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Healing & repairPeptideEvidence B3 cited

Thymosin Alpha-1

Immune Modulating Peptide

aka Ta1 · Thymalfasin · Zadaxin · thymosin alpha 1

A naturally occurring peptide research describes as a potent modulator of T-cell maturation and adaptive immunity.

Molecular wt
3108.3g/mol
Formula
C129H215N33O55
CAS
62304-98-7
Half-life
2 h
clinical
Tmax
2 h
Route
Subcutaneous injection
PubChem
16130571

Sequence

One-letter28 residues

SDAAVDTSSEITTKDLKEKKEVVEEAEN

Three-letter

Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH

Read this before quoting the sequence
28 residues, N-terminally acetylated (the acetyl group accounts for the difference between the free-peptide mass 3066.3 and the labelled 3108). Corresponds to residues 2-29 of human prothymosin alpha (UniProt P06454). INN: thymalfasin. The three-letter string above is quoted verbatim from the ZADAXIN label.
Source ↗

Mechanism of action

Thymosin Alpha-1 enhances the immune response by promoting the maturation of T-cells, which are crucial for adaptive immunity. It increases the production of cytokines, which help in coordinating the immune response. Additionally, it modulates the activity of dendritic cells, enhancing their ability to present antigens and activate T-cells.

What the evidence actually shows

Grade B

There are several human clinical trials demonstrating Thymosin Alpha-1's efficacy in enhancing immune function, particularly in viral infections like hepatitis B and C. However, more large-scale, randomized controlled trials are needed to confirm these findings and explore other potential applications. | REGULATORY: FDA Category 2 reclassification to Category 1 expected (announced Feb 2026).

Regulatory status

Status
Approved outside the United States. Per SciClone Pharmaceuticals' SEC Form 10-K, 'ZADAXIN is approved in over 34 countries, primarily in Asia, the Middle East and Latin America.' Not FDA-approved in the US (verified absent from Drugs@FDA and DailyMed); the FDA has granted thymalfasin orphan designation for malignant melanoma and hepatocellular carcinoma, and the EU orphan designation for hepatocellular carcinoma.
Approved as
ZADAXIN (thymalfasin) for injection. Principal approved indication: chronic hepatitis B in adults with compensated liver disease and HBV replication; vaccine adjuvant and (in some countries) HCV and chemotherapy-adjuvant indications.
Clinical stage
Approved ex-US; ClinicalTrials.gov lists 63 thymalfasin studies spanning phases 1-4.
WADA
Not named on the WADA 2026 Prohibited List.
UK
prescription_only

In the UK, Thymosin Alpha-1 is available by prescription for specific conditions like hepatitis B and C, under the supervision of a healthcare provider.

Source ↗

Pharmacokinetics

Half-life
2 h
Tmax
2 h
Absorption
subcutaneous
Elimination
renal
Washout
3 days
Low-confidence pharmacokinetics
These figures are recorded as clinical rather than measured in a published PK study. Treat them as an order of magnitude. Anything downstream of them — accumulation, steady state, washout — inherits that uncertainty.

Dosing — what backs each figure

Thymosin alpha-1 (thymalfasin, ZADAXIN) has well-documented human dosing: 1.6 mg subcutaneously twice weekly for 6 months in chronic hepatitis B, and 1.6 mg SC once or twice daily for about 7 days in sepsis. It is not FDA- or EMA-approved (it holds an EMA orphan designation, EU/3/02/110, only) but is registered in a number of other countries, so 'approved dosing' claims should be attributed to those registrations, not to the FDA.

ClinicalApproved labelling or a published human trial

Handling and storage

Lyophilized
ZADAXIN label: store the lyophilised vial 'between 2 and 8 C (36 and 46 F)' - refrigerated, not frozen.
Reconstituted
ZADAXIN label: 'It should be used immediately after reconstitution.' No hold time is authorised.
Solvent
1.0 mL Sterile Water for Injection, supplied with the vial.

Storage taken from the ZADAXIN (thymalfasin) 1.6 mg package insert as filed with the Indonesian regulator BPOM. The label gives no light-protection statement and no freeze-thaw data, so those remain unknown. This directly contradicts the ported '-20 C / 4 weeks reconstituted' boilerplate.

Source ↗
→ Reconstitution walkthrough→ Reconstitution calculator

Safety

Commonly reported
  • ·Injection site reactions
  • ·Fatigue
Rarely reported
  • ·Severe allergic reactions
Contraindications
  • ·Known hypersensitivity to Thymosin Alpha-1
Drug interactions
  • ·Immunosuppressants: May reduce the efficacy of Thymosin Alpha-1 by counteracting its immune-enhancing effects.

Injection-site reactions; generally well tolerated

Reported combinations

Reported as synergistic
  • ·Interferon-alpha: May enhance antiviral effects when used together.
Reported as antagonistic
  • ·Corticosteroids: May reduce the immune-enhancing effects of Thymosin Alpha-1.

Combination claims in this dataset are largely unsourced and should be treated as folk knowledge until a citation appears beside them.

References (3)

Data provenance

Chemistry and citations on this page were checked against primary sources on 2026-08-14. Values that could not be verified were left blank rather than filled with a plausible guess.

Could not verify
storage.lightSensitive

Research use only
This profile is educational reference material. It is not medical advice, not a prescription, and not an endorsement of self-administration. Compounds discussed here are research chemicals and most are not approved for human therapeutic use.

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