Head to head
Thymosin Alpha-1 against Thymopentin
Two thymus-derived immune peptides that reached clinical use in different countries, a 28 residue peptide and a five residue fragment of thymopoietin. Both are immune modulators rather than immune boosters, which is a distinction their marketing tends to lose.
Column A
Thymosin Alpha-1Thymosin Alpha-1 (Thymalfasin)
An immune-modulating thymic peptide approved in many countries for hepatitis and used as an immune adjuvant.
Column B
ThymopentinThymopentin (TP-5, thymopoietin fragment)
A pentapeptide fragment of thymopoietin studied and used in some countries as an immune modulator.
Side by side, on the facts we can check
| Attribute | Thymosin Alpha-1 | Thymopentin |
|---|---|---|
| Category | Immune | Immune |
| FDA status | Not FDA-approved (orphan status); approved in 30+ countries as Zadaxin | Not FDA-approved (used in some countries) |
| Half-life | ~2 hours | Very short (~30 seconds native) |
| Molecular weight | 3,108 Da | 679.8 Da |
| Mechanism | Enhances T-cell maturation and function, modulates dendritic cells and cytokine signaling, and supports both adaptive and innate immune responses. | Reproduces the active region of thymopoietin to promote T-cell differentiation and immune regulation. |
| Human studies cited | 2 | 3 |
| Legal status, US | Not fully approved; orphan-drug designation only | Not approved; research use only |
Frequently asked questions
What is the difference between Thymosin Alpha-1 and Thymopentin?
Thymosin Alpha-1: An immune-modulating thymic peptide approved in many countries for hepatitis and used as an immune adjuvant. Thymopentin: A pentapeptide fragment of thymopoietin studied and used in some countries as an immune modulator.
Which has stronger research evidence, Thymosin Alpha-1 or Thymopentin?
This database does not grade compounds. It counts what was run in people: 2 of the 4 studies cited on the Thymosin Alpha-1 profile were human work, against 3 of 3 for Thymopentin. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.
Are Thymosin Alpha-1 and Thymopentin FDA-approved?
Thymosin Alpha-1: Not FDA-approved (orphan status); approved in 30+ countries as Zadaxin. Thymopentin: Not FDA-approved (used in some countries).
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.