TB-500 vs Thymosin beta-4: evidence, status and structure
A side-by-side look at TB-500 and Thymosin beta-4, using the data on each VALREXA profile. Neither comparison is a recommendation.
Key differences
- Thymosin beta-4 has stronger human evidence (Controlled trials) than TB-500 (Preclinical).
- Their U.S. status differs: TB-500 falls under Compounding allowed (Not FDA-approved); Thymosin beta-4 falls under Not FDA-approved (Not FDA-approved).
- Thymosin beta-4 is about 5.6× heavier than TB-500 (~4,963.4 vs ~889.0 Da).
| TB-500 | Thymosin beta-4 | |
| Research class | Repair & Tissue Biology | Repair & Tissue Biology |
| Human evidence | Preclinical | Controlled trials |
| U.S. status | Not FDA-approved | Not FDA-approved |
| 2026 compounding decision | Allowed for 503A pharmacies under FDA enforcement discretion (Oct 2026) | — |
| Amino acids | 7 (fragment) | 43 |
| Molecular weight | ~889.0 Da | ~4,963.4 Da |
| Formula | Varies by form | Varies by form |
| Sequence | — | — |
| Research period | Thymosin β4 research: 1980s | 1966 |
| Safety summary | TB-500 is not FDA-approved as a therapeutic product. | Regulatory status depends on formulation and jurisdiction; not a general FDA-approved injectable therapy. |
How they differ
Thymosin beta-4 (Tβ4) is a natural 43-amino-acid protein found in most human cells, where it binds actin. TB-500 is a short synthetic fragment based on Tβ4's actin-binding region. Results from studies of the full protein, including clinical trials of Tβ4 eye drops, cannot automatically be applied to the fragment. That is why the two have different evidence grades.
What each one is
TB-500: Commercial term often used for thymosin β4 or a fragment; the label does not define one unique molecule. Molecular weight, sequence, research history, human evidence and regulatory status.
Thymosin beta-4: Naturally occurring actin-binding peptide involved in cytoskeletal dynamics. Molecular weight, sequence, research history, human evidence and regulatory status.
Educational reference only. Nothing here is medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error.