TB-500 FRAG
TB-500 Fragment · T-Beta-4 Fragment · AC-LKKTETQ
TB-500 FRAG (also called TB4 Active Site, Thymosin β-4 Fragment, or LKKTETQ peptide) is the synthetic 7-amino-acid active site peptide of Thymosin Beta-4 (Tβ4 / TB-500), corresponding to the central actin-binding region (residues 17-23 of the 43-residue parent) - sequence Leu-Lys-Lys-Thr-Glu-Thr-Gln. The full TB-500 / Tβ4 molecule has multiple bioactive regions: actin-binding (this fragment), N-terminal acetylated dipeptide (Ac-SDKP, an angiogenic / anti-fibrotic motif), and a C-terminal region implicated in cell migration. The isolated active-site fragment retains the actin-sequestering / tissue-migration activity but lacks the parent molecule's N-terminal anti-fibrotic motif and overall systemic profile.
Inject any time of day. Reconstitute with bacteriostatic water; refrigerate. Can be co-injected with BPC-157 in the 'Wolverine stack' since both are linear peptides without Met/Cys conflicts. Daily dosing typical given the shorter half-life vs full TB-500.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
TB-500 FRAG (LKKTETQ) is the actin-binding active site of Thymosin β-4. The full Tβ4 protein is the most abundant intracellular actin-sequestering peptide in vertebrates, regulating G-actin pool availability for cytoskeletal dynamics. The isolated active site retains key elements of this function:
Actin Sequestering
Binds G-actin monomers, regulating the G-actin / F-actin equilibrium that governs cell shape, migration, and division. This is the primary biochemical action.
Cell Migration
Modulation of actin dynamics is required for cell migration to injury sites - keratinocytes for wound closure, endothelial cells for revascularization, immune cells for inflammation resolution.
Pro-Angiogenic
Tβ4 (and to lesser extent the active-site fragment) promotes endothelial cell migration and tube formation - basis of pro-angiogenic activity in cardiac and dermal repair contexts.
Anti-Inflammatory
Modulates NF-κB signaling and reduces inflammatory cytokine production at injury sites.
Smaller Molecule Advantage
7 vs 43 amino acids - faster synthesis, lower cost, theoretically better tissue penetration. Trade-off: lacks the parent molecule's N-terminal Ac-SDKP anti-fibrotic motif, which is a separately bioactive segment of full TB-500.
No Met or Cys
Linear peptide without sulfur-containing residues - chemistry-compatible with copper-conjugated peptides like GHK-Cu. Wolverine-stack-friendly.
What to expect
Week 1-2: subjective improvements possible in acute injury contexts.
Week 4-6: peak tissue repair activity in acute injury.
Week 8-12+: chronic injury contexts may require longer cycles.
Evidence
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Exact-molecule abstract evidence. ESearch was run and 5 source-candidate PMIDs were EFetch-checked; no usable exact-molecule abstract sentence was found.
Dose/route: 500mcg-1mg; Subcutaneous (SubQ) injection; 1x daily. No selected live abstract sentence verified this complete regimen.
Mechanism as written in source JSON. No selected live abstract sentence verified the complete mechanism at the card formulation/route and relevant population/model.
Primary safety claim as written in source JSON. No selected live abstract sentence verified the complete safety claim for this exact formulation and route.
Side effects & safety
Commonly reported
- Injection site reaction (mild)
- Mild fatigue (early doses, rare)
- Mild headache (early doses)
Less common & notes
- Theoretical concerns about cell migration / angiogenesis enhancers in users with active malignancy.
- Long-term safety beyond research-chemical community use is uncharacterized.
- Allergic reactions to peptide are rare.
- Manufacturer purity varies - low-quality vendors may include contaminants that drive injection-site reactions.
Pharmacokinetics
Plasma (shorter than full TB-500 ~2 days)
SubQ
Functional window
subQ ~60-70%
Daily dosing typical
Renal/peptidase
Storage. Lyophilized vial: refrigerate (2-8°C / 36-46°F) or freeze (-20°C) for long-term storage. After reconstitution with bacteriostatic water: refrigerate, use within 21-28 days. Light-sensitive. Discard if cloudy, discolored, or beyond use-by window.
Regulatory status
Not FDA-approved for any indication. Has not entered Phase 1 clinical trials in isolation (full TB-500 has had limited clinical work). Available only as research chemical from peptide-supply vendors. WADA prohibited under class S2 (peptide hormones, growth factors) by Tβ4-family classification. Sale for human use is prohibited by FDA regulation.
Put it to work
Calculate, log & track
Open TB-500 FRAG straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
Open TB-500 FRAG in the app →Go deeper
The guide & community
The complete TB-500 FRAG walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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