TB-500

Status

No approved product. No approved drug product. Injectables sold as TB-500 contain a synthetic fragment of the protein, not the protein itself, and are research chemicals. In July 2026 the FDA's Pharmacy Compounding Advisory Committee recommended adding it to the 503A bulk drug substances list — a recommendation to the agency, not a rule. No proposed rule had followed at the time of writing, so it is still not on the 503A bulks list, and the recommendation did not approve any product or change the status of anything already being sold.

What it is

Thymosin beta-4 is a 43-amino-acid peptide found in nearly every human cell, involved in cell migration and actin building — the mechanics tissue repair runs on. What is sold as TB-500 is not that protein: the FDA's compounding briefing describes it as a seven-amino-acid synthetic fragment, sold under inconsistent names and salt forms.

What published research measured

The full protein, thymosin beta-4, was studied in trials for corneal healing and cardiac repair. The FDA's briefing on the nominated TB-500 fragment found no human exposure data for the fragment itself, and flagged immunogenicity, impurity and identity concerns for injection. The protein's trials say nothing about the fragment in a vial.

Source

FDA Pharmacy Compounding Advisory Committee briefing on TB-500 bulk drug substances; no FDA-approved product Primary source

Sources

• FDA Pharmacy Compounding Advisory Committee briefing on TB-500 bulk drug substances; no FDA-approved product