Thymosin Alpha-1
Aliases: Ta1 · Zadaxin · Timozin alfa-1
Last verified: 2026-09-23
The short version
Thymosin alpha-1 is one of the most studied immunomodulatory peptides: approved in 30+ countries for chronic hepatitis B and C (as adjunct), with a real clinical program behind it. The effect is moderate, and in Western medicine it has been marginalized by potent antivirals. In the post-COVID era there are new small trials, but no breakthrough. It is a solid, approved peptide with a narrowed place in therapy.
Identity & type
- Molecular type
- peptide
- Sequence / structure
- 28 aa, acetiliran N-terminus
- Molecular weight
- ~3108 Da
- Origin
- Natural thymic peptide, N-terminally acetylated; approved in many countries (Zadaxin) for certain hepatitis indications and immunomodulation.
Mechanism of action
Activates TLR9/MyD88 and TLR2 pathways in dendritic cells, enhances Th1 responses, increases MHC-I expression and NK-cell function.
Dosing & routes
Official / clinical context
Approved drug — indications, dosing and warnings are defined by the official label. 1.6 mg SC twice weekly (approved regimen); protocols use 1.6–3.2 mg 2–3× weekly.
Regulator-approved labeling and published study designs — never a recommendation.
Community-reported practice
1.6 mg SC twice weekly (approved regimen); protocols use 1.6–3.2 mg 2–3× weekly. In clinical practice (approved in 30+ countries): support in chronic viral infections; the community uses it for an "immune reset" during autumn/winter and alongside vaccinations.
Unverified self-reports. Not medical advice. Not endorsement.
Expected effects (community)
In clinical practice (approved in 30+ countries): support in chronic viral infections; the community uses it for an "immune reset" during autumn/winter and alongside vaccinations.
Protocol — official vs community
Official / label
Approved in 30+ countries (Zadaxin), not the US: 1.6 mg SC twice weekly (3.2 mg/week) for hepatitis B/C and immune-adjunct indications.
- 01Flat 1.6 mg SC twice weekly
Duration: Indication-defined, often 6–12 months.
One of the most-approved peptides in the world that Americans have to gray-market.
Community (anecdotal)
1.6 mg SC twice weekly, mirroring the label.
- Cycle:
- 6–12 weeks in immune-adjunct use.
- Break:
- Reassess after course.
Community use hews closest to the label of any gray-market peptide — because the label exists.
Human evidence
Approved in multiple countries; meta-analyses in hepatitis B/C show a moderate antiviral adjunct to interferon.
Preclinical evidence
The preclinical phase was completed and submitted to regulators as part of registration; pharmacology and toxicology details are part of the official label.
Known risks
- Rare injection-site reactions; profile is mildcharacterized
- Autoimmune concerns remain theoreticaltheoretical
Teal: characterized in clinical/labeling contexts. Amber: theoretical or reported outside controlled settings.
Unknowns & evidence gaps
- Place in modern therapy beside new antivirals
Frequently asked questions
References
- Zadaxin (thymosin alpha-1) — regulatory documentation and meta-analyses