LL-37 / Cathelicidin

LL-37 is the C-terminal peptide derived from the human cathelicidin antimicrobial protein (hCAP18). It is the only known human cathelicidin and has broad-spectrum antimicrobial activity. It also modulates immune responses and has been implicated in various inflammatory diseases.

PubMed results: 13 · Human studies: 8 · Animal studies: 10

Ranges reflect protocols studied in published research and animal-model extrapolation. Presented for research purposes only, not a recommendation or instruction for human use.

• Topical — standard range Various formulations

~1 hour (preclinical) (low confidence)

• Broad-spectrum antimicrobial activity (Strong preclinical): LL-37, the only human cathelicidin peptide, has demonstrated bactericidal and antiviral activity in vitro and in animal infection models via membrane disruption and immune modulation.
• Innate immune modulation (Moderate clinical): Human and translational studies link LL-37 expression to host defense and inflammation, including research contexts involving vitamin D status, periodontitis, rosacea, and sepsis biology.
• Wound and barrier defense research (Strong preclinical): Preclinical work has examined LL-37 for effects on epithelial repair, chemotaxis, and angiogenesis pathways relevant to barrier tissues.

• Pro-inflammatory or cytotoxic effects at high local concentrations — Moderate, Not established. In vitro and animal data show that high LL-37 concentrations can be cytotoxic and amplify inflammatory signaling; human dosing safety for exogenous peptide is not well established.
• Local irritation in experimental delivery — Mild, Anecdotal. Local tissue irritation has been noted in early experimental delivery contexts; formal frequency data in controlled trials remain limited.

• Active inflammatory skin disease under uncontrolled study conditions (Theoretical / Preclinical): LL-37 is elevated in several inflammatory dermatoses (e.g., rosacea pathways); exogenous peptide could theoretically worsen dysregulated innate responses.
• Known hypersensitivity to cationic antimicrobial peptides (Theoretical / Preclinical): Peptide membrane activity and immune adjuvancy create theoretical risk of severe local or systemic reaction in susceptible research subjects.

Lyophilized (powder): Frozen (-20°C), Up to 24 months. Light sensitive: yes, store dark

Reconstituted (solution): Refrigerated (2-8°C), 4-6 weeks. Solvent: Bacteriostatic water

• NCT02930434 — Effects of Antarctic Environment on Vitamin D Status and Health Risk Biomarkers of Its Inhabitants (NA), status: COMPLETED. Indications: Vitamin D Deficiency
• NCT07490587 — To Investigate the Effects of Bifidobacterium Animalis Subsp. Lactis XLTG11 on Growth and Development, Incidence of Allergy and Immune Function in Infants (PHASE2), status: RECRUITING. Indications: Healthy Children
• NCT03923218 — Effects of Smoking and Vitamin D3 on the Levels of Human Cathelicidin Peptide LL-37, status: COMPLETED. Indications: Periodontitis
• NCT01398280 — Effects of Aminocaproic Acid (ACA) on Rosacea-specific Inflammation (EARLY_PHASE1), status: COMPLETED. Indications: Rosacea
• NCT00788320 — Vitamin D in Active Tuberculosis (TB) Study (NA), status: WITHDRAWN. Indications: Tuberculosis
• NCT01689441 — Randomized Controlled Trial of Calcitriol vs. Placebo Among Critically-ill Patients With Sepsis (PHASE2), status: COMPLETED. Indications: Severe Sepsis or Septic Shock
• NCT01372995 — Vitamin D in Ventilated ICU Patients (PHASE2), status: COMPLETED. Indications: Respiratory Failure
• NCT02138591 — Therapeutic Benefit of Preoperative Supplemental Vitamin D in Patients Undergoing Major Surgical Procedures. (PHASE3), status: WITHDRAWN. Indications: Vitamin d Deficiency
• NCT02945683 — Effects of Lactobacillus Reuteri Plus Vitamin D3 in Children With Atopic Dermatitis (NA), status: COMPLETED. Indications: Atopic Dermatitis
• NCT00407979 — Comparison of Cathelicidin Expression in Skin and Saliva in Patients With Atopic Dermatitis and Psoriasis, status: COMPLETED. Indications: Atopic Dermatitis, Psoriasis
• NCT02278172 — The Effects of Vitamin D Supplementation on Aerobic Fitness in Athletes (PHASE4), status: COMPLETED. Indications: Aerobic Fitness (VO2max)
• NCT06867250 — Peri-implant Vitamin D and Cathelicidin (LL-37) Levels, status: COMPLETED. Indications: Peri-Implantitis and Peri-implant Mucositis
• NCT05094570 — Interleukin-4Ra Blockade by Dupilumab Decreases Staphylococcus Colonization and Increases Microbial Diversity in CRSwNP (PHASE4), status: RECRUITING. Indications: Nasal Polyps, Staphylococcus Aureus
• NCT06552364 — Air Pollution and Inhaled Corticosteroids in COPD (PHASE4), status: NOT_YET_RECRUITING. Indications: COPD
• NCT01026363 — hCAP18 Levels and Vitamin D Deficiency in Chronic Kidney Disease (NA), status: WITHDRAWN. Indications: Chronic Kidney Disease, Vitamin D Deficiency
• NCT01758081 — Effects of Vitamin D and Omega-3 Fatty Acids on Infectious Diseases and hCAP18 (VITAL Infection) (NA), status: ACTIVE_NOT_RECRUITING. Indications: Infections, Human Cathelicidin Antimicrobial Peptide (hCAP-18)
• NCT05244018 — Outcome of High Dose Vitamin D on Prognosis of Sepsis Requiring Mechanical Ventilation (PHASE4), status: COMPLETED. Indications: Sepsis
• NCT07280754 — Evaluation of 25(OH)D3 and LL-37 Levels in Periimplant Sulcus Fluid, status: NOT_YET_RECRUITING. Indications: Peri Implantitis, Peri Implant Mucositis
• NCT02178488 — Efficacy Study of Vitamin D Supplementation to Meticillin Resistant Staphylococcus Aureus (MRSA) Carriers (PHASE2), status: COMPLETED. Indications: Methicillin Resistant Staphylococcus Aureus, Vitamin D3 Deficiency
• NCT05969275 — Umbilical Mesenchymal Stromal Cells as Cellular Immunotherapy for Septic Shock (PHASE2), status: RECRUITING. Indications: Septic Shock, Sepsis, Pathologic Processes, Shock, Systemic Inflammatory Response Syndrome, Inflammation, Infections