TB-500: Is It Legal, and What Do the Studies Show?

TB-500 is often sold next to BPC-157 as part of a "Wolverine" healing blend. This page covers TB-500 on its own: the legal answer, the short list of what has been studied, and the risks FDA named. The status box is checked against FDA's own lists.

Legal status of TB-500

Waiting on FDA after a favorable vote

TB-500 won a favorable but nonbinding advisory committee vote in July 2026, and FDA has not acted on it ^[3]. It still cannot be legally compounded or sold as a drug ^[1].

FDA status

FDA removed it from Category 2 in April 2026 because the nominators withdrew their nominations ^[7]. That removal did not make it legal to compound ^[8]. FDA now lists it as "nominated but withdrawn," which is outside every category ^[9]. It is not in Category 1 and is not on the 503A bulks list, so a 503A pharmacy may not lawfully compound it today ^[1]. FDA found no clinical studies, no human drug level data and no published case reports for TB-500 ^[4].

Advisory committee

On July 23, 2026, the committee voted 8 yes, 6 no and 1 abstain to recommend adding TB-500 to the 503A bulks list ^[2]. The committee reviewed it for wound healing ^[18]. FDA staff had recommended against listing it ^[4]. FDA has not posted its own vote count on the meeting page ^[18]. Advisory committee votes are not binding. Nothing changes until FDA acts ^[10].

FDA-approved products

None. We found no FDA-approved drug that contains TB-500.

Sports (WADA)

Prohibited at all times under class S2 (growth factors). The list names thymosin beta-4 and its derivatives, such as TB-500 ^[5].

What happens next

To add it to the 503A bulks list, FDA must go through notice-and-comment rulemaking, starting with a proposed rule. FDA could also place it in Category 1 or announce enforcement discretion in the meantime ^[10]. As of Oct 16, 2026, FDA had not started rulemaking or moved any of these peptides to Category 1 ^[3]. HHS has sent an "Interim Access Policy for Compounding Using Certain Peptides" to the White House budget office for review. Holland & Knight dates that submission Oct 14, 2026 ^[3], while the AP reported it appeared on a government website on Oct 15 ^[11]. The policy has not been issued and its text is not public ^[3]; reporting on Oct 21, 2026 still described it as under review ^[12]. Reports say it would cover some popular peptides, but we could not confirm whether TB-500 is one of them ^[11]. One law firm says there is no reliable timetable for final action ^[10]. A drug safety group petitioned FDA on Oct 16, 2026 not to allow it ^[13].

Checked against FDA sources on Oct 24, 2026. We update this box when FDA acts. Report a change: [email protected].

Can you get TB-500 legally right now?

No. A 503A compounding pharmacy can use a bulk ingredient only if it has a USP or NF monograph, is part of an FDA-approved drug, or is on FDA's 503A bulks list ^[6]. TB-500 meets none of the three, and it is not in Category 1, the interim group FDA lets pharmacies use while it decides ^[1]. A prescription does not change that, because the limit applies to the ingredient.

FDA took TB-500 out of Category 2, its list of substances with significant safety risks, in April 2026 after the nominators withdrew ^[7]. A pharmacy law firm wrote that removal from Category 2 "does not render these bulk drug substances eligible for compounding" ^[8]. FDA now files it as nominated but withdrawn ^[9].

The July 2026 committee vote is the reason people expect change. FDA could write a rule, place TB-500 in Category 1, or announce enforcement discretion, and one law firm says there is no reliable timetable for any of it ^[10]. HHS sent an interim peptide access policy to the White House budget office in mid-October 2026; its text is not public, and we could not confirm that TB-500 is covered ^{[3] [11]}. Reports on Oct 21, 2026 still described the policy as under review ^[12].

Pressure is also coming from the other side. On Oct 16, 2026, the Partnership for Safe Medicines filed a citizen petition asking FDA not to allow compounding of seven peptides, TB-500 among them, whether by rule, Category 1 placement or enforcement discretion ^[13].

TB-500 and thymosin beta-4: what the name means

Thymosin beta-4 is a natural protein. TB-500 is not the whole protein. FDA's briefing describes it as "a synthetic N-acetylated heptapeptide" matching amino acids 17 through 23 of thymosin beta-4 ^[4]. FDA also notes that TB-500 is a common name, not an official adopted drug name, and that different salts and forms are sold under the same name ^[4]. So a vial labeled TB-500 may not contain what a buyer assumes.

That matters for evidence too. Studies of the full thymosin beta-4 protein are not studies of TB-500, and neither is related research on thymosin alpha-1, a different peptide. When you see "thymosin beta 4 benefits" online, check which molecule was tested.

What FDA found when it looked for human data

For the July 2026 meeting, FDA staff reviewed the published record on TB-500 and its acetate salt. They wrote that "no articles were found in which TB-500 was administered to humans" and that they found no human studies of how it is absorbed or cleared ^[4]. What does exist:

• A lab study in which TB-500 itself "appeared to be devoid of wound-healing properties," while one of its breakdown products showed a small wound-closure effect ^[4].
• A drug level study in thoroughbred horses, where blood levels could no longer be measured between 6 and 10 hours after the dose ^[4].
• No studies of cancer-causing potential ^[4].

FDA staff recommended against listing it, citing poor chemical characterization, no documented history of use in compounding, no evidence it works for wound healing and no human safety data. They also noted that FDA-approved wound treatments already exist ^[4]. The committee voted the other way, but the staff findings on evidence did not change.

Side effects nobody has measured

Because no human study has been published, there are no TB-500 side effect rates. Lists of side effects on seller and forum sites are not drawn from trials. FDA's concerns are about the product itself: injected peptides "may pose a significant risk for immunogenicity," meaning an immune reaction, and impurities in TB-500 acetate can be present at up to 1.0% with no information on what they are ^[4].

Research-use-only vials and enforcement

Vials sold as "research use only" are not a legal way to buy TB-500 for your own use. FDA rejected that label in a 2025 warning letter to an online peptide seller ^[14]. Arent Fox Schiff noted that FDA's August 2026 letters to peptide sellers did not name any of the six peptides the committee backed in July, TB-500 included ^[15]. That reflects which products FDA chose to cite, not a change in the law. In April 2026, a federal grand jury in Utah indicted a physician on charges tied to misbranded drugs from China, including TB-500 and BPC-157, given to more than 200 patients; those are allegations, and he is presumed innocent ^[16]. More cases are on our FDA warning letters page. Telehealth sellers that list TB-500 include FrontCare ^[19] and PeRx ^[20]; we rate both Avoid.

TB-500 and drug testing

TB-500 is on the World Anti-Doping Agency's 2026 Prohibited List under class S2, growth factors. The list names "Thymosin-ß4 and its derivatives e.g. TB-500" and bans the class at all times ^[5]. Athletes in tested sports face a violation whether or not the product worked.

Legal options and what to watch

If you were looking at TB-500 for a tendon, muscle or wound problem, a doctor can go over FDA-approved treatments for that diagnosis. To compare peptides that can be prescribed today, see the legal peptide price tracker and tesamorelin, an FDA-approved peptide drug. Our BPC-157 page covers the other half of the Wolverine pairing, and the KLOW page covers four-peptide blends. Watch for three things: an FDA proposed rule, a Category 1 listing, or a published interim access policy that names TB-500. Our peptide status tracker changes the day any of them appears.

TB-500 status timeline

Newest first, each with its source.

• Oct 16, 2026: The Partnership for Safe Medicines filed a citizen petition asking FDA not to allow compounding of this and six other peptides, by rule, Category 1 placement or enforcement discretion ^[13].
• Oct 14, 2026: HHS sent an interim peptide access policy to the White House budget office for review, per Holland & Knight ^[3]. The AP reported it appeared on Oct 15 ^[11]. It has not been issued ^[3].
• Jul 23, 2026: On July 23, 2026, the committee voted 8 yes, 6 no and 1 abstain to recommend adding TB-500 to the 503A bulks list ^[2].
• May 15, 2026: FDA staff briefing documents recommended against adding it to the 503A bulks list ^[4].
• Apr 22, 2026: The removal took effect around this date. FDA now lists it as nominated but withdrawn, which does not allow compounding ^{[9] [8]}.
• Apr 15, 2026: FDA gave seven days' notice that it would remove 12 peptides, including this one, from Category 2 because the nominators withdrew ^[7].
• Sep 29, 2023: FDA placed it in Category 2, citing significant safety risks ^[21].

The other peptides FDA's committee weighed in July 2026: KPV, MOTS-c, Semax, epitalon and DSIP. For approved peptide drugs, see PT-141 and SS-31.

How we checked this page

On Oct 24, 2026 we rechecked FDA's 503A categories document (last updated May 14, 2026), FDA's advisory committee pages and recent law firm and news reports for any FDA action on TB-500 ^{[1] [17]}. FDA has not posted minutes for the July meeting, so the vote count comes from law firm reports ^{[18] [2]}. We do not link to sellers. Our method is in our editorial standards.