Thymosin alpha-1 is an immune-modulating peptide marketed as Zadaxin in several countries. It has been studied across infectious-disease and oncology settings, but it is not FDA-approved in the United States. Evidence from one indication or jurisdiction does not establish broad immune-support benefits.
Thymic peptide / immune modulator
Thymosin Alpha-1
Thymosin alpha-1 is an immune-modulating peptide marketed as Zadaxin in several countries. It has been studied across infectious-disease and oncology settings, but it is not FDA-approved in the United States. Evidence from one indication or jurisdiction does not establish broad immune-support benefits.
Regulatory watch
Last reviewed Jul 1, 2026
Next review Jul 29, 2026
Evidence snapshot
Thymosin Alpha-1 is approved in 30+ countries (including China, Italy, and parts of Southeast Asia) for chronic hepatitis B, hepatitis C, and immune adjuvant use, but has never received FDA approval in the United States.
FDA Fast Track designation was granted for certain indications (including malignant melanoma), reflecting regulatory interest, but Phase 3 trials have not resulted in US approval to date.
Over 100 clinical trials have been registered on ClinicalTrials.gov studying thymosin alpha-1 across infectious disease, oncology, and immune support contexts.
During COVID-19, thymosin alpha-1 was studied as an immune modulator in severe cases; retrospective data suggested potential mortality benefit in critically ill patients, but randomized controlled trial evidence remains limited.
King & Tuthill (2016) published a comprehensive review of immune modulation with thymosin alpha-1 in Expert Review of Clinical Immunology, summarizing its mechanism and clinical development history.
Research record
What the evidence record says
- Evidence grade
- Not Graded
- Regulatory status
- Thymosin Alpha-1 regulatory status has not been fully reviewed by Peptide Report editorial team. See company profiles and regulatory watch for current status.
Evidence records
Studies, registries, reviews, and regulatory records
Evidence review pending
- Detailed evidence review for Thymosin Alpha-1 is pending editorial assessment. Current summary reflects available public records.
Records: Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov, Immune Modulation with Thymosin Alpha 1, Zadaxin (thymosin alpha-1) Product Information
Evidence timeline
What changed, and when
Peptide Report last reviewed Thymosin Alpha-1 on 2026-07-01.
Records: Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov
Direct answers
Frequently asked questions
What is Thymosin Alpha-1?
Thymosin Alpha-1 is a thymic peptide / immune modulator tracked by Peptide Report. See the full profile for current editorial assessment.
Open research questions
What is still unknown
- What is the complete human evidence base for Thymosin Alpha-1?
- What are the long-term safety considerations for Thymosin Alpha-1?
Tracked claims
Thymosin Alpha-1 is approved in over 30 countries but not FDA-approved in the United States.
Evidence level: Primary regulatory
Sources: Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov, Immune Modulation with Thymosin Alpha 1
How to read this: Approval status should be verified against current FDA records and international regulatory databases on each review cycle. The Fast Track designation does not constitute FDA approval.
Thymosin Alpha-1 was investigated as an immune-modulating therapy for severe COVID-19 during the pandemic.
Evidence level: Peer reviewed
Sources: Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov, Immune Modulation with Thymosin Alpha 1
How to read this: COVID-19 studies are largely retrospective or small-scale. Do not imply proven efficacy. Update if larger randomized controlled trial data become available.
Thymosin Alpha-1 has been studied in over 100 clinical trials across multiple indications.
Evidence level: Primary regulatory
Sources: Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov
How to read this: The number of registered trials reflects research interest, not confirmed efficacy. Verify the current count on ClinicalTrials.gov at each review.
Free report
Get the source-quality checklist
Use the same checklist Peptide Report uses to separate Thymosin Alpha-1 claims, source records, supplier documentation, and media signals.
V1 collects email, role, and topic interest only. No medication, health-condition, dosing, or current-use data is collected in this form.
Formspree processes this submission for Peptide Report. Privacy notice.
Sources on this page
Each source record is linked to the claim or evidence note it supports.
Thymosin Alpha-1 Clinical Trial Registry Entries: ClinicalTrials.gov
ClinicalTrials.gov registry search showing 100+ interventional studies of thymosin alpha-1 across infectious disease, oncology, and immune support contexts, including COVID-19 trials.
6 linked pagesOpen original ·
clinicaltrials-gov-thymosin-alpha-1Immune Modulation with Thymosin Alpha 1
King R, Tuthill C (2016) comprehensive review (PMID 26653168) of thymosin alpha-1's immune-modulating mechanism, clinical development history, and therapeutic applications including hepatitis, oncology, and sepsis.
6 linked pagesOpen original ·
pubmed-king-tuthill-2016Zadaxin (thymosin alpha-1) Product Information
SciClone Pharmaceuticals product information for Zadaxin (thymosin alpha-1), approved in over 30 countries for chronic hepatitis B, hepatitis C, and immune adjuvant use. Not FDA-approved in the United States.
6 linked pagesOpen original ·
sciclone-zadaxin-product-infoRelated compounds
5-Amino-1MQ
5-Amino-1MQ is a small-molecule NNMT inhibitor with published efficacy findings limited to cell and rodent studies. No e...
Regulatory watchAOD-9604
AOD-9604 is a synthetic fragment of human growth hormone developed as a weight-loss candidate. Its Phase 2 obesity progr...
Regulatory watchArgireline (acetyl hexapeptide-8)
Small studies have reported modest wrinkle changes with some Argireline formulations, but results are inconsistent and o...
Evidence reviewBPC-157
BPC-157 is an experimental peptide with extensive animal research but very limited human evidence. A Phase 1 registry re...
Regulatory watchStay informed