LL-37

Cancer Type

LL-37 Effect

Mechanism

Evidence Grade

Ovarian cancer

PRO-TUMOR

MSC (mesenchymal stem cell) recruitment via FPRL1 → tumor stroma formation; enhanced fibrovascular network; VEGF induction; tumor growth promotion. LL-37 overexpressed in ovarian tumors.

A — Coffelt et al. 2009 [6] PNAS; in vitro and in vivo; LL-37 neutralization reduces tumor growth

Breast cancer

PRO-TUMOR

EGFR transactivation → cell proliferation; invasion promotion; LL-37 overexpressed in breast tumor epithelium.

B — multiple in vitro + tumor histology studies

Lung cancer

PRO-TUMOR

Overexpressed in NSCLC; promotes invasion and angiogenesis.

B — tumor histology; cell line studies

Melanoma

PRO-TUMOR

LL-37 correlates positively with T stage (invasion depth); CXCL5/IL23A/MMP9 induction → invasion and angiogenesis. Ohuchi et al. 2023.

B — Ohuchi 2023 Cancers (correlation with T stage severity)

Prostate cancer

PRO-TUMOR

Overexpressed; knockdown reduces proliferation and invasive potential.

B — in vitro and in vivo knockdown studies

Colon cancer

ANTI-TUMOR

Apoptosis induction via mitochondrial pathway; tumor suppression. Underexpressed in colon tumors vs normal mucosa.

B — multiple in vitro and animal studies

Gastric cancer

ANTI-TUMOR

Apoptosis induction; tumor suppression; reduced expression in gastric tumors.

B — in vitro and animal models

THE ACTIVE MALIGNANCY POSITION — THE MOST NUANCED IN THIS BOOK

LL-37's cancer pharmacology requires a more nuanced position than the standard 'active malignancy = contraindication' applied to growth factors in this book. For compounds like IGF-LR3, the pro-tumor mechanism is one-directional and well-established; the contraindication is clear. For LL-37: (1) In ovarian, breast, lung, melanoma, and prostate cancers: the pro-tumor evidence is substantial — LL-37 is overexpressed in these tumors, and in vitro/in vivo studies show it promotes growth, invasion, and angiogenesis. Exogenous LL-37 in individuals with these cancers or a strong history of these cancers represents a meaningful risk. (2) In colon and gastric cancers: LL-37 shows anti-tumor activity — adding exogenous LL-37 could theoretically be beneficial (or at minimum not harmful). (3) For unknown malignancy: anyone with undetected early-stage ovarian, breast, lung, or melanoma cancer cannot be identified by available screening and might inadvertently receive pro-tumor stimulation. The practical position: active malignancy of ovarian, breast, lung, melanoma, or prostate type — do not use LL-37. Active colon or gastric cancer — the risk profile is different and requires oncologist evaluation. No active malignancy: the concern applies to theoretical subclinical pre-malignant lesions (which cannot be reliably excluded).

LL-37: 37 amino acids. Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES. N-terminal LL (Leu-Leu). MW 4.5 kDa. Net charge +6 at physiological pH (cationic — drives electrostatic attraction to negatively charged bacterial membranes). Amphipathic alpha-helical secondary structure when in contact with membranes — hydrophobic face (Leu, Ile, Phe, Val residues) and hydrophilic face (Lys, Arg residues) allow simultaneous membrane insertion and aqueous phase interaction. Derived from the C-terminus of hCAP18 (18 kDa) by proteolytic cleavage: neutrophil proteinase 3 cleaves hCAP18 to release LL-37 in neutrophil extracellular environments; skin kallikrein 5 (KLK5) cleaves hCAP18 in skin; other proteases in other tissues. The cleavage site is precisely positioned to release the active helical antimicrobial domain.

LL-37 is produced in a tissue-specific and stimulus-dependent manner. Primary producing cells: neutrophils (stored pre-formed in secondary granules; released upon activation); keratinocytes (inducible, under microbial invasion, UV exposure, and vitamin D stimulation); macrophages (both constitutive and inducible); mast cells; NK cells; mucosal epithelial cells (respiratory, GI, genitourinary tract). Inducers of LL-37 expression: (1) Vitamin D3 (1,25-dihydroxyvitamin D3 / calcitriol) — the most potent physiological inducer; VDR binding directly transcribes the CAMP gene; this is why vitamin D deficiency is associated with increased susceptibility to infection — reduced endogenous LL-37; (2) Bacterial LPS, peptidoglycan, lipoteichoic acid — PAMPs that trigger innate immune expression; (3) Tissue injury, UV radiation, wounds; (4) Short-chain fatty acids (butyrate, propionate — produced by gut microbiome). Suppressors of LL-37: (1) Certain pathogenic bacteria actively suppress LL-37 expression (Staphylococcus aureus, some Streptococci); (2) Elevated cortisol/glucocorticoids reduce expression.

The direct transcriptional regulation of LL-37 by vitamin D is one of the most clinically important regulatory relationships in innate immunology. The CAMP gene promoter contains multiple vitamin D response elements (VDREs) that bind the VDR-RXR heterodimer to directly drive hCAP18/LL-37 transcription. Population studies consistently show that individuals with lower vitamin D status have lower LL-37 levels and higher susceptibility to respiratory infections, skin infections, and chronic wound complications. Intervention studies show that vitamin D supplementation in deficient individuals significantly increases LL-37 expression and antimicrobial capacity. The practical guidance: anyone considering exogenous LL-37 for immune support should first optimize their vitamin D status — targeting serum 25-OH vitamin D ≥60 ng/mL. This approach increases endogenous LL-37 production through the natural physiological pathway, avoids the cytotoxicity threshold concerns of exogenous LL-37, and avoids the cancer risk uncertainty.

LL-37 kills bacteria through direct disruption of the bacterial membrane — a fundamentally physical-chemical mechanism that is categorically different from all conventional antibiotic mechanisms (enzyme inhibition, protein synthesis disruption, DNA replication interference). The mechanism: (1) Electrostatic attraction: LL-37's net positive charge (+6) is attracted to the negatively charged bacterial membrane surface — composed of phosphatidylglycerol, cardiolipin, and lipopolysaccharide in Gram-negative bacteria; lipoteichoic acid in Gram-positive. Mammalian cell membranes are predominantly zwitterionic (phosphatidylcholine, sphingomyelin) and are less strongly attracted, providing the selectivity window. (2) Membrane insertion and disruption: the amphipathic helix inserts into the membrane with the hydrophobic face embedded in the lipid bilayer and the hydrophilic face in the aqueous phase; this disrupts membrane integrity; pore formation and membrane leakage cause rapid cell death. (3) Additional antimicrobial activities: LL-37 can sequester intracellular targets after membrane disruption; it disrupts lipid-enveloped viruses by the same membrane mechanism.

Standard antibiotics work by inhibiting specific bacterial enzymes or protein synthesis machinery — molecular targets where a single point mutation can confer resistance. LL-37's membrane disruption mechanism targets the entire lipid bilayer rather than a single protein, making resistance development much harder: any modification of the lipid bilayer sufficient to resist LL-37 disruption would likely impair bacterial viability itself. In serial passage experiments — the standard test for resistance potential — no bacterial resistance to LL-37 has been documented after more than 30 passages. This includes MRSA, which rapidly develops resistance to conventional antibiotics. This no-resistance property is one of the most clinically significant features of LL-37 and drives interest in its potential as a template for anti-infective development.

One of LL-37's most important antimicrobial properties is its ability to prevent biofilm formation at concentrations far below those required for direct bacterial killing (minimum inhibitory concentration, MIC). Overhage et al. (2008 [5], Infection and Immunity): LL-37 prevents Pseudomonas aeruginosa biofilm formation at 0.5 μg/mL — approximately 1/128 of the MIC. LL-37 kills established S. aureus biofilm bacteria within 5 minutes; vancomycin requires days to achieve comparable reductions and often fails to eradicate established biofilm entirely. The mechanism: LL-37 disrupts the quorum-sensing signaling that bacteria use to coordinate biofilm formation; it also penetrates the extracellular polysaccharide matrix of established biofilms better than most conventional antibiotics. Chronic wound infections are predominantly biofilm-associated — this is the mechanistic basis for LL-37's clinical application in chronic wounds that fail to respond to conventional antibiotics.

Pathogen Class

Activity

Evidence

Clinical Relevance

Gram-positive bacteria (S. aureus, MRSA, S. pyogenes, Enterococcus)

Bactericidal; membrane disruption

In vitro; animal wound models

MRSA wound infections; chronic wounds

Gram-negative bacteria (P. aeruginosa, E. coli, K. pneumoniae)

Bactericidal + anti-biofilm; LPS neutralization

In vitro; animal models

Chronic wound biofilms; hospital-acquired infections

Biofilm (all types)

Prevention and disruption at sub-MIC concentrations

Overhage 2008; multiple animal wound studies

Chronic wounds; implant-associated infections

Fungi (Candida spp., dermatophytes)

Fungicidal; membrane disruption

In vitro; some animal models

Skin and wound fungal infections

Enveloped viruses (influenza, RSV, HIV)

Disrupts lipid envelope; blocks entry

In vitro; Barlow 2011 influenza model

Respiratory infection defense; skin viral protection

Bacterial LPS (endotoxin)

Sequestration/neutralization

In vitro; animal sepsis models

LPS-driven inflammation reduction

LL-37 activates FPRL1 (formyl peptide receptor-like 1, also known as FPR2) — a G-protein-coupled receptor expressed on neutrophils, monocytes, macrophages, and endothelial cells. FPRL1 activation by LL-37: stimulates neutrophil and monocyte chemotaxis (recruitment to sites of infection); activates dendritic cell maturation and antigen presentation; promotes macrophage phagocytosis; stimulates angiogenesis via VEGF induction in endothelial cells (Koczulla et al., 2003) [2]. The FPRL1-mediated chemotaxis explains how LL-37, released at sites of infection, coordinates the entire cellular arm of innate immunity — not just killing pathogens directly but recruiting the specialized immune cells needed for comprehensive defense and repair.

LL-37 has potent LPS (lipopolysaccharide) neutralizing activity. LPS — the outer membrane component of Gram-negative bacteria — is the primary trigger for the systemic inflammatory response that drives septic shock. LL-37 binds LPS with high affinity, sequestering it and preventing its interaction with TLR4 (the LPS recognition receptor) and CD14, blocking the NF-κB-mediated inflammatory cascade. This anti-LPS activity of LL-37 provides a mechanistic basis for its potential role in sepsis management. The anti-inflammatory property of LL-37 against LPS coexists with its pro-inflammatory EGFR transactivation and keratinocyte cytokine induction — context and concentration determine which predominates.

LL-37 drives multiple parallel pathways required for wound healing: (1) Re-epithelialization — LL-37 directly stimulates keratinocyte migration and proliferation, critical for wound closure; Heilborn et al. (2003) documented that LL-37 expression is upregulated in wound fluid during normal healing but is deficient in chronic, non-healing wounds — the observation that drove the clinical wound healing trials. (2) Angiogenesis — via FPRL1/VEGF signaling, LL-37 promotes new blood vessel formation to supply the healing tissue with oxygen and nutrients; Koczulla et al. (2003) demonstrated that mice deficient in the murine LL-37 analog (mCRAMP) showed decreased neovascularization of skin lesions; rabbit hind-limb ischemia models show LL-37 stimulates collateral vessel formation. (3) Fibroblast activation — LL-37 stimulates fibroblast proliferation and extracellular matrix deposition; provides structural scaffolding for tissue repair. (4) EGFR transactivation — LL-37 transactivates the epidermal growth factor receptor (EGFR) on keratinocytes, enhancing the proliferative response that drives wound closure. These four parallel wound healing mechanisms, combined with the anti-biofilm and antimicrobial activity, explain why LL-37-deficient chronic wounds fail to heal while LL-37-supplemented wounds show dramatically accelerated closure.

LL-37 promotes adaptive immune responses beyond the innate immune mechanisms: dendritic cell maturation and antigen-presenting capacity enhancement — critical for priming antigen-specific T and B cells; neutrophil survival prolongation — LL-37 inhibits neutrophil apoptosis, extending their functional lifespan at infection sites; T-cell and B-cell chemotaxis via FPRL1; facilitating the presentation of self-DNA to plasmacytoid dendritic cells, amplifying the interferon response to viral infection. The innate-to-adaptive immune bridge function is the most sophisticated and most therapeutically relevant of LL-37's non-antimicrobial activities — and the most context-dependent.

The rosacea paradox has specific practical implications: (1) Anyone with a history of rosacea: LL-37 is specifically and mechanistically contraindicated; exogenous LL-37 adds to the already-excessive endogenous production that drives their condition. (2) Anyone with rosacea-prone phenotype (Fitzpatrick type I-II skin, frequent facial flushing, history of sun-induced facial redness): elevated concern; KLK5 activity may be constitutively elevated even in the absence of clinical rosacea. (3) Duration and dose: short-course low-dose topical LL-37 for wound healing is likely safe even in rosacea-prone individuals (the clinical context is controlled, not chronic); repeated systemic injection for general immune support is the concerning protocol.

Grönberg A, Mahlapuu M, Ståhle M, Whately-Smith C, Rollman O. (2014 [3], Wound Repair and Regeneration): the first-in-man controlled trial of LL-37. Design: n=34 patients with venous leg ulcers (VLUs) that had failed to heal with standard compression treatment; 3-week open-label placebo run-in period to establish baseline; 4-week randomized, double-blind treatment phase with twice-weekly application of topical LL-37 at 0.5, 1.6, or 3.2 mg/mL vs placebo; 4-week follow-up. Primary endpoint: wound healing rate constant (area reduction). Results: 0.5 mg/mL LL-37 achieved approximately 6-fold higher healing rate constant vs placebo (p=0.003); 1.6 mg/mL achieved approximately 3-fold higher (p=0.088); 3.2 mg/mL showed less benefit than lower doses — a dose-dependent inverted-U effect consistent with LL-37's known biphasic biology. The 6-fold healing acceleration at the lowest dose is a clinically remarkable result. Safety: no serious adverse events; well-tolerated. Grade B: n=34; DBRPC; topical; Phase II design.

The HEAL LL-37 Phase IIb trial (multicenter, prospective, randomized, placebo-controlled) enrolled a larger VLU cohort to confirm the Phase I/II findings. Published circa 2022 in PMC (Wound Repair and Regeneration). The multicenter design addressed single-center bias from the Grönberg trial. Results: positive; confirmed the direction and clinical meaningfulness of topical LL-37 for VLU healing. Grade B — larger and more rigorous than Phase I/II; multicenter; confirms the wound healing signal.

Ahadieh et al. (2023 [4], Archives of Dermatological Research): Randomized, double-blind, controlled trial of LL-37 cream for diabetic foot ulcers (DFUs) with mild infection. DFUs are characterized by near-zero LL-37 expression in wound tissue — the low-expression chronic wound context that makes LL-37 replacement mechanistically appropriate. Results: LL-37 cream significantly improved wound healing rate, reduced IL-1α and TNF-alpha inflammatory cytokines in wound fluid, and reduced aerobic bacterial colonization vs placebo. Grade B — Indonesian multicenter; specific DFU population; objective wound measurement; positive outcomes.

Indication

Grade

Best Evidence

Clinical Translation

Venous leg ulcer healing

B

Grönberg 2014 (n=34, 6x healing rate at 0.5 mg/mL, p=0.003); HEAL Phase IIb (multicenter positive)

Topical twice-weekly application; 4-week course; Phase III not yet completed

Diabetic foot ulcer healing

B

Jakarta RCT 2023; improved healing rate + reduced inflammation + reduced bacterial load

Topical cream; twice weekly; 4 weeks

MRSA/biofilm wound infection

B

Animal models; sub-MIC biofilm prevention; no resistance development

Strong preclinical; limited human controlled data for wound infection specifically

Systemic immune support

E

No controlled human trial; community use based on mechanism extrapolation

Grade E; not the tested application

Sepsis/LPS neutralization

C

LPS neutralization mechanism established; animal sepsis models positive

No completed human RCT for this indication

Topical rosacea treatment

D

Paradox — LL-37 CAUSES rosacea; research into blocking LL-37 for rosacea treatment

Contraindicated in rosacea context

LL-37 becomes cytotoxic to mammalian cells at concentrations of approximately 1-10 μM (4.5-45 μg/mL). This threshold varies by cell type: keratinocytes are the most resistant (~10 μM); red blood cells (hemolysis) are more sensitive (~1-3 μM); immune cells intermediate. The therapeutic window for wound healing applications: the clinical trials used topical concentrations of 0.5-3.2 mg/mL (approximately 110-710 μM measured as stock concentration). At the wound surface, the local concentration is diluted by wound fluid and tissue — effective local concentrations in the nanomolar to low micromolar range. The 6x superior healing at 0.5 vs lower efficacy at 3.2 mg/mL in Grönberg 2014 is consistent with the cytotoxicity threshold beginning to affect keratinocyte function at higher concentrations. For injectable systemic LL-37: the systemic concentration achievable from community-dose injection could reach or approach cytotoxic thresholds in tissues, particularly in sites with less protein-binding dilution.

LL-37 shows a biphasic dose-response for many of its activities. Low concentrations (nanomolar): pro-healing, anti-biofilm, chemotactic, anti-inflammatory (LPS sequestration dominant). Intermediate concentrations (low micromolar): maximum wound healing stimulation; antimicrobial. High concentrations (approaching cytotoxic threshold): pro-inflammatory; cytotoxic; potentially pro-tumor amplification. This biphasic profile means that more LL-37 is not better. The 0.5 mg/mL clinical trial dose outperformed 3.2 mg/mL for wound healing — a real-world demonstration that dose optimization within the therapeutic window matters. Community protocols using high-dose injectable LL-37 may be operating in the wrong part of the dose-response curve.

The clinical trial evidence for LL-37 is entirely topical — applied directly to wound surfaces where local concentrations can be controlled and the compound is not absorbed systemically in meaningful amounts. Topical LL-37 for wound healing is pharmacologically appropriate: the compound is delivered to the LL-37-deficient chronic wound environment where low endogenous LL-37 is the problem. Injectable systemic LL-37 is a completely different pharmacological intervention: the compound distributes systemically, potentially exposing LL-37-sensitive tumor cells throughout the body, reaching the skin (rosacea risk), and potentially achieving cytotoxic concentrations in some tissues. The community use of injectable LL-37 for 'immune support' does not correspond to any of the controlled clinical trial contexts and adds the cancer and rosacea risks described above. The injectable route should be approached with significantly more caution than the clinical topical use.

LL-37 is susceptible to proteolytic degradation by multiple peptidases present in tissues and body fluids. In chronic wound environments, excess protease activity (MMP-2, MMP-9, elastase) can degrade exogenous LL-37 rapidly — one of the practical challenges for topical wound healing applications. In cystic fibrosis, LL-37 is inactivated by interaction with DNA, F-actin, and mucins present in the airways — explaining reduced antimicrobial defense in CF patients despite normal production. For community injectable use, plasma proteases limit the effective half-life of circulating LL-37. Stability of reconstituted LL-37 is limited: reconstituted solution should be stored at -20°C and used promptly; repeated freeze-thaw cycles degrade the peptide.

Partially true, substantially misleading. LL-37 coordinates innate and adaptive immune responses at wound sites and mucosal surfaces — this is genuine immune function. But the systemic effects of exogenous LL-37 are not simply 'boost immunity.' It recruits immune cells, stimulates angiogenesis, activates inflammatory pathways, and — most importantly — provides pro-tumor signals in multiple cancer-relevant tissues. 'Immune booster' framing omits the most important safety information about the compound.

Endogenous does not mean safe at exogenous doses. Cortisol is endogenous — supraphysiological cortisol causes Cushing's syndrome. LL-37 is endogenous — supraphysiological LL-37 causes rosacea and may promote multiple tumor types. The endogenous status establishes that the molecule has physiological functions; it does not establish that exogenously administered LL-37 at doses or in compartments different from physiological production is safe.

The no-resistance property is genuinely important and motivates substantial pharmaceutical research into LL-37-based drug development. But LL-37 is not currently approved as an antibiotic. Its cytotoxicity threshold limits systemic antibiotic use; its cancer risk profile limits chronic systemic use. The pharmaceutical development direction is LL-37 analogs and fragments with retained antimicrobial activity but reduced cytotoxicity and eliminated pro-tumor properties. Community use of LL-37 as a systemic antibiotic alternative is pharmacologically premature.

The clinical trial evidence (Grönberg 2014; HEAL Phase IIb; Jakarta DFU) is for topical wound healing in LL-37-deficient chronic wounds. Topical application to an LL-37-deficient wound is pharmacologically rational — replacing a locally deficient signaling molecule in the tissue where it is needed. Systemic injection for general immune optimization is pharmacologically different: LL-37 is delivered to all tissues simultaneously, not to a specific LL-37-deficient wound, and the cancer and rosacea risks apply throughout. These are not equivalent applications.

Agerberth B, Charo J, Werr J et al. (2000) [1]. The human antimicrobial and chemotactic peptides LL-37 and alpha-defensins are expressed by specific lymphocyte and monocyte populations. Blood. 96(9):3086-3093. [Characterization of LL-37 expression in immune cell populations; tissue distribution.]

Koczulla AR, von Degenfeld G, Kupatt C et al. (2003). An angiogenic role for the human peptide antibiotic LL-37/hCAP-18. Journal of Clinical Investigation. 111(11):1665-1672. [The definitive angiogenesis mechanism paper; FPRL1/VEGF pathway; ischemia models; mCRAMP knockout mice.]

Grönberg A, Mahlapuu M, Ståhle M, Whately-Smith C, Rollman O. (2014). Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial. Wound Repair and Regeneration. 22(5):613-621. [n=34; DBRPC; 0.5 mg/mL: 6x healing rate, p=0.003. The landmark Phase I/II wound healing trial.]

Ahadieh S et al. (2023). Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial. Archives of Dermatological Research. PMC10514151. [DBRCT; DFU; improved healing rate + reduced IL-1α/TNF-α + reduced bacterial load; second positive RCT for LL-37 wound healing.]

Overhage J, Campisano A, Bains M, Torfs EC, Rehm BH, Hancock RE. (2008). Human host defense peptide LL-37 prevents bacterial biofilm formation. Infection and Immunity. 76(9):4176-4182. PMID 18591225. [Sub-MIC biofilm prevention at 1/128 of MIC; Pseudomonas; no resistance development after 30 passages.]

Coffelt SB, Marini FC, Watson K et al. (2009). The pro-inflammatory peptide LL-37 promotes ovarian tumor progression through recruitment of multipotent mesenchymal stromal cells. Proceedings of the National Academy of Sciences USA. 106(10):3806-3811. PMC2656161. [The foundational pro-tumor paper; MSC recruitment via FPRL1; in vivo tumor growth; LL-37 neutralization reduces tumor growth. Key ovarian cancer evidence.]

Ouhara K, Komatsuzawa H, Yamada S et al. (2005) [7]. Susceptibilities of periodontopathogenic and cariogenic bacteria to antibacterial peptides including LL-37 produced by human epithelial cells. Journal of Antimicrobial Chemotherapy. [Comprehensive antimicrobial spectrum data.]

Yamasaki K, Di Nardo A, Bardan A et al. (2007) [8]. Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea. Nature Medicine. 13(8):975-980. [The definitive rosacea mechanism paper; KLK5 overactivity → excess LL-37 → TLR-2 → rosacea inflammatory cascade.]

Gombart AF, Borregaard N, Koeffler HP. (2005) [9]. Human cathelicidin antimicrobial peptide (CAMP) gene is a direct target of the vitamin D receptor and is strongly up-regulated in myeloid cells by 1,25-dihydroxyvitamin D3. FASEB Journal. 19(9):1067-1077. [The definitive vitamin D-CAMP gene transcription paper; VDR direct binding; the mechanistic basis for vitamin D supplementation as a strategy to enhance LL-37 production.]

• Topical wound healing (venous leg ulcers, diabetic foot ulcers): Grade B evidence; physician-supervised; topical application twice weekly; 0.5 mg/mL dose (most effective in trial); avoid in rosacea patients; this is the appropriate and evidence-supported application.
• Immune optimization — the correct approach: optimize vitamin D3 to achieve serum 25-OH vitamin D 60-80 ng/mL; increases endogenous LL-37 safely through physiological pathway; the evidence-based alternative to exogenous LL-37.
• Active malignancy — ovarian, breast, lung, melanoma, prostate: absolute contraindication; LL-37 is documented as pro-tumor in these histologies. No use of exogenous LL-37 without oncologist consultation.
• Rosacea or rosacea-prone skin: contraindicated for systemic/injectable use; topical wound healing applications require physician assessment.
• Systemic injectable LL-37 for immune optimization: not supported by controlled evidence; cancer and rosacea risks apply; vitamin D optimization is the safer, more evidence-supported alternative for the cathelicidin pathway.

— End of LL-37 —

THE PEPTIDE BIBLE | LL-37 | For Research & Educational Purposes Only