ACCESS STATUS · GENERAL INFORMATION, NOT ADVICE
TB-500 Legal Status, FDA 503A Category, and Compounding Access
Where access actually stands — read as a status board, not a storefront. The current FDA facts, the active 2026 review that may expand access, and the lawful compounding pathway in general terms. General information, not medical or legal advice, and not an offer to supply anything.
Access is under active FDA review and may expand in 2026
The TB-500 legal status picture has a forward-looking fact at its front: access is under active FDA review and may expand in 2026. "TB-500 (free base)" and "TB-500 acetate" are 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.
That is momentum, and it is real — but it is a scheduled evaluation and discussion only. It is not a listing decision, not a reclassification, and not a change in current status. A PCAC discussion is advisory; inclusion on a final 503A bulks list is decided by FDA rulemaking informed by that committee [20]. Being on the agenda means TB-500 is under evaluation, not that any outcome has occurred or been dated. Nothing on this page should be read as predicting how that meeting will resolve.
The current fact: FDA 503A Category 2
Here is the present-tense status, stated as FDA states it. FDA lists the 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 FDA's September 29, 2023 update to the list of nominated substances, citing concerns including potential immunogenicity for certain routes of administration and a lack of important safety information [21].
Two consequences follow directly. As a Category 2 substance, TB-500 is NOT within FDA's enforcement-discretion policy for 503A compounding — the policy under which FDA stated it does not intend to act against compounding with eligible Category 1 substances does not extend to it [20]. And TB-500 is not an FDA-approved drug; FDA approval of a finished drug is a separate question from whether a bulk substance may be used in compounding, and TB-500 has neither [20]. FDA's own list entry is also what establishes the identity relationship used throughout this site: TB-500 is the LKKTETQ fragment associated with thymosin beta-4 [21].
What changes — and what does not — between status and a decision
The interim policy framework explains why "under review" and "currently Category 2" are both true at once. FDA's interim policy sorted nominated bulk substances into Category 1 (covered by enforcement discretion while under evaluation) and Category 2 (identified as raising significant safety risks; not covered) [20]. On January 7, 2025, FDA finalized a revised policy under which it no longer places newly nominated substances into these numbered categories; substances already in Category 1 may continue under the interim enforcement-discretion policy, while substances in Category 2 are not afforded that discretion [20]. TB-500's Category 2 placement therefore stands as the last FDA action confirmable from FDA.gov.
What would change that is an FDA decision, not a committee discussion — and that has not happened. Reports of a broader early-2026 reclassification of Category 2 peptides, or of specific dated "removals" of these substances, could not be confirmed as completed, effective FDA actions from an authoritative FDA source, and are not treated as fact here [20]. The fact that TB-500 remains on the July 2026 PCAC agenda "being considered for inclusion" is itself consistent with its evaluation being ongoing rather than resolved [19]. This page states only the present-tense, FDA-citable status, and frames the 2026 meeting strictly as a scheduled discussion.
How lawful compounded access works, in general terms
In the United States, a legally compounded medication is prepared only after an individual patient is evaluated by a licensed prescriber who determines a compounded preparation is appropriate and issues a valid, patient-specific prescription [22]. The preparation is then made by a state-licensed 503A compounding pharmacy (patient-specific) or, for larger volumes, sourced from an FDA-registered 503B outsourcing facility [22]. Telehealth can serve as the front-end channel for that prescriber evaluation, but it does not change which substances are eligible to be compounded and does not remove the need for a legitimate clinical evaluation and a valid prescription [22].
The ingredient-eligibility caveat is decisive here. A compounder may use a bulk active ingredient only if it is permitted under the 503A/503B framework — covered by a USP/NF monograph, a component of an FDA-approved drug, or on the applicable FDA bulks list — and ingredients FDA has flagged for significant safety risks are not eligible for routine 503A compounding while that status stands [22]. Because TB-500 sits in Category 2 today, that eligibility gate is the practical limit on its routine 503A compounding for now, regardless of the access channel. This is general information about the regulatory landscape, not medical or legal advice, and not an offer to sell or supply any substance. It names no pharmacy, clinic, telehealth provider or vendor, gives no dosing, and describes no way to obtain any substance outside the lawful framework.
Is TB-500 legal?
TB-500 is not an FDA-approved drug, and FDA placed the LKKTETQ fragment in 503A Category 2 — bulk substances that may present significant safety risks — so it is not within FDA's enforcement-discretion policy for 503A compounding [21][20]. It is also WADA-prohibited in sport. This is general regulatory information, not legal advice.
Can you get TB-500 from a compounding pharmacy?
A 503A pharmacy may compound a substance only if its bulk ingredient is eligible under the 503A framework, and ingredients FDA has flagged for significant safety risks are not eligible for routine 503A compounding while that status stands [22]. TB-500 is currently in Category 2 [21], which is the practical limit on its routine 503A compounding now.
What is the FDA 503A status of TB-500?
FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2, effective with its September 29, 2023 update, citing potential immunogenicity for certain routes and a lack of important safety information [21]. It is individually named on the July 23–24, 2026 PCAC agenda for evaluation — a scheduled discussion, not a decision [19].
Is TB-500 FDA approved?
No. TB-500 has no approved therapeutic indication and is not approved by the FDA for human use; it is a research-chemical and veterinary-context substance [21]. FDA approval of a finished drug is separate from whether a bulk substance may be compounded, and TB-500 has neither approval nor eligibility for routine 503A compounding while in Category 2 [20].
Is TB-500 banned by WADA and in competitive sports?
Yes. TB-500 and thymosin beta-4 fall under WADA's prohibited peptide, growth-factor and tissue-repair categories, banned in and out of competition for the relevant classes, and detectable by LC-MS anti-doping assays in equine and human matrices [13]. It has been encountered as a designer substance in racehorses, prompting dedicated detection methods.