Immune

Thymosin alpha-1

Peptilex evidence grade ABCDEUpdated 19 Oct 2026 How grades work

Type: Natural 28-amino-acid peptide from the thymus (thymalfasin)
Main use or focus: Approved in some countries for chronic hepatitis B; promoted for "immune support"
Also known as: Zadaxin, thymalfasin

Key results

Complete response, chronic hepatitis B% of patients · randomized · thymosin alpha-1 vs controls

Thymosin alpha-1Controls

Thymosin alpha-1Chien et al.

40.6%

9.4%

98 participants.

Source: Chien et al. · Hepatology 1998

30+

countries where it is approved as a medicine (Zadaxin)

Approved medicineApproval status

trials in a 2026 meta-analysis linking it to fewer chemotherapy side effects in gastric cancer

Meta-analysisMeta-analysis · 2026

2,500

people in the phase 3 trial after colorectal cancer surgery that is under way

Registered trialPhase 3Colorectal cancer

Where it stands

Approved in more than 30 countries (Zadaxin). A 2026 meta-analysis of 20 trials linked it to fewer chemotherapy side effects in gastric cancer; a phase 3 trial in 2,500 people after colorectal cancer surgery is under way.

Go deeper

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What it is, how it acts, the key studies, risks and open questions.

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Research at a glance

Publications by typePubMed, all years

All papers622

Human studies374

Animal studies only185

Randomized trials39

Meta-analyses & systematic reviews12

Source: PubMed and ClinicalTrials.gov via the Peptilex study database

Registered trials by phaseClinicalTrials.gov · name in study title

ongoing / startingcompleted / other

Phase 12

Phase 221

Phase 32

Phase 46

Other8

Source: PubMed and ClinicalTrials.gov via the Peptilex study database

Trial starts per yearClinicalTrials.gov · by start date (planned starts included)

52016

22018

12020

22022

72024

22026

Source: PubMed and ClinicalTrials.gov via the Peptilex study database

Registered trials

ClinicalTrials.gov · name in study title · ongoing first

Study	Phase	Status	Participants	Start
Thymosin Alpha 1 Combined With Anti-PD-1 Monoclonal Antibody in Elderly Patients With Advanced Melanoma NCT07644897Sun Yat-sen University	Phase 2	Recruiting	55	May 2023
"Thymalfasin Immunotherapy Study with Triple Regimen in Advanced MSS/pMMR Colorectal Cancer" NCT06829355Beijing Friendship Hospital	Phase 2	Recruiting	52	Feb 2025
Thymalfasin and Recombinant Human IL-2 Injections in Treating Lymphocytopenia for Patients With Malignant Hematological Tumors NCT06584006The First Affiliated Hospital of Xiamen University	Phase 2	Recruiting	50	Sep 2024
Phase II Trial of Neoadjuvant Thymalfasin, PD-1 Inhibitor, and Chemoradiotherapy for cStage III GEJ Adenocarcinoma NCT07277439The First Affiliated Hospital with Nanjing Medical University	Phase 2	Recruiting	48	Dec 2025
Efficacy and Safety of Anti-PD-1, Thymalfasin, and SOX in Neoadjuvant Treatment of cStage III Gastric/Gastroesophageal Junction Adenocarcinoma NCT06461910Zekuan Xu	Phase 2	Recruiting	30	Jun 2024
Neoadjuvant Chemoradiotherapy Combined With PD-1 Inhibitor and Thymalfasin for pMMR/MSS Locally Advanced Mid-low Rectal Cancer NCT06056804Beijing Friendship Hospital	Phase 2	Running	20	Jan 2024
Protective Effect of Ulinastatin and Thymosin α1 Against Negative Immune Dysregulation and Organ Dysfunction After Acute Aortic Dissection Surgery (PANDA XI) NCT06966687Nanjing Medical University	–	Enrolling	200	Apr 2025
Thymalfasin for Immune Recovery in Adults With Sepsis NCT07866118Shanghai Zhongshan Hospital	–	Recruiting	60	Oct 2026
Study of Adebrelimab Combined With Thymalfasin and Chemotherapy for Neoadjuvant Treatment of Esophageal Cancer NCT07780721The Affiliated Hospital of Putian University	Phase 2	Starting soon	31	Aug 2026
Radiotherapy With Sequential Chemotherapy Combined With PD-1 Inhibitor and Thymalfasin for BRPC NCT06573398Ruijin Hospital	Phase 2	Starting soon	20	Sep 2024

Show 15 moreShow fewer

Study	Phase	Status	Participants	Start
Thymosin Alpha 1 in the Prevention of Pancreatic Infection Following Acute Necrotizing Pancreatitis NCT02473406Weiqin Li	Phase 4	Completed	508	Mar 2018
Efficacy Study of Thymosin alpha1 & Pegylated Interferon-alpha2a to Treat Chronic Hepatitis B NCT00291616Seoul National University Hospital	Phase 4	Completed	52	Dec 2005
Efficacy of Thymosin Alpha 1 on Improving Monocyte Function for Sepsis NCT02883595Sun Yat-sen University	Phase 4	Completed	20	Mar 2016
Thymosin Alpha-1 in Combination With Peg-Interferon Alfa- 2a and Ribavirin for the Therapy of Chronic Hepatitis C Nonresponsive to the Combination of IFN and Ribavirin. NCT01178996sigma-tau i.f.r. S.p.A.	Phase 3	Completed	552	Dec 2004
Thymosin Alpha 1, Interferon Alpha, or Both, in Combination With Dacarbazine in Patients With Malignant Melanoma NCT00911443sigma-tau i.f.r. S.p.A.	Phase 2	Completed	488	Jul 2002
Thymosin Alpha 1 to Prevent COVID-19 Infection in Renal Dialysis Patients NCT04428008William B. Ershler, MD	Phase 2	Completed	189	Jan 2021
A Pilot Study to Evaluate ZADAXIN's® (Thymalfasin) Ability to Enhance Immune Response to the H1N1sw Influenza Vaccine NCT01031966sigma-tau i.f.r. S.p.A.	Phase 2	Completed	120	Nov 2009
Phase II Trial for Combination Treatment of PEG-Tα1 and Adefovir for HBeAg Positive Chronic Hepatitis B NCT02366208Jiangsu Hansoh Pharmaceutical Co., Ltd.	Phase 2	Completed	116	May 2011
The Impact of Thymosin α-1 on the Efficacy of Concurrent Chemoradiotherapy Followed by Immunotherpay Consolidation for Locally Advanced NSCLC NCT06139419Sun Yat-sen University	Phase 2	Completed	114	Jul 2023
Study of Thymosin α1 to Reduce Acute Pneumonia For Bulky None-small Cell Lung Cancer NCT03659578Sun Yat-sen University	Phase 2	Completed	69	Aug 2018
A Trial of Thymalfasin in Adult Patients With Hepatocellular Carcinoma NCT00082082SciClone Pharmaceuticals	Phase 2	Completed	–	–
Zadaxin and HIV-positive Patients With Immune Reconstitution Disorder NCT04963712Shanghai Public Health Clinical Center	Early phase 1	Completed	20	Sep 2021
Protective Effect of Thymosin α1 Against Negative Immune Dysregulation and Organ Dysfunction After Acute Aortic Dissection Surgery (PANDA II) NCT05339529Nanjing Medical University	–	Completed	600	Jul 2022
Efficacy of Thymosin alpha1 for Severe Sepsis NCT00711620Sun Yat-sen University	–	Completed	366	May 2008
Neoadjuvant Chemoradiotherapy Combined With PD-1 Inhibitor and Thymalfasin for Locally Advanced Mid-low Rectal Cancer NCT06024356Beijing Friendship Hospital	Observational	Completed	47	Sep 2023

Showing 25 of 39 matching registered studies. See all on ClinicalTrials.gov.

Latest key papers

PubMed · newest first

2026
Efficacy and safety of thymosin α1 combined with chemotherapy for gastric cancer: a systematic review and meta-analysis of randomized controlled trials
Meta-analysisWang Z et al. · Frontiers in ImmunologyPMID 42827862
2025
Thymosin alpha 1 alleviates inflammation and prevents infection in patients with severe acute pancreatitis through immune regulation: a systematic review and meta-analysis
Meta-analysisTian Y et al. · Frontiers in ImmunologyPMID 40599771
2024
Thymosin Alpha 1 Plus Routine Treatment for the Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis
Meta-analysisCao A et al. · Journal of the College of Physicians and Surgeons--PakistanPMID 39648386
2024
Comprehensive Review of the Safety and Efficacy of Thymosin Alpha 1 in Human Clinical Trials
Systematic reviewDinetz E et al. · Alternative Therapies in Health and MedicinePMID 38308608
2024
A Prospective and Randomized Control Study on Effects of Thymalfasin for Injection on Perioperative Immune Function and Long-term Prognosis of Patients with Colorectal Cancer
Human RCTNiu W et al. · Biotechnology & Genetic Engineering ReviewsPMID 37248723
2023
The efficacy of thymosin alpha-1 therapy in moderate to critical COVID-19 patients: a systematic review, meta-analysis, and meta-regression
Meta-analysisSoeroto AY et al. · InflammopharmacologyPMID 37845598
2023
A pilot trial of Thymalfasin (Ta1) to prevent covid-19 infection and morbidities in renal dialysis patients: Preliminary report
Human RCTTuthill CW et al. · International ImmunopharmacologyPMID 36881981
2022
Immune enhancement in patients with predicted severe acute necrotising pancreatitis: a multicentre double-blind randomised controlled trial
Human RCTKe L et al. · Intensive Care MedicinePMID 35713670

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