Short answer. Appendix B describes enforcement discretion for TB-500 acetate, as a specific short peptide, for subcutaneous or intramuscular dosage forms [2]. The full-length protein people sometimes mention in the same breath is not the substance that sentence names. As of Oct 29, 2026.

The sequence the policy prints

TB-500 acetate, as Appendix B identifies it, has molecular formula C38H68N10O14·CH3COOH, molecular weight 949.1 g/mol, and the sequence Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH as the acetate [2]. That is seven amino acids. It is a fragment associated with thymosin beta-4, not the whole protein.

The routes in the discretion sentence are subcutaneous or intramuscular injectable dosage forms, from an ingredient with a certificate of analysis that meets the policy [2]. The policy does not add an oral or topical row for TB-500.

The policy says TB-500 was in Category 2 from September 29, 2023 until April 22, 2026, and that this did not change its status under section 503A. It says CDER recommended against listing either form, and the advisory committee voted in favor of both forms [2]. The discretion sentence that follows is still about the acetate and those two injectable routes [2].

Two different kinds of "use"

HHS says historical compounding use is now documented, where CDER had not identified a pharmacy compounding TB-500, and that the safety concerns CDER raised were inferential rather than observed [2]. HHS also points to a human safety record for the parent protein and says the fragment is rapidly truncated in human serum [2].

Hold that next to FDA's July briefing. Our comparison page reports that FDA said it found no studies in which TB-500 itself was given to people BPC-157 vs TB-500. Documented compounding is not a clinical trial. A record for the parent protein is not a record for this fragment. The policy does not say otherwise, and it does not approve TB-500 [1].

No dose appears in the discretion sentence. Sommar Club does not prescribe or sell TB-500. Evidence page: TB-500.

FAQ

Is thymosin beta-4 the same as TB-500 under this policy? The policy prints a 7-residue acetate. Match that identity, not a longer protein sold under a similar name [2].

Did the policy find TB-500 safe and effective? It explains why HHS is using enforcement discretion. It does not approve the peptide [1][2].

Sources

1. HHS notice, FR Doc. 2026-22192, filed Oct 28, 2026. https://public-inspection.federalregister.gov/2026-22192.pdf

2. HHS policy, Appendix B, TB-500. https://www.hhs.gov/sites/default/files/hhs-503a-peptide-enforcement-discretion-policy-appendix-b.pdf

Education only. Not medical or legal advice. As of Oct 29, 2026.