Thymosin Alpha-1

Overview

Thymosin Alpha-1 (Ta1) is a 28-amino-acid thymic peptide (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN) approved as Zadaxin in 35+ countries for chronic hepatitis B/C and as an immune adjuvant. It is NOT FDA-approved in the US.

Mechanism of Action

Thymosin Alpha-1 primes dendritic cells via TLR9-MyD88-IRF7 (driving IFN-alpha) and TLR2-MyD88-NF-kB (driving IL-12, TNF-alpha, IL-6). It promotes T-cell maturation and thymic output, enhances NK cytotoxicity, upregulates MHC class I antigen presentation, and induces IDO to balance inflammation with tolerance. It is a context-dependent immunomodulator that can both restore deficient responses and moderate overactive ones.

Research Summary

Thymosin alpha-1 has been studied in 90+ clinical trials. A meta-analysis by Yang et al. (Antiviral Research 2008, PMID 18078676) in chronic hepatitis B found antiviral efficacy comparable to interferon-alpha. Tuthill, Rios & McBeath (Ann N Y Acad Sci 2010, PMID 20536460) reviewed the global Zadaxin program across HBV, HCV, melanoma, HCC, and vaccine adjuvancy. Romani et al. (Blood 2006, PMID 16741252) established the TLR9 / IDO dendritic-cell mechanism that underlies Ta1's dual pro-inflammatory / tolerogenic effects. During the COVID-19 pandemic, Liu et al. (Clin Infect Dis 2020, PMID 32442287) reported reduced mortality (11.11% vs 30.00%, p=0.044) in severe lymphopenic COVID-19 patients via restoration of exhausted T cells. A 2024 systematic review by Dinetz & Lee (Altern Ther Health Med, PMID 38308608) covering 30+ trials and 11,000+ subjects concluded Ta1 is a well-tolerated and effective immune modulator, and argued the FDA's 2023 restriction appeared unfounded given the clinical evidence. US regulatory status: NOT FDA-approved; removed from 503A Category 2 in September 2024 after nominator withdrawal; PCAC voted AGAINST inclusion on the 503A Bulks List on December 4, 2024.

Vendors selling Thymosin Alpha-1

Scored vendors carrying Thymosin Alpha-1, ranked by trust grade. Grades are computed from indexed Certificates of Analysis. Full $/mg pricing is on the comparison page.

Prescribers who offer Thymosin Alpha-1

86 prescribers in our directory work with Thymosin Alpha-1, each confirmed from their own website. Peptides like Thymosin Alpha-1 require a prescription from a licensed provider — telehealth options are available.

Reported Side Effects

• Injection site reactions (most common)
• Transient mild fatigue
• Rare low-grade fever (typically reflects immune activation)
• Transient lymphocyte subset shifts (generally asymptomatic)
• Excellent overall safety profile across 11,000+ trial subjects

Biomarkers researchers track for Thymosin Alpha-1

These biomarkers appear in the research literature as measures of response and safety for this compound.

Related Peptides

Compare Thymosin Alpha-1 with Others

Research References

• Tuthill C, Rios I, McBeath R. Thymosin alpha 1: past clinical experience and future promise. Ann N Y Acad Sci. 2010;1194:130-135. (PMID 20536460)
• Romani L, et al. Thymosin alpha1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance. Blood. 2006;108(7):2265-2274. (PMID 16741252)
• Yang YF, et al. Comparison of the efficacy of thymosin alpha-1 and interferon alpha in the treatment of chronic hepatitis B: a meta-analysis. Antiviral Res. 2008;77(2):136-141. (PMID 18078676)
• Liu Y, et al. Thymosin Alpha 1 Reduces the Mortality of Severe COVID-19 by Restoration of Lymphocytopenia and Reversion of Exhausted T Cells. Clin Infect Dis. 2020;71(16):2150-2157. (PMID 32442287)
• Dinetz E, Lee E. Comprehensive Review of the Safety and Efficacy of Thymosin Alpha 1 in Human Clinical Trials. Altern Ther Health Med. 2024;30(1):6-12. (PMID 38308608)

Frequently asked questions

Has Thymosin Alpha-1 been independently lab-tested?

Disclosed Labs has collected 73 Certificates of Analysis (COA) for Thymosin Alpha-1 from 12 independent testing labs. 28 vendors have submitted material for testing. Products average 99.6% tested purity across the corpus. Full testing data is available at https://www.disclosedlabs.com/peptides/thymosin-alpha-1/testing.

What is the average purity of Thymosin Alpha-1 on the market?

Based on 73 COAs analyzed by Disclosed Labs, Thymosin Alpha-1 products average 99.6% (±0.3%) tested purity. Individual vendor results vary; see per-vendor COA data at https://www.disclosedlabs.com/peptides/thymosin-alpha-1/coas.

Which labs have tested Thymosin Alpha-1?

Independent labs that have tested Thymosin Alpha-1 include: ILS Labs (Grade B), Ethos Analytics (Grade C). Full lab credibility grades and profiles are at https://www.disclosedlabs.com/labs.

Where can researchers source Thymosin Alpha-1?

8 vendors with Disclosed Labs trust grades currently list Thymosin Alpha-1, including Glacier Aminos, Ion Peptide, Peptide Partners. Compare live prices and lab-verified COAs at https://www.disclosedlabs.com/prices/thymosin-alpha-1.

Which prescribers offer Thymosin Alpha-1 with a prescription?

86 prescribers in the Disclosed Labs directory work with Thymosin Alpha-1, each confirmed from their own website, with telehealth options available. Thymosin Alpha-1 requires a prescription from a licensed provider. Browse them at https://www.disclosedlabs.com/prescribers?peptide=Thymosin%20Alpha-1.

How does Thymosin Alpha-1 work?

Thymosin Alpha-1 primes dendritic cells via TLR9-MyD88-IRF7 (driving IFN-alpha) and TLR2-MyD88-NF-kB (driving IL-12, TNF-alpha, IL-6). It promotes T-cell maturation and thymic output, enhances NK cytotoxicity, upregulates MHC class I antigen presentation, and induces IDO to balance inflammation with tolerance. It is a context-dependent immunomodulator that can both restore deficient responses and moderate overactive ones.

What does the research say about Thymosin Alpha-1?

Thymosin alpha-1 has been studied in 90+ clinical trials. A meta-analysis by Yang et al. (Antiviral Research 2008, PMID 18078676) in chronic hepatitis B found antiviral efficacy comparable to interferon-alpha. Tuthill, Rios & McBeath (Ann N Y Acad Sci 2010, PMID 20536460) reviewed the global Zadaxin program across HBV, HCV, melanoma, HCC, and vaccine adjuvancy. Romani et al. (Blood 2006, PMID 16741252) established the TLR9 / IDO dendritic-cell mechanism that underlies Ta1's dual pro-inflammatory / tolerogenic effects. During the COVID-19 pandemic, Liu et al. (Clin Infect Dis 2020, PMID 32442287) reported reduced mortality (11.11% vs 30.00%, p=0.044) in severe lymphopenic COVID-19 patients via restoration of exhausted T cells. A 2024 systematic review by Dinetz & Lee (Altern Ther Health Med, PMID 38308608) covering 30+ trials and 11,000+ subjects concluded Ta1 is a well-tolerated and effective immune modulator, and argued the FDA's 2023 restriction appeared unfounded given the clinical evidence. US regulatory status: NOT FDA-approved; removed from 503A Category 2 in September 2024 after nominator withdrawal; PCAC voted AGAINST inclusion on the 503A Bulks List on December 4, 2024.