Educational guide

Cathelicidin (hCAP-18 / Synthetic Derivatives) vs LL-37 — Peptide Comparison

At a Glance Quickcomparison Dose Range Cathelicidin (hCAP-18 / Synthetic Derivatives) 0.5–5 mg LL-37 0.5–1.6 mg/mL (topical) Frequency Once daily Administration Topical application (primary research route) Topical application (wound healing) Cycle Length 4-6 w

Written by Peptide Therapy Guide Editorial TeamPublished August 30, 2026

For education only

This guide cannot diagnose a condition or recommend a personal treatment plan. Discuss medical questions with a qualified professional.

At a Glance

Quickcomparison

Dose Range

Cathelicidin (hCAP-18 / Synthetic Derivatives)

0.5–5 mg

LL-37

0.5–1.6 mg/mL (topical)

Frequency

Once daily

Administration

Topical application (primary research route)

Topical application (wound healing)

Cycle Length

4-6 weeks

12+ weeks

Onset Speed

Rapid (hours to days)

Moderate (1-2 weeks)

Evidence Level

Moderate human trials (Phase 1-2)

Efficacy

Benefitratings

Antibiotic-Resistant Infections

Biofilm Destruction

Immune System Support

Wound Healing

Fighting Infections

Immune Boost

Technical Data

Compoundspecifications

Molecular Formula

hCAP-18: ~18 kDa precursor protein (170 AA); SAAP-148: C155H253N49O31 (approximate), MW 3,267.1 Da

Molecular Weight

hCAP-18 precursor: ~18,000 Da; SAAP-148: 3,267.1 Da; OP-145: ~2,900 Da

Half-Life

Plasma half-life: minutes (proteolytic degradation); local tissue persistence: hours at therapeutic concentrations in wound environment; enhanced stability compared to LL-37 due to N-terminal acetylation and C-terminal amidation

Bioavailability

Topical bioavailability optimized in hypromellose ointment formulations; SAAP-148 retains activity in human plasma unlike LL-37; systemic bioavailability limited by proteolytic degradation

CAS Number

Not assigned (SAAP-148 and OP-145 are novel synthetic derivatives)

C205H340N60O53

4,493.26 Da

Short systemic half-life (minutes) due to protease susceptibility; local tissue persistence at wound sites is longer due to binding to extracellular matrix components and lipid membranes

Topical application achieves high local wound-bed concentrations; systemic bioavailability limited by rapid proteolytic degradation and serum protein binding; not intended for oral delivery

154947-66-7

Protocols

Dosingtiers

standard

0.5 mg/mL drops (about 100 microliters per application)

Twice daily

2 weeks

In a human phase 2a ear study, OP-145 drops at 0.5 mg per mL were applied to the affected ear twice daily for 2 weeks and were safe and well tolerated [4].

starting

0.5 mg/mL gel

Twice weekly

4 weeks

Lowest dose in the LL-37 (ropocamptide) Phase I/IIa venous leg-ulcer trial and the most effective: ~6-fold faster healing and ~68% ulcer-area reduction vs placebo, applied to the wound twice weekly [4].

1.6 mg/mL gel

Mid dose in the same trial; ~3-fold improvement and ~50% area reduction vs placebo. The highest tested concentration (3.2 mg/mL) showed no benefit over placebo, so dose escalation above this is not supported [4].

Applications

Bestsuited for

Research into next-generation antimicrobials against multidrug-resistant infections

Cathelicidin (hCAP-18 / Synthetic Derivatives) is particularly well-suited for individuals focused on research into next-generation antimicrobials against multidrug-resistant infections. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Topical antimicrobial development for wound infections with biofilm involvement

Cathelicidin (hCAP-18 / Synthetic Derivatives) is particularly well-suited for individuals focused on topical antimicrobial development for wound infections with biofilm involvement. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Understanding vitamin D-cathelicidin innate immune axis for immune optimization

Cathelicidin (hCAP-18 / Synthetic Derivatives) is particularly well-suited for individuals focused on understanding vitamin d-cathelicidin innate immune axis for immune optimization. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Development of anti-biofilm therapeutics for chronic device-related and wound infections

Cathelicidin (hCAP-18 / Synthetic Derivatives) is particularly well-suited for individuals focused on development of anti-biofilm therapeutics for chronic device-related and wound infections. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Treatment of chronic non-healing wounds including venous leg ulcers and diabetic ulcers

LL-37 is particularly well-suited for individuals focused on treatment of chronic non-healing wounds including venous leg ulcers and diabetic ulcers. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Immune defense against antibiotic-resistant bacterial infections (MRSA, Pseudomonas)

LL-37 is particularly well-suited for individuals focused on immune defense against antibiotic-resistant bacterial infections (mrsa, pseudomonas). Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Anti-biofilm strategies for chronic wound infections and medical device-associated infections

LL-37 is particularly well-suited for individuals focused on anti-biofilm strategies for chronic wound infections and medical device-associated infections. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Boosting innate immune defense in immunocompromised or aging individuals

LL-37 is particularly well-suited for individuals focused on boosting innate immune defense in immunocompromised or aging individuals. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Safety Profile

Sideeffects

Common

Local application site irritation

Local inflammatory response

Mild wound exudate increase

Uncommon

Localized urticaria

Transient pain at injection site

Serious

Hemolytic activity at supratherapeutic doses

Local site irritation

Transient stinging or burning

Mild perilesional erythema

Increased wound exudate

Allergic contact reaction

Hemolytic activity at systemic concentrations

Research Status

Safety& evidence

FDA Status

Research compound

Safety Overview

Cathelicidin peptides (natural and synthetic) are not FDA-approved and have no completed human clinical trials. Animal studies demonstrate broad-spectrum antimicrobial activity without systemic toxicity at therapeutic concentrations. However, concern exists regarding immunological tolerance—cathelicidin derivatives can trigger innate immune activation and inflammatory responses at high concentrations. The peptide's mechanism on immune cells is incompletely understood in humans, and effects on chronic immune signaling, tolerance development, or off-target immune activation remain uncharacterized. Bacterial resistance development to cathelicidin-based therapeutics is theoretically possible but not yet documented clinically.

Contraindications

xKnown hypersensitivity to cathelicidin-derived peptides or formulation components

xPregnancy and breastfeeding — insufficient reproductive safety data for synthetic derivatives

xActive autoimmune conditions involving cathelicidin dysregulation (e.g., rosacea, psoriasis) — exogenous cathelicidin peptides may exacerbate inflammation

xSevere systemic immunodeficiency without medical supervision — immune modulation effects may be unpredictable

LL-37 is an endogenous cathelicidin antimicrobial peptide naturally produced by immune cells and epithelial tissues, conferring inherent biocompatibility and low toxicity at physiological concentrations. Synthetic LL-37 shows excellent safety in in vitro immune assays and animal models with no hepatotoxicity, nephrotoxicity, or genotoxicity at relevant doses. At elevated concentrations, the cationic amphipathic structure can cause hemolysis and cell membrane damage, but therapeutic doses are far below these thresholds. Injection site reactions are minimal in research applications.

xKnown hypersensitivity to cathelicidin peptides or formulation components

xActive hemolytic conditions — LL-37 demonstrates concentration-dependent hemolytic activity

xPregnancy and breastfeeding — insufficient reproductive safety data from clinical trials

xSevere renal impairment — peptide clearance may be altered

Decision Guide

Which isright for you?

Choose Cathelicidin (hCAP-18 / Synthetic Derivatives) if...