Not FDA-approved (approved in some other countries)Thymic peptideImmune research
Thymosin alpha-1 (thymalfasin)
Thymosin alpha-1 (thymalfasin, Zadaxin) is a 28-amino-acid thymic peptide approved in some countries for hepatitis B; it is not FDA-approved.
What is Thymosin alpha-1?
Thymosin alpha-1 (thymalfasin, Zadaxin) is a 28-amino-acid thymic peptide approved in some countries for hepatitis B; it is not FDA-approved. Thymosin alpha-1 (thymalfasin) is not approved by the FDA (approved in some other countries); products sold online in the US are labeled for research use only.
Key takeaways
- Thymosin alpha-1 (thymalfasin) is not approved by the FDA (approved in some other countries); products sold online in the US are labeled for research use only.
- PubMed indexes 59 papers on Thymosin alpha-1 (11 tagged as clinical trials) as of October 19, 2026.
- ClinicalTrials.gov lists 65 registered studies using Thymosin alpha-1.
- 36 vendors in our directory listed Thymosin alpha-1 in their public catalog on October 19, 2026.
Structure
Amino-acid sequence of Thymosin alpha-1, 28 residues: 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
Regulatory & access status
Thymosin alpha-1 (thymalfasin) is not approved by the FDA (approved in some other countries); products sold online in the US are labeled for research use only.
Sellers that market unapproved peptides for human use can receive FDA warning letters; our vendor directory links any letter we found on fda.gov.
How much research exists on Thymosin alpha-1 (thymalfasin)?
PubMed indexes 59 papers mentioning Thymosin alpha-1 (thymalfasin) in the title or abstract, 26 of them from the last five years and 11 tagged as clinical trials (search run October 19, 2026; repeat the search).
Most relevant recent papers
- Neoadjuvant immunochemotherapy plus thymalfasin in locally advanced gastric cancer: a prospective clinical trial. — BMC Med, 2026 · clinical trial
- Thymalfasin in the treatment of hepatitis B and C. — Ann N Y Acad Sci, 2010 · review
- Thymalfasin: an immune system enhancer for the treatment of liver disease. — J Gastroenterol Hepatol, 2004 · review
- Thymalfasin therapy accelerates COVID-19 pneumonia rehabilitation through anti-inflammatory mechanisms. — Pneumonia (Nathan), 2023
- Thymalfasin: an immune system enhancer for the treatment of liver disease. — J Gastroenterol Hepatol, 2004 · review
- Identification and determination of structurally related peptide impurities in thymalfasin by liquid chromatography-high-resolution mass spectrometry. — Anal Bioanal Chem, 2022
Registered clinical studies
ClinicalTrials.gov lists 65 studies with Thymosin alpha-1 (thymalfasin) as an intervention (see all). Most recent:
- Study of Thymosin α1 to Reduce Acute Pneumonia For Bulky None-small Cell Lung Cancer — NCT03659578 · Phase 2 · completed · started 2018-08-09
- Efficacy of Thymosin alpha1 for Severe Sepsis — NCT00711620 · N/A · completed · started 2008-05
- Therapeutic Safety and Efficacy of REP 2139 (REP 9AC') in HBV Infected Patients — NCT02646189 · Phase 1/Phase 2 · completed · started 2011-08
- Neoadjuvant With Tα1 Plus Immuno-chemotherapy for Resectable NSCLC — NCT06607926 · N/A · unknown · started 2024-10-15
- Thymosin Alpha-1 for irAE Secondary to ICIs — NCT06178146 · Phase 4 · unknown · started 2023-09-01
What the evidence does not show
- Paper counts measure research attention, not whether Thymosin alpha-1 works or is safe.
- No FDA review of any "research use only" product's identity, purity, sterility or dose.
Research suppliers that list Thymosin alpha-1
36 vendors in our directory listed a product matching Thymosin alpha-1 in their public catalog on October 19, 2026. Listed alphabetically; a listing is not an endorsement. Research use only.
- Amino Amigos
- Ascension Peptides
- Atomik Labz
- Backroad Aminos
- BioGenix Peptides
- BioLongevity Labs
- Biotech Peptides
- Bulk Peptide Supply
- Costides
- Dynamic Peptide
- Eros Peptides
- Evolve BioPep
- Extreme Peptides
- Liberty Peptides
- Licensed Peptides
- Modern Aminos
- NuScience Peptides
- Paramount Peptides
- Peptide Crafters
- Peptide Partners
- Peptide Worldwide
- Pharma Grade Peptides
- Pinnacle Peptide Labs
- Plum Labs Research
- Polaris Peptides
- ProtideHealth
- Pure Lab Peptides
- Royal Peptides
- San Diego Peptides
- Science.bio
- Southern Aminos
- Sunrise BioResearch
- Swiss Chems
- Verified Peptides
- Voltera Sciences
- Xcel Peptides
Prices per mg, where we could verify them, are on our price comparison.
Thymosin alpha-1 reconstitution math
Lab arithmetic only, not dosing guidance: use the peptide calculator to turn a vial size and diluent volume into a concentration.
Thymosin alpha-1 FAQ
Is Thymosin alpha-1 FDA-approved?
Thymosin alpha-1 (thymalfasin) is not approved by the FDA (approved in some other countries); products sold online in the US are labeled for research use only.
Is Thymosin alpha-1 safe?
Safety data come from the published studies listed on this page; read them in full. Products sold as "research use only" have no FDA review of their purity, sterility or dose.
How much research is there on Thymosin alpha-1?
PubMed indexes 59 papers on Thymosin alpha-1 (11 tagged as clinical trials) as of October 19, 2026.
Who sells Thymosin alpha-1?
Amino Amigos, Ascension Peptides, Atomik Labz, Backroad Aminos, BioGenix Peptides, BioLongevity Labs and 30 more listed it on their public catalogs when we checked; a listing is not an endorsement.
Head-to-head comparisons
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