TB-500 legal status and FDA records

FDA nomination and current table

TB-500 has no FDA-approved therapeutic indication. FDA previously placed thymosin beta-4 fragment (LKKTETQ), also known as TB-500, in Category 2, the category for significant safety concerns. The recorded concerns include potential immunogenicity with certain administration routes and insufficient safety information.

On FDA’s page current as of April 22, 2026, the nomination is withdrawn and TB-500 appears in the withdrawn-nomination table, outside Category 2. The safety concerns remain recorded. Withdrawal grants neither FDA approval nor Category 1 placement and does not, by itself, authorize compounding.

I resist assigning a regulatory victory to an administrative withdrawal. The cited page supplies its current status and the continuing concerns. FDA publishes no date there for the move out of Category 2, so the record cannot support a dated account of that move.

July 23–24, 2026: the committee agenda

The Pharmacy Compounding Advisory Committee notice for July 23–24, 2026 names TB-500 free base and TB-500 acetate as substances being considered for inclusion on the 503A Bulks List. That meeting date has passed. The cited document remains a notice of planned discussion; this source set contains no later decision.

The committee gives advice, and FDA retains responsibility for the final regulatory process. The agenda leaves the outcome open. A later decision is needed before declaring a change. Any claim that the rules changed would need a later decision document.

503A pharmacies; 503B outsourcing facilities

Under the FDA compounding framework, Section 503A concerns preparation for an identified individual patient, generally by a state-licensed pharmacy or licensed physician, with a valid prescription. Section 503B concerns registered outsourcing facilities, which FDA inspects. The ingredient has to meet the applicable requirements as well.

Those requirements can involve an applicable written quality standard, an ingredient of an FDA-approved drug, or inclusion on the relevant bulks list. A nomination and its withdrawal are separate administrative events. The cited TB-500 record shows no FDA approval or final-list inclusion.

A licensed clinician’s assessment can end in refusal, and a prescription leaves the pharmacy with its own legal obligations. State and treatment also affect available options. I regard the separation of these decisions as essential to understanding access. This is general regulatory information; individual legal and medical decisions need someone qualified to make them.

Is TB-500 FDA approved?

No. FDA’s TB-500 entry records safety concerns about the fragment; it supplies no approval for a therapeutic use. The human Phase 1 study tested full thymosin beta-4 intravenously. Published tolerability findings for that substance do not grant approval to the fragment.

Compounded medicines are not FDA-approved. A clinician’s prescribing decision and permission to compound an ingredient also remain separate questions. The human exposure inspection sets out what was actually tested.

WADA and competitive sport

TB-500 and thymosin beta-4 are prohibited in tested sport under the World Anti-Doping Agency’s peptide and growth-factor rules, during and outside competition. The 2026 sports-medicine review addresses the risks of unapproved peptides, and the equine analytical paper demonstrates detection of TB-500 and its breakdown products.

The existing record also describes prescription classification in Australia and New Zealand. Location and use affect the legal question; U.S. compounding rules cannot answer every jurisdiction’s question. For sport, the prohibition stands separately from a pharmacy or prescribing decision. The applicable competition code is the document I would consult before drawing any conclusion from the existence of a medical channel.