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Thymosin Alpha-1 Results: What Studies Measured and When

What published studies measured for Thymosin Alpha-1, when those outcomes were measured, and what is still unproven.

Medically reviewed by Juan Pablo Frías, MD · · DisclosureImmune modulatorUpdated

What studies measured

Each outcome below comes from a published study, with its type and size, strongest design first. Animal and cell results are labelled as such and are not human results.

Thymosin Alpha-1 outcomes in published studies
OutcomeResultStudy typeSource
28-day all-cause mortality28-day mortality was 23.4% on thymosin alpha 1 and 24.1% on placebo (hazard ratio 0.99, P=0.93).Human RCTn = 1106BMJ 2025, PMID 39814420
Safety and secondary outcomesNo secondary or safety outcome differed significantly from placebo.Human RCTn = 1106BMJ 2025, PMID 39814420
Infection rate and ICU stayCulture-positive rates and ICU stay were lower with thymosin alpha 1.Human RCTn = 24Inflammation 2011, PMID 20549321
Response and survivalResponse was 57.1% vs 45.5%, not statistically different (P = 1.0).Human RCTn = 25Hepatology international 2009, PMID 19669251
Response rate37.5% (6 of 16) responded.Human RCTn = 16Internal medicine 2003, PMID 14606705
Low vs high doseThe low and high dose groups did not differ significantly.Human RCTn = 16Internal medicine 2003, PMID 14606705
Absorption and accumulationAbsorption was good with a Tmax of 1-2 hours across formulations.Human RCTn = 9International journal of clinical pharmacology and therapeutics 1999, PMID 10027483
Elimination half-lifeNo accumulation; elimination half-life under 3 hours.Human RCTn = 9International journal of clinical pharmacology and therapeutics 1999, PMID 10027483
Non-recovery rateAfter adjustment, thymosin alpha 1 use was associated with a higher non-recovery rate (OR 1.5); sicker patients were more likely to be treated.Human observationaln = 2282Frontiers in immunology 2021, PMID 34408744
CD4+ T cell recoveryCD4+ and CD8+ T cell increases did not differ between treated and untreated groups (p=0.851 and p=0.842).Human observationaln = 275Frontiers in immunology 2021, PMID 34149679
28-day mortality in critical typeIn the critical-type subgroup, thymosin alpha 1 was associated with lower 28-day mortality (HR 0.11, P=0.013).Human observationaln = 334International immunopharmacology 2020, PMID 32795897
All-cause mortalityPooled all-cause mortality was lower (RR 0.53) but certainty is very low.Meta-analysisn = 1349The Cochrane database of systematic reviews 2026, PMID 42713852
Histological improvement and quality of lifeLittle to no effect on quality of life or histology, with very low certainty.Meta-analysisn = 1349The Cochrane database of systematic reviews 2026, PMID 42713852
28-day mortality (all RCTs)Pooling all included RCTs, thymosin alpha 1 reduced 28-day mortality (OR 0.73, P = 0.003).Meta-analysisn = 1927Frontiers in cellular and infection microbiology 2025, PMID 40969554
High-quality and multicentre trialsHigh-quality (OR 0.82) and multicentre (OR 0.86) subgroups showed no significant mortality benefit.Meta-analysisn = 1927Frontiers in cellular and infection microbiology 2025, PMID 40969554
COVID-19 mortalityMortality was lower (RR 0.59, p = 0.02) but ventilation need and hospital stay did not differ; heterogeneity was high.Meta-analysisInflammopharmacology 2023, PMID 37845598
COVID-19 mortalityOverall mortality did not differ (RR 1.03, p = 0.92); the authors do not support use in hospitalized adults.Meta-analysisn = 5352International immunopharmacology 2023, PMID 36527881
MortalityPooled mortality was lower with thymosin alpha 1 (RR 0.59, p = 0.0001); the authors rate the evidence as low quality.Meta-analysisn = 530BMC infectious diseases 2016, PMID 27633969
Virological response vs interferonSix months after treatment, odds of virological response were 3.71 times those with interferon alpha.Meta-analysisn = 199Antiviral research 2008, PMID 18078676
Sustained response in hepatitis BSeven randomized studies reported a higher sustained response than untreated controls with 6 months of 1.6 mg twice weekly.ReviewExpert review of anti-infective therapy 2004, PMID 15482167
  • Thymosin alpha 1 (thymalfasin, Zadaxin) has no FDA label in DailyMed. Its regulatory status in other countries was not verified from a primary source, so no approval claim is made.
  • The largest and most rigorous trial, the 1106-patient phase 3 TESTS trial in sepsis (BMJ 2025), found no mortality benefit (23.4% vs 24.1%). Earlier meta-analyses of small, lower-quality trials reported lower mortality; the 2025 meta-analysis shows the benefit disappears in high-quality and multicentre trials.
  • COVID-19: meta-analyses disagree (one finds lower mortality, one finds none), and two cohort studies point in opposite directions. These are observational and confounded by severity.
  • Hepatitis B: 10 RCTs (1349 participants) in a 2026 Cochrane review; certainty is very low, studies span 1991-2018 and many used co-interventions.
  • No human study of thymosin alpha 1 for allergies was found (searches returned only an immune-regulation review and an unrelated toxicity study). The immune-system evidence rests on sepsis, COVID-19 and pancreatitis immune-parameter data.
  • Pharmacokinetics come from 9 healthy volunteers (1999); half-life is under 3 hours. Fusion-protein and PEGylated versions are different molecules and are not covered.

Typical timeline

When measurable changes appeared in studies of Thymosin Alpha-1: not reported in study abstracts (PubMed search, 2 Oct 2026).

Before-and-after photos

We don't publish before-and-after photos. They can't be verified, rarely show dose, diet or other drugs, and only the most dramatic results get posted.

Common questions

How long does Thymosin Alpha-1 take to work?

The study abstracts we summarised for Thymosin Alpha-1 do not report when outcomes were measured (PubMed search, 2 Oct 2026).

Do you show Thymosin Alpha-1 before and after photos?

No. Photos can't be verified, rarely show dose, diet or other drugs, and only the most dramatic ones get posted. We summarize measured outcomes instead.

More on Thymosin Alpha-1

DosageDoses used in published studies, with the source for each.Side effectsWhat labels and studies report, and what is unknown.PricePrice per mg and per week from dated listings. No vendor links.For immune systemWhat research says about Thymosin Alpha-1 for immune system.

Sources

  1. 1The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial.BMJ (Clinical research ed.) · 2025PMID 39814420Accessed 2 Oct 2026
  2. 2Thymosin alpha 1 is associated with improved cellular immunity and reduced infection rate in severe acute pancreatitis patients in a double-blind randomized control study.Inflammation · 2011PMID 20549321Accessed 2 Oct 2026
  3. 3A randomized controlled trial of thymalfasin plus transarterial chemoembolization for unresectable hepatocellular carcinoma.Hepatology international · 2009PMID 19669251Accessed 2 Oct 2026
  4. 4A pilot study of thymosin alpha1 therapy for chronic hepatitis B patients.Internal medicine (Tokyo, Japan) · 2003PMID 14606705Accessed 2 Oct 2026
  5. 5Pharmacokinetics of thymosin alpha1 after subcutaneous injection of three different formulations in healthy volunteers.International journal of clinical pharmacology and therapeutics · 1999PMID 10027483Accessed 2 Oct 2026
  6. 6Efficacy of Thymosin Alpha 1 in the Treatment of COVID-19: A Multicenter Cohort Study.Frontiers in immunology · 2021PMID 34408744Accessed 2 Oct 2026
  7. 7Thymosin Alpha-1 Has no Beneficial Effect on Restoring CD4+ and CD8+ T Lymphocyte Counts in COVID-19 Patients.Frontiers in immunology · 2021PMID 34149679Accessed 2 Oct 2026
  8. 8Thymosin α1 therapy in critically ill patients with COVID-19: A multicenter retrospective cohort study.International immunopharmacology · 2020PMID 32795897Accessed 2 Oct 2026
  9. 9Thymosin-ɑ1 for people with chronic hepatitis B.The Cochrane database of systematic reviews · 2026PMID 42713852Accessed 2 Oct 2026
  10. 10Efficacy of thymosin α1 for sepsis: a systematic review and meta-analysis of randomized controlled trials.Frontiers in cellular and infection microbiology · 2025PMID 40969554Accessed 2 Oct 2026
  11. 11The efficacy of thymosin alpha-1 therapy in moderate to critical COVID-19 patients: a systematic review, meta-analysis, and meta-regression.Inflammopharmacology · 2023PMID 37845598Accessed 2 Oct 2026
  12. 12Thymosin alpha1 use in adult COVID-19 patients: A systematic review and meta-analysis on clinical outcomes.International immunopharmacology · 2023PMID 36527881Accessed 2 Oct 2026
  13. 13The efficacy of thymosin α1 as immunomodulatory treatment for sepsis: a systematic review of randomized controlled trials.BMC infectious diseases · 2016PMID 27633969Accessed 2 Oct 2026
  14. 14Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis.Antiviral research · 2008PMID 18078676Accessed 2 Oct 2026
  15. 15Thymalfasin for the treatment of chronic hepatitis B.Expert review of anti-infective therapy · 2004PMID 15482167Accessed 2 Oct 2026
  16. 16PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) (956 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  17. 17PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (randomized[tiab] OR "clinical trial"[pt] OR "meta-analysis"[pt]) (136 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  18. 18PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (half-life[tiab] OR pharmacokinetic*[tiab]) (17 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  19. 19PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (sepsis[tiab] OR septic[tiab]) (51 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  20. 20PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (COVID-19[tiab] OR SARS-CoV-2[tiab]) (44 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  21. 21PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (hepatitis[tiab]) (131 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  22. 22PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND ("meta-analysis"[pt] OR "systematic review"[pt]) (25 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  23. 23PubMed search: ("thymosin alpha 1"[tiab] OR "thymosin alpha1"[tiab] OR thymalfasin[tiab] OR Zadaxin[tiab] OR Talpha1[tiab]) AND (allerg*[tiab] OR asthma[tiab] OR rhinitis[tiab]) (2 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026

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