Thymosin Alpha-1
Immunomodulatory peptide (thymic)
A 28-amino-acid peptide studied in immune-modulation research.
Also referenced as: Thymosin A1, Tα1
Overview
Thymosin alpha-1 (Thymalfasin) is a 28-amino-acid peptide originally isolated from thymosin fraction 5 of thymic tissue and later produced synthetically. It corresponds to a fragment of the precursor protein prothymosin alpha and is naturally acetylated at its N-terminus.
At a glance
What Thymosin Alpha-1 does
Thymosin alpha-1 (Talpha1) is a 28-amino-acid peptide derived from the thymic protein prothymosin alpha, and it works as a biological response modifier that tunes both innate and adaptive immunity rather than acting as a conventional antigen-specific stimulant. Its best-characterized molecular action is engagement of Toll-like receptors on antigen-presenting cells: it signals through TLR2 on myeloid dendritic cells and macrophages and through TLR9 on plasmacytoid dendritic cells, activating downstream NF-kB, p38 MAPK, and IRF3/IRF7 pathways.
The downstream consequence of that receptor engagement is dendritic-cell maturation, which then drives T-cell development and skewing. In research it has been shown to promote differentiation of CD4+ and CD8+ T cells, raise CD4/CD8 ratios, enhance cytotoxic and NK-cell activity, and increase production of Th1-type cytokines such as IL-2, IL-12, and IFN-gamma. It also influences tolerogenic pathways (e.g., IDO induction), which is why it is described as 'modulating and optimizing' immunity rather than simply amplifying it.
Among the peptides in this longevity set, thymosin alpha-1 has the strongest clinical footing. A synthetic version (thymalfasin/Zadaxin) is approved in dozens of countries and has been studied in large trials as an adjunct in chronic hepatitis B and C, certain cancers, and immune support in sepsis and viral infection. It is not FDA-approved in the United States. So while its immune-cell mechanisms are well documented and it has genuine clinical use abroad, its specific value for aging/longevity per se remains an extension of its immune-modulating pharmacology rather than a proven anti-aging effect.
Effects reported in research
- Binds TLR2 on myeloid dendritic cells and macrophages, activating NF-kB and p38 MAPK signaling to drive dendritic-cell maturation.
- Signals through TLR9 on plasmacytoid dendritic cells, engaging IRF3/IRF7 pathways and type-I interferon (IFN-alpha) production.
- Promotes differentiation and maturation of CD4+ and CD8+ T cells downstream of dendritic-cell activation, strengthening cell-mediated immunity.
- Increases CD4/CD8 ratios and enhances cytotoxic T-cell and NK-cell activity in studies.
- Stimulates Th1-type cytokine production including IL-2, IL-12, and IFN-gamma.
- Modulates tolerogenic pathways such as IDO induction, acting as an immune optimizer rather than a blunt stimulant.
- As synthetic thymalfasin (Zadaxin), studied in large human trials as an adjunct in chronic hepatitis B/C and certain cancers, and approved in dozens of countries (not FDA-approved in the US).
- Its longevity relevance is an extrapolation from immune-modulating pharmacology rather than a directly demonstrated anti-aging effect.
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
Thymosin alpha-1 acts as an immunomodulator, reported to enhance T-cell maturation and function, influence dendritic cell activity, and modulate innate immune signaling including Toll-like receptor pathways. It has been studied for augmenting responses to antigens and vaccines and for regulating immune responses in infection and cancer contexts. Its effects are attributed to broad immune-regulating activity rather than a single narrowly defined receptor.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which Thymosin Alpha-1 appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Defined 28-residue, N-terminally acetylated peptide (Thymalfasin)
- Fragment of the precursor prothymosin alpha
- One of the more clinically studied peptides in this category
- Marketed as Zadaxin in some countries for immune indications
- Studied in hepatitis, sepsis, and as a vaccine adjuvant
- Acts as a broad immunomodulator affecting T-cell and innate immunity
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. Thymosin Alpha-1 is a research compound.
Reported clinical dosing (as Zadaxin/thymalfasin) is a fixed subcutaneous dose given twice weekly over an extended course. These are reference figures for research context only, not dosing guidance for humans.
- Approved-label reference (Zadaxin): 1.6 mg (~900 mcg/m2) subcutaneously twice weekly
- Course length reference: 6-12 months in hepatitis clinical use
Short (~2 h) circulating half-life underlies the repeated twice-weekly schedule rather than daily or single dosing.
How it compares
Thymosin alpha-1 is a single, well-characterized synthetic peptide with genuine clinical trial data and approvals in some countries, unlike the research-only thymic fraction Thymalin.
Commonly studied alongside
Compounds frequently researched together with Thymosin Alpha-1 in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Compare and calculate
Side-by-side pages for the pairings the literature already documents for Thymosin Alpha-1, plus the unit-conversion reference for a reconstituted vial. Factual comparisons of documented characteristics — not a recommendation to combine or use any compound.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
Thymosin Alpha-1 sits in the Longevity & Cellular area of the PeptiDex library.
- Entry type: Research compound reference
- Longevity & Cellular category hub →
- Browse the full library →
- Glossary of terms →
Where researchers source Thymosin Alpha-1
For researchers studying Thymosin Alpha-1, third-party suppliers such as Practically Natty Peptides offer research-grade material, third-party tests every batch and provides Certificates of Analysis on request, and ship from the US. This specific listing is currently marked out of stock — check the supplier site for current availability.
Multiple supplier listings exist for this compound (e.g., dosage variants). The primary research-supplier listing is linked below.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is thymosin alpha-1?
Thymosin alpha-1 (Ta1, thymalfasin, brand Zadaxin) is an acetylated 28-amino-acid thymic peptide that acts as an immunomodulator. It is studied for enhancing T-cell maturation and dendritic-cell function, in part through Toll-like receptor signaling (TLR9/TLR2).
What is the sequence and molecular weight of thymosin alpha-1?
Its sequence is Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN, a 28-residue N-acetylated peptide with a molecular weight of about 3108 Da. The N-terminal acetylation is a defining structural feature of the native molecule.
Is thymosin alpha-1 an approved drug?
Thymosin alpha-1 is approved as Zadaxin (thymalfasin) in more than 30 countries, chiefly for chronic hepatitis B and as an immune adjunct, but it is not FDA-approved in the United States. This makes it a research chemical in the US context.
How does thymosin alpha-1 differ from thymalin?
Thymosin alpha-1 is a single, synthetically defined 28-mer with a known sequence and molecular weight, whereas thymalin is an undefined-composition thymic extract. Researchers choose thymosin alpha-1 when a standardized, single-molecule immunomodulator is needed.
What does the ~2 hour half-life imply for research design?
The circulating half-life of thymosin alpha-1 is reported at roughly 2 hours, so reported clinical protocols use repeated dosing (e.g. twice weekly over months) rather than single administration. The short half-life shapes frequency-based study designs.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.
References
Primary literature indexed in PubMed for Thymosin Alpha-1. Listing a study records that it exists and is indexed — it is not a claim of efficacy, a therapeutic indication, or an endorsement of its conclusions. Much of this literature is preclinical (in-vitro or animal-model).
- Immune Modulation with Thymosin Alpha 1 Treatment
- Historical review of thymosin α 1 in infectious diseases
- Thymosin alpha 1 treatment for patients with sepsis
Each reference was checked against its PubMed record on 2026-07-28: the PMID resolves and the title, journal and year match. Where no indexed literature exists for a compound, PeptiDex says so rather than substituting a citation about a different molecule. See the editorial policy.