Thymalin vs Thymosin α1
Two thymus peptides sold for immunity and longevity, separated by evidence quality: thymosin alpha-1 is an approved drug in dozens of countries, thymalin rests on one unreplicated program.
Thymalin
Marketed for immune restoration and longer life, but the supporting science is old, small, and almost entirely from one Russian program — and unreplicated.
Full Thymalin evidence reviewThymosin α1
Zadaxin
An approved immunomodulator in dozens of countries (for hepatitis, sepsis and severe infection, supervised) — but not FDA-approved, not the same as TB-500, and not the anti-aging injectable sold online.
Full Thymosin α1 evidence reviewSide by side
| Thymalin | Thymosin α1 | |
|---|---|---|
| Marketed for | Immune restoration, longevity | Immune support (sold for 'anti-aging') |
| Evidence grade | Clinical data | Clinical data |
| Family | Immune / metabolic | Immune / metabolic |
| Regulatory status | Not FDA-approved | Not FDA-approved |
| How it's obtained | Research-only | Compounded |
| Key human source | Khavinson, Neuro Endocrinol Lett 2003 | ETASS sepsis RCT, Crit Care 2013 |
marks a row where the two differ. Evidence grades come from our evidence matrix, which grades each molecule on the human data for the use it is marketed for.
Our verdict
Thymosin alpha-1 (Zadaxin) is a real immunomodulator, approved in dozens of countries but not FDA-approved in the United States, with a genuine supervised evidence base in chronic hepatitis B and C, severe sepsis, and serious infection. Thymalin's reputation rests largely on a single research program's multi-year elderly-cohort mortality report that no independent laboratory has replicated, with most supporting studies old, small, and published in niche or Russian-language journals. That is a real gap in evidence quality and it should be said plainly. Neither supports the anti-aging pitch: thymosin alpha-1's trials were in patients who were already ill, and in the US anything you can buy is compounded or research material rather than the approved drug.
Thymalin fits if
Thymalin makes sense to read only as the weaker sibling of the Khavinson bioregulator program, interesting as a hypothesis and unsupported as a longevity therapy.
Thymosin α1 fits if
Thymosin alpha-1 is the one with a real clinical evidence base, but it belongs to clinicians treating hepatitis, sepsis, or severe infection, not to healthy adults buying vials online.
Where to get it
Where to get peptide therapy
Clinician-led telehealth services that prescribe compounded peptides. The specific peptides offered vary by provider — confirm Thymalin availability before ordering.
