LL-37

LL-37 is the sole human antimicrobial peptide in the cathelicidin family. Cleavage at the C-terminal region of hCAP18 produces it, and neutrophils, epithelial cells and skin are its main sites of expression. Its antimicrobial spectrum includes bacteria such as MRSA, as well as fungi and viruses. Research also examines immune regulation, wound repair and antitumor activity. LL-37 remains restricted to research use.

Research schedules name a low starting amount and a titrated standard amount without numeric doses. Frequency depends on the protocol, and the route varies.

Responses differ between individuals. Begin with the lowest dose and observe your response carefully. Speak with your clinician before use and report unexpected symptoms. Human adverse effects are not fully characterized for every compound.

• Antimicrobial Activity

  Effective

  Laboratory investigations demonstrate activity against a broad range of microbes.

• Wound Infection Prevention

  Moderate

  It may reduce the ability of microbes to colonize wounds.

• Immune Activation

  Moderate

  Its activity stimulates innate defenses that respond to pathogens.

• Medications

  Caution

  Ask your prescriber to review any medication before combining treatments.

• BPC-157

  Compatible

• NAD+

  Compatible

• Vitamin D

  Compatible

Diluent: Use bacteriostatic water; avoid saline because precipitation may occur.

1. Let the refrigerated vial stand at room temperature for 15–20 minutes before preparation.
2. Disinfect the stopper using an alcohol swab, then wait until it has dried fully in the air.
3. Measure the calculated quantity of bacteriostatic water with a sterile syringe. Use only this diluent; avoid saline because precipitation may occur.
4. Add the water gradually against the inner vial wall. Keep the stream away from the powder itself.
5. Rotate the vial with a gentle swirling motion. Do not shake forcefully, because this can degrade the contents.
6. Wait 2–3 minutes for the powder to dissolve completely, and check that the liquid is transparent and has no color.
7. Use an insulin syringe to withdraw the calculated amount for injection beneath the skin.
8. Inject in the thigh, abdomen or upper arm. Change the injection location each time to help prevent lipodystrophy.
9. Refrigerate the mixed solution at 2–8°C. Use it within a maximum of 28 days after preparation.

Week 1–2

During the first 1–2 weeks, early effects may accompany an adjustment period. Watch for adverse reactions.

Week 2–4

By weeks 2–4, the main effects may start becoming apparent. Make dose changes only according to your clinician’s guidance.

Week 4–8

During weeks 4–8, the principal effects are expected to be established. Review your progress with your clinician.

Week 8+

From week 8 onward, review the results and decide with your clinician whether to continue, cycle or change the dose.

• Mild pain, bruising or redness around the injection location
• Possible allergic reaction; stop use if hives or a rash develops

LL-37: not approved in the US.

• US

  Not approved

  FDA: no approval for human treatment; research use only. No 503A ban is identified; compounding authorization remains unknown. Telehealth is not applicable.

  Rx required

  No

  Telehealth

  N/A

1. LL-37, the only human member of the cathelicidin family of antimicrobial peptides (2012)

2. The antimicrobial peptide LL-37 inhibits biofilm formation (2011)

3. Rosacea: Pathogenesis and Therapeutic Correlates. (2024)

   PMID 38450615DOI 10.1177/12034754241229365

4. LL-37 antimicrobial peptide: Molecular characterisation and its role in oral health and disease-A narrative review. (2026)

   PMID 41544412DOI 10.1016/j.archoralbio.2026.106516

5. Mookherjee N & Hancock RE — LL-37 review (2007) (2007)

6. LL-37 studies on ClinicalTrials.gov (2024)