WhatPeptide

LL-37

LL-37 is the only known human cathelicidin antimicrobial peptide, constitutively expressed in neutrophils and induced by infection and vitamin D signaling. It is studied for broad-spectrum antimicrobial defense, immune modulation, biofilm disruption, and potential roles in gut mucosal immunity. Placed on FDA Category 2 list (September 29, 2023) as 'Cathelicidin LL-37.'

Preliminary evidence FDA Category 2 Antimicrobial

Written by WhatPeptide Editorial Team · Last updated 2026-03-17

FDA Category 2 — compounding availability may be limited.

Half-life

Short; susceptible to protease degradation in vivo

Dosage range

Not established clinically; preclinical studies use mcg-range doses

Administration

Subcutaneous injection

Research level

Preliminary

How LL-37 works

LL-37 disrupts bacterial membranes through electrostatic interactions with anionic lipopolysaccharides, forming pores that cause rapid bacterial lysis across a broad spectrum including antibiotic-resistant strains. Beyond direct antimicrobial activity, LL-37 modulates innate immune responses by acting on formyl peptide receptor-like 1 (FPRL1), promoting chemotaxis of neutrophils and monocytes, and stimulating epithelial wound healing. Its role in gut mucosal defense and modulation of inflammatory bowel conditions is an active area of investigation.

Also known as: Cathelicidin, hCAP-18 C-terminal peptide, CAMP peptide

Research relevance

Immune Support
Moderate relevance 75
Gut Health
Some relevance 45

Side effects & safety

Injection site pain and inflammation Potential autoimmune activation Cytokine release at high doses

Contraindications

Autoimmune conditions without supervision
Pregnancy
Active inflammatory bowel disease flare without physician oversight

Consult a healthcare provider before use if any of these apply to you.

Key studies

FAQ

What is LL-37? +
LL-37 is the only known human cathelicidin antimicrobial peptide, constitutively expressed in neutrophils and induced by infection and vitamin D signaling. It is studied for broad-spectrum antimicrobial defense, immune modulation, biofilm disruption, and potential roles in gut mucosal immunity. Placed on FDA Category 2 list (September 29, 2023) as 'Cathelicidin LL-37.' Its mechanism of action is based on preliminary or early-stage research.
What is LL-37 researched for? +
LL-37 has the strongest research relevance for Immune Support, Gut Health. Evidence is based on preliminary or early-stage research.
What are the side effects of LL-37? +
Reported side effects include Injection site pain and inflammation, Potential autoimmune activation, Cytokine release at high doses. Key contraindications: Autoimmune conditions without supervision; Pregnancy; Active inflammatory bowel disease flare without physician oversight.
Is LL-37 FDA approved? +
LL-37 is classified as FDA Category 2, meaning compounding availability may be limited.
How is LL-37 administered? +
LL-37 is typically administered via subcutaneous route. Researched dosage range: Not established clinically; preclinical studies use mcg-range doses. Half-life: Short; susceptible to protease degradation in vivo.

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