Cathelicidin (hCAP-18 / Synthetic Derivatives) vs LL-37
Human cationic antimicrobial protein-18 (hCAP-18) precursor and its synthetic derivative SAAP-148 — a next-generation 24-amino-acid cathelicidin-based peptide with broad-spectrum bactericidal activity against multidrug-resistant ESKAPE pathogens including MRSA biofilms, superior potency to its parent fragment LL-37, and retained efficacy under physiological salt and plasma conditions
Human cathelicidin-derived antimicrobial peptide (37 amino acids) that disrupts bacterial membranes at MIC 0.62 μM against S. aureus, neutralizes endotoxin (LPS) to prevent septic shock, and has reached Phase II clinical trials as Ropocamptide for wound healing — achieving 6-fold accelerated healing at 0.5 mg/mL in venous leg ulcers
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Cathelicidin (hCAP-18 / Synthetic Derivatives)
0.5–0.5 mg/mL
LL-37
1.6–1.6 mg/mL
Frequency
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Once daily
LL-37
Once daily
Administration
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Topical application (primary research route)
LL-37
Topical application (wound healing)
Cycle length
Cathelicidin (hCAP-18 / Synthetic Derivatives)
4-6 weeks
LL-37
12+ weeks
Onset speed
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Rapid (hours to days)
LL-37
Moderate (1-2 weeks)
Evidence level
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Moderate human trials (Phase 1-2)
LL-37
Moderate human trials (Phase 1-2)
Benefit ratings
Antibiotic-Resistant Infections
Biofilm Destruction
Immune System Support
Wound Healing
Fighting Infections
Immune Boost
Compound specifications
Cathelicidin (hCAP-18 / Synthetic Derivatives)
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)
LL-37
Molecular formula
C205H340N60O53
Molecular weight
4,493.26 Da
Half-life
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
Bioavailability
Topical application achieves high local wound-bed concentrations; systemic bioavailability limited by rapid proteolytic degradation and serum protein binding; not intended for oral delivery
CAS number
154947-66-7
Dosing compared
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Topical
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].
LL-37
Topical
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
Twice weekly · 4 weeks
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].
Best suited for
Cathelicidin (hCAP-18 / Synthetic Derivatives)
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.
LL-37
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.
Side effects
Cathelicidin (hCAP-18 / Synthetic Derivatives)
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
LL-37
Common
- Local site irritation
- Transient stinging or burning
- Mild perilesional erythema
- Increased wound exudate
Uncommon
- Allergic contact reaction
Serious
- Hemolytic activity at systemic concentrations
Safety & evidence
Cathelicidin (hCAP-18 / Synthetic Derivatives)
Evidence level
Moderate human trials (Phase 1-2)
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
- Known hypersensitivity to cathelicidin-derived peptides or formulation components
- Pregnancy and breastfeeding — insufficient reproductive safety data for synthetic derivatives
- Active autoimmune conditions involving cathelicidin dysregulation (e.g., rosacea, psoriasis) — exogenous cathelicidin peptides may exacerbate inflammation
- Severe systemic immunodeficiency without medical supervision — immune modulation effects may be unpredictable
LL-37
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
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.
Contraindications
- Known hypersensitivity to cathelicidin peptides or formulation components
- Active hemolytic conditions — LL-37 demonstrates concentration-dependent hemolytic activity
- Pregnancy and breastfeeding — insufficient reproductive safety data from clinical trials
- Severe renal impairment — peptide clearance may be altered
Which is right for you?
Choose Cathelicidin (hCAP-18 / Synthetic Derivatives) if...
- Research into next-generation antimicrobials against multidrug-resistant infections
- Topical antimicrobial development for wound infections with biofilm involvement
- Understanding vitamin D-cathelicidin innate immune axis for immune optimization
- Development of anti-biofilm therapeutics for chronic device-related and wound infections
Choose LL-37 if...
- Treatment of chronic non-healing wounds including venous leg ulcers and diabetic ulcers
- Immune defense against antibiotic-resistant bacterial infections (MRSA, Pseudomonas)
- Anti-biofilm strategies for chronic wound infections and medical device-associated infections
- Boosting innate immune defense in immunocompromised or aging individuals