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Approved AbroadImmune Modulator+2 more

Thymosin Alpha-1

A 28-amino-acid immune-modulating peptide. We read all 60 studies. The protocol is below.

Updated 03 May 2026Read 12 minEvidence ●●●○○Citations 60
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The Thymosin Alpha-1 Report · $19

Everything you need to start: dose, sourcing, safety, our verdict.

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Built from 60 cited studies.

Status
Compounded
Class
Immune Modulator
Evidence
3/ 5●●●○○
Approved abroad
$19 ↓
FDA status (US)
$19 ↓
Years of clinical use
$19 ↓
Read this if
  • you have hepatitis B or C and you're outside the US where it's actually approved
  • you're a long-COVID or chronic-fatigue patient working with an integrative MD
  • you're a cancer survivor in remission running it as part of an anti-recurrence protocol with your oncologist
Skip this if
  • you're a healthy adult shopping for "immune support" — that indication isn't validated in healthy people
  • **you have a diagnosed autoimmune disease — rheumatoid arthritis, lupus, MS, IBD, Hashimoto's flare-state.** Tα1's mechanism is immune *restoration* — it turns the immune dial UP via T-cell maturation and dendritic-cell signaling. That's the wrong direction when the immune dial is already pathologically high; the autoimmune-amplification risk is real and is the part that doesn't show up in marketing copy
  • you have an autoimmune disease that's poorly controlled
  • you're on immunosuppressants for transplant — don't modulate immune signaling without your transplant team
The 4 ways you can buy Thymosin Alpha-1
Brand
✗
Not available
Not available in US
No FDA-approved Tα1; Zadaxin is import-only and not legally available to US patients.
Compounded 503A
⚠
Rx
$180–$400/mo where still sold
Compounders shipping Tα1 vary in legal posture; some pharmacies pulled it.
RUO (research-only)
✓
Sold 'for research only'
$80–$200/mo
The dominant US supply path. Synthesis is well-established but identity by mass spec is the only h…
Gray market
✓
Unregulated overseas import
Suspended — not currently shipping via user's vendor
User's primary gray vendor marked Tα1 SUSPENDED in 2026 list; available via other overseas raws bu…
Click any lane for the full Sourcing breakdown.
First 90 days · Thymosin Alpha-1
Weeks 1–2
Nothing perceptible. The healing-acceleration effect — if it's going to work — isn't a week-one signal. If you 'feel something' immediately, that's expectation, not the peptide.
Weeks 4–8
Subtle improvement on the target injury if it's going to work. Range of motion, less morning stiffness, less acute pain on load.
Week 12 — decide
Honest decision point. Either the injury is materially better than the no-peptide trajectory would have been, or it isn't. The clinical literature in humans is thin enough that your n=1 trial IS the evidence base.
Quit if
  • Any unusual symptoms — especially relevant if you have a personal or family cancer history (angiogenesis mechanism for BPC-157, TB-500).
  • 12 weeks with no perceived improvement vs the no-peptide trajectory.
  • New pain or symptoms at injection site that don't resolve in 48 hours.
Identity

What it is.

Thymosin alpha-1 (Tα1) is a 28-amino-acid naturally produced by the thymus gland — the small organ behind the breastbone that trains T-cells. The synthetic version is thymalfasin, sold as Zadaxin.

Unlike most peptides on this site, Tα1 is an approved drug in roughly 35 countries, including across Europe, Asia, and Latin America. The approved indications are mostly hepatitis B, hepatitis C (as adjunct therapy), and immune support during chemotherapy. It is not FDA approved in the US — SciClone never completed the US regulatory path — but it's been in clinical use abroad since the 1990s.

Mechanism: it modulates T-cell maturation and shifts the immune response toward Th1, the arm that handles viral and intracellular pathogens. It doesn't kill anything directly. It tunes the immune response.

TL;DR

TL;DR. 30-second version.

The compressed verdict — what Thymosin Alpha-1 actually is, what the human evidence shows, and the watch-for in three bullets. Locked.

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Mechanism

Mechanism.

Mechanism · in the Thymosin Alpha-1 report

How the molecule actually works — receptor profile, downstream signaling, what to expect mechanistically.

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Evidence

Evidence. What we actually know in humans.

Evidence · in the Thymosin Alpha-1 report

The trial breakdown — phase, n, primary endpoint, who funded, what hit, what didn't.

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Human-Evidence Factbox
Approved abroad
$19 ↓
FDA status (US)
$19 ↓
Years of clinical use
$19 ↓
Sepsis RCTs
$19 ↓
Mechanism
$19 ↓
Major adverse events flagged
$19 ↓
Autoimmune-amplification risk
$19 ↓
Long-COVID evidence quality
$19 ↓
Dose

Dose. The actual protocol.

Dose · in the Thymosin Alpha-1 report

The specific protocol — dose, titration schedule, cycle pattern, frequency, route.

We read 60 studies to write this report.
Get the report · $19 ↓
Sourcing

Sourcing. Where the cohort actually buys.

Sourcing · in the Thymosin Alpha-1 report

Sourcing breakdown — vendor methodology, red flags, our published test results, COA checklist.

We read 60 studies to write this report.
Get the report · $19 ↓
Safety

Safety. Side effects.

Safety · in the Thymosin Alpha-1 report

The watch-for list — contraindications, drug interactions, monitoring labs, when to stop.

Get the report · $19 ↓
Editorial Position

Editorial position.

Editorial Position · in the Thymosin Alpha-1 report

Our editorial position — explicit yes / no / depends, with the reasoning behind it.

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Citations

Citations.

  1. 01Ancell CD, et al. Thymosin alpha-1. American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists. 2001;58(10):879-85; quiz 886-8. PMID: 11381492.
  2. 02Wu J, et al. The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial. BMJ (Clinical research ed.). 2025;388:e082583. PMID: 39814420.
  3. 03Simonova MA, et al. Aging and Thymosin Alpha-1. International journal of molecular sciences. 2025;26(23). PMID: 41373628.
  4. 04Shehadeh F, et al. A Pilot Trial of Thymalfasin (Thymosin-α-1) to Treat Hospitalized Patients With Hypoxemia and Lymphocytopenia Due to Coronavirus Disease 2019 Infection. The Journal of infectious diseases. 2023;227(2):226-235. PMID: 36056913.
  5. 05Wu X, et al. Thymosin alpha-1 treatment in chronic hepatitis B. Expert opinion on biological therapy. 2015;15 Suppl 1:S129-32. PMID: 25640173.
+Show all 60 citations
  1. 06Matteucci C, et al. Thymosin alpha 1 and HIV-1: recent advances and future perspectives. Future microbiology. 2017;12:141-155. PMID: 28106477.
  2. 07Pei F, et al. Thymosin alpha 1 treatment for patients with sepsis. Expert opinion on biological therapy. 2018;18(sup1):71-76. PMID: 30063866.
  3. 08Pica F, et al. Serum thymosin alpha 1 levels in normal and pathological conditions. Expert opinion on biological therapy. 2018;18(sup1):13-21. PMID: 30063864.
  4. 09Wei Y, et al. Thymosin α-1 in cancer therapy: Immunoregulation and potential applications. International immunopharmacology. 2023;117:109744. PMID: 36812669.
  5. 10Liaw YF. Thymalfasin (thymosin-alpha 1) therapy in patients with chronic hepatitis B. Journal of gastroenterology and hepatology. 2004;19 Suppl 6:S73-5. PMID: 15546254.
  6. 11King R, et al. Immune Modulation with Thymosin Alpha 1 Treatment. Vitamins and hormones. 2016;102:151-78. PMID: 27450734.
  7. 12Wei YT, et al. Thymosin α-1 Reverses M2 Polarization of Tumor-Associated Macrophages during Efferocytosis. Cancer research. 2022;82(10):1991-2002. PMID: 35364609.
  8. 13Camerini R, et al. Historical review of thymosin α 1 in infectious diseases. Expert opinion on biological therapy. 2015;15 Suppl 1:S117-27. PMID: 26098768.
  9. 14Goldstein AL. Clinical applications of thymosin alpha-1. Cancer investigation. 1994;12(5):545-7. PMID: 7922712.
  10. 15Liaw YF. Thymalfasin (thymosin-alpha 1) therapy in patients with chronic hepatitis B. Journal of gastroenterology and hepatology. 2004;19(12):S73-5. PMID: 15641208.
  11. 16Liu K, et al. Thymosin α1 reverses oncolytic adenovirus-induced M2 polarization of macrophages to improve antitumor immunity and therapeutic efficacy. Cell reports. Medicine. 2024;5(10):101751. PMID: 39357524.
  12. 17Cao A, et al. Thymosin Alpha 1 Plus Routine Treatment for the Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis. Journal of the College of Physicians and Surgeons--Pakistan : JCPSP. 2024;34(12):1497-1507. PMID: 39648386.
  13. 18Soeroto AY, et al. The efficacy of thymosin alpha-1 therapy in moderate to critical COVID-19 patients: a systematic review, meta-analysis, and meta-regression. Inflammopharmacology. 2023;31(6):3317-3325. PMID: 37845598.
  14. 19Bepler G. Thymosin alpha-1 as adjunct for conventional therapy of malignant tumors: a review. Cancer investigation. 1994;12(5):491-6. PMID: 7922706.
  15. 20Dinetz E, et al. Comprehensive Review of the Safety and Efficacy of Thymosin Alpha 1 in Human Clinical Trials. Alternative therapies in health and medicine. 2024;30(1):6-12. PMID: 38308608.
  16. 21Liu J, et al. Efficacy of Thymosin Alpha 1 in the Treatment of COVID-19: A Multicenter Cohort Study. Frontiers in immunology. 2021;12:673693. PMID: 34408744.
  17. 22Armirotti A, et al. Bioactive Thymosin Alpha-1 Does Not Influence F508del-CFTR Maturation and Activity. Scientific reports. 2019;9(1):10310. PMID: 31311979.
  18. 23Mao L. Thymosin alpha 1 - Reimagine its broader applications in the immuno-oncology era. International immunopharmacology. 2023;117:109952. PMID: 36871535.
  19. 24Minutolo A, et al. Thymosin alpha 1 restores the immune homeostasis in lymphocytes during Post-Acute sequelae of SARS-CoV-2 infection. International immunopharmacology. 2023;118:110055. PMID: 36989892.
  20. 25Hoch K, et al. Structures of Thymosin Proteins. Vitamins and hormones. 2016;102:1-24. PMID: 27450728.
  21. 26Wang T, et al. [Thymosin alpha 1 for the adjuvant treatment of coronavirus disease 2019: a retrospective cohort study]. Zhonghua wei zhong bing ji jiu yi xue. 2022;34(5):497-501. PMID: 35728851.
  22. 27Umeda Y, et al. Thymosin alpha 1 restores NK-cell activity and prevents tumor progression in mice immunosuppressed by cytostatics or X-rays. Cancer immunology, immunotherapy : CII. 1983;15(2):78-83. PMID: 6553515.
  23. 28Garaci E, et al. Thymosin alpha 1 in the treatment of cancer: from basic research to clinical application. International journal of immunopharmacology. 2000;22(12):1067-76. PMID: 11137613.
  24. 29Tuthill C, et al. Thymosin alpha 1: past clinical experience and future promise. Annals of the New York Academy of Sciences. 2010;1194:130-5. PMID: 20536460.
  25. 30Yao S, et al. The efficacy and safety of thymosin alpha-1 combined with lenvatinib plus sintilimab in unresectable hepatocellular carcinoma: a retrospective study. Scientific reports. 2025;15(1):13960. PMID: 40263352.
  26. 31Rustgi V. Combination therapy of thymalfasin (thymosin-alpha 1) and peginterferon alfa-2a in patients with chronic hepatitis C virus infection who are non-responders to standard treatment. Journal of gastroenterology and hepatology. 2004;19(12):S76-8. PMID: 15641209.
  27. 32Espinar-Buitrago MS, et al. Enhanced Immunomodulatory Effects of Thymosin-Alpha-1 in Combination with Polyanionic Carbosilane Dendrimers against HCMV Infection. International journal of molecular sciences. 2024;25(4). PMID: 38396631.
  28. 33Tian Y, et al. Thymosin alpha 1 alleviates inflammation and prevents infection in patients with severe acute pancreatitis through immune regulation: a systematic review and meta-analysis. Frontiers in immunology. 2025;16:1571456. PMID: 40599771.
  29. 34Garaci E, et al. Thymosin alpha(1) in combination with cytokines and chemotherapy for the treatment of cancer. International immunopharmacology. 2003;3(8):1145-50. PMID: 12860169.
  30. 35Zhou J, et al. Thymosin alpha 1 in the prevention of infected pancreatic necrosis following acute necrotising pancreatitis (TRACE trial): protocol of a multicentre, randomised, double-blind, placebo-controlled, parallel-group trial. BMJ open. 2020;10(9):e037231. PMID: 32994239.
  31. 36Gökkusu C, et al. Thymosin alpha 1 protects liver and aorta from oxidative damage in atherosclerotic rabbits. Life sciences. 1996;59(13):1059-67. PMID: 8809225.
  32. 37Sherman KE. Thymosin alpha 1 for treatment of hepatitis C virus: promise and proof. Annals of the New York Academy of Sciences. 2010;1194:136-40. PMID: 20536461.
  33. 38McClure JE, et al. Immunochemical studies on thymosin: radioimmunoassay of thymosin alpha 1. Journal of immunology (Baltimore, Md. : 1950). 1982;128(1):368-75. PMID: 7054279.
  34. 39Naruse H, et al. Immunoreactive thymosin alpha 1 in human thymus and thymoma. The Journal of thoracic and cardiovascular surgery. 1993;106(6):1065-71. PMID: 8246540.
  35. 40Garaci E, et al. Thymosin alpha 1: from bench to bedside. Annals of the New York Academy of Sciences. 2007;1112:225-34. PMID: 17600290.
  36. 41Maio M, et al. Large randomized study of thymosin alpha 1, interferon alfa, or both in combination with dacarbazine in patients with metastatic melanoma. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2010;28(10):1780-7. PMID: 20194853.
  37. 42McGillis JP, et al. Circadian rhythm of thymosin-alpha 1 in normal and thymectomized mice. Journal of immunology (Baltimore, Md. : 1950). 1983;131(1):148-51. PMID: 6863916.
  38. 43Tomati V, et al. Thymosin α-1 does not correct F508del-CFTR in cystic fibrosis airway epithelia. JCI insight. 2018;3(3). PMID: 29415893.
  39. 44Nevo N, et al. Thymosin alpha 1 as an adjuvant to hyperthermic intraperitoneal chemotherapy in an experimental model of peritoneal metastases from colonic carcinoma. International immunopharmacology. 2022;111:109166. PMID: 35994852.
  40. 45Wang Z, et al. Thymosin Alpha-1 Has no Beneficial Effect on Restoring CD4+ and CD8+ T Lymphocyte Counts in COVID-19 Patients. Frontiers in immunology. 2021;12:568789. PMID: 34149679.
  41. 46Incefy GS, et al. A radioimmunoassay for thymosin alpha-1. Journal of immunological methods. 1986;89(1):9-17. PMID: 3701071.
  42. 47Yang YF, et al. Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis. Antiviral research. 2008;77(2):136-41. PMID: 18078676.
  43. 48Wu X, 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. 2018;18(sup1):61-69. PMID: 30063860.
  44. 49Espinar-Buitrago MS, et al. Immune modulation via dendritic cells by the effect of Thymosin-alpha-1 on immune synapse in HCMV infection. International immunopharmacology. 2023;125(Pt A):111103. PMID: 38149577.
  45. 50Low TL, et al. Isolation of thymosin alpha 1 from thymosin fraction 5 of different species by high-performance liquid chromatography. Journal of chromatography. 1983;266:533-44. PMID: 6630360.
  46. 51Naz RK, et al. Thymosin alpha 1 levels in human seminal plasma and follicular fluid: implication in germ cell function. International journal of fertility. 1987;32(5):375-9. PMID: 2889684.
  47. 52Liu Y, et al. Thymosin Alpha 1 Reduces the Mortality of Severe Coronavirus Disease 2019 by Restoration of Lymphocytopenia and Reversion of Exhausted T Cells. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2020;71(16):2150-2157. PMID: 32442287.
  48. 53Yang Z, et al. Thymosin alpha-1 blocks the accumulation of myeloid suppressor cells in NSCLC by inhibiting VEGF production. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie. 2020;131:110740. PMID: 32942159.
  49. 54Panatto 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;52(3):111-5. PMID: 22010537.
  50. 55Hadden JW, et al. Immunotherapy with natural interleukins and/or thymosin alpha 1 potently augments T-lymphocyte responses of hydrocortisone-treated aged mice. International journal of immunopharmacology. 1995;17(10):821-8. PMID: 8707447.
  51. 56Franco FJ, et al. Thymosin alpha 1 is a native peptide in several tissues. Biochimica et biophysica acta. 1992;1120(1):43-8. PMID: 1554740.
  52. 57Ciancio A, et al. Thymosin alpha-1 with peginterferon alfa-2a/ribavirin for chronic hepatitis C not responsive to IFN/ribavirin: an adjuvant role?. Journal of viral hepatitis. 2012;19 Suppl 1:52-9. PMID: 22233415.
  53. 58Chen SJ, et al. Serum thymosin-alpha 1: lack of association between elevated levels and HIV infection. Clinical and experimental immunology. 1987;70(2):263-7. PMID: 3427822.
  54. 59Peng D, et al. The clinical efficacy and adverse effects of Entecavir plus Thymosin alpha-1 combination therapy versus Entecavir Monotherapy in HBV-related cirrhosis: a systematic review and meta-analysis. BMC gastroenterology. 2020;20(1):348. PMID: 33076834.
  55. 60Rinaldi Garaci C, et al. Receptors for thymosin alpha 1 on mouse thymocytes. Cellular immunology. 1985;91(1):289-93. PMID: 3882244.
The Thymosin Alpha-1 Report · $19

Everything you need to start.

Dose, sourcing, safety, our verdict. One purchase. Yours forever.

Built from 60 cited studies.

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