TB-500 legal status: FDA and sport
An ingredient list, a medicine approval and a sport rule answer different questions. The dated FDA record needs all of its qualifications.
FDA approval and nomination history
TB-500 has no FDA approval for human use. FDA’s bulk-substance safety-risk page records its historical Category 2 entry, effective September 29, 2023. The agency cited possible immunogenicity with certain routes of administration and a lack of sufficient safety information.
On FDA’s page current as of April 22, 2026, the nomination is withdrawn and TB-500 is no longer in Category 2. FDA gives no date for that change. The withdrawal establishes neither safety nor approval, and it does not establish availability from a compounding pharmacy.
I regard the absent permission as essential to this account. A removed list entry is easy to turn into an encouraging headline. The agency’s actual record gives a narrower answer, with the safety rationale still present.
Compounding under Section 503A
Under the FDA framework for Section 503A bulk drug substances, patient-specific compounding and the eligibility of the raw ingredient are separate requirements. A prescription alone cannot settle which bulk substances a pharmacy may use. FDA has not clarified a current permission for local pharmacies to prepare TB-500 following the withdrawn nomination.
Category 1 has supported an interim enforcement policy for certain substances during review; Category 2 did not provide that policy. Treating the end of a Category 2 listing as an automatic passage into Category 1 goes beyond the confirmed record. General compounding rules explain the issue; they supply no personal route to obtaining TB-500 here.
July 2026: the advisory agenda
The July 23–24, 2026 advisory-committee agenda named TB-500 free base and TB-500 acetate for discussion about the 503A Bulks List. An advisory discussion and a finished FDA decision are different actions. As of September 2026, the record described on this site contains no published committee vote or final agency permission.
The agenda’s chemical forms also deserve modest treatment: their inclusion establishes what was considered, with no finding that either form is safer in people. Only a final FDA action would persuade me that compounding permission had been settled. The FDA bulk-substances page is the place to examine that question.
WADA and racehorse testing
TB-500 and thymosin beta-4 are prohibited in tested sport, in and out of competition, under World Anti-Doping Agency rules. The sports-medicine review discusses the regulatory and safety problems around unapproved peptides. This sport prohibition operates separately from FDA medicine and pharmacy rules.
Ho and colleagues’ equine detection paper documents the analytical history: TB-500 and its metabolites were identified in horse plasma and urine to control misuse in equine sport. For me, the unusual shape of the fragment’s literature becomes clearer in this history. Some of its most direct experiments establish how to find it in a sample, while the human healing question remains open.