TB-500 vs LL-37
It is sold as an injection for healing torn muscles and tendons. No study has tested it for injuries in people or animals. It is sold as an injected natural antibiotic and healer. The only trials used it on skin sores and gave mixed results, and injecting it has never been studied in people.
Both sit at grade C: animal and cell studies. Neither is FDA approved.
Evidence
CAnimal and cell studies
CAnimal and cell studies
Human studies cited
Animal or cell studies cited
Why the grade
There are no published human trials of TB-500 itself. The only TB-500-specific papers are doping-control chemistry studies that identified the peptide in gray-market and veterinary products and detected it in horses. Human trials exist for full-length thymosin beta-4 (a venous-ulcer safety study planned for 72 patients and an 18-patient eye-drop trial), but those tested a different, larger molecule.
Two randomized placebo-controlled trials exist, both of LL-37 applied topically to chronic wounds: 148 patients with venous leg ulcers (negative on the primary endpoint) and a smaller diabetic foot ulcer trial. The injected 'immune support' use sold online has no human data at all. The rest of the human literature is observational work on the body's own LL-37 in wounds, psoriasis, and rosacea, plus cell and mouse mechanism studies. For the use it is sold for, that is C.
FDA
Not approved
TB-500 is not approved by the FDA for any use and is sold as a research chemical. In July 2026 an FDA advisory committee recommended it for the list of substances pharmacies may compound. On 28 October 2026 HHS issued an enforcement discretion policy covering TB-500 acetate for injection under the skin or into muscle. Licensed pharmacies and physicians may compound it for a named patient if they meet sourcing, testing, labeling and reporting conditions. That is not an approval, and the bulks list decision still needs a rule.
Not approved
Not approved by the FDA for any use and sold as a research chemical. LL-37 was nominated for the FDA's compounding bulk-substances list and placed in Category 2 (significant safety risk); the nomination was withdrawn, the FDA removed it from the category in April 2026, and a Pharmacy Compounding Advisory Committee review is planned before the end of February 2027.
Sold for
TB-500 is sold online as an injectable healing peptide for torn muscles, tendons and ligaments, often paired with BPC-157.
LL-37 is sold as an injectable 'natural antibiotic' that fights infections, breaks up biofilms, heals wounds, and modulates immunity.
Studies say
Nothing published tests TB-500 for injury in humans or animals; the evidence for its parent protein comes from small trials in wounds and the eye, so the grade is C.
Topical LL-37 has two small wound-healing trials with mixed results, the body's own LL-37 is well studied and drives inflammation in psoriasis and rosacea, and there are no human data on injecting it, so the evidence for the marketed use is grade C.
Class
Synthetic Tβ4 fragment
Host-defense antimicrobial peptide
Route
Injection
Injection