of it to prevent infections in healthy adults.

The Cochrane review included 10 trials with 1,349 people who had chronic hepatitis B. The trials came out between 1991 and 2018. The peptide may cut deaths from any cause and serious side effects. Even so, the reviewers were not sure of these effects. They cited flaws in the studies, wide margins of error and small numbers of people.

The TESTS trial enrolled 1,106 adults with sepsis at 22 sites in China. They got the peptide or a placebo as a shot under the skin every 12 hours for 7 days. By day 28, 23.4 percent had died in the peptide group and 24.1 percent with placebo. The authors found no clear sign that it lowers deaths in sepsis. A search of the FDA drug approvals database on 27 September 2026 found no US approval for it.

Sources

1. Naing C, Ni H, Aung HH, et al. Thymosin-ɑ1 for people with chronic hepatitis B Cochrane Database Syst Rev (2026). PMID 42713852 doi:10.1002/14651858.CD014610.pub2 Cochrane review of 10 randomised trials (1,349 people) in chronic hepatitis B; certainty very low for all outcomes except serious adverse events (low).
2. Wu J, Pei F, Zhou L, et al. The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial BMJ (2025). PMID 39814420 doi:10.1136/bmj-2024-082583 TESTS phase 3 trial, 1,106 adults with sepsis; 28-day death rate 23.4% vs 24.1% with placebo.
3. Minutolo A, Petrone V, Fanelli M, et al. Thymosin alpha 1 restores the immune homeostasis in lymphocytes during Post-Acute sequelae of SARS-CoV-2 infection Int Immunopharmacol (2023). PMID 36989892 doi:10.1016/j.intimp.2023.110055 Lab (ex vivo) study of immune cells from people with long COVID; not a patient trial.