Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of Thymosin Alpha-1 and Thymulin — mechanism, side effects, legal status, and pricing.
Thymosin Alpha-1 (Tα1) is a 28-amino-acid acetylated peptide (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN) corresponding to the N-terminus of prothymosin α. Marketed as Zadaxin / thymalfasin and approved in 35+ countries for chronic hepatitis B/C and as an immune adjuvant, but NOT FDA-approved in the US — Phase 3 HCV trials ended without approval. Outside the US it is one of the most clinically validated immune-modulating peptides.
Thymulin is a zinc-dependent nonapeptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic epithelial cells, originally isolated by Bach and colleagues in the 1970s as 'facteur thymique sérique' (FTS). It is NOT the same compound as Thymalin (a Russian bovine thymus extract) or Thymosin alpha-1 (a separate 28-amino-acid thymic peptide). Thymulin is not FDA-approved; use is research/investigational only.
Thymosin Alpha-1
Thymulin
Category
Legal Status
Mechanism
Half-life
Side Effects
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
Thymosin Alpha-1
Thymulin
COA corpus from Disclosed Labs — independently tested batches only.
Thymosin Alpha-1
69
COAs
99.6%
Avg purity
12
Labs
Thymulin
5
COAs
99.5%
Avg purity
4
Labs
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.
Key references
Bach and Dardenne originally characterized FTS/thymulin and its absolute zinc dependency (Bach & Dardenne, Med Oncol Tumor Pharmacother 1989, PMID 2657247). Prasad et al. (J Clin Invest 1988, PMID 3262625) showed that serum thymulin activity falls in human zinc deficiency and recovers with zinc supplementation. Mocchegiani et al. (Int J Immunopharmacol 1995, PMID 8582782) demonstrated partial reversal of thymic involution with zinc in aged mice. Dardenne & Pleau reviewed zinc-thymulin interactions (Met Based Drugs 1994, PMID 18476235). Safieh-Garabedian et al. (Br J Pharmacol 2002, PMID 12110619) reported analgesic/anti-inflammatory activity of a thymulin-related peptide in rats. There are NO large, modern RCTs of exogenous thymulin in humans; clinical use is experimental.
Thymosin Alpha-1 and Thymulin are both in the Immune category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Key references
Disclosed Labs