What are TB-500 and LL-37?

TB-500 commonly refers to N-acetyl-LKKTETQ, a seven-residue fragment of full-length 43-residue thymosin beta-4. LL-37 is a 37-residue human cathelicidin peptide. Parent thymosin beta-4 trial outcomes are not TB-500 outcomes.

Which has direct human treatment evidence?

No controlled human TB-500 fragment treatment study was identified in the C25 dossier. Native topical LL-37 has three published wound-trial populations, with a larger venous-ulcer trial negative in the full population.

Can either be assumed effective for wound infection or repair?

No. LL-37 cream improved selected granulation measures without significantly reducing measured aerobic bacterial colonization; TB-500 fragment cell assays and parent-protein studies do not establish human repair.

TB-500 vs LL-37: Evidence and Limits (2026)

Dossier labels summarize each dossier's research scope. They do not establish comparative treatment benefit or safety. Read the comparison below in that context.

The identity distinction

TB-500 commonly denotes N-acetyl-LKKTETQ, a seven-residue fragment corresponding to thymosin beta-4 residues 17–23. Full-length thymosin beta-4 is a 43-residue protein; its human or animal trial results cannot be assigned to the fragment. LL-37 is the active 37-residue human cathelicidin peptide processed from hCAP18. FDA TB-500 identity review · LL-37 identity, PMID 8681941

Evidence question	TB-500 fragment	Native LL-37
Direct selected evidence	Analytical and cell-assay fragment work; no cited human treatment trial	Three published topical wound-trial populations; separate tiny melanoma registry
Therapeutic-claim grade	Very low for human repair	Low for broad wound or infection benefit
Key limit	Parent Tβ4 trials do not transfer	Topical results do not establish systemic benefit

A 2012 TB-500 study detected the fragment in a veterinary preparation and equine samples, a detection result rather than tissue repair. A 2024 fibroblast scratch assay found statistically significant activity for the Ac-LKKTE metabolite, not parent TB-500. Full-length thymosin beta-4 corneal and cardiac findings are indirect for the fragment. PMID 23084823 · PMID 38382158 · parent Tβ4 corneal trial, PMID 36613994

The 34-person LL-37 venous-ulcer pilot reported selected healing signals. A later 148-person phase IIb trial did not find significant healing benefit for the full cohort; its large-ulcer subgroup finding was post hoc. Diabetic-foot-ulcer LL-37 cream improved granulation measures but not measured aerobic bacterial colonization. LL-37 topical pilot, PMID 25041740 · larger phase IIb trial, PMID 34687253 · diabetic-foot-ulcer trial, PMID 37480520

An intratumoral LL-37 melanoma record posts four-person results, without establishing antitumor efficacy or general safety. A separate engineered L. lactis product expressing LL-37 had no significant overall viral-negative-time result; it is not a native peptide wound trial. NCT02225366 · PMID 37605995

FDA reports no identified human drug-product exposure data for the TB-500 fragment and insufficient safety information for compounded LL-37. Neither safety conclusion can be inferred from natural origin or parent-protein experience. FDA TB-500 review · FDA compounding safety review

The selected evidence contains no direct TB-500-versus-LL-37 or combination trial. This is an educational comparison, not treatment guidance.

TB-500 vs LL-37

TB-500

LL-37

The identity distinction

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