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Research compound · not FDA-approved

Thymosin alpha-1

Also written Thymosin alpha 1.

Thymosin alpha-1 is a peptide 28 amino acids long, first pulled out of calf thymus extract in the 1970s. It acts on how T cells mature and signal.

What matters first

Why people look it up
It is sold for immune support: long COVID, chronic infection, and general resilience.
What the evidence shows
It carries a large trial record, and that record is about acutely unwell hospital patients rather than healthy adults. Under the name thymalfasin it is an approved medicine in several countries, mainly for chronic hepatitis B. Its largest trial gave it to 1,106 people with sepsis. By day 28, 23.4% had died on the drug against 24.1% on placebo.
Dose status
Thymosin alpha-1 is not FDA-approved, so no dosing label exists for it. The sections below explain what researchers tested and what remains unknown.

Medically reviewed by Kenneth Montecillo, MD2026-09-07open the primary sources

What is known about Thymosin alpha-1

Thymosin alpha-1 is a peptide that affects how T cells mature and send signals. It is sold as thymalfasin in several countries, mainly for chronic hepatitis B. It has never been approved in the United States. Large trials used 1.6 mg under the skin. The timing changed by condition.

Thymosin alpha-1 research and regulatory details: evidence quality, approval status, doses, handling, and presentation.
TopicValue
Strongest sourcelimited human data
FDA approvalNot FDA-approved
Studied dosing1.6 mg twice a week, for 26 or 52 weeks, in a 98-patient randomized trial in chronic hepatitis B — from clinical trials
Studied dosing1.6 mg once daily for the first week, then twice a week to week 12, in a 120-patient randomized trial in hepatitis-B-related acute-on-chronic liver failure — from clinical trials
Studied dosing1.6 mg every 12 hours for up to seven days — the regimen of the 1,106-participant phase 3 trial that found no mortality benefit — from clinical trials
Studied dosing1.6–6.4 mg on days 8–11 and 15–18 of each 28-day cycle — the three arms (1.6, 3.2 and 6.4 mg) of a 488-participant phase 2 dose-ranging trial in metastatic melanoma — from clinical trials
Typical vials5 mg · 10 mg

Every row links back to a source listed below. These facts are for reference, not a personal recommendation.

What the evidence for Thymosin alpha-1 is

People have received this compound in a documented setting, or it has approval outside the United States. The available human evidence is still too limited to show a clear dose-and-result pattern for US use.

limited human data
What it establishes
It shows that people have received it and that some human information exists.
What it does not establish
It does not prove that the same dose is appropriate in the United States or that uncommon and long-term risks are known.

Check the country, study size and reason it was used. Do not treat limited human data as an FDA-approved schedule.

Evidence snapshot and shareable image

Evidence snapshot

Foreign approval or limited human data

The fastest way to see what kind of evidence this page is built on.

Regulation
Not FDA-approvedNo US prescribing label
Dose source
Human study4 reported dose rows
Safety evidence
3 listed safety findingsCommon and serious effects shown apart
Sources
6 cited sourcesMedical review complete · 2026-09-07
Open the shareable evidence image
Thymosin alpha-1 at a glance: foreign approval or limited human data, dosing basis, regulatory status, safety coverage, and cited-source count. These details summarize the available sources; they are not treatment recommendations.

Where Thymosin alpha-1 is in clinical trials

51 registered studies; the program has reached phase 4, and 8 are still enrolling.

The soonest a running study expects to finish measuring people is December 2026. That is when the sponsor expects to finish collecting the main measurement. It is not a results date, and not a date anything goes on sale.

  • Phase 4Completed

    Thymosin Alpha 1 in the Prevention of Pancreatic Infection Following Acute Necrotizing Pancreatitis

    Weiqin Li · Pancreatitis, Acute Necrotizing · 508 participants · started March 2018

    Main measurement due December 2020

    NCT02473406 on ClinicalTrials.gov

  • Phase 4Completed

    Efficacy of Thymosin Alpha 1 on Improving Monocyte Function for Sepsis

    Sun Yat-sen University · Sepsis · 20 participants · started March 2016

    Main measurement due September 2016

    NCT02883595 on ClinicalTrials.gov

  • Phase 4Completed

    Optimized Treatment and Regression of HBV-induced Early Cirrhosis

    Beijing Friendship Hospital · Liver Cirrhosis · 82 participants · started June 2013

    Main measurement due December 2016

    NCT01938820 on ClinicalTrials.gov

Searched under the name thymosin alpha 1, which is how the registry files it.

A registered study means a sponsor filed a plan and started enrolling. It is not evidence the drug works, and most drugs tested in people never reach a pharmacy. Sponsors write and update these sources themselves; the National Library of Medicine publishes them without checking them.

ClinicalTrials.gov · retrieved 2026-09-27

Every compound we track, and what stage each one has reached →

Regulatory status

An approval elsewhere is real evidence, and it is not an American one.

The review standard, the permitted claims and the safety follow-up all belong to the jurisdiction that granted it. The practical gap shows up in the vial. Trials dissolve 1.6 mg of powder in 1 mL and inject that.

Research vials sold under this name hold 5 mg or 10 mg. So one 10 mg vial holds more than six trial doses. Any quantity quoted from the approved labeling describes a different container entirely.

Full regulatory tracker →

Where to go next on Thymosin alpha-1

The related pages keep each topic with its evidence.

Every reaction on the Thymosin alpha-1 page, with its frequency

1 common and 2 serious Thymosin alpha-1 reactions, each carrying its own source.

Thymosin alpha-1 concentration in the Thymosin alpha-1 dosage calculator

The concentration in mg/mL for every Thymosin alpha-1 vial and water pairing, printed in full.

Reconstituting Thymosin alpha-1 at 10 mg, step by step

The 10 mg Thymosin alpha-1 table itself, not a general rule applied to an unrelated vial size.

Choosing a water volume for a 5 mg Thymosin alpha-1 vial

How the water volume changes concentration, draw size and doses per 5 mg Thymosin alpha-1 vial.

Mixing math for any vial, not just Thymosin alpha-1

One calculator for every vial on this site, with Thymosin alpha-1 as one example

Where Thymosin alpha-1 sits among the immune support compounds

3 compounds people take for immune support, and what each was measured against, with Thymosin alpha-1 as one example

What backs the Thymosin alpha-1 numbers, and what backs the rest

Every row states whether a label, a trial or nothing stands behind it, including Thymosin alpha-1

Where the Thymosin alpha-1 program has actually got to

A registration is a plan and never gets reported as a result, with Thymosin alpha-1 as context

Primary regulatory documents, including Thymosin alpha-1

Every URL was fetched and live on its retrieval date, Thymosin alpha-1 or otherwise.

Explore the research behind Thymosin alpha-1 and other compounds

Explore approval status and published research related to Thymosin alpha-1.

Safety notes

  • Approved outside the United States only — no American labeling exists for any use
  • The largest trial included 1,106 people with sepsis. It found no survival benefit
  • These studies treated very ill hospital patients. None tested healthy adults, longevity or general immune support
  • Trials mixed 1.6 mg in 1 mL. Research vials hold 5 mg or 10 mg, so the amounts do not transfer
  • Acts on T-cell function, so it is not a neutral addition for anyone with autoimmune disease or on immunosuppressive treatment
  • Research-grade material is not the pharmaceutical product any approval or trial refers to

Questions about Thymosin alpha-1

Is Thymosin alpha-1 FDA-approved?

No. There is no prescribing label for it, so no approved dose exists — the regulatory status section above has the detail.

How is Thymosin alpha-1 taken?

By injection under the skin, twice a week.

How does Thymosin alpha-1 differ from the other compounds in this class?

Thymosin alpha-1 has been studied in people, but it works through a different system from GLP-1 and amylin drugs. Its doses and results are not directly comparable with theirs.

What is not known about Thymosin alpha-1?

It does not prove that the same dose is appropriate in the United States or that uncommon and long-term risks are known.

Questions readers ask

What is the peptide thymosin alpha-1 used for?

Outside the United States it is an approved medicine called thymalfasin, used mainly in chronic hepatitis B and as an immune adjuvant. Registered trials have also run it in hepatitis C, liver failure, sepsis, pancreatitis and cancer care.

It acts on how T cells mature and signal. Every regimen on record went to acutely unwell people in hospital — none studied healthy adults, longevity or general immune support.

How long does it take thymosin alpha 1 to work?

Trials report course length, not a time to onset. Sepsis used one dose every 12 hours, for up to seven days. Chronic hepatitis B used twice a week, for 26 or 52 weeks.

The liver-failure trial gave it daily for a week, then twice a week to week 12. So the schedule moves with the illness and the quantity holds still, at 1.6 mg.

What are the risks of using thymosin alpha 1?

In the largest trial, unwanted events were just as common on placebo: 66.4% against 67.6%, among 1,089 adults with sepsis. Serious ones ran 26.8% against 29.3%, with no meaningful difference.

The sharper risks sit off that table. It acts on T-cell function, so it is not a neutral addition for anyone with autoimmune disease or on immune-suppressing treatment.

What is the best peptide for boosting the immune system?

No trial has ranked peptides against each other for immune function, so nobody can name a best one honestly.

Thymosin alpha-1 has the largest registered record of the immune-facing peptides here, and it is approved abroad as thymalfasin. Its biggest test still failed: a 1,106-participant phase 3 in sepsis found no survival benefit.

6primary sources, each with the day we read it — open the documents used on this page