Thymalfasin

Summary

Thymalfasin (thymosin alpha-1) is a 28-amino acid synthetic peptide identical to endogenous thymosin alpha-1 derived from thymosin fraction 5. It is approved in multiple countries for treatment of chronic hepatitis B and C, as an adjuvant to vaccines in immunocompromised patients, and has been investigated for sepsis, malignancies, and COVID-19. It is marketed under the brand name Zadaxin by SciClone Pharmaceuticals.

Mechanism of Action

Synthetic version of thymosin alpha-1; promotes T-cell maturation and differentiation, enhances Th1 cytokine production (IL-2, IFN-γ), upregulates MHC class I expression on tumor and virus-infected cells, and augments NK cell and dendritic cell activity, thereby restoring immune competence in immunocompromised states.

Routes of Administration

Goals & Uses

• Chronic Hepatitis C treatmentAntiviralHigh
• Chronic Hepatitis B treatmentAntiviralHigh
• Sepsis adjunctive therapyCritical Care / ImmunomodulationModerate
• Cancer immunoadjuvantOncologyModerate
• Immune reconstitution in immunocompromised patientsImmunomodulationModerate
• COVID-19 adjunctive treatmentAntiviral / ImmunomodulationLow

Contraindications

• Hypersensitivity to thymalfasin or excipientsAllergyHigh
• Autoimmune diseases (active)ImmunologicalModerate
• Organ transplant recipients on immunosuppressive therapyImmunologicalModerate

Adverse Effects

• Flu-like symptomsSystemic/ImmunologicalUncommon
• Hypersensitivity / allergic reactionsImmunologicRare
• Injection site reactionsLocalCommon
• NauseaGastrointestinalUncommonFeeling of sickness or urge to vomit
• FatigueGeneralUncommonLow energy or tiredness

Drug Interactions

• Immunosuppressants (e.g., corticosteroids, cyclosporine, tacrolimus)Moderate
• Interferon-alphaLow
• Vaccines (influenza, hepatitis B)Low

Population Constraints

• PregnancyReproductive SafetyRelative
• Pediatric patientsAgeRelative
• LactationReproductiveRelative
• Elderly patientsAgeRelative

Regulatory Status

• European UnionUnapprovedNot granted EMA marketing authorization; available in some EU member states under national frameworks or named-patient programs.
• United StatesUnapprovedNot FDA-approved; has orphan drug designation for certain indications; available under compassionate use or research protocols.
• United KingdomUnknownNo MHRA full marketing authorization; may be available via named-patient or special import schemes.

Approved in over 35 countries including China, Italy, and other Asian and Eastern European nations for chronic hepatitis B and C. Not FDA-approved in the United States; has received orphan drug designation and has been studied under IND applications. EMA has not granted full marketing authorization.

Evidence & Sources

No sources recorded yet.