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Immunology and inflammation Research use only

Thymosin α1

Thymalfasin, an N-acetylated 28-residue peptide

A peptide first isolated from the thymus, studied for its role in T-cell maturation. As thymalfasin it is licensed as a medicine in some countries outside the US, UK and EU, mainly for hepatitis B.

Reviewed 26 October 2026 · Sources listed at the end of the page

Structure

A 28-residue, strongly acidic peptide originally isolated from thymus tissue, acetylated at the N-terminus. Select any residue to see what it is.

Non-polarPolarAcidic (negative)Basic (positive)
Select a residue above. Position 1 is the N-terminus.

Evidence at a glance

Where the published research on Thymosin α1 comes from, by type of study.

Many studies

Cell studies

T-cell and dendritic cell maturation, toll-like receptor signalling.

Several studies

Animal studies

Infection, vaccine response and tumour models in mice.

Clinical trials

Human studies

Clinical trials of thymalfasin in hepatitis B, sepsis and as a vaccine adjuvant, with mixed results.

Worth knowing. Research-grade powder is not the licensed medicine. Licensed status abroad does not make it legal to sell for human use in the US, UK or EU.

Research areas

What laboratories have studied Thymosin α1 for, and in which models. These are research questions, not proven uses.

T-cell maturation

Human immune cell culture
  • Promotes maturation of T cells and dendritic cells in vitro.
  • Acts through toll-like receptors on immune cells.

Infection and vaccines

Mouse infection modelsVaccine studies
  • Studied as an adjuvant to boost vaccine responses.

Legal status

Thymosin α1 is not an approved medicine anywhere we cover. Suppliers may sell it for laboratory research only, and regulators judge that by the whole website, not the label.

United States Not approved

Not FDA-approved. It has orphan-drug designations for some conditions, which is not approval.

United Kingdom Not licensed

No MHRA licence. Sold with medicinal claims it counts as a medicine under the Human Medicines Regulations 2012.

European Union Not authorised

No EMA authorisation. Under Directive 2001/83/EC a substance can be a medicine by function, whatever its label says.

Sport Check S0

Not approved for human use, so it falls under WADA's S0 non-approved substances class. Check the current list.

Lab handling

General good practice for research materials. Follow the supplier's datasheet where it differs.

Storage

Keep the sealed material at −20 °C, dry and away from light. Let the vial reach room temperature before opening to stop condensation.

Solubility

Soluble in sterile water or buffer. Add solvent down the vial wall and swirl gently rather than shaking.

Aliquots

Split solutions into single-use aliquots, label with lot number and date, and freeze. Avoid repeated freeze-thaw cycles.

Work out your stock solution

Stock concentration, molarity and dilutions for Thymosin α1, using MW 3108.28 g/mol.

Open the lab calculator

Before you buy for your lab

Tick each check as you confirm it with the supplier. Do not order until all six are done.

0 of 6
RecommendedPasses all six checks and sells no GLP-1 research compounds.
CautionResearch-only marketing and COAs, but sells GLP-1 or other closely watched compounds.
AvoidDosing or human-use claims, or an FDA warning letter. Never linked.
Supplier comparison for Thymosin α1 is in progress. Labels follow our editorial policy. Until listings go live, run any supplier through the vendor check. All products from any supplier are for laboratory research use only.

Questions researchers ask

What is Thymosin α1?

A peptide first isolated from the thymus, studied for its role in T-cell maturation. As thymalfasin it is licensed as a medicine in some countries outside the US, UK and EU, mainly for hepatitis B.

What is the molecular weight of Thymosin α1?

About 3108.28 g/mol for the free peptide. Salt forms such as acetate weigh more, so use the figure on your batch certificate of analysis.

Is Thymosin α1 approved for human use?

No. Not FDA-approved. It has orphan-drug designations for some conditions, which is not approval.

How should Thymosin α1 be stored in the lab?

Keep the sealed material cold, dry and away from light, typically at −20 °C. Once in solution, split it into single-use aliquots and freeze to avoid repeated freeze-thaw cycles.

Does this page give doses?

No. We publish laboratory and educational information only, never doses, injection guidance or treatment advice.

Sources

For research and educational purposes only. Thymosin α1 is not approved for human or veterinary use. Some links on this site are affiliate links. · Disclosure · Disclaimer · Editorial policy · Contact · Privacy policy · © 2026 Peptides in Lab