Head to head
Thymalin against Thymosin Alpha-1
The thymic peptide used clinically in Russia since the 1980s against the thymic peptide approved in many countries for hepatitis. One has a large single-tradition literature; the other has international approvals and adjuvant use.
Column A
ThymalinThymalin (thymic peptide bioregulator)
A calf-thymus peptide preparation used clinically in the Soviet Union and Russia since the 1980s, with a large Russian clinical literature, a 6 to 8 year cohort reporting roughly twofold lower mortality, and a 92-patient open-label randomized COVID-19 trial. None of it has been replicated outside that tradition.
Column B
Thymosin Alpha-1Thymosin Alpha-1 (Thymalfasin)
An immune-modulating thymic peptide approved in many countries for hepatitis and used as an immune adjuvant.
Side by side, on the facts we can check
| Attribute | Thymalin | Thymosin Alpha-1 |
|---|---|---|
| Category | Immune | Immune |
| FDA status | Not FDA-approved. Not among the seven peptides reviewed by the FDA Pharmacy Compounding Advisory Committee in July 2026 | Not FDA-approved (orphan status); approved in 30+ countries as Zadaxin |
| Half-life | Short | ~2 hours |
| Molecular weight | Mixture of thymic polypeptides, so no single molecular weight; the manufacturer describes a low-kilodalton fraction | 3,108 Da |
| Mechanism | Thymalin supplies a mixture of thymic signalling peptides intended to substitute for the falling output of the involuting thymus. In cultured human hematopoietic stem cells it reduced the stem marker CD44 and the intermediate marker CD117 2 to 3-fold and raised CD28, a marker of mature T lymphocytes, 6.8-fold, which the authors read as a push toward mature T-cell differentiation. Two dipeptides are proposed as its active components: Lys-Glu, reported to activate macrophages, lymphocytes, thymocytes and neutrophils, and Glu-Trp, which was isolated from Thymalin by reversed-phase HPLC in the 1990s and developed separately as the drug Thymogen. Because Thymalin is an extract rather than a defined molecule, batch composition is not fixed, and no single molecular weight or potency unit describes it. | Enhances T-cell maturation and function, modulates dendritic cells and cytokine signaling, and supports both adaptive and innate immune responses. |
| Human studies cited | 4 | 2 |
| Legal status, US | Not approved; research use only | Not fully approved; orphan-drug designation only |
Frequently asked questions
What is the difference between Thymalin and Thymosin Alpha-1?
Thymalin: A calf-thymus peptide preparation used clinically in the Soviet Union and Russia since the 1980s, with a large Russian clinical literature, a 6 to 8 year cohort reporting roughly twofold lower mortality, and a 92-patient open-label randomized COVID-19 trial. None of it has been replicated outside that tradition. Thymosin Alpha-1: An immune-modulating thymic peptide approved in many countries for hepatitis and used as an immune adjuvant.
Which has stronger research evidence, Thymalin or Thymosin Alpha-1?
This database does not grade compounds. It counts what was run in people: 4 of the 8 studies cited on the Thymalin profile were human work, against 2 of 4 for Thymosin Alpha-1. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.
Are Thymalin and Thymosin Alpha-1 FDA-approved?
Thymalin: Not FDA-approved. Not among the seven peptides reviewed by the FDA Pharmacy Compounding Advisory Committee in July 2026. Thymosin Alpha-1: Not FDA-approved (orphan status); approved in 30+ countries as Zadaxin.
Related posts
Blog articles that cover Thymalin or Thymosin Alpha-1, newest first.
Reviewed Sep 2026. This page sets two published records side by side. It is educational, it is not medical advice, and it contains no dosing protocols or recommendations for personal use.