Thymosin Alpha-1
Tα1 · Zadaxin · Thymalfasin
Immune-modulating thymic peptide; 1.6 mg twice weekly is the typical Zadaxin regimen
Overview
Thymosin Alpha-1 (Tα1) is a 28-amino-acid peptide originally isolated from thymic tissue, where it contributes to maturation and regulation of T-cells. As a pharmaceutical, the synthetic peptide is known as thymalfasin and marketed under the brand name Zadaxin.
Its principal interest is immune modulation. Tα1 is reported to enhance T-cell function and dendritic-cell activity and to help regulate inflammatory and antiviral responses. It is approved in several countries outside the United States for indications such as chronic hepatitis B and as an adjuvant in certain settings, and has been studied as a supportive immune agent in other contexts.
In the United States, Thymosin Alpha-1 is not FDA-approved and is handled as research material. The regimen summarized here reflects the typical Zadaxin dosing; figures should be verified against the relevant product information and primary literature.
Key parameters
- Dose range
- 1.6 mg per dose (typical Zadaxin)
- Frequency
- 2× weekly (typical)
- Half-life
- ~2 hours
- Route
- Subcutaneous
- Vial sizes
- 5 mg · 10 mg
- Regulatory status
- Approved in some countries (Zadaxin/thymalfasin); not FDA-approved; research use in the US. Marketed in several countries outside the US for indications such as chronic hepatitis B and as an immune adjuvant; US-supplied research material is labeled for laboratory use only.
Mechanism of action
T-cell maturation and function
Promotes differentiation and activity of T-lymphocytes, supporting adaptive immune responses.
Dendritic-cell and innate immune modulation
Reported to enhance dendritic-cell function and signaling through pattern-recognition receptors, bridging innate and adaptive immunity.
Cytokine regulation
Associated with a more balanced cytokine profile, supporting antiviral responses while moderating excessive inflammation.
Dosing protocol & phases
| Phase | Weeks | Dose | Notes |
|---|---|---|---|
| Typical regimen (Zadaxin) | Ongoing | 1.6 mg twice weekly | Reflects the commonly cited thymalfasin/Zadaxin schedule; confirm against product information for the relevant indication. |
| Community variations | Ongoing | Varies (e.g., daily during acute use) | Some community protocols increase frequency during acute illness; daily dosing is not the established Zadaxin schedule. |
Reconstitution guide
For educational and research reference only. Not intended for human consumption, not medical advice. Compounds discussed are sold and used for laboratory research purposes only.
5 mg vial + 2 mL bacteriostatic water
Concentration2,500 mcg/mL · 2.5 mg/mL
| Target dose | Draw volume | U-100 units |
|---|---|---|
| 800 mcg | 0.32 mL | 32 |
| 1,600 mcg | 0.64 mL | 64 |
Convenient mix for the 1.6 mg twice-weekly dose.
10 mg vial + 2 mL bacteriostatic water
Concentration5,000 mcg/mL · 5 mg/mL
| Target dose | Draw volume | U-100 units |
|---|---|---|
| 1,600 mcg | 0.32 mL | 32 |
Higher-strength mix; keeps the 1.6 mg dose to a smaller draw.
Reconstitution calculator
Pre-filled with Thymosin Alpha-1's vial sizes. Adjust the water volume and target dose to see the exact draw, with warnings for doses that are hard to measure or won't fit a syringe.
At 2,500 micrograms per millilitre, a 800 microgram dose is 0.32 millilitres, or 32 units on a U-100 syringe, giving 6 doses per vial.
Supplies needed
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Recommended supply
Thymosin Alpha-1 — research vial
From our verified partner Dynotides, with a third-party certificate of analysis per batch.
Injection supplies
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Bacteriostatic water
Diluent for reconstituting lyophilized vials.
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Insulin syringes (U-100)
0.3–0.5 mL, 29–31 G for accurate small draws.
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Alcohol prep pads
Sterile swabs for the vial stopper and site.
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Sharps container
Safe disposal of used needles.
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Storage fridge
Keeps reconstituted vials at 2–8 °C.
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Insulated travel case
Cooled, TSA-friendly case for travel.
Missed-dose guidance
For the approved product, follow the dosing information for the specific indication and prescriber guidance. In general, a missed twice-weekly dose is taken when remembered if reasonably close to schedule, otherwise skipped rather than doubled.
Side effects & safety
| Category | Effect | Trial incidence |
|---|---|---|
| Injection site | Local reactions (redness, discomfort)Most commonly reported category in approved use. | — |
| General | Generally well tolerated in approved useSerious adverse effects are uncommon at the standard 1.6 mg twice-weekly dose. | — |
Clinical trials & evidence
Chronic hepatitis B studies
Clinical (approved indication abroad)Typically 6–12 months · Adults with chronic hepatitis B
Thymalfasin (Zadaxin) is used as an immune-modulating therapy for chronic hepatitis B in several countries, alone or with antivirals; response rates vary by regimen and population.
Trial identifier needs verification
Immune-adjuvant and sepsis investigation
Clinical (varied)Varies · Adults (e.g., severe infection, vaccine response, oncology adjuvant)
Studied as a supportive immune modulator across several settings, including a large sepsis trial; evidence is mixed and indication-dependent.
Trial identifier needs verification
Storage & handling
- Lyophilized
- Refrigerate lyophilized powder at 2–8 °C, protected from light; follow the product information for the approved formulation.
- Reconstituted
- Refrigerate at 2–8 °C and use within ~28 days; do not freeze.
Comparisons
| Vs. | Target | Half-life | Dosing | Efficacy | Status |
|---|---|---|---|---|---|
| KPV | Immune-modulating peptide vs anti-inflammatory alpha-MSH fragment | ~2 h vs short | ~2× weekly vs daily | Different roles (broad immune modulation vs local anti-inflammatory) | Approved in some countries vs research-only |
| VIP | Thymic immune peptide vs VPAC-receptor neuropeptide | ~2 h vs ~1–2 min | ~2× weekly vs intranasal/SC daily | Approved immune modulator abroad vs negative pivotal IV trial | Approved in some countries vs investigational |
Sources & references
Frequently asked questions
Is Thymosin Alpha-1 approved?
It is approved in several countries outside the United States as thymalfasin (brand name Zadaxin) for indications such as chronic hepatitis B and as an immune adjuvant. It is not FDA-approved, and in the United States it is handled as research material.
What is the typical dose?
The commonly cited Zadaxin regimen is 1.6 mg administered subcutaneously twice weekly. Specific dosing depends on the indication and should be confirmed against the relevant product information.
What does Thymosin Alpha-1 do?
It is an immune-modulating peptide that supports T-cell maturation and function and helps regulate inflammatory and antiviral responses. It is studied primarily for its effects on immune function rather than for direct tissue repair.
Related protocols
KPV
Lys-Pro-Val
Tripeptide C-terminal fragment of alpha-MSH studied for anti-inflammatory activity (preclinical)
VIP
Vasoactive Intestinal Peptide
28-amino-acid neuropeptide; the definitive aviptadil COVID-19 trial (TESICO) showed no benefit
Looking to match this protocol to a verified research vial? Our partner supplier publishes a certificate of analysis per batch.
For educational and research reference only. Not intended for human consumption, not medical advice. Compounds discussed are sold and used for laboratory research purposes only.