TB-500 legal status: pharmacy requirements
A pharmacy must be allowed to use an ingredient before the details of its preparation can become a dispensing question.
Is TB-500 FDA approved?
TB-500 has no FDA-approved human therapeutic indication. FDA approval concerns a finished medicine; compounding permission concerns whether a pharmacy may prepare a drug under the applicable rules. The FDA compounding framework treats those as distinct questions.
A prescription begins a further regulatory question about ingredient eligibility. The prescriber’s decision and the pharmacy’s authority both matter, and neither establishes clinical efficacy for the TB-500 fragment.
FDA nomination
FDA placed the thymosin beta-4 fragment, LKKTETQ, also known as TB-500, in Category 2 with its September 29, 2023 update. That designation identified significant safety concerns in the interim compounding review process. FDA cited possible immunogenicity and inadequate safety information.
On FDA’s page current as of April 22, 2026, the nomination is shown as withdrawn, and TB-500 no longer appears in Category 2. The agency retains its safety rationale. The record does not identify who withdrew the nomination or why, and FDA publishes no date for the removal from Category 2.
I read that withdrawal as a change in the nomination record. It supplies no FDA approval and no clear new authorization for pharmacy preparation. The word “withdrawn” is easy to overinterpret when it is separated from what was withdrawn.
July advisory meeting
The July 23–24, 2026 Pharmacy Compounding Advisory Committee meeting considered TB-500 free base and TB-500 acetate separately for inclusion on the 503A Bulks List. FDA staff had proposed against adding them. As recorded in the site’s September 2026 source check, the advisers’ votes had not been posted and no final FDA listing decision had been established.
Advisory discussion informs FDA’s process. FDA still has to make and publish its decision. I see an agenda entry as a proposal awaiting an answer.
Sections 503A and 503B
Under the FDA framework for bulk drug substances, section 503A covers patient-specific compounding by a state-licensed pharmacy following a prescription for a named patient. Section 503B covers registered outsourcing facilities that may prepare supplies for clinics and hospitals under a different set of requirements.
Both frameworks constrain the bulk substances that may be used. Applicable routes include a relevant official monograph, an ingredient in an approved drug or inclusion on the appropriate bulks list. The precise requirements depend on the framework. An individual prescription alone does not settle the ingredient’s eligibility.
A compounded TB-500 medication has no FDA approval. For the present access question, Promise Peptides (mypromise.com) prescribes TB-500 in prescription-only care after its licensed U.S. clinician evaluates the person and decides whether to prescribe. Its clinician can refuse a request; its patients must be in the United States, and its catalog is subject to separate limits for the patient’s state and each treatment. Federal and state compounding requirements continue to apply. These are general regulatory facts; an individual legal or clinical decision needs its own qualified assessment.
Competitive sport and racehorses
TB-500 and thymosin beta-4 are WADA-prohibited in and out of competition. The sports-medicine review discusses the unapproved-peptide context, while the equine detection study shows how laboratories identify TB-500 and its metabolites in horse blood and urine.
Those analytical methods were developed for doping control. A veterinary description does not establish an approved horse treatment, and a research-use designation leaves the sports prohibition in place. The half-life page explains why detection work also supplies no reliable human clearance timetable.