Thymosin Alpha-1
10 mg · Lyophilized powder
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28-amino-acid acetylated peptide (thymosin α1).
Need larger quantities? Wholesale pricing for qualified businesses
For laboratory research use only by qualified researchers. Not for human or veterinary use. Not a drug, dietary supplement, cosmetic or food. Not evaluated by the FDA for any use.
Quick Summary
Not FDA-approved — marketed in some other countriesThymosin α1 is a 28-amino-acid peptide with an acetylated N-terminus, first isolated from calf thymus in 1977. It has been studied as an immune modulator in viral hepatitis, cancer, sepsis and vaccine research. A synthetic version, thymalfasin (Zadaxin), is marketed in some countries outside the U.S., but FDA has approved no thymosin α1 product.
Areas of research
- Chronic viral hepatitis
- Sepsis
- Oncology
- Vaccine response
- Immunology
- Amount
- 10 mg
- Form
- Lyophilized powder
- References
- 6 cited
- COA
- Batch report pending
- Free U.S. shipping on orders of $150 or more
- Lyophilized powder in a sealed vial
Research Use Notice. This product is intended for laboratory and research purposes. It is not intended for human consumption or personal medical use. Product information is provided for scientific and educational context only. See our Research Use Policy.
Why Researchers Study It
- Immune signaling through Toll-like receptors on dendritic cells
- T-cell maturation and immune function in immunocompromised states
- Chronic viral hepatitis, in small and mostly unblinded trials
- Sepsis, including a negative 2025 phase 3 trial
- Vaccine response and cancer, in exploratory studies
What It Is
Thymosin α1 is a peptide of 28 amino acids whose first amino acid carries an acetyl group.
Thymosin α1 is a peptide of 28 amino acids whose first amino acid carries an acetyl group. It was isolated from a calf thymus extract (thymosin fraction 5) and sequenced in 1977.
The chemically made version, identical in sequence, is called thymalfasin and has been sold as Zadaxin. A 2020 review describes approval in more than 35 countries for hepatitis B and C. FDA reports it is not approved in the United States, Japan or Europe (except Italy), and notes it could not independently verify the manufacturer's approval claims.
It has been studied as an immune modulator. FDA's 2024 review describes its activity as mediated at least partly through Toll-like receptor 9 on dendritic and lymphoid progenitor cells.
Clinical studies have covered hepatitis B and C, HIV, several cancers, sepsis, COVID-19 and vaccine response. FDA's 2024 review judged the evidence insufficient to establish effectiveness for each of these uses.
How It Works
2 established · 3 proposed or under investigation
Established
- Sequence and N-terminal acetylation are characterized; thymalfasin is identical in sequence to the natural peptide
- Acts on immune cells at least partly through Toll-like receptor 9, according to FDA's 2024 review
Proposed / under investigation
- Activation of dendritic and natural killer cells and support for T-cell maturation (described in reviews)
- Toll-like receptor 2 activity in myeloid and dendritic cells (described in a 2020 review)
- Restoring immune balance in sepsis, which a 2025 phase 3 trial did not support with a mortality difference
Research Status & Evidence
Not FDA-approved — marketed in some other countries
FDA states it has approved no thymosin α1 product and judged the evidence insufficient for every use it reviewed. A 2025 phase 3 sepsis trial found no reduction in 28-day mortality.
Types of evidence
- Available: Cell & lab studies
- Not available: Animal studies
- Not available: Early human studies
- Available: Clinical trials
- Available: Approved medical use
Thymosin α1 has more human data than most research peptides, but much of it comes from small, unblinded or single-country studies, and FDA's 2024 review found insufficient evidence of effectiveness for every use it examined. A 361-patient single-blind sepsis trial reported a borderline mortality difference; the larger double-blind TESTS phase 3 trial (1,106 patients) found none. Approved use exists only outside the U.S.
Areas of research
- Chronic viral hepatitishepatitis B and C, small trials
- Sepsisrandomized trials in China, including a negative phase 3
- Oncologymelanoma, liver and lung cancer studies
- Vaccine responseexploratory adjuvant studies
- ImmunologyToll-like receptor and T-cell research
Limitations
- No thymosin α1 product is FDA-approved; FDA states it is not approved in the U.S., Japan or Europe (except Italy)
- FDA's 2024 review found insufficient evidence of effectiveness for hepatitis B and C, HIV, COVID-19, sepsis, several cancers and vaccine use
- The 2025 TESTS phase 3 trial found no reduction in 28-day mortality in sepsis (23.4% vs 24.1% with placebo)
- FDA has raised immunogenicity concerns and a possible risk of worsening graft-versus-host disease after stem-cell transplant, and its 2024 review weighed against adding it to the 503A bulks list
- Listed among withdrawn Category 2 nominations on FDA's compounding safety-risk page, with FDA noting possible immunogenicity
Specifications
10 mg · Lyophilized powder · CAS 62304-98-7
- Product
- Thymosin Alpha-1
- Category
- Peptides
- Size
- 10 mg
- Form
- Lyophilized powder
- Synonyms
- Thymosin α1; Tα1; Thymalfasin; Zadaxin; Ta1
- CAS number
- 62304-98-7
- Molecular formula
- C129H215N33O55
- Molecular weight
- 3108.3 g/mol
- Sequence
- Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH
- SKU
- REN-TA1-10
Molecular data: Free base (thymalfasin), not the acetate salt, per FDA's December 2024 Pharmacy Compounding Advisory Committee presentation.
Testing & COA Batch report pending
Research References (6)
Linked sources · last reviewed October 2026
- Goldstein AL et al. Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide. Proc Natl Acad Sci U S A 1977 · PubMed 265536
- Dominari A et al. Thymosin alpha 1: A comprehensive review of the literature. World J Virol 2020 · PubMed 33362999
- Wu J et al. The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial. Crit Care 2013 · PubMed 23327199
- Wu J et al. (TESTS Study Collaborator Group). The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial. BMJ 2025 · PubMed 39814420
- FDA. Thymosin alpha-1 (Ta1) related bulk drug substances. Pharmacy Compounding Advisory Committee presentation, December 4, 2024 · fda.gov
- FDA. Certain bulk drug substances for use in compounding that may present significant safety risks (updated April 2026) · fda.gov
Summaries are written by Renuvia Labs from the sources above for educational context only. Last reviewed October 30, 2026.
Frequently Asked Questions
Is thymosin alpha-1 the same as thymalfasin?
They have the same sequence. Thymosin α1 is the 28-amino-acid peptide first isolated from calf thymus; thymalfasin is the chemically made version, sold in some countries as Zadaxin. FDA reports it is not approved in the United States.
What are the thymosin alpha-1 molecular weight and CAS number?
As the free base (thymalfasin), thymosin α1 has the formula C129H215N33O55, a molecular weight of 3108.3 g/mol and CAS number 62304-98-7, per FDA's December 2024 Pharmacy Compounding Advisory Committee presentation.
Is thymosin alpha-1 related to TB-500?
Only by name. Thymosin α1 and thymosin β4 are different proteins. TB-500 is a short fragment of thymosin β4, not of thymosin α1.
When will Thymosin Alpha-1 be available?
Thymosin Alpha-1 is sold out right now. Use "Email me when it's available" on this page and we send one email when it is back in stock. Every lot is listed in the COA library with its Certificate of Analysis once the lab issues it.
What size is the Thymosin Alpha-1 vial?
Thymosin Alpha-1 is supplied as a single 10 mg lyophilized vial (10 mg total peptide content stated on the label).
What is Thymosin Alpha-1?
Thymosin α1 is a 28-amino-acid peptide with an acetylated N-terminus, first isolated from calf thymus in 1977. It has been studied as an immune modulator in viral hepatitis, cancer, sepsis and vaccine research. A synthetic version, thymalfasin (Zadaxin), is marketed in some countries outside the U.S., but FDA has approved no thymosin α1 product.
Is there a Thymosin Alpha-1 coupon or discount code?
There is no public coupon code. New customers get a first-order discount for joining the Renuvia email list, volume pricing starts at 2 vials of Thymosin Alpha-1, and U.S. shipping is free over $150. Codes on third-party coupon sites are not valid here.
What are other names for Thymosin Alpha-1?
Thymosin Alpha-1 is also referred to as Thymosin α1, Tα1, Thymalfasin, Zadaxin, Ta1.
What are the CAS number and molecular weight of Thymosin Alpha-1?
Thymosin Alpha-1: CAS number 62304-98-7; molecular formula C129H215N33O55; molecular weight 3108.3 g/mol. Sequence: Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH. (Free base (thymalfasin), not the acetate salt, per FDA's December 2024 Pharmacy Compounding Advisory Committee presentation.)
What sizes is Renuvia Labs Thymosin Alpha-1 available in?
Thymosin Alpha-1 is listed in 10 mg, supplied as lyophilized powder in a sealed glass vial. It is sold for laboratory research use only.
Where is the Certificate of Analysis for Thymosin Alpha-1?
Certificates of Analysis are published per lot in the Renuvia Labs COA library, searchable by product, SKU or lot number. Thymosin Alpha-1 shows "pending" there until the current lot's report exists; it is then linked on this page too.
Is this in stock?
Yes, unless the page says sold out. You reserve it with no payment today, and we email payment instructions in approximately 1–2 business days. Your order ships once payment arrives.
What form is this product supplied in?
Peptides and research compounds ship as lyophilized (freeze-dried) powder in a sealed glass vial. The fill amount printed on the product page and label is the total content of the vial.
Is this product for human use?
No. All Renuvia Labs products are sold strictly for laboratory research use. They are not for human or animal consumption and are not intended to diagnose, treat, cure or prevent any disease.
Do you offer volume pricing?
Yes. Per-vial pricing drops automatically at 2, 3 and 5 vials of the same product; the current tiers are shown next to the price. For larger quantities, see our wholesale program.
How much is shipping?
Free U.S. shipping on orders of $150 or more; $8.95 flat rate below that.
Do you ship outside the U.S.?
No. Renuvia Labs ships to U.S. addresses only. Research institutions outside the U.S. can enquire through the wholesale program.
