Is TB-500 legal in the US?

Approved vs compoundable vs “research-use” — the distinction that matters

An FDA-approved drug has cleared full clinical trials. A compoundable substance is one a licensed pharmacy may prepare to prescription, even without full approval, if it sits on the 503A Category 1 list. As of April 2026 TB-500 was removed from Category 2 because the original nominations were withdrawn — but it was not moved to Category 1, so compounding is still not authorized and it is not covered by FDA enforcement discretion. Products labeled “for research use only” are not authorized for human use. This page does not provide sourcing, dosing, or preparation guidance.

What happened on July 23

The FDA’s Pharmacy Compounding Advisory Committee heard the evidence and voted to recommend adding TB-500 to the 503A list for wound healing. That vote is advisory only; the FDA must still issue a final rule before any pharmacy could legally compound it. Realistic patient access, if it happens at all, is 2027 at the earliest — as of September 2026 the FDA has not issued a proposed rule. BPC-157 and TB-500 went before the committee on the same day and drew the same 8–6 vote; BPC-157 vs TB-500 sets the two side by side.

“Legal” means three different things here

Three separate questions get collapsed into one word, and keeping them apart is the difference between knowing TB-500’s status and guessing at it.

Controlled-substance law. TB-500 is not listed in Schedules I–V of the Controlled Substances Act, and no state has scheduled it separately. Possessing it is not a drug-scheduling offence. This is what most “is it illegal” questions are actually asking, and the answer is no.

Federal drug law. That is not the same as lawful. Under the Federal Food, Drug and Cosmetic Act, a substance sold or labelled for human use without FDA approval is an unapproved new drug, and selling it for human use is a violation whatever its scheduling status. “Research use only” is the label vendors use to stay outside that framing — it is a marketing posture, not an authorisation.

Compounding law. A licensed 503A pharmacy may prepare a non-approved substance only if it appears on the FDA’s Category 1 bulks list, has a USP monograph, or is a component of an approved drug. TB-500 is none of these today. The July 2026 recommendation is a step toward the first — not the first itself.

State enforcement runs on a separate track, and it has not yet reached TB-500 in court. The public cases so far — Connecticut against a distributor selling “research grade” semaglutide and tirzepatide direct to consumers in 2025, Alabama against a clinic injecting the same material later that year — both concerned GLP-1 drugs. The state measure that does reach TB-500 is the Alabama Board of Medical Examiners notice of May 2026, which directs licensed physicians, physician assistants and nurse practitioners not to prescribe, supply or administer non-FDA-approved research-grade peptides of any kind, whatever the patient signs. Our explainer on US peptide regulation sets out how the state and federal layers fit together. This section describes the regulatory framework; it is not legal advice.

Banned in sport, explicitly and at all times

TB-500 is named on the WADA Prohibited List, not merely caught by it. The 2026 list places thymosin-β4 and its derivatives under S2.3, growth factors and growth factor modulators, with TB-500 given as the example. The prohibition applies at all times, in and out of competition, and the substance is non-specified — the category carrying the heaviest sanction band.

Two things catch people out. Enforcement does not depend on a positive test: use, attempted use and possession are each violations in their own right and can be established from records or admissions. And a favourable FDA vote would change nothing here — anti-doping and drug approval are unrelated regimes, and a substance can be compoundable by prescription and still cost an athlete four years.

Outside the US, TB-500 is named again: the annex to Germany’s Anti-Doping Act lists thymosin-beta-4 and its derivatives, a regime separate from German medicines law. Europe & DACH: does the FDA vote change anything? →

Primary sources: FDA 503A interim list (Category 2, 2023) · FDA Advisory Committee Calendar; Federal Register docket FDA-2025-N-6895 · Controlled Substances Act schedules · WADA 2026 Prohibited List, S2.3 · Alabama Board of Medical Examiners, official notice on the prescribing of non-FDA-approved (research-grade) peptides (May 2026).