Overview
Thymosin alpha-1 is a 28-amino-acid acetylated peptide originally isolated from thymosin fraction 5, a calf-thymus extract studied by Allan Goldstein and colleagues in the 1970s. It is derived from the larger precursor prothymosin alpha and is now produced synthetically under the INN thymalfasin.
As Zadaxin, thymalfasin has been registered in more than 30 countries, mainly in Asia, Latin America and the Middle East, for indications including chronic hepatitis B and as an immune adjuvant. It is not approved by the FDA or centrally by the EMA. Clinical research has also examined it in sepsis, vaccine non-responders and oncology settings, with mixed results across trials of varying quality. In the laboratory it is used to study T-cell maturation and innate immune signalling. Our product is the research-grade peptide for immunology studies, not a medicinal product.
Mechanism studied
- Thymosin α1
- Dendritic cells (TLR)
- T-cell maturation
- Immune response
Thymosin alpha-1 is reported to act on innate immune cells through Toll-like receptors, particularly TLR2 and TLR9 on dendritic cells, activating MyD88-dependent signalling and downstream NF-κB and p38 MAPK pathways. This promotes dendritic-cell maturation and the release of cytokines such as IL-12 and interferons, which in turn support differentiation of T-helper type 1 cells and cytotoxic T-cell responses. Studies also describe increased expression of MHC class I molecules, potentially improving antigen presentation.
Research highlights
- 0128-residue acetylated peptide isolated from calf-thymus fraction 5
- 02Registered as Zadaxin in more than 30 countries; not FDA- or EMA-approved
- 03Activates dendritic cells via Toll-like receptor signalling
- 04Clinical studies in hepatitis B, sepsis and vaccine response show mixed results
- 05Widely used as a reference immunomodulatory peptide in research
Research areas
- T-cell maturation research
- Dendritic cell & TLR signalling
- Vaccine response studies
- Viral hepatitis research
Evidence & regulatory status
Overall status: Approved in several countries (not in the US or EU)
Key references
- [1]Camerini & Garaci, 2015 — Expert Opin Biol Ther
- [2]Zadaxin® product information — national registrations
Latest published research
630 papers on PubMed →Thymosin α-1 in cancer therapy: Immunomodulatory mechanisms, clinical applications, and translational perspectives
Chuang SC et al. · European journal of pharmacology · 2026 Oct 28 · PMID 42641753
Clinical Applications and Evidence Landscape of Thymosin Alpha 1 as an Immunomodulatory Adjunct in Cancer Care: A Scoping Review
Kim SD et al. · Pharmaceuticals (Basel, Switzerland) · 2026 Sep 19 · PMID 42797537
Thymosin Alpha-1 Provides Direct Neuroprotection by Engaging the Orexin Receptor HCRTR1 to Suppress Neuronal Necroptosis
Kang X et al. · Advanced science (Weinheim, Baden-Wurttemberg, Germany) · 2026 Sep 3 · PMID 42693587
Thymosin Alpha-1 Restores Chemotherapy-Induced Antitumor Immunity by Chaperoning a MicroRNA Ligand of TLR7 in Dendritic Cells
Wei Y et al. · Cancer research · 2026 Sep 2 · PMID 42295795
A prospective clinical study on the effectiveness of Phellinus igniarius decoction in treating immune dysfunction in colorectal cancer patients following chemfotherapy
Zhang H et al. · Journal of traditional and complementary medicine · 2026 Sep · PMID 42698582
Thymosin α1 Augments CD8⁺ T-Cell Activation and Reverses Exhaustion In Vitro
Mishra S et al. · Asian Pacific journal of cancer prevention : APJCP · 2026 Jun 1 · PMID 42345155
IL-15 Plus Thymosin α1 Reduces Senescent Hepatic CD8(+) T Cells in Hepatocellular Carcinoma via PI3K/AKT Suppression
Wu F et al. · Journal of gastroenterology and hepatology · 2026 May · PMID 41883056
Preliminary results from a phase II trial of spatially fractionated radiotherapy combined with immunotherapy and anti-angiogenic therapy in patients with bulky solid tumors: early evidence of promising efficacy and favorable safety
Zhou Y et al. · Radiation oncology (London, England) · 2026 Apr 30 · PMID 42063096
Live feed from PubMed (NCBI) for “Thymosin Alpha-1”, updated 2026-10-30. Listing a paper is not an endorsement of its findings.
Registered studies
66 on ClinicalTrials.gov →- Not yet recruitingPhase 2
Thymalfasin Combined With Chemotherapy and Immunotherapy in TNBC Neoadjuvant Treatment
NCT07884201 · Fudan University · 2026-11-08
- RecruitingPhase 2Phase 3
Thymosin-α1 for Recurrent Implantation Failure
NCT07675980 · Fakih IVF Fertility Center · 2026-02-11
- Recruiting
Thymalfasin for Immune Recovery in Adults With Sepsis
NCT07866118 · Shanghai Zhongshan Hospital · 2026-10-06
- Completed
Protective Effect of Thymosin α1 Against Negative Immune Dysregulation and Organ Dysfunction After Acute Aortic Dissection Surgery (PANDA II)
NCT05339529 · Nanjing Medical University · 2022-07-01
- Not yet recruitingPhase 2
Study of Adebrelimab Combined With Thymalfasin and Chemotherapy for Neoadjuvant Treatment of Esophageal Cancer
NCT07780721 · The Affiliated Hospital of Putian University · 2026-08-30
- CompletedPhase 2
The Impact of Thymosin α-1 on the Efficacy of Concurrent Chemoradiotherapy Followed by Immunotherpay Consolidation for Locally Advanced NSCLC
NCT06139419 · Sun Yat-sen University · 2023-07-25
- RecruitingPhase 1
Thymalfasin (Thymosin Alpha 1; Ta1) as an Enhancer of Vaccine Response Among Older Adults Receiving Booster Doses of COVID-19 Vaccine
NCT06821100 · The Methodist Hospital Research Institute · 2024-12-02
- Completed
Neoadjuvant Chemoradiotherapy Combined With PD-1 Inhibitor and Thymalfasin for Locally Advanced Mid-low Rectal Cancer
NCT06024356 · Beijing Friendship Hospital · 2023-09-20
From the public ClinicalTrials.gov registry for “Thymosin Alpha-1”, updated 2026-10-30. Shown for research context only; Purity Peptides products are not for human use.
FAQ
No. Thymalfasin has orphan designations in the US but no FDA approval, and it is not centrally authorised in the EU. It is registered in a number of other countries. Our product is a research reference peptide intended solely for laboratory immunology studies.
Lyophilized Thymosin Alpha-1 is normally kept sealed at −20 °C, protected from light and moisture. Once reconstituted for laboratory work, aliquots are held at 2–8 °C for short-term use or frozen, avoiding repeated freeze–thaw. Follow the lot-specific guidance on the certificate of analysis.
Every lot of Thymosin Alpha-1 ships with a certificate of analysis reporting HPLC purity, mass-spectrometry identity against the expected molecular weight, appearance and lot number. Match the COA lot to the vial label and keep it with your experimental records.
Last updated October 2026 · Reviewed by the Purity Peptides research team · Information is a summary of published literature and is not a recommendation for any use.
