TB-500 (thymosin beta-4 fragment): legal status, evidence and risks
As of October 15, 2026, TB-500 is not FDA-approved, is not on the 503A bulks list and sits in none of FDA’s interim compounding categories, so a U.S. pharmacy has no established federal route to compound it. FDA staff told its advisory committee it had found no human exposure data for the substance. A July 2026 committee vote to recommend it is advice only; FDA has not acted.
Status at a glance
| Check | Status as of October 15, 2026 | Source · read date |
|---|---|---|
| FDA approval | Not approved. | FDA · read October 15, 2026 |
| 503A interim category | In no interim category. FDA lists “Thymosin beta-4, fragment (LKKTETQ), also known as TB-500” as nominated but withdrawn from Category 2 (page current as of April 22, 2026; categories PDF updated May 14, 2026). | FDA · read October 15, 2026; FDA categories PDF |
| FDA advisory committee (PCAC) | Reviewed July 23, 2026 for wound healing. FDA staff: “we propose not adding TB-500 (free base) or TB-500 acetate to the 503A Bulks List.” Reported vote 8–6, one abstention, to recommend. No FDA final action. | FDA · read October 15, 2026; McDermott (reported) |
| WADA 2026 Prohibited List | S2.3: “Thymosin-β4 and its derivatives e.g. TB-500.” Prohibited at all times. | World Anti-Doping Agency · read October 15, 2026 |
| FDA warning letters, 2026 | None found naming TB-500 in the 2026 peptide-seller letters we reviewed. | FDA warning letters · read October 15, 2026 |
| WADA 2027 list | Entry unchanged on the 2027 list (approved September 10, published September 21, in force January 1, 2027). | World Anti-Doping Agency · read October 15, 2026 |
What TB-500 is
TB-500 is the name sellers use for a short synthetic fragment of thymosin beta-4, a protein the body makes. FDA identifies it by its amino-acid sequence, LKKTETQ. It is marketed for injury recovery and wound healing; wound healing was the use FDA evaluated at its July 2026 advisory meeting.
It is often sold alongside BPC-157 as a “recovery stack”. The two substances have the same regulatory position: no approval, no compounding category, and a committee recommendation FDA has not acted on.
Human evidence
FDA’s summary is blunt: “FDA has not identified any human exposure data drug products containing Thymosin Beta-4, Fragment” (FDA). In other words, FDA did not find data on people taking the product TB-500 sellers actually sell.
Research on the full thymosin beta-4 protein is a different question from research on this fragment, and we have not re-read that literature for this update. We do not cite any human trial for TB-500 because we could not source one.
Animal and laboratory evidence
Claims about faster healing come mainly from animal and laboratory work. Those findings may explain why the substance was nominated, but they do not show benefit or safety in people, and we do not present them as if they did.
Risks
With no human exposure data, there is no reliable picture of side effects, interactions or long-term safety. Injected peptides bought outside the pharmacy system add contamination, sterility and dose-accuracy risks that nobody checks. FDA staff’s recommendation against listing reflects those gaps.
Legal sourcing: who can supply it
TB-500 is in the same position as BPC-157: no approved product, no USP pathway we found, not on the 503A bulks list and not in Category 1. As of October 15, 2026, a licensed pharmacy has no established federal route to compound it. See the peptide legality guide and BPC-157.
The lawful route for a prescription peptide in the United States is a licensed clinician who examines you and writes a prescription, filled by a state-licensed 503A pharmacy or an FDA-registered 503B outsourcing facility that is allowed to use that substance. Websites that sell peptides “for research use only” or “not for human consumption” are not a lawful source of medicine for people. On August 24, 2026, FDA sent warning letters to five such sellers — Peptide Partners, Peak Performance Peptides, Royal Peptides, NuScience Peptides and Tex Peptides — calling their products unapproved new drugs. FDA wrote that the research-use labels did not change its view because the websites showed the products were meant for human use.
October 2026: what changed
- April 2026 — Category 2 withdrawals. FDA moved BPC-157, TB-500, CJC-1295, ipamorelin, AOD-9604, injectable GHK-Cu and other peptides off its Category 2 list after the nominators withdrew them. FDA lists them as “nominated but withdrawn” (page current as of April 22, 2026). They were not moved into Category 1.
- July 23–24, 2026 — advisory committee. FDA’s Pharmacy Compounding Advisory Committee reviewed BPC-157, KPV, TB-500, MOTs-C, emideltide (DSIP), Semax and Epitalon. FDA staff proposed not adding BPC-157 or TB-500. A law-firm account reports the committee voted 8–6 (one abstention) to recommend BPC-157, KPV and TB-500 (McDermott, July 27, 2026). A vote is advice; FDA has taken no final action.
- October 14–15, 2026 — interim access policy under White House review. The OIRA review site lists “Interim Access Policy for Compounding Using Certain Peptides” from HHS/FDA (RIN 0910-ZD94, stage: Notice), received October 14, 2026 and pending review; no text has been published (reginfo.gov). Reuters reported the filing on October 15 (Reuters), and the AP, citing two people, said it would let pharmacies make some popular peptides, including BPC-157. Which peptides, on what terms and from when are not public. Our running table: peptide legal status 2026.
For TB-500: it was one of the three peptides with the 8–6 recommendation vote, and press reports on the interim policy describe “popular peptides”, but no list has been published. Until FDA publishes a policy that names TB-500, nothing about its status has changed. See all peptide statuses.
Frequently asked questions
Is TB-500 FDA-approved?
No. TB-500 is not an approved drug, and FDA said it had not identified any human exposure data for products containing the thymosin beta-4 fragment. It is also not on the 503A bulks list or in any of FDA’s interim compounding categories as of October 15, 2026.
Is TB-500 the same as thymosin beta-4?
No. TB-500 is a short fragment of thymosin beta-4 with the sequence LKKTETQ, which is how FDA lists it. Research on the full protein does not automatically apply to the fragment, and WADA prohibits both thymosin beta-4 and its derivatives.
Did the FDA committee vote for TB-500?
A law-firm account reports the Pharmacy Compounding Advisory Committee voted 8–6, with one abstention, on July 23, 2026 to recommend TB-500 for the 503A bulks list. FDA staff had proposed not adding it. The vote is advisory, and FDA had not acted as of October 15, 2026.
Is TB-500 banned for athletes?
Yes. The 2026 WADA Prohibited List names TB-500 under S2.3 as a derivative of thymosin beta-4, prohibited at all times. A positive test can lead to a sanction whatever the source of the product.
New this month: what is known about FDA’s peptide interim access policy · a status table for 16 peptides (FDA and WADA).
Sources
- FDA — Certain bulk drug substances for use in compounding that may present significant safety risks (page current as of April 22, 2026) (read October 15, 2026)
- FDA — Interim policy categories for 503A and 503B bulk drug substances (PDF, updated May 14, 2026) (read October 15, 2026)
- FDA — Bulk drug substances used in compounding under section 503A (page current as of May 14, 2026) (read October 15, 2026)
- FDA — PCAC briefing document on TB-500, July 2026 (read October 15, 2026)
- FDA — July 23–24, 2026 meeting of the Pharmacy Compounding Advisory Committee (page current as of August 6, 2026) (read October 15, 2026)
- McDermott Will & Schulte — PCAC backs majority of peptides in two-day public meeting (July 27, 2026; reported vote counts) (read October 15, 2026)
- World Anti-Doping Agency — Prohibited List (2026 list in force) (read October 15, 2026)
- FDA warning letter — Royal Peptides LLC, 734884 (August 24, 2026) (read October 15, 2026)
- OIRA (reginfo.gov) — Interim Access Policy for Compounding Using Certain Peptides, RIN 0910-ZD94 (pending EO 12866 review) (read October 15, 2026)
- Reuters via Yahoo News — FDA takes step to change peptide compounding access (October 15, 2026) (read October 15, 2026)
- World Anti-Doping Agency — 2027 Prohibited List (published September 21, 2026; in force January 1, 2027) (read October 15, 2026)