The immune-modulating peptide approved in 35+ countries — strengthens T-cell immunity without overstimulation, used for chronic infection, post-COVID recovery, and Lyme.
Thymosin Alpha-1 (TA1 or Tα1) is a 28 amino acid peptide naturally produced by the thymus gland. Its synthetic form (branded Zadaxin / Thymalfasin) is approved in more than 35 countries for chronic hepatitis B, hepatitis C, sepsis, and as an adjunctive immune therapy in cancer.
Unlike broad immune stimulants, TA1 modulates — it boosts under-functioning T-cell responses without triggering inflammatory overshoot. This makes it valuable for chronic infections, immunosenescence, and post-illness recovery.
Approved in 35+ countries (not US). Not WADA prohibited. Available through international pharmacies and research suppliers.
Promotes maturation of naive T-cells into effector cells in the thymus — compensating for age-related thymic involution.
Restores balance between Th1 (antiviral, antibacterial) and Th2 (antibody) responses. Corrects the skew toward chronic inflammation seen in aging and chronic infection.
Enhances natural killer cell activity and dendritic cell antigen presentation — critical for clearing infected or transformed cells.
Paradoxically tamps down excessive inflammation — protective in sepsis and autoimmune settings. It is a regulator, not just a booster.
| Benefit | Evidence |
|---|---|
| Chronic hepatitis B/C | Phase 3 trials show meaningful viral response and histological improvement |
| Sepsis | Earlier ETASS-era meta-analyses suggested reduced 28-day mortality, but the TESTS Phase 3 trial (Wu 2025, PMID 39814420, n=1,089) — the largest Tα1 trial ever — was negative (28-day mortality 23.4% Tα1 vs 24.1% placebo, p=0.93). The current best evidence does not support a sepsis benefit. |
| COVID-19 | Liu et al. (2020): reduced mortality in severely ill COVID patients with lymphocytopenia |
| Chronic Lyme | Used off-label for immunomodulation in chronic Lyme protocols |
| Cancer adjunct | Improves response to chemo and immunotherapy in several cancer trials |
| Vaccine response | Enhanced antibody response to influenza and hepatitis B vaccines in elderly |
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeSome protocols use 1.6 mg daily for the first 2–4 weeks during acute infection, then drop to 2×/week maintenance.
Commonly supplied as 5 mg or 10 mg lyophilized powder.
5 mg vial + 2 mL BAC water = 2500 mcg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 800 mcg | 0.32 mL | 32 units |
| 1.6 mg | 0.64 mL | 64 units |
5 mg vial at 1.6 mg 2×/week = ~10 days
Pre-filled with a typical Thymosin Alpha-1 setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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One of the most tolerable peptides in clinical use — decades of approved use worldwide with excellent safety.
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Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNo in the US, yes in 30+ other countries. Thymosin Alpha-1 (synthetic INN: thymalfasin, brand name Zadaxin by SciClone) is approved in countries including Italy, Spain, Mexico, China, India, Brazil, Russia, and others for chronic hepatitis B/C and as an adjunct to vaccination. In the US it has had orphan-drug designation for various indications but no full FDA approval. Sold in the US only as a research chemical or through 503A compounding (its regulatory status under the 2024-2026 PCAC review is unsettled).
Zadaxin label: 1.6 mg subcutaneously twice weekly (typically Mondays and Thursdays). Community / 503A-compounded use often runs at the same dose, sometimes daily for acute use. Higher doses (3–5 mg) have been used in case reports for severe immune dysregulation but lack RCT validation.
Zadaxin ships as a 1.6 mg vial with supplied diluent — follow the label procedure. For research-grade lyophilized Tα1 (commonly 5 mg or 10 mg vials), a typical reconstitution is 5 mg + 2 mL bacteriostatic water, yielding 2.5 mg/mL. A 1.6 mg dose draws to 0.64 mL (64 units on a 100-unit insulin syringe). Many users prefer 5 mg + 4 mL = 1.25 mg/mL so a single dose is a more measurable ~1.28 mL.
Tα1 acts as an immunomodulator (not a pure immunostimulant). It activates dendritic cells via TLR-9 and TLR-2/6 signaling, drives indoleamine 2,3-dioxygenase (IDO) expression, and shifts T-cell differentiation toward Th1 responses. The net effect depends on baseline immune state — it amplifies appropriate responses rather than driving generic "immune boosting." This is the basis for its use as a hepatitis B/C adjunct, sepsis adjunct (Chinese clinical use), and exploratory cancer-immunotherapy combination.
Pharmacokinetics: Tmax 1–2 hours SC, plasma half-life ~2 hours (Rost 1999, PMID 10027483). Biological effect outlasts plasma exposure because the action is via cellular signaling (IDO induction, DC programming) rather than continuous receptor occupancy. For acute viral or septic indications, immunomodulatory effects emerge within days. For chronic immune-support use, weeks-to-months timeframes are typical.
Not specifically named on the WADA Prohibited List as of 2025–2026. WADA reserves discretion under S0 (Non-Approved Substances) and S2 (Peptide Hormones) — Tα1 has been the subject of WADA monitoring conversations in the past. Competitive athletes should verify the current-year list and consider it potentially problematic.
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