Key messages
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In adults with chronic hepatitis B, thymosin-alpha1 may reduce death from any cause and serious unwanted effects. We are less sure about its effects on well-being, hepatitis B-related illness or death, non-serious unwanted effects and liver health.
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Future studies should use more robust methods and include more people.
What is chronic hepatitis B?
Chronic hepatitis B is caused by infection with the hepatitis B virus (HBV). HBV attacks the liver, making it become inflamed – red, painful, and swollen. HBV infection can be short-term (acute) or long-term (chronic). Chronic HBV infection is when the condition lasts for more than six months. If not successfully treated, it may progress to chronic hepatitis, cirrhosis and other liver diseases, liver failure, cancer, and death.
What is thymosin-alpha 1?
Thymosin-alpha 1 is a substance made by a small gland in the chest called the thymus, which helps the body fight infections and disease. It may stop HBV from replicating and boost the body's immune system, helping it fight the virus. It is given as an injection under the skin.
What did we want to find out?
We wanted to know whether, in people with chronic hepatitis B, thymosin-alpha 1 is an effective treatment given alone, or with an additional treatment (called standard, regular, or supportive treatment), compared with placebo (dummy treatment) no treatment or the same additional treatment.
We were interested in whether thymosin-alpha 1:
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caused death for any reason
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caused serious unwanted effects (any event that led to death, disability or hospitalisation)
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improved people's well-being
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reduced HBV-related illness
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reduced risk of dying from chronic HBV infection
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reduced the risk of non-serious unwanted effects (events less serious than those above), and
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improved liver health.
What did we do?
We searched for studies that investigated thymosin-alpha 1 for people with chronic hepatitis B. Studies could include additional treatments as long as everyone in the study got the same additional treatment. Otherwise, people not receiving thymosin-alpha 1 received placebo or no treatment.
Studies could take place anywhere in the world. People in the studies could be men or women, and receive treatment by injection anywhere on the body and at any dose.
What did we find?
We found 10 studies involving 1349 adults with chronic hepatitis B. The studies investigated thymosin-alpha 1, given alone or with an additional treatment, compared with placebo (2 studies), no treatment (2 studies) or the same additional treatment (6 studies). The additional treatments were standard treatments for chronic HBV infection, including interferon, peginterferon, lamivudine, and tenofovir or entecavir.
The smallest study included 12 people, and the largest 690. The studies were funded by universities, the pharmaceutical industry, national bodies or research grants.
Thymosin-alpha 1 may:
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reduce the risk of death from any cause; in three studies, 14 of 460 people (3%) who received thymosin-alpha 1 died, compared with 26 of 447 people (5.8%) who received the control intervention from 6 months to 24 months after treatment;
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result in a small reduction in serious unwanted events; in five studies, 54 of 534 people (10.1%) who received thymosin-alpha 1 experienced a serious unwanted event, compared with 70 of 522 people (13.4%) who received the control intervention from 6 months to 24 months after treatment.
We are less certain that thymosin-alpha 1 may:
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make no difference to people's well-being five years after treatment (1 study, 161 people);
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make no difference to HBV-related illnesses. In three studies, 33 of 433 people (7.6%) who received thymosin-alpha 1 and 37 of 421 people (8.8%) who received the control intervention developed HBV-related illness from 6 to 24 months after treatment;
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reduce the risk of dying from chronic HBV. In three studies, 14 of 460 people (3%) who received thymosin-alpha 1 died from chronic HBV, compared with 26 of 447 people (5.8%) who received the control intervention up to 24 months after treatment;
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reduce the risk of non-serious unwanted effects; in five studies, 16 of 151 people (10.6%) who received thymosin-alpha 1 experienced a non-serious unwanted effect, compared with 32 of 149 people (21.5%) who received the control intervention from 12 months to 24 months after treatment;
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make no difference to improved liver health. In two studies, based on changes seen in liver samples, 146 of 358 people (40.8%) who received thymosin-alpha 1 had improved liver health compared with 163 of 344 people (47.4%) who received the control intervention from 12 months to 24 months after treatment.
What are the limitations of the evidence?
All 10 studies had problems with design and methods. Overall, we have little confidence in the results because only a few studies provided information on the outcomes we were interested in, results varied across studies, and many studies included a small number of participants.
How up-to-date is this evidence?
The evidence is current to June 2026.
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Objectifs
To assess the benefits and harms of thymosin-ɑ1 therapy in people with chronic hepatitis B.
Stratégie de recherche documentaire
We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, four other databases and six trials registers, in addition to reference checking, citation searching, and contacting study authors to identify trials for inclusion. The latest search date was 10 June 2026.
Conclusions des auteurs
We assessed the certainty of evidence as very low for all outcomes except for serious adverse events (low). Therefore, we are not sure whether thymosin-α1 monotherapy versus placebo or no intervention, or with the same co-interventions, reduces all-cause mortality, serious adverse events, HBV-related mortality, and non-serious adverse events, nor whether it has any effect on quality of life (based on one trial) and histological improvement. The effect of thymosin-ɑ1 on HBV-related morbidity is very uncertain.
We observed no statistically significant differences between trials with and without cointerventions.
We found no ongoing trials.
Financement
This Cochrane review had no dedicated funding.
Enregistrement
Protocol available via DOI: 10.1002/14651858.CD014610.
