Thymosin Alpha-1
Originally isolated from thymus tissue. It is approved in a number of countries outside the U.S. as an immune therapy.
Quick chart
Change these and every table below updates.
Dosing schedules (as studied)
The Zadaxin® label, approved for chronic hepatitis B in several countries outside the U.S., gives a single regimen: 1.6 mg twice a week for 6 to 12 months. The 6-month course is shown.
Label regimen
Approved outside U.S.1.6 mg injected under the skin twice a week. Patients under 40 kg receive 40 mcg/kg instead.
| Phase | Weeks | Dose per injection | Syringe units | Volume | Doses per vial* |
|---|---|---|---|---|---|
| Treatment | 1–26 | 1.6 mg | 32 | 0.32 mL | 6 |
* Limited by the vial's contents or the 28-day use limit after mixing, whichever comes first.
The label specifies injection under the skin only, not into a vein.
- 9 × 10 mg vials (each vial is used for at most 28 days after mixing)
- 18 mL bacteriostatic water (2 mL per vial)
- 52 × 0.5 mL (50-unit) U-100 insulin syringes
- 113 alcohol prep pads, plus a sharps container
Reconstitution for this setup
- Let the 10 mg vial reach room temperature and wipe both stoppers with alcohol.
- Slowly add 2 mL of bacteriostatic water, aiming down the inside wall of the vial.
- Swirl gently until clear. Never shake.
- Label the vial: 5 mg/mL, with today's date. Refrigerate and use within 28 days.
Label details
| Use | Dose | Schedule | Duration |
|---|---|---|---|
| Chronic hepatitis B (adults) | 1.6 mg | Twice weekly, injected under the skin | 6 to 12 months |
- The label specifies injection under the skin only, not into a vein.
- Patients under 40 kg receive a weight-based dose instead (40 mcg per kg).
Research summary
Thymosin alpha-1 helps regulate T-cell function. A synthetic version, thymalfasin, is approved in a number of countries for chronic hepatitis B and C and as an immune support in some cancer treatments.
What the research shows
- It has decades of clinical use outside the U.S. with a generally favorable safety record.
- Studies in sepsis and COVID-19 had mixed results.
- It is not FDA approved in the United States.
References
- Zadaxin® (thymalfasin) product information, Singapore Health Sciences Authority. View source
- Zadaxin drug information, RxList. View source
Related compounds
Last reviewed: November 2026