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Peptide Profile

Thymosin Alpha-1

Thymosin Alpha · Tα1 · Zadaxin

Thymosin alpha-1 (thymalfasin; Zadaxin) is a 28-amino-acid synthetic peptide corresponding to the N-terminal sequence of prothymosin alpha, developed as a biological response modifier with established clinical use outside the…

Immune & ThymicResearch Only
Used forlongevity
Half-life
2 hours
Routes
subcutaneous
Find providers View evidence

Educational research information — not medical advice. Review primary sources and consult a qualified professional before any decision.

Educational research tools — not medical advice.

Overview

What Thymosin Alpha-1 is

About Thymosin Alpha-1

Tα1 modulates both innate and adaptive immune responses by stimulating the differentiation and maturation of T-cells, dendritic cells, and natural killer cells. It upregulates MHC class I and II expression, enhancing antigen presentation. It also promotes the production of key cytokines including interferon-γ and interleukin-2, which are central to immune surveillance.

Thymosin alpha-1 (thymalfasin; Zadaxin) is a 28-amino-acid synthetic peptide corresponding to the N-terminal sequence of prothymosin alpha, developed as a biological response modifier with established clinical use outside the United States for chronic viral hepatitis and as an immune adjuvant in cancer and immunocompromised patients. Thymalfasin modulates innate and adaptive immune responses by upregulating Toll-like receptor expression and dendritic cell maturation, enhancing T-helper 1 cytokine signaling, and potentiating antigen-specific T-cell responses in settings of impaired immune function. A prospective multicenter randomized controlled trial demonstrated that combination therapy with thymosin alpha-1 and entecavir improved serological outcomes in HBV-related compensated cirrhosis compared to entecavir alone, and cumulative RCT evidence supports its role as an immune adjuvant in hepatitis B and C treatment. Thymosin alpha-1 is approved in approximately 35 countries — including China, Italy, and other Asian and Eastern European markets — for hepatitis B and hepatitis C adjuvant therapy, but has not received FDA approval in the United States and is available in US-adjacent research contexts only as an investigational compound. Thymosin alpha-1 dosage: in approved clinical protocols (hepatitis B adjuvant therapy), thymalfasin is administered as 1.6 mg subcutaneously twice weekly for 26–52 weeks. This dosing schedule is derived from the pivotal trials conducted by SciClone Pharmaceuticals, which developed Zadaxin. In COVID-19 research during 2020–2021, Chinese clinical centers studied thymosin alpha-1 as an immune adjuvant in severe and critical COVID-19 patients, with published observational and small RCT data; this research context brought renewed attention to the peptide's immune-modulating properties outside the hepatitis indication. Within the recovery and immune-support peptide landscape, thymosin alpha-1 is most closely compared to thymosin beta-4 (TB-500) — the two peptides share the thymosin nomenclature but have distinct mechanisms and research profiles. Thymosin alpha-1 is an immune activator (TH1 upregulation); thymosin beta-4 is primarily studied for tissue repair and actin dynamics. Providers offering immune-modulating peptide compounds are listed in the PeptideBase directory.

Thymosin Alpha-1 Benefits & Research Areas

TH1 immune activation via Toll-like receptor upregulationhepatitis B and C treatment adjuvant — approved in 35+ countriesdendritic cell maturation and antigen-specific T-cell potentiationCOVID-19 immune support research (2020–2021 Chinese clinical data)

Research Signals

Commonly researched in the context of

Hormonal ChangesSedentary

Population research notes

40s50+

These signals reflect research interest areas, not treatment indications.

Pharmacokinetics

Thymosin Alpha-1 half-life calculator

Compound & timing

Half-lifefrom PeptideBase data
Source: "2 hours" · Thymosin Alpha-1 (PeptideBase)
to show amount remaining
2 h
0%25%50%75%100%02.14.26.28.310time since dose (h)
Plasma decay curve for Thymosin Alpha-1: 50% remaining at 2 h after the dose.
plasma level
50%remaining in plasmaat 2 h after the dose
Half-life
2 h
~97% cleared after
10 h

Model: single-dose, first-order (single-compartment) estimate. Real clearance is multi-compartment and varies by individual and route.

The Research

What the evidence says about Thymosin Alpha-1

Research Evidence

based on 2 studies · 1 RCT · most recent 2026

Regulatory Status

Availability Status
Research Only
FDA Status
Source
View FDA source →

Approved as Zadaxin in China, Italy, and other countries but NOT FDA-approved. Not on FDA 503A Category 1 bulks list. Research use only in US. Immunomodulatory thymic peptide.

Regulatory status reflects publicly available information and may change. This is not legal or medical advice.

Research Sources

2 sources cited · 1 strong · 1 weak

1 RCT · 1 Animal

  • Combination of entecavir with thymosin alpha-1 in HBV-related compensated cirrhosis: a prospective multicenter randomized open-label study

    Expert Opinion on Biological Therapy · 2018

    Research in a prospective multicenter randomized trial found that combination therapy with thymosin alpha-1 plus entecavir was well tolerated and showed a tendency to inhibit hepatocellular carcinoma development during the 52-week treatment period compared with entecavir monotherapy in patients with HBV-related compensated cirrhosis, supporting thymosin alpha-1 as an immunomodulatory adjunct to antiviral therapy.

    RCTn=690StrongPMID 30063860

  • IL-15 Plus Thymosin α1 Reduces Senescent Hepatic CD8(+) T Cells in Hepatocellular Carcinoma via PI3K/AKT Suppression.

    J Gastroenterol Hepatol · 2026

    # Summary Research found that combining interleukin-15 (IL-15) with thymosin alpha 1 (Tα1) synergistically reduced senescent CD8+ T cells in hepatocellular carcinoma by suppressing overactive PI3K/AKT signaling, thereby restoring anti-tumor immune function and prolonging survival in an aged mouse model. This study demonstrated that the dual approach—rescuing existing senescent T cells while simultaneously replenishing the T cell pool through thymic rejuvenation—represents a more effective strategy than either agent alone for overcoming immune dysfunction in liver cancer.

    AnimalWeakPMID 41883056

Thymosin Alpha-1 Side Effects & Safety Considerations

Research-use compound with limited human data. Evidence strength varies — see the Evidence section.

Absolute contraindications

Under clinical review

Being verified by our medical team before we display contraindications for this peptide.

Consult a qualified healthcare professional before making any health decisions. This information is educational only and does not constitute medical advice.

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Thymosin Alpha-1

Third-party testing data

5 verified COAs

Median tested purity

99.8%

Median tested purity of 99.8% across 5 verified third-party lab COAs (interquartile range 99.7%–99.9%), as reported by the independent testing labs below. PeptideBase reports these lab-published figures and does not itself test, endorse, or certify any product.

Independent labs
Freedom Diagnostics, Janoshik Analytical
Most recent test
July 2026

PeptideBase provides educational research tools and provider discovery. It does not provide medical advice, diagnosis, treatment, prescribing guidance, or dosing instructions. Consult a qualified healthcare professional before making health decisions.

Certificates of Analysis

Cross-vendor verified18 COAs on record for Thymosin Alpha-1

PeptideBase reports these lab-published figures and does not itself test, endorse, or certify any product. Confirmed by lab results were matched against the issuing laboratory's own records — either the lab served the document, or its own hosted copy matches ours byte for byte. For every other result the badge states what is known about the lab: that it can be checked and no result is recorded yet, that it can't be checked, or that we have not reviewed it.

PeptideBase provides educational research tools and provider discovery. It does not provide medical advice, diagnosis, treatment, prescribing guidance, or dosing instructions. Consult a qualified healthcare professional before making health decisions.

Community Experience

What people report about Thymosin Alpha-1

n=33high confidence

Self-reported, anecdotal experiences aggregated from public Reddit discussions — community sentiment, not clinical evidence or medical advice.

Outcome distribution

42%improved
Improved
14 · 42%
Mixed
10 · 30%
No clear effect
6 · 18%
Worse
3 · 9%

Outcomes by goal · improved % · reports

Infection recovery47% improved · 15 reports
Immune support27% improved · 11 reports
General recovery60% improved · 5 reports

Side effects people mention

Counts are mentions across reports, not incidence rates.

Fatigue8
Joint pain2
Elevated heart rate1
Hair thinning1
Mood changes1
Vivid dreams1
Water retention1

Most reported

What they wish they'd known

Based on 33 community reports · Updated

Frequently Asked Questions — Thymosin Alpha-1

Thymosin alpha-1 (thymalfasin; Zadaxin) is a 28-amino-acid synthetic peptide corresponding to the N-terminal sequence of prothymosin alpha, developed as a biological response modifier with established clinical use outside the United States for chronic viral hepatitis and as an immune adjuvant in cancer and immunocompromised patients. Thymalfasin modulates innate and adaptive immune responses by upregulating Toll-like receptor expression and dendritic cell maturation, enhancing T-helper 1 cytokine signaling, and potentiating antigen-specific T-cell responses in settings of impaired immune function.

TH1 immune activation via Toll-like receptor upregulation, hepatitis B and C treatment adjuvant — approved in 35+ countries, dendritic cell maturation and antigen-specific T-cell potentiation, COVID-19 immune support research (2020–2021 Chinese clinical data).

Research on Thymosin Alpha-1 primarily documents effects related to TH1 immune activation via Toll-like receptor upregulation and hepatitis B and C treatment adjuvant — approved in 35+ countries and dendritic cell maturation and antigen-specific T-cell potentiation and COVID-19 immune support research (2020–2021 Chinese clinical data). These are areas covered in preclinical and clinical literature — individual response varies and effects depend on context of use.

For Thymosin Alpha-1, its FDA status is Nomination Withdrawn, and it is designated for research use only. Regulatory status reflects publicly available information and may change. This is not legal or medical advice.

167 providers in the directory currently offer Thymosin Alpha-1.

Across 41 research vendors tracked on PeptideBase, Thymosin Alpha-1 has a median price of about $7.71 per mg, typically ranging $6.50–$9.20 per mg. This reflects research-use vendor pricing, not clinical or prescription costs.

Research in a prospective multicenter randomized trial found that combination therapy with thymosin alpha-1 plus entecavir was well tolerated and showed a tendency to inhibit hepatocellular carcinoma development during the 52-week treatment period compared with entecavir monotherapy in patients with HBV-related compensated cirrhosis, supporting thymosin alpha-1 as an immunomodulatory adjunct to antiviral therapy.

Thymosin Alpha-1 is featured in the following research stacks on PeptideBase: Thymosin Alpha-1 + LL-37: Immune Support.

Access

How to get Thymosin Alpha-1

Market Pricing

41 vendors
$6.50/mgBudget
$7.71/mgMedian
$9.20/mgPremium
$6.50
$7.71
$9.20

Price per mg varies by quantity, vendor type, and formulation. Research use only.

Data verified August 2026 · Thymosin Alpha-1 price intelligence

Compare 41 vendors →
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Where to buy Thymosin Alpha-1

167 providers
●131 Clinics●7 Telehealth●1 Pharmacy●25 Online Vendors●3 Physicians214 in stock1 on request
View all 167 providers →

Research stacks

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Commonly stacked with

LL-37

Questions to ask your provider

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Tools & Guides

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How to Reconstitute Peptides

Step-by-step guide: BAC water, vial prep, and storage after mixing.

Peptide Dosage Guide

Key factors that determine dosing in clinical practice.

Peptide Storage Guide

How to store lyophilized and reconstituted peptides.

Cite this page

Data last updated August 26, 2026

Free to reference and republish with attribution to PeptideBase. Choose a format:

PeptideBase. (2026). Thymosin Alpha-1 — Per-mg Price Benchmark. Retrieved September 11, 2026, from https://peptidebase.io/peptides/thymosin-alpha-1
https://peptidebase.io/peptides/thymosin-alpha-1MethodologyLicenseDownload JSONDownload CSV

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