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immune

Thymosin Alpha-1

Also known as: Ta1, Zadaxin, Thymalfasin
FDA: Not FDA-approved in US WADA: Not listed

Thymosin Alpha-1 (Ta1) is a 28-amino-acid peptide originally isolated from thymic tissue (thymosin fraction 5) by Allan Goldstein in the 1970s. It is one of the most clinically validated peptides in immunology, approved in 37+ countries under the brand name Zadaxin (thymalfasin) for chronic hepatitis B and C, and as an immune adjuvant in cancer therapy. It has not received FDA approval in the United States, though it was granted orphan drug designation for hepatocellular carcinoma. Ta1 works by enhancing both innate and adaptive immune responses without causing immune overactivation in healthy individuals. For educational purposes only. Not medical advice.

This content is for educational and research purposes only. VialBase does not provide medical advice. Consult a healthcare professional before using any peptide.

Molecular weight 3,108.29 Da
Half-life ~2 hours
CAS number —
Route Subcutaneous
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Mechanism

Immune modulator — enhances T-cell maturation, dendritic cell function, NK cell activity, and TLR signaling; modulates Treg/Teff balance

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Dosing

DOSE RANGE 1500–3000 mcg
FREQUENCY 2-3x weekly
CYCLE LENGTH 4-12 weeks

Clinical dose in approved countries: 1.6 mg SubQ twice weekly. Research protocols up to 3.2 mg. Used clinically in 37+ countries for immune support.

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Research summary

Study Type Year Key Finding
A Case Report of a Multisystemic Immune-Related Adverse Event Caused by Sintilimab in Combination With Thymosin Alpha-1 Case report 2026 Nasopharyngeal carcinoma patient developed multisystem irAEs after sintilimab + Ta1
Neoadjuvant serplulimab + SOX + thymalfasin for stage III G/EGJ adenocarcinoma Phase II clinical trial 2026 30% pathological complete response (pCR) rate
Thymosin alpha1-induced secretion of the IL-15/RA complex by THP-1-derived dendritic cells restrains HIV latency in vitro In vitro 2026 Ta1 induced IL-15/IL-15RA complex secretion from THP-1-derived dendritic cells
IL-15 Plus Thymosin alpha1 Reduces Senescent Hepatic CD8+ T Cells in HCC via PI3K/AKT Suppression Preclinical (aged mouse model + in vitro human cells) 2026 IL-15 + Ta1 combination suppressed tumor growth and prolonged survival in aged HCC mice
Thymosin alpha1 improves the outcomes of patients with HBV-related ACLF by restoring immune balance Open-label RCT 2026 Ta1 + SMT significantly increased 90-day transplant-free survival vs SMT alone
Thymosin Alpha-1 as Immune Adjuvant for COVID-19 Vaccination — — —
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Stacking & interactions

Immune + gut healing

Immune modulation + anti-inflammatory

Immune + anxiolytic/cognitive support

28-day resets featuring Thymosin Alpha-1

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Sourcing

Current prices

Updated today

5mg

10mg

Size unspecified

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What bloodwork do I need?

Reference ranges are general guidelines. Consult your physician for interpretation.

PRE-CYCLE
  • CMP
  • CBC with differential
  • CRP
  • ESR
  • Immunoglobulins (IgG, IgA, IgM)
DURING CYCLE
  • CBC with differential
  • CRP
POST-CYCLE
  • CMP
  • CBC with differential
  • Immunoglobulins
Safety & Regulatory Status
FDA STATUS Not FDA-approved in US. Approved in 37+ countries as Zadaxin (thymalfasin)
WADA STATUS Not listed

Regulatory status for Thymosin Alpha-1 may change. Verify current status with your jurisdiction before use. This is not legal or medical advice.

References

  1. Li T, Wu BL, Yu CL, Jin LY. A Case Report of a Multisystemic Immune-Related Adverse Event Caused by Sintilimab in Combination With Thymosin Alpha-1. Clin Case Rep (2026). PMID: 41669704
  2. Phase II Trial investigators. Neoadjuvant serplulimab + SOX + thymalfasin for stage III G/EGJ adenocarcinoma. BMC Med (2026). PMID: 41749205
  3. Chen C, Xun J, Wang J, et al.. Thymosin alpha1-induced secretion of the IL-15/RA complex by THP-1-derived dendritic cells restrains HIV latency in vitro. Virulence (2026). PMID: 41824632
  4. Wu F, Guo Z, Guan J, et al.. IL-15 Plus Thymosin alpha1 Reduces Senescent Hepatic CD8+ T Cells in HCC via PI3K/AKT Suppression. J Gastroenterol Hepatol (2026). PMID: 41883056
  5. Li ZH, Wu LL, Zhu YQ, et al.. Thymosin alpha1 improves the outcomes of patients with HBV-related ACLF by restoring immune balance. Immunopharmacol Immunotoxicol (2026). PMID: 41887933
  6. Thymosin Alpha-1 as Immune Adjuvant for COVID-19 Vaccination.