Generic Name
DrugBank Accession Number

Thymalfasin is a chemically synthesized version of thymosin alpha 1 that is identical to human thymosin alpha 1. Thymosin alpha 1 is an acetylated polypeptide. Thymosin alpha 1 is now approved in 35 developing countries for the treatment of Hepatitis B and C. It is also used to boost the immune response in the treatment of other diseases.

Biologic Classification
Protein Based Therapies
Interleukin-based products
Protein Structure
Protein Chemical Formula
Protein Average Weight
3108.2755 Da
Download FASTA Format
  • Thymalfasin
  • Thymosin alpha1 (human)



Indicated as an adjuvant for influenza vaccine in elderly patients and as an adjuvant for both influenza and hepatitis B vaccines in chronic hemodialysis patients who failed to achieve adequate antibody titers from previous immunization.

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Associated Conditions
Associated Therapies
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Thymalfasin is a 28-amino acid polypeptide produced synthetically but originally isolated from thymosin fraction 5, a bovine thymus extract containing a number of immunologically active peptides. In vitro studies have shown that Thymalfasin can influence T-cell production and maturation, stimulate production of Th1 cytokines such as interferon-gamma and interleukin-2, and activate natural killer cell-mediated cytotoxicity.

Mechanism of action

The mechanism of action of thymalfasin is not completely understood but is thought to be related to its immunomodulating activities, centered primarily around augmentation of T-cell function. In various in vitro assays, thymosin alpha 1 has been shown to promote T-cell differentiation and maturation; for example, CD4+, CD8+, and CD3+ cells have all been shown to be increased. Thymosin alpha 1 has also been shown to increase production of IFN-g, IL-2, IL-3, and expression of IL-2 receptor following activation by mitogens or antigens, increase NK cell activity, increase production of migratory inhibitory factor (MIF), and increase antibody response to T-cell dependent antigens. Thymosin alpha 1 has also been shown to antagonize dexamethasone-induced apoptosis of thymocytes in vitro. In vivo administration of thymosin alpha 1 to animals immunosuppressed by chemotherapy, tumor burden, or irradiation showed that thymosin alpha 1 protects against cytotoxic damage to bone marrow, tumor progression and opportunistic infections, thereby increasing survival time and number of survivors. Many of the in vitro and in vivo effects of thymosin alpha 1 have been interpreted as influences on either differentiation of pluripotent stem cells to thymocytes or activation of thymocytes into activated T-cells. Thymalfasin also has been shown in vitro to upregulate expression of toll like receptors (TLR) including TLR2 and TLR9 in mouse and human dendritic cells, as well as activate NF-kB and JNK/P38/AP1 pathways. Thymalfasin's activation of dendritic cells provides another possible pathway explaining thymalfasin's immunomodulatory and antiviral effects.


Rapidly absorbed with peak serum levels achieved at approximately 2 hours.

Volume of distribution

Not Available

Protein binding

Not Available

Not Available
Route of elimination

Not Available


Approximately 2 hours. There is no evidence of accumulation following multiple subcutaneous doses.


Not Available

Adverse Effects
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There are no reported instances of deliberate or accidental overdosage in humans. Animal toxicology studies have shown no adverse reactions in single doses up to 20 mg/kg and in repeated doses up to 6 mg/kg/day for 13 weeks, which were the highest doses studied. The highest single dose tested in animals represents 800-times the clinical dose.

Not Available
Pharmacogenomic Effects/ADRs
Not Available


Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
Darbepoetin alfaThe risk or severity of Thrombosis can be increased when Darbepoetin alfa is combined with Thymalfasin.
ErythropoietinThe risk or severity of Thrombosis can be increased when Erythropoietin is combined with Thymalfasin.
Methoxy polyethylene glycol-epoetin betaThe risk or severity of Thrombosis can be increased when Methoxy polyethylene glycol-epoetin beta is combined with Thymalfasin.
PeginesatideThe risk or severity of Thrombosis can be increased when Peginesatide is combined with Thymalfasin.
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Food Interactions
Not Available


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International/Other Brands


Drug Categories
Chemical TaxonomyProvided by Classyfire
Not Available
Organic Compounds
Super Class
Organic Acids
Carboxylic Acids and Derivatives
Sub Class
Amino Acids, Peptides, and Analogues
Direct Parent
Alternative Parents
Not Available
Not Available
Molecular Framework
Not Available
External Descriptors
Not Available
Affected organisms
  • Humans and other mammals

Chemical Identifiers

CAS number


Synthesis Reference

Christian Birr, Ulrich Stollenwerk, "Method of preparing thymosin alpha 1 and derivatives thereof." U.S. Patent US4466918, issued April, 1979.

General References
  1. Chien RN, Liaw YF: Thymalfasin for the treatment of chronic hepatitis B. Expert Rev Anti Infect Ther. 2004 Feb;2(1):9-16. [Article]
  2. Sjogren MH: Thymalfasin: an immune system enhancer for the treatment of liver disease. J Gastroenterol Hepatol. 2004 Dec;19 Suppl 6:S69-72. [Article]
  3. Liaw YF: Thymalfasin (thymosin-alpha 1) therapy in patients with chronic hepatitis B. J Gastroenterol Hepatol. 2004 Dec;19 Suppl 6:S73-5. [Article]
  4. Sjogren MH: Thymalfasin: an immune system enhancer for the treatment of liver disease. J Gastroenterol Hepatol. 2004 Dec;19(12):S69-72. [Article]
  5. Liaw YF: Thymalfasin (thymosin-alpha 1) therapy in patients with chronic hepatitis B. J Gastroenterol Hepatol. 2004 Dec;19(12):S73-5. [Article]
  6. Vemuri S: Comparison of assays for determination of peptide content for lyophilized thymalfasin. J Pept Res. 2005 Apr;65(4):433-9. [Article]
  7. Rustgi VK: Thymalfasin for the treatment of chronic hepatitis C infection. Expert Rev Anti Infect Ther. 2005 Dec;3(6):885-92. [Article]
  8. Rustgi VK: Thymalfasin for the treatment of chronic hepatitis C infection. Ann N Y Acad Sci. 2007 Sep;1112:357-67. Epub 2007 Jun 28. [Article]
  9. Gramenzi A, Cursaro C, Andreone P, Bernardi M: Thymalfasin: clinical pharmacology and antiviral applications. BioDrugs. 1998 Jun;9(6):477-86. [Article]
  10. Pierluigi B, D'Angelo C, Fallarino F, Moretti S, Zelante T, Bozza S, De Luca A, Bistoni F, Garaci E, Romani L: Thymosin alpha1: the regulator of regulators? Ann N Y Acad Sci. 2010 Apr;1194:1-5. doi: 10.1111/j.1749-6632.2010.05465.x. [Article]
PubChem Substance
RxList Drug Page

Clinical Trials

Clinical Trials
4CompletedTreatmentCirrhosis of the Liver2
4Unknown StatusTreatmentCurable Hepatitis B Virus-Related Hepatocellular Carcinoma1
3CompletedTreatmentChronic Hepatitis C Virus (HCV) Infection1
3CompletedTreatmentChronic Hepatitis C Virus (HCV) Infection / Hepatitis C Virus (HCV) Infection2
3RecruitingPrevention2019 Novel Coronavirus Infection / Coronavirus Disease 2019 (COVID‑19)1
3RecruitingTreatmentHuman Immunodeficiency Virus Type 1 (HIV-1) Infection1
3RecruitingTreatmentStage II Colorectal Cancer / Stage III Colorectal Cancer1
2CompletedSupportive CareEnd Stage Renal Disease (ESRD)1


Not Available
Not Available
Dosage Forms
Injection, powder, for solution
Injection, powder, lyophilized, for solutionIntramuscular; Subcutaneous
InjectionSubcutaneous1.6 mg/vial
Powder1.6 mg/1ml
Not Available
Not Available


Experimental Properties
Not Available

Drug created at October 21, 2007 22:23 / Updated at February 21, 2021 18:51