Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of LL-37 and TB-500 — mechanism, side effects, legal status, and pricing.
LL-37 is the only human cathelicidin antimicrobial peptide — a 37-amino-acid peptide (starting with two leucines) cleaved from the hCAP-18 precursor. It has broad-spectrum antimicrobial activity and immunomodulatory roles, but is also implicated in the pathogenesis of autoimmune and inflammatory skin diseases including psoriasis, rosacea, and lupus. Not FDA-approved; research-use only.
TB-500 is a synthetic N-acetylated heptapeptide (Ac-LKKTETQ) corresponding to amino acids 17–23 of thymosin β4, the actin-binding region of the native 43-residue protein. Despite widespread vendor labeling, TB-500 is NOT identical to full-length thymosin β4 (Tβ4); it is a short fragment containing the central actin-binding motif. It is sold as a research chemical and is not FDA-approved for any human indication.
LL-37
TB-500
Category
Legal Status
Mechanism
Half-life
Side Effects
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
LL-37
TB-500
COA corpus from Disclosed Labs — independently tested batches only.
LL-37
31
COAs
99.2%
Avg purity
8
Labs
TB-500
170
COAs
99.3%
Avg purity
16
Labs
TB-500 is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. LL-37 remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
LL-37 was characterized in the mid-1990s as the processed antimicrobial product of hCAP-18 (Gudmundsson et al., 1996). Dürr et al. (2006, Biochim Biophys Acta, PMID 16716248) provided a foundational review of its structure and activity as the sole human cathelicidin. Overhage et al. (2008, Infection and Immunity, PMID 18591225) showed LL-37 prevents Pseudomonas aeruginosa biofilm formation at 0.5 µg/mL — far below its MIC. A randomized, placebo-controlled Phase 1/2 trial (Grönberg et al., 2014, Wound Repair and Regeneration, PMID 25041740) found topical LL-37 safely accelerated healing of hard-to-heal venous leg ulcers at low doses. Its dual role in autoimmunity is well established: Lande et al. (2014, Nature Communications, PMID 25470744) identified LL-37 as a T-cell autoantigen in two-thirds of moderate-to-severe plaque psoriasis patients. No FDA approval exists for any indication. Injectable grey-market protocols for Lyme, biofilm, or mold illness lack controlled clinical evidence and carry theoretical autoimmune risk given LL-37's role in psoriasis, lupus, and rosacea pathogenesis.
Key references
Animal studies of full-length Tβ4 show accelerated dermal wound reepithelialization (Malinda et al., 1999, PMID 10469335), increased angiogenesis, improved cardiac function after ischemic injury via an ILK/Akt pathway (Bock-Marquette et al., Nature 2004, PMID 15565145), and corneal healing (Sosne & Kleinman review, 2015, PMID 26241398). The short Ac-LKKTETQ peptide sold as TB-500 was characterized analytically in the anti-doping literature as a substance with suspected doping potential (Esposito et al., 2012, PMID 22962027); controlled human efficacy trials of injected TB-500 do not exist. Full-length synthetic Tβ4 (RGN-259) has been evaluated in Phase II/III ophthalmic trials for dry eye disease and neurotrophic keratopathy with mixed results — one Phase III NK trial met healing endpoints, while a later European Phase III missed its primary endpoint. No clinically validated human injection dose exists for the short TB-500 peptide; all circulating dosing figures derive from vendor and forum protocols, not controlled trials.
LL-37 (Immune) and TB-500 (Recovery) are in different categories and target different biological pathways. This is a common pattern in multi-compound research protocols. Researchers should monitor the biomarkers from both profiles and watch for interactions listed in each compound’s contraindications. Consult a licensed healthcare provider before combining any research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Key references
Disclosed Labs