Comparison
Thymosin alpha-1 vs Thymosin beta-4
They share a name and almost nothing else. One is an immune modulator with approvals in more than thirty countries; the other is a repair peptide still in trials. Sharing a prefix has done more harm here than in any other pair on this site.
The name is an accident of history. Both were isolated from thymus extract, so both carry the word thymosin — but they are unrelated molecules with different sequences, different targets and different evidence.
Thymosin alpha-1 acts on the immune system and is approved in a number of countries for hepatitis B and as an adjunct in sepsis. Thymosin beta-4 acts on actin and cell migration, and is the one behind wound healing and injury repair claims.
The confusion runs one way and costs something. Alpha-1's approvals get borrowed to make beta-4 sound established, when beta-4's human evidence is a handful of phase 2 trials, most of them ophthalmic.
| Attribute | Thymosin alpha-1 | Thymosin Beta-4 |
|---|---|---|
| What it acts on | The immune system | Actin and cell migration |
| Evidence level | Approved for another indication | Clinical trials |
| Best-supported use | Chronic hepatitis B | Dry eye and corneal wounds |
| Route | Subcutaneous | Subcutaneous or topical |
| Half-life | About 2 hours | Not established in humans |
| Regulatory approvals | Yes, in many countries | None |
| Related to the other | No | No |
Things worth knowing
- This is the single most useful thing to know about either: they are not variants of one compound. Nothing established about alpha-1 transfers to beta-4, and nothing reported about beta-4 says anything about alpha-1.
- Beta-4's strongest human data is in the eye. The musculoskeletal repair use it is best known for is largely animal work and community practice, which is a different weight of evidence from the one the name lends it.
- Both are sold as research chemicals under names that blur the distinction further, TB-500 among them. TB-500 is a fragment rather than full-length beta-4, which is a third thing again.
Full profile
Thymosin alpha-1
An immune-modulating peptide approved in more than thirty countries for hepatitis B, and studied in sepsis and as a vaccine adjuvant. Not approved in the United States.
Full profile
Thymosin Beta-4
The full 43-amino-acid protein that TB-500 is a fragment of. It reached phase 2 trials in humans. TB-500 never has.
Related
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice.