# TB-500 Legal Status, FDA 503A Category, and Compounding Access | TB-500 > TB-500 legal status: FDA placed the LKKTETQ fragment in 503A Category 2, it is not FDA-approved, and it is WADA-prohibited. Access is under active FDA review for 2026 — read straight from FDA. The present-tense facts, read straight from FDA: Category 2, not FDA-approved, WADA-prohibited — and an individually-named slot on the July 2026 PCAC agenda that means access is under active review. ## TB-500 legal status: the present-tense FDA facts TB-500 legal status, on the current record, has a clear present-tense reading — and a forward-leaning one worth stating up top. The momentum first: access is under active FDA review and may expand in 2026. FDA's Pharmacy Compounding Advisory Committee (PCAC) has a meeting scheduled for July 23–24, 2026, and "TB-500 (free base)" and "TB-500 acetate" appear individually on its published agenda as bulk drug substances "being considered for inclusion on the 503A Bulks List" — the same agenda that lists BPC-157, KPV, and MOTs-C [16]. That is a scheduled evaluation and discussion only. It is not a listing decision, not a reclassification, and not a change in current status [16]. Now the fact that stands today. FDA lists this substance as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" — FDA's own entry establishes that TB-500 is the LKKTETQ fragment of thymosin beta-4 — and placed it in 503A "Category 2" (bulk substances that may present significant safety risks), effective with 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]. As a Category 2 substance, TB-500 is not within FDA's enforcement-discretion policy for 503A compounding, and it is not an FDA-approved drug [17]. Those two readings are not in tension. A substance can be in Category 2 today and on a PCAC agenda for evaluation tomorrow — being discussed by PCAC is a step in evaluation, not a final listing decision [18]. The honest line is the one this whole site is built to hold: the present status is Category 2; the future is genuinely under review; and no reclassification has occurred, been dated, or been made certain. ## What the 503A / 503B framework means here Under the Federal Food, Drug, and Cosmetic Act, drug compounding runs through two sections. Section 503A covers traditional, patient-specific compounding by state-licensed pharmacies, federal facilities, and licensed physicians, generally pursuant to a valid prescription for an individual patient. Section 503B covers registered "outsourcing facilities" that may compound larger batches under cGMP-style oversight and FDA registration and inspection [18]. A compounder may use a bulk drug substance — an active ingredient used as a starting material, rather than an FDA-approved finished drug — only if that substance has an applicable USP/NF monograph, is a component of an FDA-approved drug, or appears on the relevant FDA bulks list. Substances not yet on a bulks list are evaluated by FDA through a public nomination process, with input from PCAC [18]. FDA's interim policy sorted nominated substances into categories. Category 1 substances may be eligible for the bulks list and are covered by FDA's enforcement-discretion policy while under evaluation; Category 2 substances are those FDA identified as raising significant safety risks, and they are not afforded that discretion — FDA stated it would consider taking action against a compounder for compounding with a Category 2 substance [18]. On January 7, 2025, FDA finalized a revised interim policy under which it does not place newly nominated substances into these numbered categories; substances already in Category 2 are not afforded enforcement discretion even if nominations are updated [18][19]. TB-500's Category 2 placement is the last FDA action confirmable from FDA.gov, so it is the status stated here. ## How legally compounded peptide access works Legally compounded access in the U.S. follows one pathway, and it begins with a clinician, not a catalog. 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 [20]. Telehealth is one front-end channel for the prescriber-evaluation step. It is a route to a licensed-prescriber consultation and prescription, not a separate legal status — it does not expand which substances may be compounded, and it does not remove the need for a legitimate clinical evaluation and a valid prescription [20]. The ingredient-eligibility caveat is the load-bearing one for TB-500. A compounder may use a requested active ingredient only if that ingredient is eligible under the 503A/503B bulk-substance rules. An ingredient FDA has flagged for significant safety risks is not eligible for routine 503A compounding while that status stands [20]. TB-500 is currently a Category 2 substance [17] — so while that status holds, it is not eligible for routine 503A compounding, regardless of the channel a prescription comes through. This is general information about the regulatory landscape, not medical or legal advice, and not an offer to sell or supply any substance. ## The regulatory and anti-doping status flags ### Is TB-500 FDA Approved? No. TB-500 has no FDA-approved therapeutic indication, and it is not an FDA-approved drug [17]. FDA approval of a finished drug is a separate question from whether a bulk substance may be used in compounding — and on both questions the answer for TB-500 is no approval and Category 2 standing [18]. FDA placed the LKKTETQ fragment in Category 2 citing potential immunogenicity for certain routes and a lack of important safety information [17]. ### Is TB-500 banned by WADA and in competitive sports? Yes. TB-500 and thymosin beta-4 fall under prohibited peptide, growth-factor, and tissue-repair categories on the World Anti-Doping Agency Prohibited List, banned both in and out of competition for the relevant classes. They are detected by LC-MS anti-doping assays, and TB-500 has been encountered as a designer drug in racehorses, prompting equine and human detection methods. In some jurisdictions, such as Australia and New Zealand, it is classified as a prescription medicine. The two flags reinforce the same read: a substance with no approved human indication, a Category 2 compounding status, and a place on the anti-doping list. The forward-leaning note — the July 2026 PCAC evaluation [16] — sits alongside these present-tense facts, not in place of them. --- A phosphor-terminal reading of the TB-500 record — the Ac-LKKTETQ fragment logged green where its studies hold, every full-length thymosin beta-4 substitution flagged as a checksum mismatch, and the empty human-trial line left blinking NULL; no clinic behind the screen and nothing here dispensed or sold.