Thymosin Alpha-1

A natural thymus peptide that strengthens T-cell responses. Approved in dozens of countries (not the US) for hepatitis B and immune support.

Evidence: Ongoing clinical research
Half-life: ~2 hours
Sources: 2 cited

Is thymosin Alpha-1 FDA-approved?

Approved in many countries outside the US. Not FDA-approved.

Overview

Thymalfasin is a lab-made copy of thymosin alpha-1, first isolated from the thymus gland. It's approved in many countries, mainly for chronic hepatitis B and as a vaccine helper in people with weak immune systems. In a large 2025 trial in sepsis, it didn't lower the risk of death.

How it works

It helps T cells mature and boosts signaling through toll-like receptors on immune cells, sharpening the body's response to infection.

How long does thymosin Alpha-1 stay in the body?

About 2 hours after a shot.

What it's studied for

Chronic hepatitis B and C
Sepsis
Vaccine response
Cancer immunotherapy (add-on)

Reported side effects

Injection-site discomfort

Related: FOXO4-DRI, KPV, Humanin, LL-37.

Sources

The studies and prescribing labels this page is written from.