Thymosin alpha-1
thymalfasin · Zadaxin · Tα1
A peptide from the thymus gland, studied mainly in chronic hepatitis B. It is a medicine in Italy (Zadaxin) and reported as one in other countries. Not in the US register.
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- Type
- Peptide
- Stage
- Medicine outside EU and US
- Safety
- Little data
- Risk of fakes
- Not known
- Checked
- Not yet
Doping. It is not on the WADA list. The ban does not cover substances approved by an authority, and it is approved in Italy.
Safety. Given to thousands of patients with infections, according to a 2015 review. We found no similar data in healthy people. Sources: study 1.
Risk of fakes. We found no tests of products sold outside pharmacies.
Is it legal
| Where | Status | Checked | |
|---|---|---|---|
| PL | No approval | The European medicines database (EMA) lists no such medicine in Poland (9 October 2026). The Polish register was down, so we could not check it directly. Source | Not yet |
| EU | Approved medicine | No EU-wide approval. Zadaxin (thymalfasin) is approved in Italy (European medicines database, EMA, 9 October 2026). Source | Not yet |
| US | No approval | The FDA drug register has no such medicine. Source | Not yet |
How much research exists
Scientific papers per year 2015–2025
These are search results. A count shows how much exists, not how good the studies are. 1 Nov 2026.
Reported side effects
What doctors, patients and companies reported to the US medicines agency (FDA), and single cases described in medical journals. A report says what happened to someone after taking the substance. It does not prove the substance caused it, and it does not say how often it happens. Reports do not change any grade.
Reports to the FDA (USA)
- Reports
- 251
- Of these, serious
- 200
| Most often reported | Reports |
|---|---|
| Pneumonia | 15 |
| Anaemia (too few red blood cells) | 14 |
| Low white blood cells | 14 |
| Diarrhoea | 12 |
| Low platelets | 12 |
| Upset gut bacteria | 11 |
| Liver damage | 10 |
| Low white blood cells (neutrophils) | 10 |
Serious means the person went to hospital, their life was in danger, they were left with lasting harm, or they died. One report can list several side effects.
Cases described in medical journals
- Long-term asymptomatic SARS-CoV-2 infection associated with deficiency on multiple immune cells.
- Clinical remission of a critically ill COVID-19 patient treated by human umbilical cord mesenchymal stem cells: A case report.
- Severe Gastric Mycormycosis Infection Followed by Cytomegalovirus Pneumonia in a Renal Transplant Recipient: A Case Report and Concise Review of the Literature.
- Chronic active EBV infection associated with NK cell lymphoma and hemophagocytic lymphohistiocytosis in a 27-year-old woman: A case report.
- The role of Tα1 on the infective patients after hematopoietic stem cell transplantation.
- Chronic hepatitis B: current and future treatment options.
FDA reports come from openFDA, cases from a PubMed search. The editors have not read these cases yet. Titles stay in the original language. As of 3 Nov 2026.
More papers we found
We found these papers automatically in PubMed. The editors have not read them yet, and they do not affect any grade. Titles stay in the original language.
Short answers
- Does Thymosin alpha-1 work?
- A peptide from the thymus gland, studied mainly in chronic hepatitis B. It is a medicine in Italy (Zadaxin) and reported as one in other countries. Not in the US register. We have not graded the studies yet. The number of papers in the databases is shown on the page.
- Is Thymosin alpha-1 legal?
- PL: No approval. The European medicines database (EMA) lists no such medicine in Poland (9 October 2026). The Polish register was down, so we could not check it directly. EU: Approved medicine. No EU-wide approval. Zadaxin (thymalfasin) is approved in Italy (European medicines database, EMA, 9 October 2026). US: No approval. The FDA drug register has no such medicine.
- Is Thymosin alpha-1 banned in sport?
- Not on the list, WADA 2026. It is not on the WADA list. The ban does not cover substances approved by an authority, and it is approved in Italy.
- Is Thymosin alpha-1 safe?
- Little data. Given to thousands of patients with infections, according to a 2015 review. We found no similar data in healthy people.