Thymosin Alpha-1
Published research and evidence base
Thymosin alpha-1 (Ta1, thymalfasin) is a 28-amino-acid peptide derived from prothymosin alpha and originally isolated from thymic tissue. It acts largely through Toll-like receptor signalling on dendritic cells and monocytes, influencing T-cell differentiation, thymic output and cytokine balance. It is registered as a prescription immunomodulator in a number of countries, principally for chronic hepatitis B and as an adjuvant in sepsis and oncology, and has been studied in more than thirty controlled human trials. It is not approved by the FDA or EMA.
- Studies cited
- 16
- Published 2023+
- 11
- Newest paper
- 2026
- Last reviewed
- Aug 2026
Recurring themes in the literature
- immunomodulation
- T-cell maturation and thymic output
- Toll-like receptor signalling
- sepsis and septic immunoparalysis
- chronic hepatitis B
- oncology adjuvant and checkpoint-inhibitor combination
- immunosenescence
- COVID-19 and viral infection
Compound identifiers
- CAS
- 62304-98-7
- PubChem
- 16130571
What Thymosin Alpha-1 is, chemically.
- Molecular formula
- C129H215N33O55
- Molecular weight
- 3108.3 g/mol
- CAS number
- 62304-98-7
- PubChem CID
- 16130571
Thymalfasin, Thymosin alpha 1, Zadaxin
These figures come from the PubChem record for this compound and describe the free base. Lyophilised peptide is normally supplied as an acetate or trifluoroacetate salt and carries residual water, so the mass of powder in a vial is not the same quantity as the molecular weight above would suggest. Chromatographic purity on a certificate of analysis does not resolve that difference either — how to read a certificate of analysis explains why.
16 published studies.
Ordered by strength of study design, then by recency. Every entry links to its source record so the finding can be checked against the paper rather than taken on our word.
- 01Systematic review2025
Efficacy of thymosin α1 for sepsis: a systematic review and meta-analysis of randomized controlled trials
Gu B, et al. · Frontiers in Cellular and Infection Microbiology · Meta-analysis with trial sequential analysis, 11 RCTs, 1927 patients with sepsis
Pooled 28-day mortality favoured thymosin alpha-1 (OR 0.73, 95% CI 0.59 to 0.90), but the effect disappeared in high-quality (OR 0.82, 95% CI 0.65 to 1.03) and multicentre (OR 0.86, 95% CI 0.68 to 1.08) subgroups. Trial sequential analysis indicated the cumulative sample size remained inadequate.
- 02Systematic review2025
Thymosin alpha 1 alleviates inflammation and prevents infection in patients with severe acute pancreatitis through immune regulation: a systematic review and meta-analysis
Tian Y, et al. · Frontiers in Immunology · Systematic review and meta-analysis of controlled trials in severe acute pancreatitis (PROSPERO CRD42024570517)
Thymosin alpha-1 was associated with fewer bloodstream (RR 0.60, 95% CI 0.38 to 0.94) and abdominal (RR 0.38, 95% CI 0.19 to 0.78) infections and a lower APACHE II score, but did not significantly shorten hospital stay or reduce lung infections.
- 03Systematic review2024
Thymosin Alpha 1 Plus Routine Treatment for the Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis
Cao A, et al. · Journal of the College of Physicians and Surgeons Pakistan · Meta-analysis of 39 randomised controlled trials, 3329 patients with acute exacerbation of COPD
Adjunctive thymosin alpha-1 was associated with higher FEV1 (MD 0.29 L), lower arterial CO2 partial pressure, shorter hospital stay (MD -5.39 days) and higher CD4+ counts and CD4+/CD8+ ratio. The authors noted that most included trials were of limited methodological quality.
- 04Systematic review2023
The efficacy of thymosin alpha-1 therapy in moderate to critical COVID-19 patients: a systematic review, meta-analysis, and meta-regression
Soeroto AY, et al. · Inflammopharmacology · Meta-analysis and meta-regression of 8 studies in moderate to critical COVID-19
Pooled mortality was lower with thymosin alpha-1 (RR 0.59, 95% CI 0.37 to 0.93) with high heterogeneity (I2 = 84%), but there was no difference in need for mechanical ventilation or length of stay. The authors stated that randomised trials were still required to confirm the finding.
- 05Systematic review2011
Thymic peptides for treatment of cancer patients
Wolf E, et al. · Cochrane Database of Systematic Reviews · Cochrane systematic review of randomised trials of purified thymus extracts and synthetic thymic peptides in adult cancer patients
Purified thymus extracts conferred no benefit on overall survival, disease-free survival or tumour response, though they reduced severe infectious complications (RR 0.54, 95% CI 0.38 to 0.78). For thymosin alpha-1 specifically the pooled overall survival risk ratio was 1.21 (95% CI 0.94 to 1.56), a non-significant trend; most trials carried at least moderate risk of bias.
- 06Human clinical2026
Thymosin α1 improves the outcomes of patients with hepatitis B virus-related acute-on-chronic liver failure by restoring immune balance
Li ZH, et al. · Immunopharmacology and Immunotoxicology · Open-label randomised controlled trial (NCT03082885), 73 patients with HBV-related acute-on-chronic liver failure
Thymosin alpha-1 treatment increased 90-day transplant-free survival and was associated with reduced frequencies of regulatory T cells and CD226-low Treg subsets at weeks 4 to 8. The authors reported moderation of the late hyperinflammatory response without suppressing early immune activation.
- 07Human clinical2026
Neoadjuvant immunochemotherapy plus thymalfasin in locally advanced gastric cancer: a prospective clinical trial
Xu H, et al. · BMC Medicine · Prospective phase II trial, 30 patients with cStage III gastric/gastro-oesophageal junction adenocarcinoma; serplulimab plus SOX plus thymalfasin
At a median follow-up of 14.0 months one nodal relapse and no deaths were recorded; grade 3 or higher adverse events occurred in 26.7% of patients. Flow cytometry and RNA sequencing showed CD8+ T-cell expansion and upregulation of antigen-presentation and type I interferon genes associated with thymalfasin.
- 08Human clinical2025
The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial
Wu J, et al. · BMJ · Multicentre double-blind placebo-controlled phase 3 RCT, 1106 adults with sepsis, 22 centres in China
28-day all-cause mortality was 23.4% with thymosin alpha-1 versus 24.1% with placebo (hazard ratio 0.99, 95% CI 0.77 to 1.27; P=0.93), and no secondary or safety outcome differed significantly. The authors concluded there was no clear evidence that thymosin alpha-1 reduces 28-day mortality in sepsis.
- 09Human clinical2025
The efficacy and safety of thymosin alpha-1 combined with lenvatinib plus sintilimab in unresectable hepatocellular carcinoma: a retrospective study
Yao S, et al. · Scientific Reports · Retrospective cohort, 92 patients with unresectable hepatocellular carcinoma
Adding thymosin alpha-1 was associated with longer median progression-free survival (7 versus 4 months, P=0.006) and a higher objective response rate (55.8% versus 34.7%, P=0.042). Rates of grade 1-2 and grade 3-4 adverse events did not differ between groups.
- 10Human clinical2024
Role of thymosin α1 in restoring immune response in immunological nonresponders living with HIV
Chen C, et al. · BMC Infectious Diseases · Single-arm open-label study, 20 immunological non-responders on antiretroviral therapy, 24 weeks of subcutaneous thymosin alpha-1
CD4+ T-cell count and sjTREC rose as a trend without reaching significance at week 24, while naive CD4+ and CD8+ T-cell proportions increased significantly and PD-1 expression on CD4+ and CD8+ T cells fell. No severe adverse events occurred and HIV viral load remained stable.
- 11Human clinical2022
Immune enhancement in patients with predicted severe acute necrotising pancreatitis: a multicentre double-blind randomised controlled trial
Ke L, et al. · Intensive Care Medicine · Multicentre double-blind placebo-controlled RCT, 508 patients with predicted severe acute necrotising pancreatitis
Infected pancreatic necrosis occurred in 15.7% of the thymosin alpha-1 group versus 18.1% of placebo (difference -2.4%, 95% CI -7.4 to 5.1; P=0.48), with no difference across four predefined subgroups. New-onset organ failure, bleeding and gastrointestinal fistula rates were also similar.
- 12Human clinical2018
Combination of entecavir with thymosin alpha-1 in HBV-related compensated cirrhosis: a prospective multicenter randomized open-label study
Wu X, et al. · Expert Opinion on Biological Therapy · Prospective multicentre randomised open-label study, 690 patients with HBV-related compensated cirrhosis, 52 weeks of treatment
Cumulative incidence of liver decompensation, hepatocellular carcinoma or death was similar between entecavir plus thymosin alpha-1 and entecavir alone, as were virologic, serologic and biochemical responses at week 104. Both regimens were well tolerated and the combination showed only a non-significant tendency to reduce hepatocellular carcinoma.
- 13Human clinical2013
The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial
Wu J, et al. · Critical Care · Multicentre single-blind RCT, 361 patients with severe sepsis, six teaching hospitals in China
28-day all-cause mortality was 26.0% with thymosin alpha-1 versus 35.0% in controls, a marginal difference (relative risk 0.74, 95% CI 0.54 to 1.02). Monocyte HLA-DR expression improved more in the treated group at days 3 and 7, and no serious drug-related adverse events were recorded.
- 14Human clinical2010
Large randomized study of thymosin alpha 1, interferon alfa, or both in combination with dacarbazine in patients with metastatic melanoma
Maio M, et al. · Journal of Clinical Oncology · Randomised five-arm trial, 488 patients with metastatic melanoma
Median overall survival was 9.4 months with thymosin alpha-1 versus 6.6 months in the control arm (hazard ratio 0.80, 95% CI 0.63 to 1.02; P=0.08), with a similar non-significant trend for progression-free survival. Adding thymosin alpha-1 did not increase toxicity.
- 15Animal in vivo2026
Thymosin Alpha-1 Restores Chemotherapy-Induced Antitumor Immunity by Chaperoning a MicroRNA Ligand of TLR7 in Dendritic Cells
Wei Y, et al. · Cancer Research · Tumour-bearing mice plus patient plasma samples; dendritic cell mechanistic work
Circulating thymosin alpha-1 fell after chemotherapy in both patients and tumour-bearing mice; the peptide protected apoptotic-body-derived miR146a-5p from lysosomal degradation, enabling TLR7-dependent dendritic cell maturation. Supplementation synergised with chemotherapy to control established tumours in a TLR7-dependent manner.
- 16Review2025
Aging and Thymosin Alpha-1
Simonova MA, et al. · International Journal of Molecular Sciences · Narrative review of thymic involution and immunosenescence
The review summarised preclinical and clinical evidence that thymosin alpha-1 stimulates T-cell differentiation and thymic output and can improve vaccine responses in older adults. The authors noted that long-term efficacy and safety in geriatric populations remain unvalidated.
What this evidence does not establish.
The largest and most rigorous trial to date, the phase 3 TESTS study, found no mortality benefit in sepsis, and the pooled meta-analytic signal disappears when analysis is restricted to high-quality multicentre trials; the same pattern of positive small trials and null large trials recurs in pancreatitis and hepatitis B cirrhosis. The great majority of randomised evidence originates from China and Italy, thymosin alpha-1 is not approved by the FDA or EMA, and there are no controlled human trials testing it as a longevity or healthy-ageing intervention.
Common questions about the research.
- What is Thymosin Alpha-1?
Thymosin Alpha-1 is a 28-amino-acid acetylated peptide first isolated from thymosin fraction 5, a thymic tissue extract. Its synthetic form carries the international non-proprietary name thymalfasin. It is supplied here as a lyophilised research material.
- Is Thymosin Alpha-1 an approved medicine?
As neutral regulatory background: review articles record that thymalfasin is approved in more than 35 countries, under the trade name Zadaxin in several of them, for hepatitis B and hepatitis C. That approval applies to licensed pharmaceutical product in those jurisdictions. It does not apply to this research material, which is not an approved medicine and is not supplied for human use.
- How does it differ from TB-500 and Thymosin Beta-4?
Despite the shared name, the alpha and beta thymosins are unrelated molecules from the same original tissue fractionation. Thymosin Alpha-1 is a 28-amino-acid peptide studied for immune signalling; Thymosin Beta-4 — and its fragment TB-500 — is a 43-amino-acid actin-sequestering peptide studied in tissue-repair models.
Available from our catalog
For research purposes only. Not for human consumption, diagnosis, treatment, or prevention of any condition. Nothing on this page is medical advice, and no study summarised here should be read as a recommendation.