Thymosin Alpha-1: the immune peptide explained

Short answer: Thymosin Alpha-1 is a 28 amino acid peptide first found in the thymus, the gland that trains the immune system's T cells. Its synthetic form, thymalfasin (brand name Zadaxin), is approved as a medicine in more than 30 countries, mainly for chronic hepatitis B and as immune support. It helps regulate immune responses rather than simply boosting them. It is one of the better studied peptides, but it is still a prescription treatment that a physician should choose and monitor.

Key facts

• Natural source: the thymus gland, which shrinks steadily after puberty.
• Medical name: thymalfasin. Brand name Zadaxin.
• Approved uses abroad: chronic hepatitis B and C in several countries, and immune support in some cancer and vaccine settings. It is not approved by the US FDA.
• How it works: helps T cells mature and helps dendritic cells recognise threats.
• Usual schedule: injections under the skin, often twice a week, for a set course.
• Our product: Thymosin Alpha-1 9 mg, 3 ml prefilled pen, 1,740 SAR.

What does the thymus have to do with ageing?

The thymus is a small gland behind the breastbone. In childhood it trains T cells to recognise infections without attacking the body. From puberty onwards it slowly turns into fat, and by older age it produces far fewer new T cells. This is one reason older adults respond less well to vaccines and recover more slowly from infections. Thymosin Alpha-1 is one of the signals the thymus uses, which is why it attracts interest for immune ageing.

What does the research show?

Thymosin Alpha-1 has decades of clinical use. The strongest data are in chronic hepatitis B, where it is used alone or with antiviral drugs. Trials have also looked at it as an add-on in sepsis, some cancers and to improve vaccine response in older or immune-weakened people. Results in these areas are mixed but generally show a good safety profile. During COVID-19 it was used in some hospitals in China and Italy, with conflicting results.

For healthy people who simply want "stronger immunity", there are no good trials. Physicians who use it in that setting rely on its safety record and how it works.

Who asks about Thymosin Alpha-1?

• Adults who get frequent infections or recover slowly.
• Older adults looking at immune ageing as part of a longevity plan.
• People recovering from a long illness, with their physician's agreement.

It is in our immune and longevity collection, along with Epithalon and Humanin.

Thymosin Alpha-1 vs Thymosin Beta-4 (TB-500)

The names are similar but the peptides are different. Thymosin Alpha-1 acts on the immune system. Thymosin Beta-4, and its fragment TB-500, act on tissue repair and are used for injuries. TB-500 is part of our Wolverine stack. See what the research shows on BPC-157 and TB-500.

Safety and who should avoid it

In trials the most common side effect was mild redness or discomfort at the injection site. Because it acts on the immune system, it needs extra care in:

• People with autoimmune diseases, such as lupus, rheumatoid arthritis or autoimmune thyroid disease.
• Organ transplant patients on anti-rejection medicines.
• Pregnancy and breastfeeding, where there are not enough data.

Common questions

Does Thymosin Alpha-1 prevent colds and flu?

That has not been proven in healthy people. Vaccination, sleep, exercise and vitamin D sufficiency remain the best-supported ways to protect yourself.

How long is a course?

Courses vary, often several weeks to a few months with twice-weekly injections. Your physician will set the plan.

Can I take it with other peptides?

It is often combined with longevity peptides such as Epithalon. Your physician will check for overlap with your medicines.

Is it approved in Saudi Arabia?

Treatments are dispensed only by prescription after a physician's assessment. Read our guide on whether peptides are legal in Saudi Arabia.

Information on this website is for education only and does not replace a physician's advice. Treatments are dispensed by prescription only, after assessment by a licensed physician.

Keep reading

• Epithalon and longevity peptides
• KPV peptide for gut and inflammation
• Are peptides legal in Saudi Arabia?
• Immune and longevity peptides

Book a consultation to discuss immune support with a physician.