Thymosin Alpha-1
A 28-amino acid immune peptide used clinically for hepatitis and increasingly by longevity-focused users to support immune resilience.
Last updated: August 2026
Category
Immune / Longevity
Frequency
Twice weekly (community practice, no trial)
Research
Clinical (Approved in Asia/Europe)Peptide length
28 aa
Hepatitis B trial dose (PMID 15850471)
1.6 mg
Brand name
Zadaxin
What is Thymosin Alpha-1?
You know the feeling. Every cold that goes around the office finds you. Every flight leaves you with a sore throat. You have read about immune peptides online and now you want to know what Thymosin Alpha-1 actually does and whether it makes sense for someone living in Vietnam.
Thymosin Alpha-1, often abbreviated TA-1, is a 28-amino acid peptide fragment of prothymosin alpha. It is naturally produced by your thymus gland, the small organ behind your breastbone that trains your T-cells. As you age, your thymus shrinks, and TA-1 production declines with it. The synthetic version is called thymalfasin, sold under the brand name Zadaxin in some Asian and European countries.
TA-1 was first sequenced in 1977 by Allan Goldstein at George Washington University. It has been used clinically for hepatitis B and C treatment in parts of Asia and Europe for decades. The mechanism is not immune suppression, it is immune regulation. TA-1 helps your immune system function more effectively without overstimulating it. Browse our full peptide library for related compounds.
In Vietnam, TA-1 access is mainly through research-grade suppliers or international hospitals with hepatology departments. Zadaxin is not commonly stocked at standard pharmacies. Most expats sourcing TA-1 go through research-grade peptide suppliers or order from regional sources. For information on how this works, see the peptide legality guide.
How It Works
Toll-Like Receptor Activation: TA-1 acts on TLR-2 and TLR-9 on dendritic cells and myeloid cells. This primes your innate immune system to recognize and respond to pathogens more effectively.
T-Cell Maturation: TA-1 stimulates the maturation of T-cells, specifically CD4+ helper T-cells and CD8+ cytotoxic T-cells. This is the same function your thymus performs naturally when it is healthy.
Natural Killer Cell Activation: TA-1 enhances the activity of NK cells, your first line of defense against virally infected cells and early-stage cancer cells.
Cytokine Modulation: TA-1 reduces the production of pro-inflammatory cytokines like IL-1 beta and TNF-alpha while promoting balanced immune signaling. This is regulation, not suppression.
Benefits
- Enhanced immune response to chronic viral infections (hepatitis B/C, HPV, CMV)
- Support for aging immune systems (immunosenescence)
- Adjunct therapy potential for autoimmune conditions
- Post-illness recovery support
- Cancer adjunct in clinical settings (with oncologist oversight)
- Reduced frequency of respiratory infections in some users
- Improved vaccine response in immunocompromised patients
Dosing Described in Research and Labels
| Phase | Dose | Frequency | Duration |
|---|---|---|---|
| Randomised hepatitis B trial (thymalfasin) | 0.8mg or 1.6mg (trial doses, not a recommendation) | Subcutaneous | 24 weeks, followed to week 72 (PMID 15850471) |
| Any wellness or immune-support use | No established dose | Subcutaneous | Not established, and no approved label defines one |
These figures summarise what published research and approved labels describe. They are educational, not a recommendation or a personal protocol. Any dose, schedule, or decision to use a compound belongs with a licensed prescriber.
Side Effects
Common
- ⚠Mild injection site reaction (redness, minor swelling)
- ⚠Temporary fatigue in first few doses
- ⚠Mild headache reported by some users
Rare
- •Temporary elevation in ALT liver enzymes (monitor if concerned)
- •Flu-like symptoms during initial immune activation
Who Should NOT Use Thymosin Alpha-1
- ✕Pregnancy or breastfeeding (insufficient safety data)
- ✕Transplant recipients on immunosuppressants (do not stimulate rejection)
- ✕Active chemotherapy (consult oncologist first)
- ✕Intentional immunosuppression therapy (contradicts treatment goal)
What to Expect
Most users feel nothing dramatic. Some report mild fatigue or flu-like symptoms as immune system activates. This typically resolves within days.
Users focused on chronic infection support may notice subtle improvements. Energy levels often stabilize. Some report feeling "less susceptible" to whatever is going around.
Cumulative immune benefits become more apparent. Users with chronic viral loads may see improvements in relevant bloodwork. General resilience improves.
Completing a cycle and assessing, then returning seasonally, is the commonly reported pattern (community practice, no trial). No trial has established a cycle length for wellness use and no approved label defines one. The only trial duration on record is 24 weeks, for chronic hepatitis B (PMID 15850471).
Notes from Ho Chi Minh City
Thymosin Alpha-1 comes up around the immune dip after long-haul flights into Tan Son Nhat, where cabin air plus HCMC humidity reliably puts travelers sideways for a week. Its research context is immune modulation, and the approved Zadaxin product exists for specific clinical indications rather than general travel use. On availability, Zadaxin is not stocked at Long Châu or Pharmacity and shows up only occasionally through FV Hospital and Vinmec Central Park hepatology clinics, while research-grade TA-1 is sourced through cold-chain importers. Dose and schedule are clinical decisions; the forum habit of chasing a number is exactly what a licensed prescriber exists to replace.
Sourcing in Vietnam
Branded Zadaxin (thymalfasin) is occasionally available through FV Hospital and Vinmec Central Park hepatology clinics in HCMC, prescription-only. Research-grade TA-1 is sourced through cold-chain importers. The only doses with a trial behind them are 0.8mg and 1.6mg for chronic hepatitis B (PMID 15850471). Not stocked at Long Châu, Pharmacity, or any retail pharmacy. See the supplier list and COA guide before purchasing.
FAQ
Q: Is Thymosin Alpha-1 legal in Vietnam?
A: TA-1 exists in a gray area similar to most research peptides in Vietnam. Zadaxin is approved in several Asian countries for hepatitis treatment, but not specifically registered with the DAV in Vietnam. Most users source research-grade TA-1 from regional suppliers. See the peptide legality guide for how this works in practice.
Q: What is the typical dose of TA-1?
A: The randomised hepatitis B trial administered: Thymalfasin at 0.8 mg or 1.6 mg, given for 24 weeks, in 316 Japanese patients with chronic hepatitis B and raised ALT. At week 72, 36.4 percent of the 1.6 mg group had normalised ALT and 22.8 percent had cleared HBe antigen; the 0.8 mg group reached similar rates (trial doses, not a recommendation). Disclaimer: that is Iino et al., Journal of Viral Hepatitis, 2005, PMID 15850471. Those amounts were given for a diagnosed viral infection under medical supervision, which is what the approved product exists for. No trial has established a dose for general immune support, and there is no approved label for that use anywhere. The 1.5 mg figure that circulates in the community for wellness use is community practice, no trial. What amount is appropriate is a clinical decision a licensed prescriber makes.
Q: How is TA-1 different from TB-500?
A: They are completely different peptides despite both containing "thymo" in the name. TB-500 (Thymosin Beta-4) is a healing peptide for tissue repair. TA-1 (Thymosin Alpha-1) is an immune modulating peptide. Different mechanisms, different uses. See TB-500 for the healing peptide.
Q: Does TA-1 cause immune suppression?
A: No. TA-1 is an immune modulator, not an immune suppressant. It enhances and regulates immune function rather than suppressing it. This is why it is contraindicated for transplant patients on immunosuppressants, because it would work against their medication.
Q: How long does a TA-1 cycle last?
A: The one duration with a trial attached: Thymalfasin at 0.8 mg or 1.6 mg for 24 weeks, in 316 Japanese patients with chronic hepatitis B, followed to week 72 (trial doses, not a recommendation). Disclaimer: that is Iino et al., Journal of Viral Hepatitis, 2005, PMID 15850471, and it describes what was administered for that diagnosis under medical supervision. Community practice reports 4 to 12 week cycles for general immune use (community practice, no trial). No trial has established a duration for any wellness use, no approved label in any market defines one, and telling readers when to break or restart would be dosing advice. That is a clinical decision.
Q: Can I stack TA-1 with other peptides?
A: No interaction study for these compounds has been published in people, so there is no evidence describing what TA-1 does alongside NAD+ therapy, BPC-157 or anything else. The claim this page used to carry, that TA-1 does not interact with healing peptides, was an unsourced safety clearance and has been removed: absence of published interaction data is not evidence of safety. TA-1 acts on the immune system, and it is contraindicated alongside immunosuppressive therapy for exactly that reason, which makes anything else in use at the same time a question for a licensed prescriber rather than a guide.
Q: Where can I buy TA-1 in Vietnam?
A: Most expats source research-grade TA-1 from regional peptide suppliers with cold-chain shipping to Vietnam. Zadaxin is not commonly available at local pharmacies. Check the supply index for verified sources. Always verify batch purity with a third-party COA.
Where to Get Thymosin Alpha-1 in Vietnam
See our community-verified supplier list with COA verification and cold-chain shipping to Vietnam.
Related Peptides
Research & Sources
- Thymosin alpha 1: A comprehensive review of the literature · Dominari A, Hathaway Iii D, Pandav K, et al. · World Journal of Virology (2020) (PMID: 33362999)
Comprehensive review of TA-1 mechanism, indications, and clinical evidence across hepatitis and immune modulation.
- Thymosin α1 and Its Role in Viral Infectious Diseases: The Mechanism and Clinical Application · Tao N, Xu X, Ying Y, et al. · Molecules (2023) (PMID: 37110771)
Mechanistic review covering TLR-2/9 activation and T-cell maturation pathways relevant to viral infection control.
- The efficacy and safety of thymosin alpha-1 in Japanese patients with chronic hepatitis B; results from a randomized clinical trial · Iino S, Toyota J, Kumada H, et al. · Journal of Viral Hepatitis (2005) (PMID: 15850471)
316 patients randomised to thymalfasin 0.8mg or 1.6mg for 24 weeks, observed to week 72. At week 72, 36.4% of the 1.6mg group normalised ALT and 22.8% cleared HBe antigen. Trial doses, not a recommendation.
- Thymosin Alpha 1 Reduces the Mortality of Severe Coronavirus Disease 2019 by Restoration of Lymphocytopenia and Reversion of Exhausted T Cells · Liu Y, Pan Y, Hu Z, et al. · Clinical Infectious Diseases (2020) (PMID: 32442287)
Observational data on TA-1 use in severe respiratory viral infection and lymphocyte recovery.
Important Disclaimer
Educational content only. Not medical advice. Peptides discussed on this page are not approved by Vietnam’s Ministry of Health (Bộ Y Tế) or the Drug Administration of Vietnam (DAV) for the indications described. Research peptides are not stocked at Long Châu, Pharmacity, or any retail pharmacy in Vietnam. Consult a licensed physician before any use.