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Home/Compounds/Thymosin Alpha-1
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Thymosin Alpha-1

Also known as: Ta1 · Zadaxin
Brands: Zadaxin

Thymic peptide approved internationally for hepatitis and immune enhancement.

A
Grade A
Multiple human RCTs
Human studies27
PubMed citations30
Typical dose1.6 mg – 6.4 mg
Routesubcutaneous
Regulatory (US)Compounding legal
Last verified2 days ago
TL;DR · 30-second summary
  • Approved in 35+ countries for hepatitis
  • Enhances vaccine response in elderly
  • Adjunct therapy for various cancers
  • Studied for COVID-19 treatment

Mechanism of action

Natural thymic peptide that enhances T-cell and dendritic cell function. Modulates cytokine production and may have direct antiviral effects.

Evidence summary

27
Human studies
30
PubMed citations
25
Clinical trials
A
Evidence grade

Approved in 35+ countries for hepatitis B/C and as immune adjuvant. Extensive safety data. Studied for COVID-19 and cancer immunotherapy.

Dosing protocols

Educational information only. Consult a licensed provider before using any peptide.
Dose range
1.6 mg – 6.4 mg

Typical: 1.6mg subcutaneous twice weekly. Cancer protocols may use higher doses.

Administration routes
subcutaneous

Side effects & safety

Reported side effects
Injection site reactionsFlu-like symptoms (rare)Generally very well tolerated
Contraindications
  • Organ transplant recipients
  • Immunosuppressed patients (context-dependent)

Interactions

No documented drug interactions on file.

Regulatory status

United States
Not FDA approved

Not FDA approved. Approved in 35+ other countries. Orphan drug status for some conditions.

Compounding
Permitted

Available through compounding pharmacies with valid prescription.

Regulatory data last verified 4/17/2026

Clinical trials

NCT07277439A Prospective, Open-label, Randomized, Controlled Phase II Clinical Trial Exploring the Efficacy and Safety of Thymosin Alpha 1 Combined With PD-1 Monoclonal Antibody and Neoadjuvant Chemoradiotherapy for cStage III Gastroesophageal Junction AdenocarcinomaRecruiting · Phase 2 · Gastric Cancer · n=48NCT06461910The Efficacy and Safety of Anti-PD-1 Combined With Thymalfasin and SOX in Neoadjuvant Treatment of cStage III Gastric or Gastroesophageal Junction Adenocarcinoma: A Prospective, Open-label, Single-arm, Phase II Clinical StudyRecruiting · Phase 2 · Gastric Cancer · n=30NCT07382375AI-assisted Immunoinflammatory Subtyping-Directed Precision Treatment in Acute Aortic Dissection: A Multicenter RCT-based ExplorationNot Yet Recruiting · N/A · Aortic Aneurysm and Dissection · n=300NCT06552598Phase I/II Clinical Study to Evaluate the Safety, Tolerability, and Preliminary Efficacy of Local Administration of Recombinant Oncolytic Adenovirus Injection (KD01) in Patients With Gynecologic MalignanciesRecruiting · Phase 1 · Cervical Cancer · n=97NCT07103395A Phase II Study Evaluating Neoadjuvant Chemotherapy, Concurrent Chemoradiotherapy Combined With Dual Immune Checkpoint Blockade (PD-1/CTLA-4) in Patients With Locally Advanced Non-Small Cell Lung CancerRecruiting · Phase 2 · Lung Cancer (NSCLC) · n=56NCT06966687Protective Effect of Ulinastatin and Thymosin α1 Against Negative Immune Dysregulation and Organ Dysfunction After Acute Aortic Dissection Surgery (PANDA XI)Enrolling By Invitation · N/A · Aortic Dissection · n=200NCT06139419A Prospective Phase II Controlled Study to Evaluate the Impact of Thymosin Alpha 1 on the Completion Rate of Consolidation Immunotherapy After Radical Radiochemotherapy for Locally Advanced Non-Small Cell Lung CancerActive Not Recruiting · Phase 2 · Non-small Cell Lung Cancer · n=114NCT04428008A Pilot Trial of Thymalfasin (Ta1) to Prevent COVID-19 Infection in Renal Dialysis PatientsCompleted · Phase 2 · COVID-19 · n=262NCT07103408A Phase II Study Evaluating Concurrent Chemoradiotherapy Combined With Dual Immune Checkpoint Blockade (PD-1/CTLA-4) for Limited-stage Small Cell Lung CancerNot Yet Recruiting · Phase 2 · Small-Cell Lung Cancer (SCLC) · n=56NCT06821100Thymalfasin (Thymosin Alpha 1; Ta1) as an Enhancer of Vaccine Response Among Older Adults Receiving Booster Doses of COVID-19 VaccineRecruiting · Phase 1 · Vaccine Response · n=75NCT06056804Efficacy and Safety of Neoadjuvant Chemoradiotherapy Combined With PD-1 Inhibitor and Thymalfasin in pMMR/MSS Locally Advanced Middle and Low Rectal Cancer: An Open, Multi-center, Prospective, Single-arm Phase II Clinical StudyActive Not Recruiting · Phase 2 · Locally Advanced Rectal Cancer · n=20NCT06829355Efficacy and Safety Study of Thymalfasin in Combination with Targeted Immunotherapy (Regorafenib and Tislelizumab) in Patients with Advanced PMMR/MSS Colorectal Cancer Who Failed Standard of Care: a Multicenter, Open-label, Randomized, Controlled Clinical StudyRecruiting · Phase 2 · MCRC · n=52

Showing 12 of 25 indexed studies. View all on ClinicalTrials.gov →

Citations

PMID 41373628Simonova MA, Ivanov I et al. · Aging and Thymosin Alpha-1.International journal of molecular sciences (2025)HumanPMID 39867848Aynekulu Mersha DG, Fromme SE et al. · Indications for an antidepressive effect of thymosin alpha-1 in a small open-label proof of concept study in common variable immune deficiency patients with depression.Brain, behavior, & immunity - health (2025)PMID 40227409Erten F, Er B et al. · Effects of Integrated Extracts of Trigonella foenum-graecum and Asparagus racemosus on Hot Flash-like Symptoms in Ovariectomized Rats.Antioxidants (Basel, Switzerland) (2025)HumanPMID 38903817Garaci E, Paci M et al. · Phenotypic drug discovery: a case for thymosin alpha-1.Frontiers in medicine (2024)HumanPMID 38396631Espinar-Buitrago MS, Magro-López E et al. · Enhanced Immunomodulatory Effects of Thymosin-Alpha-1 in Combination with Polyanionic Carbosilane Dendrimers against HCMV Infection.International journal of molecular sciences (2024)HumanPMID 38131310Quagliata M, Papini AM et al. · Therapeutic applications of thymosin peptides: a patent landscape 2018-present.Expert opinion on therapeutic patents (2024)HumanPMID 39694701Tang S, Tang R et al. · Personalized neoantigen hydrogel vaccine combined with PD-1 and CTLA-4 double blockade elicits antitumor response in liver metastases by activating intratumoral CD8+CD69+ T cells.Journal for immunotherapy of cancer (2024)HumanPMID 39357524Liu K, Kong L et al. · Thymosin α1 reverses oncolytic adenovirus-induced M2 polarization of macrophages to improve antitumor immunity and therapeutic efficacy.Cell reports. Medicine (2024)HumanPMID 37028279Matteucci C, Nepravishta R et al. · Thymosin α1 interacts with Galectin-1 modulating the β-galactosides affinity and inducing alteration in the biological activity.International immunopharmacology (2023)HumanPMID 36527881Shang W, Zhang B et al. · Thymosin alpha1 use in adult COVID-19 patients: A systematic review and meta-analysis on clinical outcomes.International immunopharmacology (2023)HumanPMID 34717926Laurino A, Gencarelli M et al. · The 3-iodothyronamine (T1AM) and the 3-iodothyroacetic acid (TA1) indicate a novel connection with the histamine system for neuroprotection.European journal of pharmacology (2022)HumanPMID 31327156Zucchi R, Rutigliano G et al. · Novel thyroid hormones.Endocrine (2020)HumanPMID 30983971Landucci E, Laurino A et al. · Thyroid Hormone, Thyroid Hormone Metabolites and Mast Cells: A Less Explored Issue.Frontiers in cellular neuroscience (2020)HumanPMID 32277204Donnell CC, Clark MV · Mandibular third molars: 'naughty' or NICE?British dental journal (2020)HumanPMID 30063867Stincardini C, Renga G et al. · Cellular proteostasis: a new twist in the action of thymosin α1.Expert opinion on biological therapy (2019)HumanPMID 30063860Wu X, Shi Y et al. · Combination of entecavir with thymosin alpha-1 in HBV-related compensated cirrhosis: a prospective multicenter randomized open-label study.Expert opinion on biological therapy (2019)HumanPMID 27350088Pica F, Chimenti MS et al. · Serum thymosin α 1 levels in patients with chronic inflammatory autoimmune diseases.Clinical and experimental immunology (2017)HumanPMID 26098768Camerini R, Garaci E · Historical review of thymosin α 1 in infectious diseases.Expert opinion on biological therapy (2016)HumanPMID 25640173Wu X, Jia J et al. · Thymosin alpha-1 treatment in chronic hepatitis B.Expert opinion on biological therapy (2016)HumanPMID 22010537Panatto D, Amicizia D et al. · Utility of thymosin alpha-1 (Zadaxin) as a co-adjuvant in influenza vaccines: a review.Journal of preventive medicine and hygiene (2011)Human

Showing 20 of 30 papers. View all on PubMed →