# TB-500 Legal Status, FDA 503A Category, and Compounding Access | TB-500 > TB-500 legal status, set out from the FDA record: the 503A Category 2 placement effective September 29, 2023, the July 2026 PCAC evaluation, WADA-prohibited standing, and how compounded access works. Stated present-tense from the FDA record, with the access pathway described in general terms only. This is general information about the regulatory landscape — not medical or legal advice, and not an offer to supply anything. ## The current FDA fact TB-500 legal status starts with one citable FDA fact. The FDA lists this substance as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" and placed it in 503A "Category 2" — bulk substances that may present significant safety risks — effective with the FDA's September 29, 2023 nominated-substances update, citing concerns including potential immunogenicity for certain routes of administration and a lack of important safety information [17]. Two consequences follow directly. As a Category 2 substance, TB-500 is not within the FDA's enforcement-discretion policy for 503A compounding — the policy that applies to Category 1 substances does not extend to it [17]. And TB-500 is not an FDA-approved drug; whether a finished drug is approved is a separate question from whether a bulk substance may be used in compounding, and the fragment is neither approved nor inside the discretion policy [18]. The FDA's own list entry establishes the identity relationship this whole site turns on: TB-500 is the LKKTETQ fragment associated with thymosin beta-4, described by the FDA in the same entry [17]. That is the regulator stating, in its own record, that the marketed name and the fragment are the same thing. ## Under active review — and what that does and does not mean Access to this substance is under active FDA review and may expand in 2026 — and the reason to say so is on the FDA's own calendar. "TB-500 (free base)" and "TB-500 acetate" appear, individually named, on the published agenda of the FDA Pharmacy Compounding Advisory Committee (PCAC) meeting scheduled for July 23–24, 2026, as bulk drug substances "being considered for inclusion on the 503A Bulks List" [19]. The same agenda also lists BPC-157, KPV, and MOTs-C [19]. That is forward motion worth tracking. It is also, precisely, a scheduled evaluation and discussion — not a listing decision, not a reclassification, and not a change in current status [19]. Inclusion on a final 503A bulks list is decided by FDA rulemaking informed by the PCAC; being discussed by the committee is a step in evaluation, and a PCAC discussion is advisory rather than a final FDA decision [18]. No outcome of the July 2026 meeting should be assumed, dated, or read as already decided. The honest frame is momentum without a verdict: the question of compounded access is open and moving, the regulator has put TB-500 on the table for evaluation, and as of now the Category 2 standing is the last FDA action confirmable from FDA.gov. A reader watching this space should watch the FDA's record, not a prediction. ## Is TB-500 banned in sport? Yes. TB-500 — and thymosin beta-4 — fall under the World Anti-Doping Agency's prohibited peptide, growth-factor, and tissue-repair categories and are banned both in and out of competition for the relevant classes. Anti-doping laboratories detect TB-500 by LC-MS in equine and human samples, and the compound has been encountered as a designer substance in racehorses, which is part of why those detection methods were developed. WADA standing is independent of the FDA compounding question. A substance can be prohibited in sport regardless of its compounding eligibility, and the two records answer different questions: one governs competitive eligibility, the other governs whether a bulk substance may be used to compound a medication. ## How legally compounded peptide access works Compounded medications are made within a defined federal framework, and describing that framework in general terms is the useful, lawful thing to do here. Under the Federal Food, Drug, and Cosmetic Act, Section 503A covers traditional, patient-specific compounding by state-licensed pharmacies and physicians pursuant to a valid prescription for an individual patient, while Section 503B covers FDA-registered "outsourcing facilities" that compound larger batches under cGMP-style oversight [18]. The pathway, in general terms, runs in one direction. A patient is evaluated by an appropriately licensed prescriber — in person or through a compliant telehealth encounter — who determines whether a compounded preparation is clinically appropriate. If it is appropriate and lawful, the prescriber issues a valid, patient-specific prescription. That prescription is then dispensed by a state-licensed 503A compounding pharmacy, or, for office and batch use, sourced from an FDA-registered 503B outsourcing facility [18]. Telehealth sits at the front of that pathway and only there. It is one channel for the prescriber-evaluation step — a route to a licensed-prescriber consultation and a prescription — not a separate legal status. Telehealth does not expand which substances may be compounded and does not remove the need for a legitimate clinical evaluation and a valid prescription [18]. The ingredient-eligibility caveat governs everything above. A compounder may use a bulk drug substance only if it has an applicable USP/NF monograph, is a component of an FDA-approved drug, or appears on the relevant FDA bulks list; substances the FDA has flagged for significant safety risks are not eligible for routine 503A compounding while that status stands [18]. Because TB-500 sits in Category 2, that eligibility caveat is the operative fact, and it is the standing the July 2026 PCAC evaluation is set to examine [17][19]. This page names no pharmacy, clinic, telehealth provider, or vendor, gives no dosing, and describes no way to obtain any substance outside the lawful framework — by design, and because the access framework does not turn on any of those. ### Is TB-500 legal? TB-500 has no FDA-approved human indication and is in FDA 503A Category 2, a bulk-substance status outside the enforcement-discretion policy for compounding [17]; it is also WADA-prohibited [16]. Legal standing varies by jurisdiction and use context, and this is general information rather than legal advice. ### Is TB-500 FDA approved? No. TB-500 has no FDA-approved therapeutic indication; the FDA lists it as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" and placed it in 503A Category 2 — bulk substances that may present significant safety risks — effective with the September 29, 2023 update [17]. ### Is TB-500 banned by WADA and in competitive sports? Yes. TB-500 and thymosin beta-4 fall under WADA-prohibited peptide, growth-factor, and tissue-repair categories and are banned in and out of competition; anti-doping LC-MS assays detect it in equine and human samples [16]. ### Can you get TB-500 from a compounding pharmacy? Compounding access turns on ingredient eligibility under the 503A/503B framework. Because the FDA placed TB-500 in Category 2 (significant-safety-risk bulk substances, outside enforcement discretion), it is not eligible for routine 503A compounding while that status stands [17][18]; legally compounded medications otherwise require a licensed-prescriber evaluation and a valid, patient-specific prescription. ### What is the FDA 503A status of TB-500? The FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 — bulk substances that may present significant safety risks — effective with its September 29, 2023 nominated-substances update, which means it is not covered by the enforcement-discretion policy for 503A compounding [17]. "TB-500 (free base)" and "TB-500 acetate" are on the agenda of the July 23–24, 2026 PCAC meeting as substances being considered for the 503A bulks list — a scheduled discussion, not a decision [19]. --- A risograph reading of the TB-500 record, where the Ac-LKKTETQ fragment overlaps its parent protein thymosin beta-4 the way two inks overlap on the page — each finding plated to its study, the human-evidence panel left blank, and the FDA 503A standing printed first; no clinic behind the press and nothing here dispensed or sold.