TB-500 Legal Status, FDA 503A Category, and Compounding Access

TB-500 legal status: under active FDA review, with a real chance of change in 2026

TB-500 legal status is, right now, an open file that the FDA has scheduled to reopen. The single most consequential fact for anyone reading this: TB-500 — listed by the FDA as "TB-500 (free base)" and "TB-500 acetate" — is named individually on the published agenda of the FDA Pharmacy Compounding Advisory Committee (PCAC) meeting scheduled for July 23-24, 2026 as a bulk drug substance being considered for inclusion on the 503A Bulks List ^[18]. The same agenda also lists BPC-157, KPV, and MOTS-c ^[18]. Access to legally compounded TB-500 is under active review and may expand in 2026.

That is the forward-leaning part, and it is bounded carefully. A PCAC listing is a scheduled evaluation and discussion only. It is not a listing decision, not a reclassification, and not a change in TB-500's current status ^[18]. Inclusion on a final 503A bulks list is decided by FDA rulemaking informed by the committee; being discussed by PCAC is a step in evaluation, not a final listing ^[19]. No outcome of the July 2026 meeting should be assumed ^[18].

This page is general information about the regulatory landscape. It is not medical or legal advice, and it is not an offer to sell or supply any substance.

The current fact: 503A Category 2, not FDA-approved

As of now, the FDA standing is specific and citable. The FDA identified "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" as a bulk drug substance that may present significant safety risks and placed it in 503A Category 2, effective with the FDA's September 29, 2023 update to the nominated-substances list, citing concerns including potential immunogenicity for certain routes of administration and a lack of important safety information ^[20]. The FDA's own list entry establishes the relationship: TB-500 is the LKKTETQ fragment associated with thymosin beta-4 ^[20].

Category 2 has a defined meaning. Under the FDA's interim policy, Category 2 bulk drug substances are those nominated with sufficient information for the FDA to evaluate but which the FDA has identified as raising significant safety risks; they are not covered by the enforcement-discretion policy that applies to Category 1, and the FDA stated it would consider taking action against a compounder for compounding with a Category 2 substance ^[19]. So as a Category 2 substance, TB-500 is not within the FDA's enforcement-discretion policy for 503A compounding, and it is not an FDA-approved drug ^[20].

Two separate questions sit behind that. FDA approval of a finished drug (a New Drug Application or Biologics License Application) is distinct from whether a bulk substance may be used in compounding; TB-500 is neither an approved drug nor, while Category 2 stands, eligible for routine 503A compounding ^[19][20].

How legally compounded peptide access works

Compounded medication access follows a defined, prescriber-anchored pathway. A legally compounded preparation is made only after an individual patient is evaluated by an appropriately licensed prescriber who determines a compounded preparation is clinically appropriate and issues a valid, patient-specific prescription ^[21]. 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 operating under cGMP-style oversight ^[21].

Telehealth fits at the front end, not as a separate legal status. It can serve as the channel through which a patient is evaluated and a prescription is issued, but it does not change which substances are eligible to be compounded and it does not remove the need for a legitimate prescriber-patient relationship and a valid prescription ^[21].

The ingredient-eligibility caveat is the operative limit here. A compounder may use a bulk drug substance only if it is the subject of an applicable USP/NF monograph, is a component of an FDA-approved drug, or appears on the relevant FDA bulks list ^[19]. A substance the FDA has flagged for significant safety risks — a Category 2 substance such as TB-500 — is not eligible for routine 503A compounding while that status stands ^[21]. None of this is dosing guidance, and none of it names or endorses any pharmacy, clinic, telehealth provider, or vendor.

Regulatory FAQ

Direct answers to the regulatory questions, drawn only from the audited FDA reference. Present-tense facts; no future FDA action is stated as decided or dated.

Is TB-500 FDA approved?

No. TB-500 is not an FDA-approved drug and has no approved therapeutic indication. The FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 — bulk substances identified as raising significant safety risks — effective with its September 29, 2023 update, citing potential immunogenicity for certain routes and a lack of important safety information ^[20].

Is TB-500 legal?

There is no single yes/no answer, and this is general information, not legal advice. In the U.S. compounding context, the FDA placed TB-500 in 503A Category 2, so it is not within the FDA's enforcement-discretion policy for routine 503A compounding and is not an FDA-approved drug ^[19][20]. Separately, TB-500 is prohibited in sport by WADA ^[22]. Status varies by jurisdiction and context.

Can you get TB-500 from a compounding pharmacy?

Legally compounded medications require a licensed-prescriber evaluation and a valid, patient-specific prescription, dispensed by a 503A pharmacy or 503B outsourcing facility ^[21]. A compounder may use an ingredient only if it is eligible under the 503A/503B bulk-substance rules; a Category 2 substance the FDA has flagged for significant safety risks is not eligible for routine 503A compounding while that status stands ^[19][21].

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 drug substances that may present significant safety risks — effective with its September 29, 2023 nominated-substances update ^[20]. Category 2 substances are not covered by the FDA's enforcement-discretion policy for 503A compounding ^[19]. TB-500 is also named on the July 23-24, 2026 PCAC agenda for evaluation, which is a scheduled discussion, not a decision ^[18].