Immune & Antiviral
CAS
62304-98-7
Molecular Weight
3108
Da
A naturally occurring thymic peptide first isolated from calf thymus by Allan Goldstein's laboratory in 1977. The synthetic form — thymalfasin — is marketed as Zadaxin and approved in more than 35 countries for chronic hepatitis B, chronic hepatitis C, and as an immune adjuvant. The most extensively studied thymic peptide in clinical research, with more than 30 published randomized controlled trials and over 11,000 human subjects. Not FDA approved for use in the United States but available through licensed providers in many international markets and through some US specialty compounding pharmacies for off-label use.
Injectable
Intranasal Suitable
No
Prescription
Community signal is smaller than the compound's strong formal evidence base would predict. Thymosin Alpha-1 is more widely used clinically (particularly in Asia and Eastern Europe where it's approved) than discussed in Western biohacking communities. Immune support during illness and as a post-illness recovery tool are the primary reported use cases. Cancer adjunct use appears in some anecdotal reports, consistent with its clinical applications. The community that does discuss it tends to be more medically sophisticated and research-aware than average. Injection tolerance is generally reported as good. The gap between clinical evidence quality and community awareness makes Thymosin Alpha-1 an underrated compound in the biohacking consensus.
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Thymosin Alpha-1 is derived from the precursor protein prothymosin-alpha and is naturally produced in the thymus gland. The thymus is central to T-cell education and immune identity, Thymosin Alpha-1 is one of the primary signaling peptides through which the thymus orchestrates adaptive immune function. Thymic output and Tα1 levels decline with age as the thymus involutes, which has generated significant interest in exogenous supplementation as an immune restoration strategy in aging populations. FDA approved the orphan drug thymalfasin (Zadaxin) for treatment of malignant melanoma, chronic active hepatitis B, DiGeorge anomaly with immune defects, and hepatocellular carcinoma due to its immunomodulatory and anti-tumor effect.
Tα1 activates Toll-like receptors TLR2 and TLR9 on dendritic cells and macrophages, triggering downstream IRF3/NF-κB and p38 MAPK signaling that drives dendritic cell maturation, T-cell differentiation toward Th1/cytotoxic phenotypes, and NK cell activation. Thymosin Alpha-1 induces differentiation of murine T-cell precursors and human thymocytes, induces terminal differentiation of functionally immature cord blood lymphocytes, and induces production of IL-2, high affinity IL-2 receptors, and B-cell growth factors by peripheral blood mononuclear cells. What makes Tα1 mechanistically distinctive is its immunomodulatory rather than simply immunostimulatory profile, it does not uniformly amplify immune activity but rather normalizes dysregulated immune responses, enhancing surveillance where it is deficient while modulating excessive inflammation where it is harmful. This dual capacity has made it relevant to both immunosuppressed states (viral infections, cancer) and hyperinflammatory states (sepsis, cytokine storm).
Thymosin Alpha-1's strongest evidence base is in chronic viral hepatitis. Multiple randomized controlled trials across thousands of patients with chronic hepatitis B and C demonstrate improved virological response rates, enhanced T-cell counts, and reduced disease progression compared to standard of care alone. These trials form the basis of its approval in over 35 countries.
Clinical trials with Thymosin Alpha-1 for diseases including DiGeorge syndrome, non-small cell lung cancer, hepatocellular carcinoma, hepatitis B and C, HIV, and melanoma have been conducted and yielded promising results.
Sepsis is an emerging high-priority application, multiple Chinese RCTs demonstrate reduced mortality and improved immune recovery in septic patients treated with Tα1, with the mechanism involving restoration of the lymphopenia and T-cell exhaustion that characterize sepsis-induced immunosuppression.
The immunosuppressive effects of the SARS-CoV-2 viral envelope in inducing cytokine storm may be modulated with Thymosin Alpha-1 therapy, which would be especially beneficial in preventing catastrophic events such as cytokine storm in more severe cases.
In the longevity and biohacking community Tα1 is used for general immune optimization, cancer prevention support, and post-illness immune recovery, applications that are off-label and not supported by the formal regulatory approvals.
Thymosin Alpha-1 and its synthetic analogue thymalfasin have well-studied safety profiles and are well-tolerated with only minor side effects. Injection site reactions are the most commonly reported adverse event. No significant organ toxicity, immunosuppression, or serious adverse effects have been identified across decades of clinical use and thousands of trial participants. The immunomodulatory rather than immunostimulatory mechanism reduces the theoretical risk of autoimmune activation compared to broadly immunostimulatory compounds. Long-term safety data is robust given the decades of clinical use in approved markets.
Available as a lyophilized powder for subcutaneous injection, typically supplied in vials of 1.6mg (the standard Zadaxin dose). Administered subcutaneously twice weekly in approved indications. The pharmaceutical-grade Zadaxin formulation is the only validated clinical form. Research-grade lyophilized powder is available through research compound suppliers but lacks the manufacturing quality controls of the pharmaceutical product. Prescription required for legitimate clinical use.
The only FDA-approved form of Thymosin Alpha-1 is Zadaxin (thymalfasin), a prescription drug used in the treatment of certain cancers and for chronic hepatitis B and C. Approved in over 35 countries across Asia, South America, and Eastern Europe. Not approved for general immune enhancement or longevity use in any market. Any other use of Tα1 is considered off-label and is not approved by the FDA. Doctors with specialty clinics may prescribe Tα1 for off-label use, it is important to ensure they use pharmaceutical-grade peptides, not research-grade ones.
https://pubmed.ncbi.nlm.nih.gov/265536/
https://pmc.ncbi.nlm.nih.gov/articles/PMC7747025/
https://pmc.ncbi.nlm.nih.gov/articles/PMC8366398/
https://pubmed.ncbi.nlm.nih.gov/11137613/
LL-37, KPV, BPC-157, Humanin
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