Compound Profile
TB-500 and Thymosin Beta-4: One Is a Fragment of the Other
Published: August 24, 2026
TL;DR
TB-500 and thymosin beta-4 are related, but they are not interchangeable names for one molecule. FDA's substance registry identifies TB-500 as Ac-LKKTETQ, the acetylated seven-amino-acid fragment corresponding to residues 17-23 of the 43-residue parent protein. The registered clinical trial record, by contrast, is filed under "Thymosin Beta 4" and concerns full-length or recombinant material. That distinction affects how papers, trial entries, and certificates of analysis should be read. Curo's TB-500 5 mg research listing appears in the broader laboratory research catalog, with lot records available through the COA database.
The molecule behind the name
Start with the identity record. FDA's UNII registry catalogs TB-500 as UNII QHK6Z47GTG and thymosin beta-4 as the separate UNII 549LM7U24W, and it defines TB-500 as the N-terminal acetylated 17-23 fragment of thymosin beta-4. In sequence terms that is Ac-LKKTETQ: seven amino acids, synthesized, against a parent protein of 43.
Thymosin beta-4 itself is a G-actin-binding protein involved in cytoskeletal remodeling. The fragment carries one short stretch of that sequence. Seven shared residues out of 43 is a real relationship, but it is not the same molecule, and a paper on thymosin beta-4 is not automatically a paper on the material sold as TB-500.
The naming overlap is partly historical and partly commercial. Research groups tend to use the precise molecular name; community and vendor language uses TB-500 more loosely. The UNII records are the stable way to tell which one a document means.
What the research literature covers
The larger literature belongs mainly to full-length thymosin beta-4. In vitro and animal studies examine actin binding, cell migration, cytoskeletal organization, dermal and corneal models, cardiac biology, inflammation, and progenitor-cell activity. These papers establish why the parent protein became a research subject, but their scope remains tied to the molecule, model, and route each team studied.
The strict Ac-LKKTETQ fragment has a much smaller direct record, and one 2024 analytical study is worth knowing in detail. Rahaman and colleagues, writing in the Journal of Chromatography B, developed a method to quantify TB-500 alongside its metabolites and then screened those species for wound-healing activity in vitro. Ac-LKKTETQ itself did not enhance wound healing in that assay. A shorter metabolite, Ac-LKKTE, did. The finding matters because it measures the fragment as its own analyte, and because it raises the possibility that a breakdown product, rather than the intact heptapeptide, carries the activity researchers have been attributing to it.
Community discussion also frequently pairs the name TB-500 with BPC-157 under the "Wolverine" label. That convention describes how the compounds are discussed, not a shared evidence base. Curo's BPC-157 and TB-500 research pairing groups the materials commercially, while the sibling profile on BPC-157's research and trial record covers that compound separately.
Where the trial record stands
Clinical trial registries make the identity split especially visible. The registered entries are filed under "Thymosin Beta 4," not "TB-500," and the active substance descriptions refer to full-length or recombinant material.
RegeneRx registered RGN-352 as injectable thymosin beta-4 for acute myocardial infarction. ClinicalTrials.gov lists NCT01311518 as withdrawn and states that the study was never initiated. It produced no participant dataset.
Beijing Northland Biotech later sponsored a Phase IIa study of recombinant human thymosin beta-4. NCT05485818 is listed as completed on November 18, 2021. The same sponsor's Phase IIc study of recombinant human thymosin beta-4 injection, NL005, is another parent-protein program. NCT07586865 lists a May 18, 2026 start date and remains not yet recruiting.
Taken together, these records describe a clinical development program for thymosin beta-4. The seven-residue fragment has its own, much shorter registry footprint, which is worth holding separately when reading either one.
Regulatory status in 2026
FDA's 2026 compounding review names the fragment directly. An April 16, 2026 Federal Register notice scheduled a Pharmacy Compounding Advisory Committee meeting for July 23 and 24 and listed "TB-500 (free base)/TB-500 acetate" among nominated bulk drug substances, with wound healing as the indication considered. The committee recommended it. Voting separately on the free base and the acetate, it backed each by 8 in favor to 6 against with one abstention, the same split it gave BPC-157 and KPV that day. Hyman, Phelps & McNamara reported the result, and Pharmaceutical Executive and McDermott Will & Schulte published the same figures. FDA's own staff had recommended against listing, its briefing document for TB-500 citing no human exposure data and potential immunogenicity, aggregation and impurity concerns for injectable use.
A committee recommendation is advisory. Adding a substance to the section 503A list requires formal FDA rulemaking, so TB-500 is not on that list today.
Thymosin beta-4 also has a separate historical designation. FDA granted orphan drug designation to "Thymosin beta 4" on May 28, 2004 for epidermolysis bullosa. Its status is "Designated," which is not an approval, and the record names the parent protein rather than TB-500 fragment material.
For sport, WADA's 2026 Prohibited List took effect January 1, 2026 and places thymosin-beta-4 and its derivatives in section S2.3, Growth Factors and Growth Factor Modulators. They are prohibited at all times, in and out of competition, as non-Specified Substances. Enforcement is not hypothetical: USADA announced a four-year period of ineligibility for triathlete Anthony McCauley on September 17, 2025 involving TB-500 and BPC-157.
Curo supplies the material for laboratory work under its research use only policy. That commercial category is separate from the FDA substance identity, compounding review, orphan designation, and sport rules above.
Reading a TB-500 certificate of analysis
For TB-500, a COA should answer the identity question before it answers broader quality questions. The analyte name should correspond to the vial, and the record should make clear whether the tested material is Ac-LKKTETQ, the thymosin beta-4 17-23 fragment, rather than full-length thymosin beta-4.
Start with the lot number, which should match the identifier on the vial and on the published report. The guide to verifying a certificate against a specific lot walks through that check. From there, each method answers a different question. LC-MS speaks to identity and should agree with the declared fragment. HPLC reports chromatographic purity. Endotoxin testing measures something else again. Curo runs exactly those three, described in the laboratory testing standard.
The order matters here more than it does for most peptides. A high HPLC purity figure says a sample is clean; it does not say whether the clean thing in the vial is the seven-residue fragment or the 43-residue parent. Only the identity label and the LC-MS result together answer that. Once the paperwork lines up, the research-peptide storage guidance covers handling from receipt onward.
Further reading
Identity is not only a TB-500 problem. GHK-Cu raises its own version of it, because the copper complex and the free peptide carry separate registry entries and a purity figure alone will not tell them apart. That case is worked through in GHK-Cu across its cosmetic and research contexts.
CJC-1295 presents the same problem in another form, where one market name covers both a short-lived peptide and a long-acting albumin-binding conjugate. That case is set out in CJC-1295 with and without DAC.
Semax was reviewed at that same July 2026 meeting, and it reaches the agenda from an entirely different direction: decades of Russian clinical literature paired with an empty US trial registry. That case is covered in Semax and the 2026 review list.
Two other fragment-versus-parent cases are worth reading alongside this one. AOD-9604 is the 176 to 191 fragment of growth hormone, and its story is covered in the AOD-9604 profile. Thymosin alpha-1 is routinely confused with thymosin beta-4 despite being a different peptide with a different anti-doping status, which is addressed in the thymosin alpha-1 record.
The same fragment-versus-parent question arrives again inside a blend. TB-500 is one of four named peptides in KLOW, each with its own identity record on one document, as set out in One vial, four analytes: reading a KLOW certificate.
Common questions
Is TB-500 the same molecule as thymosin beta-4?
No. FDA catalogs them separately. TB-500 is the acetylated seven-amino-acid 17-23 fragment, while thymosin beta-4 is the 43-residue parent protein.
Have registered clinical trials studied the TB-500 fragment?
The registered trials described here are filed under thymosin beta-4, and their substance descriptions identify full-length or recombinant material. Direct registry entries for the Ac-LKKTETQ fragment are a separate and much smaller set.
Why are TB-500 and BPC-157 often mentioned together?
Community and commercial language commonly pairs them under the Wolverine name. Each compound still has its own molecular identity and research record, so the pairing does not combine their evidence.
What is the first identity check on a TB-500 COA?
Confirm that the lot-specific report names the TB-500 fragment, Ac-LKKTETQ or thymosin beta-4 residues 17-23, and that its LC-MS identity result aligns with that declaration.