LL-37
What do these badges mean?
Evidence tier
- AHuman-validated — Human trials showing positive results and good safety.
- BAnimal-grade — No human trials yet, but solid animal/preclinical evidence of effect and safety.
- CAnecdotal — No human or animal trials — only anecdotal/observational reports.
- DInsufficient evidence — No or insufficient evidence (encyclopedia only — never recommended by the builder).
Safety light
- 🟢 Green — Only mild, manageable side effects; reasonable safety data.
- 🟡 Yellow — Needs active management, has a meaningful contraindication/interaction, or has thin long-term data.
- 🔴 Red — Risk of a hospital-level event — treat with serious caution.
Browse-only — not on the protocol builder's curated shortlist, so the builder won't recommend it.
What is it?
LL-37 is the body’s own broad-spectrum antibiotic peptide. It’s a 37-amino-acid fragment cleaved from a precursor protein (hCAP18) that your neutrophils, macrophages, and epithelial cells release when they detect infection or injury. Synthetic LL-37 is the exogenous version people inject to lean on that system harder — usually for chronic, biofilm-driven infections that have outlasted standard antibiotics.
OHM groups LL-37 alongside KPV and VIP as part of the same “calm the inflammatory fire, support host defense, restore tissue” theme, approached from three different routes — LL-37 through direct antimicrobial and biofilm-disrupting action, KPV through NF-κB inhibition, and VIP through neuroimmune restoration. LL-37 is not currently in Alyve’s catalog — it’s a roadmap candidate for the chronic-infection/biofilm cluster, and its primary OHM-verified vendor is US Pure Peptides.
What does it do in my body?
LL-37 hits three jobs at once:
- Direct antimicrobial. Disrupts microbial membranes through its cationic / amphipathic structure → rapid kill of gram-positive and gram-negative bacteria, fungi, and some enveloped viruses.
- Biofilm disruption. Breaks apart the protective polysaccharide matrices bacteria use to form chronic, drug-resistant colonies. This is the rationale behind the chronic-Lyme, chronic-UTI, and chronic-sinusitis use cases — antibiotics can’t reach what’s inside a biofilm; LL-37 cracks the biofilm open.
- Immunomodulation. Recruits and activates immune cells, modulates cytokine signaling, and supports re-epithelialization at wound sites.
How can it help me?
- Best fit: Chronic biofilm-driven infections (Lyme, chronic UTI, chronic sinusitis), SIBO/gut dysbiosis clearance, wound healing
- Where the science stands: Strong in-vitro antimicrobial + anti-biofilm record; zero completed human clinical trials for any indication
The full evidence — every human, animal, and lab study, graded — is one tap away: use the See the deeper science → toggle at the top.
Is it dangerous? What are the side effects?
- Mild injection-site irritation; some users report flu-like symptoms shortly after injection (consistent with brief immune activation).
- Autoimmune flare in susceptible individuals — the standout caution.
- No documented organ toxicity in standard usage.
Regulatory status: Not FDA-approved for any indication. Sold as a research chemical. Not on a major sport-doping prohibited list as of mid-2026.
PCAC review July 23-24, 2026: LL-37 is one of 12 peptides going before the FDA’s Pharmacy Compounding Advisory Committee for 503A Bulk Drug Substances re-evaluation. A positive recommendation would open compounding-pharmacy access under physician prescription — a meaningful access change, but distinct from full FDA drug approval.
Typical dosing
Talk to your medical provider before starting any protocol. That said, here are the doses most people commonly use — shared for educational purposes so you can have an informed conversation. These peptides are sold for research use only and are not FDA-approved drugs, and this isn't medical advice.
- Dose (community range): 100–300 mcg/day subcutaneous. There is no validated trial dose for any indication.
- Route: subcutaneous.
- Cycle: not standardized in the literature; most users cycle 4–6 weeks on, then re-assess.
- Hard contraindication: active autoimmune disease (especially psoriasis or SLE) given the autoantigen signal.
The selectivity case for LL-37 over antibiotics. Standard antibiotics work like a blunt instrument — they kill everything indiscriminately, which is exactly why a course of antibiotics so often leaves gut dysbiosis behind: the bacteria a person actually needs get wiped out right alongside the ones causing the problem. LL-37 instead recruits and directs the immune system to modulate the microbial environment — a fundamentally different mode of action from a pharmaceutical antibiotic. This selectivity is the driving rationale behind LL-37’s SIBO and biofilm use cases.
The 3-step SIBO sequencing rule: LL-37 is not the first move. The protocol order matters:
- Get the inflammation under control (KPV does the heavy lifting here).
- Repair the gut lining (BPC-157 oral; see BPC-157).
- THEN add LL-37 to clear what’s actually driving the dysbiosis.
PCAC review July 23-24, 2026. LL-37 is one of 12 peptides going to the FDA’s Pharmacy Compounding Advisory Committee for 503A re-evaluation. The same “significant safety risk” filing language applies across the group, but the underlying concern for LL-37 specifically is speculative rather than evidence-driven. A positive vote would restore 503A compounding access; it would not constitute full FDA drug approval.
What should I avoid combining — and what's synergistic?
The comprehensive gut stack: LL-37 + KPV + larazotide (synthetic octapeptide AT-1001, a zonulin antagonist that tightens tight junctions; not currently an Alyve SKU — education-layer cross-link) running together delivers inflammation shutdown, tight-junction repair, and selective bacterial clearance all at the same time. For patients who’ve been through rounds of antibiotics and still can’t get their gut right, this layered protocol is reported to move the needle.
How can I buy this?
LL-37 is available from US Pure Peptides — use code OHM20 for 20% off. US-manufactured, ISO 17025-accredited third-party COA testing on every batch, free bacteriostatic water included.
LL-37 is also available from BioLongevity Labs — use code OHM-15 at BioLongevity for 15% off. As always, buy only from a source that publishes third-party Certificates of Analysis (COAs) confirming identity and >99% purity.
When you use my coupon code to buy peptides with these sellers, you enjoy a discount off retail price, and I make a small commission which helps me to continue to offer this peptide educational site to you for free. I only have affiliate relationships with peptide manufacturers that show evidence that their peptides are 100% manufactured in the US, 3rd party lab tested for purity, transparent COAs posted on their websites, and that have good customer service.
LL-37 is the human body’s own broad-spectrum antimicrobial peptide — a 37-amino-acid fragment your neutrophils and epithelial cells release on infection or injury. Synthetic LL-37 leans on that same defense system harder, mainly for chronic, biofilm-driven infections that have outlasted standard antibiotics. The in-vitro case is well-documented; there is no completed human clinical trial for any indication yet.
| Class | 37-amino-acid cathelicidin — a host-defense antimicrobial peptide (AMP), cleaved from the precursor protein hCAP18 |
| Mechanism (one line) | Disrupts microbial membranes, breaks apart bacterial biofilms, and modulates innate immunity |
| Route / frequency | Subcutaneous — 100–300 mcg/day (community range; no validated trial dose exists) |
| Evidence base | Strong in-vitro antimicrobial + anti-biofilm record; zero completed human clinical trials for any indication |
| Safety record | Generally well-tolerated (mild injection-site irritation, occasional flu-like symptoms); the one real caution is a documented autoantigen role in psoriasis/lupus |
| Regulatory status | Not FDA-approved; sold as a research chemical. Under FDA PCAC 503A-compounding review, July 23-24, 2026 |
| Where to buy | US Pure Peptides (5mg vial, ISO 17025-accredited COA) — use code OHM20 for 20% off. Not in Alyve’s catalog; USP is the primary OHM-verified source |
| Best-fit use | Chronic biofilm-driven infections (Lyme, chronic UTI, chronic sinusitis), SIBO/gut dysbiosis clearance, wound healing |
What it is
LL-37 is the body’s own broad-spectrum antibiotic peptide. It’s a 37-amino-acid fragment cleaved from a precursor protein (hCAP18) that your neutrophils, macrophages, and epithelial cells release when they detect infection or injury. Synthetic LL-37 is the exogenous version people inject to lean on that system harder — usually for chronic, biofilm-driven infections that have outlasted standard antibiotics.
OHM groups LL-37 alongside KPV and VIP as part of the same “calm the inflammatory fire, support host defense, restore tissue” theme, approached from three different routes — LL-37 through direct antimicrobial and biofilm-disrupting action, KPV through NF-κB inhibition, and VIP through neuroimmune restoration. LL-37 is not currently in Alyve’s catalog — it’s a roadmap candidate for the chronic-infection/biofilm cluster, and its primary OHM-verified vendor is US Pure Peptides.
How it works
LL-37 hits three jobs at once:
- Direct antimicrobial. Disrupts microbial membranes through its cationic / amphipathic structure → rapid kill of gram-positive and gram-negative bacteria, fungi, and some enveloped viruses.
- Biofilm disruption. Breaks apart the protective polysaccharide matrices bacteria use to form chronic, drug-resistant colonies. This is the rationale behind the chronic-Lyme, chronic-UTI, and chronic-sinusitis use cases — antibiotics can’t reach what’s inside a biofilm; LL-37 cracks the biofilm open.
- Immunomodulation. Recruits and activates immune cells, modulates cytokine signaling, and supports re-epithelialization at wound sites.
What the research shows
Borrelia / Lyme specific:
- Lusitani 2002 — LL-37 inhibits Borrelia burgdorferi growth in vitro.
- Flad 2009 — bacterial resistance observed at higher concentrations (300–500 µg/mL), a dose-ceiling signal.
- Eckard & Wood 2016 — synergy with tinidazole against Borrelia cystic forms in vitro.
Broader infectious disease:
- 2013 NCBI review (PMC3699762) — LL-37 evaluated as treatment for polymicrobial infected wounds. Documented antimicrobial activity vs. MRSA, E. coli, Pseudomonas, Candida, HSV, influenza in preclinical work.
The autoimmune signal:
- Kahlenberg & Kaplan 2013 documented LL-37 acting as an autoantigen in psoriasis and lupus literature. This is the one place LL-37 needs to be treated with respect — for someone with active psoriasis, SLE, or another LL-37-implicated autoimmune condition, exogenous LL-37 can plausibly drive a flare. The mechanism is real (LL-37/DNA complexes activate plasmacytoid dendritic cells in psoriasis); the magnitude of risk from injected exogenous LL-37 in autoimmune patients is not formally quantified.
Where the data stops: there are no completed human clinical trials for Lyme or any other indication. The anti-biofilm story is well-documented in vitro across other microbes; the human-translation step is what’s missing. That’s an honest read of the evidence — not a dismissal of the molecule, just a clear picture of where the science currently sits for a peptide most users learn about through chronic-Lyme communities rather than peer-reviewed RCTs.
Where experts disagree. The chronic-Lyme practitioner community treats LL-37’s biofilm-disruption mechanism as a strong reason to use it; mainstream infectious-disease medicine treats the absence of human Borrelia trials as a reason not to. Both camps are looking at the same in-vitro Borrelia data — the disagreement is about how far to extrapolate. The honest read: the mechanism is real, the in-vitro effect is documented, and human translation hasn’t been formally tested.
Real-world protocol
The doses and schedules here are for educational and informational purposes only. These peptides are sold for research use only and are not FDA-approved drugs. This is not medical advice. Consult a qualified physician before beginning any protocol.
- Dose (community range): 100–300 mcg/day subcutaneous. There is no validated trial dose for any indication.
- Route: subcutaneous.
- Cycle: not standardized in the literature; most users cycle 4–6 weeks on, then re-assess.
- Hard contraindication: active autoimmune disease (especially psoriasis or SLE) given the autoantigen signal.
The selectivity case for LL-37 over antibiotics. Standard antibiotics work like a blunt instrument — they kill everything indiscriminately, which is exactly why a course of antibiotics so often leaves gut dysbiosis behind: the bacteria a person actually needs get wiped out right alongside the ones causing the problem. LL-37 instead recruits and directs the immune system to modulate the microbial environment — a fundamentally different mode of action from a pharmaceutical antibiotic. This selectivity is the driving rationale behind LL-37’s SIBO and biofilm use cases.
The 3-step SIBO sequencing rule: LL-37 is not the first move. The protocol order matters:
- Get the inflammation under control (KPV does the heavy lifting here).
- Repair the gut lining (BPC-157 oral; see BPC-157).
- THEN add LL-37 to clear what’s actually driving the dysbiosis.
The comprehensive gut stack: LL-37 + KPV + larazotide (synthetic octapeptide AT-1001, a zonulin antagonist that tightens tight junctions; not currently an Alyve SKU — education-layer cross-link) running together delivers inflammation shutdown, tight-junction repair, and selective bacterial clearance all at the same time. For patients who’ve been through rounds of antibiotics and still can’t get their gut right, this layered protocol is reported to move the needle.
PCAC review July 23-24, 2026. LL-37 is one of 12 peptides going to the FDA’s Pharmacy Compounding Advisory Committee for 503A re-evaluation. The same “significant safety risk” filing language applies across the group, but the underlying concern for LL-37 specifically is speculative rather than evidence-driven. A positive vote would restore 503A compounding access; it would not constitute full FDA drug approval.
Side effects & management
- Mild injection-site irritation; some users report flu-like symptoms shortly after injection (consistent with brief immune activation).
- Autoimmune flare in susceptible individuals — the standout caution.
- No documented organ toxicity in standard usage.
Regulatory status
Not FDA-approved for any indication. Sold as a research chemical. Not on a major sport-doping prohibited list as of mid-2026.
PCAC review July 23-24, 2026: LL-37 is one of 12 peptides going before the FDA’s Pharmacy Compounding Advisory Committee for 503A Bulk Drug Substances re-evaluation. A positive recommendation would open compounding-pharmacy access under physician prescription — a meaningful access change, but distinct from full FDA drug approval.
Technical & analytical reference (chemistry & QC)
Verified identity values (PubChem / CAS; identity confirmed, not from the analytical capture).
| Field | Value |
|---|---|
| Molecular formula | C205H340N60O53 |
| Average MW | 4493.33 |
| CAS | 154947-66-7 |
| Sequence | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (37-mer cathelicidin) |
| PubChem CID | 16198951 |
Notable analytical / QC detail:
- Pathogen MIC profile (from capture): documented antimicrobial activity / minimum inhibitory concentrations against gram-positive and gram-negative bacteria, fungi (e.g. Candida), and some enveloped viruses; bacterial resistance has been observed at higher concentrations (a dose-ceiling signal).
- Vitamin-D / CAMP-gene axis (from capture): LL-37 is the product of the cathelicidin antimicrobial peptide gene (CAMP), whose expression is upregulated by 1,25-dihydroxyvitamin D — the vitamin-D → CAMP → LL-37 innate-immunity axis.
- QC: identity by HPLC-UV purity + LC-MS mass confirmation against the 4493.33 average mass; a 37-mer cationic amphipathic peptide, commonly synthesized as the acetate/TFA salt.
Citation leads (PeptideBiologix; until confirmed): PeptideBiologix analytical page for LL-37 (raw capture ) — pathogen-MIC table + vitamin-D/CAMP-gene axis + method detail; identity values above are from PubChem/CAS, not the capture.
Sources
- the source digest behind this article (originally built into
wiki/immune-cluster-ll37-kpv-vip.md, since split into standalone compound articles). - cluster-level grading baseline.
- analytical/QC capture (pathogen-MIC table, vitamin-D/CAMP-gene axis).
- Primary literature anchors: Lusitani 2002 (LL-37/Borrelia); Flad 2009 (dose-ceiling resistance); Eckard & Wood 2016 (Borrelia cystic-form synergy with tinidazole); Kahlenberg & Kaplan 2013 (LL-37 autoantigen); PMC3699762 (LL-37 polymicrobial wounds review).
Sources & references
- the source digest behind this article (originally built into
wiki/immune-cluster-ll37-kpv-vip.md, since split into standalone compound articles). - cluster-level grading baseline.
- analytical/QC capture (pathogen-MIC table, vitamin-D/CAMP-gene axis).
- Primary literature anchors: Lusitani 2002 (LL-37/Borrelia); Flad 2009 (dose-ceiling resistance); Eckard & Wood 2016 (Borrelia cystic-form synergy with tinidazole); Kahlenberg & Kaplan 2013 (LL-37 autoantigen); PMC3699762 (LL-37 polymicrobial wounds review).