Thymosin Alpha-1
Also known as · Thymalfasin · Tα1 · Zadaxin (approved outside US)
- EvidenceApproved
- CategoryImmunomodulator
- RoutesubQ
- Half-life~2 h
01 / Dosing schedule
Cited dosing
Thymosin Alpha-1 (Zadaxin) is approved outside the US for chronic hepatitis B, malignant melanoma, DiGeorge anomaly, and hepatocellular carcinoma. The insert lists 1.6 mg subcutaneously twice weekly for chronic hepatitis B, as monotherapy or with interferon.
Zadaxin — chronic hepatitis B
| Phase | Dose & frequency |
|---|---|
| Standard dose | 1.6 mg (900 mcg/m²) subQ twice weekly |
| Regimen | Monotherapy or combined with interferon at labeled interferon dose |
| Route | Subcutaneous only — not IV |
| Vial | 1.6 mg lyophilized powder + 1 mL diluent |
Source · SciClone Zadaxin (thymalfasin) prescribing information ↗
Source indication · Chronic hepatitis B (Zadaxin insert, non-US approval).
- Injection frequency
- Twice weekly, spaced 3–4 days apart.
- Injection sites
- Subcutaneous — typical rotation sites.
02 / Reconstitution
Reconstitution reference
Zadaxin is 1.6 mg lyophilized powder per vial, reconstituted with 1 mL of sterile water for injection immediately prior to use. Final concentration is 1.6 mg/mL. The full vial is the standard dose. For research-grade multi-dose vials, dilution math scales with the vial size and BAC water volume chosen.
03 / Overview
Protocol overview
Thymosin Alpha-1 is a 28-amino-acid peptide originally isolated from thymic tissue. It modulates T-cell maturation and shifts the innate/adaptive immune response.
It is approved in over 35 countries (including much of Europe and Asia) for chronic hepatitis B, malignant melanoma, DiGeorge syndrome, and hepatocellular carcinoma. It is not FDA-approved in the US and is available domestically only through compounding pharmacies.
The 1.6 mg twice-weekly subQ schedule is the label-standard for chronic hepatitis B and the dose used in the pivotal trials. Broader immunomodulation dosing in the literature ranges from 0.8–6.4 mg per dose.
The ~2 hour plasma half-life belies a longer functional effect on lymphocyte populations. Twice-weekly dosing has been the trial-standard cadence.
04 / References