TB-500 FDA Status: What the PCAC Vote Did and Didn't Do

Current status: TB-500 is not FDA-approved, is not on the 503A bulk drug substances list, and no US pharmacy may legally compound it today. On July 23, 2026 an FDA advisory committee recommended adding it. The recommendation is non-binding, and the indication reviewed was not the one TB-500 is sold for.

The vote

At the July 23–24, 2026 Pharmacy Compounding Advisory Committee (PCAC) meeting, TB-500 free base and TB-500 acetate were each voted on separately for the section 503A bulks list. Both reached the same result: 8–6 in favor with one abstention¹².

FDA has not published minutes, so those numbers come from trade and news reporting, and we attribute them that way.

The indication FDA actually reviewed: wound healing

FDA published the use it evaluated for every substance on the agenda in advance. For TB-500 free base and acetate, that use was wound healing³.

That is narrower than it sounds, and it is not what the athletic market buys TB-500 for. It does not mean tendon repair, ligament healing, muscle tears, joint injury, or accelerated return-to-play. No musculoskeletal or athletic indication was evaluated for TB-500, and none was voted on.

That distinction matters because it mirrors the actual evidence base. The most substantive human data for thymosin β4 concerns topical wound healing — not injected recovery from sports injury — which is exactly the gap we document in TB-500 (thymosin β4) for recovery: the evidence. The advisory vote reviewed the indication where some clinical data exists; it did not review, and did not validate, the one being marketed.

The identity problem — sharper here than anywhere

FDA's reviewers recommended against all seven peptides on the agenda, and their most fundamental objection was not efficacy but identity: material sold under one peptide name varies considerably between sources, and the agency told the committee it cannot write quality standards for a substance it cannot define⁴.

TB-500 is the cleanest illustration of that problem in the whole slate. It is not thymosin β4. It is a synthetic fragment of it — which is why FDA's own listings carry it as "Thymosin beta-4, fragment (LKKTETQ)"⁵. Vendors, forums and even some clinics use "TB-500" and "TB4" interchangeably, and they are different molecules with different sizes and different published literature. Anyone reasoning from thymosin β4 trial data to a TB-500 vial has already made the error FDA spent the meeting describing.

Who supplied the favorable margin

Eight new members were appointed to the committee shortly before the meeting, most with ties to the peptide industry. NBC News counted the votes by member and reported that on TB-500, all eight of the new appointees voted yes, with six members voting no and one abstaining². The favorable side of the vote consisted entirely of the new appointments.

What still has to happen

Nothing is listed. To add TB-500 to 21 CFR 216.23, FDA must publish a proposed rule, take public comment, and issue a final rule⁶. Only the final rule changes the list.

The only completed precedent for this pathway ran roughly three years — proposed rule December 2016, final rule effective March 21, 2019⁷. FDA has announced no timeline for this round, and the "9 to 18 months" claim circulating online traces to vendor blogs, not to any agency document.

What you should not conclude

• •Not that TB-500 is FDA approved or endorsed. It is neither. 21 CFR 216.23(d) makes it misbranding to represent a compounded drug made with a listed bulk substance as "FDA approved, or otherwise endorsed by FDA generally or for a particular indication"⁶ — a rule that binds even after a substance completes its rulemaking.
• •Not that FDA looked at injury recovery and agreed. It looked at wound healing. The stack marketing that pairs TB-500 with BPC-157 for tendons was not before the committee at all — see the BPC-157 + TB-500 stack, where the honest finding is that no human trial tests the combination.
• •Not that grey-market vials are legitimised. A future listing would govern licensed pharmacies compounding against a prescription, not "research use only" material sold online.
• •Not that anything changed in tested sport. Thymosin β4 and its fragments fall under WADA's S2 class of peptide hormones, growth factors and related substances, which is prohibited at all times and is written to capture families rather than only named examples⁸. In plain terms: TB-500 is banned in tested sport, year-round, and a prescription does not change that. You can confirm a specific compound yourself with our prohibited-substance checker, and the wider picture is in the WADA 2026 prohibited list for peptides.

Where TB-500 sits on FDA's lists today

TB-500 is not in FDA's live Category 2 table. It appears in that page's second table — substances "previously in category 2 of the interim policies" that "were withdrawn by the nominators," listed under the name "Thymosin beta-4, fragment (LKKTETQ)"⁵. Withdrawn means the nominator pulled the nomination. It is not a finding of safety and it does not make TB-500 compoundable.

None of which stops anyone buying it, so two practical questions follow. The first is what people are actually injecting, and how thin the basis for it is — that is TB-500 dosage: what people use and what's genuinely unknown, where the honest answer is that no human dose-ranging trial exists to anchor any of the circulating protocols. The second is whether anything in this category can be obtained through a licensed prescriber instead of a "research use only" vial. One route can: the GH-releasing peptides such as sermorelin, which telehealth clinicians do prescribe and which we compare provider by provider on our ranked recovery-peptide provider board. Those are still compounded rather than FDA-approved, and still banned in tested sport — the difference is that a prescriber and a licensed pharmacy stand behind them, which is not true of anything sold as TB-500.

The bottom line

A narrowly divided advisory committee recommended TB-500 for a compounding list, for wound healing, against FDA's own reviewers, with the favorable margin supplied entirely by newly appointed members. Nothing is listed, nothing is approved, and the injury-repair use that drives demand was never examined.

The full meeting breakdown is in what actually happened at the FDA peptide advisory vote. For the category's legal picture, see are peptides legal?. For the science, start with our TB-500 evidence review and the head-to-head in BPC-157 vs TB-500.