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Peptide research · Compound guide
Explore the mechanisms, study findings and evidence limits behind this research topic.
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An evidence-mapped overview of TB-500 covering compound identity, its relationship to thymosin β4, proposed pathways, published studies, laboratory considerations, and current evidence limitations.
Educational information only. TB-500 is not an FDA-approved drug for human use.
In the research-chemical marketplace, TB-500 is typically described as the N-acetylated 17–23 fragment of thymosin β4 (Tβ4): Ac-LKKTETQ. That is a 7-residue peptide, not the 43-amino-acid parent protein. The distinction is chemical, not semantic. Confiscated material labeled TB-500 has been characterized as Ac-LKKTETQ with a reported monoisotopic mass of 888.4910, versus 4963.4642 for Tβ4 (Esposito et al., 2012, PMID 22962027).
FDA Global Substance Registration System identifiers for N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln are UNII QHK6Z47GTG and CAS 885340-08-9. Those identifiers describe the heptapeptide, not full-length Tβ4.
Thymosin β4 is a 43-residue G-actin-binding polypeptide. Safer, Elzinga, and Nachmias showed that Tβ4 is indistinguishable from Fx and binds G-actin 1:1, inhibiting polymerization (PMID 1999398). That paper is about the intact protein.
Sosne, Qiu, Goldstein, and Wheater later mapped short active-site stretches inside Tβ4 (PMID 20179146). The commercially relevant point for TB-500 is that LKKTETQ (residues 17–23) is one of those stretches — and it is not the only one. Ac-SDKP (residues 1–4) is a different fragment with a different assigned activity set. Ac-SDKP is not TB-500.
Analytical work on seized or administered TB-500 products has treated the label as the acetylated heptapeptide. Esposito and colleagues identified confiscated TB-500 as Ac-LKKTETQ. Ho and colleagues reported detection of TB-500 and related signals in equine plasma and urine after a 10 mg TB-500 administration in horses (PMID 23084823). Those are identity and detection papers, not efficacy trials.
| Region | Sequence | Assigned activities in Sosne 2010 | Relation to TB-500 |
|---|---|---|---|
| Tβ4 1–4 | Ac-SDKP | Anti-inflammatory / anti-fibrotic assignment | Not TB-500. Different fragment. Those findings do not transfer to Ac-LKKTETQ. |
| Tβ4 1–15 | N-terminal stretch | Survival-related assignment | Not the marketplace TB-500 sequence. |
| Tβ4 17–23 | LKKTETQ | Angiogenesis, wound, and migration assignment | This is the stretch marketplace TB-500 is typically built from (usually N-acetylated: Ac-LKKTETQ). |
| Full Tβ4 | 43 amino acids | Intact G-actin-binding protein (~4,963 Da) | Not identical to TB-500. Most biology and all opened human Tβ4 papers below are this protein, not the heptapeptide. |
Each item below is tagged by what was actually studied. Observed means data on Ac-LKKTETQ, LKKTETQ, or a stated TB-500 preparation. Proposed means an active-site assignment or extrapolation. Tβ4-only means the experiment used full-length thymosin β4 or a different fragment.
Confiscated TB-500 characterized as Ac-LKKTETQ, MW 888.4910 versus Tβ4 4963.4642. Equine plasma/urine detection after a 10 mg TB-500 administration in horses.
Esposito 2012, PMID 22962027; Ho 2012, PMID 23084823; FDA GSRS UNII QHK6Z47GTG.
The 7-amino-acid motif was necessary for HUVEC migration and chick aortic-arch sprouting at about 50 nM. Incomplete motifs were inactive.
Philp, Huff, Gho, Hannappel, Kleinman 2003, PMID 14500546.
LKKTETQ matched Tβ4 dermal repair in 26-month-old mice. In the same paper, Tβ4 itself was used in db/db mice and rats.
Philp, Badamchian, Scheremeta, Nguyen, Goldstein, Kleinman 2003, PMID 12581423.
In a fibroblast wound screen, parent Ac-LKKTETQ was not significant. The metabolite Ac-LKKTE was. This undercuts casual claims that the intact heptapeptide is simply a more stable or more potent Tβ4.
Rahaman et al. 2024, PMID 38382158.
Sosne 2010 assigns angiogenesis, wound, and migration activities to LKKTETQ (17–23). That is a structure–function map inside Tβ4, not a demonstration that marketplace TB-500 reproduces the full Tβ4 phenotype.
Sosne, Qiu, Goldstein, Wheater 2010, PMID 20179146.
Tβ4 = Fx; 1:1 G-actin binding; inhibits polymerization. This is intact 43-aa protein biochemistry, not a TB-500 binding isotherm.
Safer, Elzinga, Nachmias 1991, PMID 1999398.
Anti-inflammatory / anti-fibrotic assignment sits on Ac-SDKP (1–4). Survival assignment sits on residues 1–15. Neither is the TB-500 sequence.
Sosne 2010, PMID 20179146.
Mouse coronary-ligation work reporting integrin-linked kinase / Akt signaling used thymosin β4, not TB-500.
Bock-Marquette et al. 2004, PMID 15565145.
Opened human papers are intravenous or topical Tβ4 (Phase 1 IV; Phase 2 ulcer gel; topical RGN-259, n=9). None is an injectable TB-500 efficacy trial.
Ruff 2010, PMID 20536472; Treadwell 2012, PMID 23050815; Sosne 2015, PMID 25826322.
Most citations in circulation around “TB-500” are Tβ4 papers. The map below separates identity chemistry, fragment/motif experiments, full-length Tβ4 biology, and human Tβ4 work. A 2026 scoping-review preprint notes that most included studies are Tβ4, that musculoskeletal evidence is sparse, and that only one TB-500 study was identified — flag that document as a preprint, not a peer-reviewed conclusion (McGuire et al., 2026, DOI 10.20944/preprints202605.1124.v1).
Seized-product characterization of TB-500 as Ac-LKKTETQ, plus equine plasma/urine detection after a labeled TB-500 administration. This cluster answers “what is on the label?” It does not answer efficacy.
Endothelial migration and chick aortic-arch sprouting at ~50 nM; dermal repair in 26-month-old mice matching Tβ4. A later fibroblast screen found parent Ac-LKKTETQ inactive and a metabolite active.
G-actin sequestration, active-site mapping (including Ac-SDKP and 1–15), and mouse coronary-ligation ILK/Akt work all used Tβ4 or other fragments — not marketplace TB-500 as the test article.
Opened human studies are IV Tβ4 Phase 1 (40 adults, 42–1260 mg), Tβ4 gel Phase 2 ulcers, and topical Tβ4 RGN-259 (n=9). No controlled human efficacy trial of injectable TB-500 is in this set.
Read the “compound actually studied” column first. Several widely cited papers are Tβ4 papers sitting next to a TB-500 product page. That adjacency is not evidence that the heptapeptide was the test article.
| Domain | Compound actually studied | System | Status | Source |
|---|---|---|---|---|
| Chemical identity | TB-500 / Ac-LKKTETQ | Confiscated product; mass spectrometry | Observed | PMID 22962027 |
| Detection | TB-500 (10 mg administration) | Horse plasma and urine | Observed | PMID 23084823 |
| Registry identity | N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln | FDA GSRS | Observed | UNII QHK6Z47GTG; CAS 885340-08-9 |
| G-actin binding | Full-length Tβ4 (Fx) | Biochemical 1:1 binding | Tβ4-only | PMID 1999398 |
| Active-site map | Tβ4 fragments, including LKKTETQ and Ac-SDKP | Structure–function review / assignment | Proposed | PMID 20179146 |
| Endothelial migration / sprouting | 7-aa actin-binding motif | HUVEC; chick aortic arch; ~50 nM | Observed | PMID 14500546 |
| Dermal repair, aged mice | LKKTETQ (and Tβ4 in other arms) | 26-month-old mice; Tβ4 also in db/db mice and rats | Observed | PMID 12581423 |
| Fibroblast wound screen | Ac-LKKTETQ vs metabolite Ac-LKKTE | In vitro fibroblast assay; rat metabolite work | Observed | PMID 38382158 |
| Cardiac repair signaling | Thymosin β4, not TB-500 | Mouse coronary ligation; ILK/Akt | Tβ4-only | PMID 15565145 |
| Human IV exposure | Thymosin β4, not TB-500 | Phase 1; 40 adults; 42–1260 mg | Tβ4-only | PMID 20536472 |
| Human ulcer gel | Thymosin β4 gel, not TB-500 | Phase 2 ulcers | Tβ4-only | PMID 23050815 |
| Human topical ocular | Topical Tβ4 (RGN-259), not TB-500 | n=9 | Tβ4-only | PMID 25826322 |
| Tβ4 review | Thymosin β4 literature | Narrative review | Tβ4-only | DOI 10.3389/fendo.2021.767785 |
| Scoping overview | Mostly Tβ4; one TB-500 study noted | Preprint scoping review; musculoskeletal sparse | Preprint | DOI 10.20944/preprints202605.1124.v1 |
Safer, Elzinga, and Nachmias: Tβ4 is indistinguishable from Fx and binds G-actin 1:1. Intact protein, not TB-500. PMID 1999398.
Philp et al.: the 7-aa motif is necessary for HUVEC migration and chick aortic-arch sprouting (~50 nM; incomplete motifs inactive). A companion paper reports LKKTETQ matching Tβ4 repair in 26-month-old mice, with Tβ4 used in db/db mice and rats. PMID 14500546; PMID 12581423.
Bock-Marquette et al.: Tβ4 after coronary ligation; ILK/Akt. Not a TB-500 study. PMID 15565145.
Sosne et al. assign Ac-SDKP (1–4), residues 1–15, and LKKTETQ (17–23) to different activity sets. Ruff et al. report IV Tβ4 in 40 adults (42–1260 mg) — not TB-500, not an efficacy claim. PMID 20179146; PMID 20536472.
Esposito et al. characterize confiscated TB-500 as Ac-LKKTETQ (MW 888.4910 vs Tβ4 4963.4642). Ho et al. detect TB-500 in equine plasma and urine after a 10 mg administration. Treadwell et al. report Tβ4 gel in a Phase 2 ulcer setting — again not TB-500. PMID 22962027; PMID 23084823; PMID 23050815.
Sosne, Dunn, and Kim: topical Tβ4 (RGN-259). Not TB-500. PMID 25826322.
Xing et al. review thymosin β4. Used here only as a Tβ4 overview pointer; this page does not repeat secondary Phase II myocardial-infarction claims from that review. DOI 10.3389/fendo.2021.767785.
Rahaman et al.: acetylated TB-500 metabolites in rats; parent Ac-LKKTETQ did not show significant fibroblast wound activity; metabolite Ac-LKKTE did. PMID 38382158.
McGuire et al. preprint: most studies are Tβ4; one TB-500 study; musculoskeletal evidence described as sparse. Flag as preprint. DOI 10.20944/preprints202605.1124.v1.
These are not open questions phrased softly. They are gaps in the opened record. Treating any of them as settled is incorrect.
Ac-LKKTETQ (7 residues, ~888 Da) is not the 43-aa protein (~4,963 Da). Identity papers exist specifically because the two were being confused.
Opened human studies are Tβ4 (IV Phase 1, ulcer gel Phase 2, topical RGN-259 n=9). They are not TB-500 efficacy trials.
Those claims are marketing language. They are not supported by a controlled human TB-500 dataset in this guide.
Bock-Marquette 2004 used thymosin β4 after coronary ligation. It is not a TB-500 cardiac study.
Ac-SDKP is Tβ4 residues 1–4. It is not the TB-500 sequence. Anti-fibrotic or anti-inflammatory assignments on Ac-SDKP stay on Ac-SDKP.
The 2024 fibroblast screen found parent Ac-LKKTETQ not significant, while metabolite Ac-LKKTE was. That is the opposite of a simple potency upgrade story.
This guide does not contain a published combination experiment of BPC-157 plus TB-500. A blended research vial is related material, not a dedicated evidence base.
There is no human TB-500 dosing, reconstitution, or administration protocol here. Research-use only; not an FDA-approved drug for human use.
Every PMID below is from the verified set used to build this page. Human Tβ4 papers are included so they are not silently re-labeled as TB-500 evidence.
Confiscated TB-500 characterized as Ac-LKKTETQ, reported MW 888.4910, versus Tβ4 4963.4642. PMID 22962027.
Horses; 10 mg TB-500; plasma and urine detection. Analytical / anti-doping context, not an efficacy trial. PMID 23084823.
Tβ4 = Fx; 1:1 G-actin binding; inhibits polymerization. PMID 1999398.
Active-site assignments: Ac-SDKP (1–4) anti-inflammatory/fibrotic; residues 1–15 survival; LKKTETQ (17–23) angiogenesis/wound/migration. Ac-SDKP is not TB-500. PMID 20179146.
7-aa motif necessary for HUVEC migration and chick aortic-arch sprouting; about 50 nM; incomplete motifs inactive. PMID 14500546.
LKKTETQ matched Tβ4 dermal repair in 26-month-old mice. Tβ4 was used in db/db mice and rats in the same paper. PMID 12581423.
Acetylated TB-500 metabolites in rats. Parent Ac-LKKTETQ was not significant in a fibroblast wound screen; metabolite Ac-LKKTE was. PMID 38382158.
Tβ4, not TB-500. Mouse coronary ligation; ILK/Akt. PMID 15565145.
IV Tβ4 Phase 1; 40 adults; 42–1260 mg. Not TB-500; not an efficacy trial of the heptapeptide. PMID 20536472.
Tβ4 gel, Phase 2 ulcers. Not TB-500. PMID 23050815.
Topical Tβ4 (RGN-259), n=9. Not TB-500. PMID 25826322.
Tβ4 review. Included as a review pointer only. This page does not repeat any Phase II myocardial-infarction “confirmed” claim from that review. DOI 10.3389/fendo.2021.767785.
Flag as preprint. Most studies Tβ4; one TB-500 study identified; musculoskeletal evidence described as sparse. DOI 10.20944/preprints202605.1124.v1.
TB-500 is an investigational research compound. It is not an FDA-approved drug for human use. This page is educational. It does not provide dosing, reconstitution, administration, or any human-use instructions.
Laboratory identity is the first practical issue. The opened analytical record treats marketplace TB-500 as Ac-LKKTETQ (~888 Da), not 43-aa Tβ4 (~4,963 Da). A method, certificate, or protocol written for the intact protein is not automatically valid for the heptapeptide, and the reverse is also true.
Biological inference has the same problem. Full-length Tβ4 G-actin biochemistry, Ac-SDKP assignments, mouse cardiac Tβ4 data, and human Tβ4 topical or intravenous exposures are not substitute evidence that Ac-LKKTETQ will behave the same way. The 2024 fibroblast screen is a reminder: the parent heptapeptide and a metabolite did not read out the same.
If a study design needs a positive control or a literature comparison, state the actual test article. “TB-500” and “thymosin β4” should not be used as synonyms in a methods section.
No. Marketplace TB-500 is typically the N-acetylated 17–23 fragment Ac-LKKTETQ (7 residues, reported MW 888.4910). Thymosin β4 is a 43-amino-acid protein (reported MW 4963.4642). Esposito et al., 2012, PMID 22962027.
Ac-LKKTETQ — N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln. FDA GSRS: UNII QHK6Z47GTG; CAS 885340-08-9.
No. Ac-SDKP is Tβ4 residues 1–4. Sosne 2010 assigns anti-inflammatory / anti-fibrotic activity to that fragment. Those findings do not apply to Ac-LKKTETQ. PMID 20179146.
This guide does not contain a controlled human efficacy trial of injectable TB-500. Opened human papers are Tβ4: IV Phase 1 (Ruff 2010, PMID 20536472), Tβ4 gel Phase 2 ulcers (Treadwell 2012, PMID 23050815), and topical Tβ4 RGN-259, n=9 (Sosne 2015, PMID 25826322).
Rahaman et al. reported acetylated TB-500 metabolites in rats. Parent Ac-LKKTETQ was not significant in a fibroblast wound screen; the metabolite Ac-LKKTE was. PMID 38382158.
No. Bock-Marquette et al. 2004 used thymosin β4 in a mouse coronary-ligation model (ILK/Akt). It is not a TB-500 study. PMID 15565145.
No. Educational information only. TB-500 is not an FDA-approved drug for human use. It is an investigational research compound.
Not in this guide. No combination study was opened for this page. A blended research vial is related material only and does not have a dedicated evidence guide here.
Because that is what most of the surrounding literature actually studied. A 2026 scoping-review preprint likewise notes that most included studies are Tβ4, that one TB-500 study was identified, and that musculoskeletal evidence is sparse. Flag that document as a preprint. DOI 10.20944/preprints202605.1124.v1.
No. There is no human dosing, reconstitution, or administration protocol on this page. Laboratory work should treat identity (Ac-LKKTETQ versus Tβ4) as a first-order variable.
Full citations for the verified set. PMIDs link to PubMed. The 2026 item is a preprint.
Educational information only. TB-500 is not an FDA-approved drug for human use. Investigational compound. Research use only.
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