LL-37

What is LL-37?

LL-37 is a 37-amino-acid peptide and the only cathelicidin produced by the human body. It is released from a larger precursor protein, hCAP18 — the product of the CAMP gene — and takes its name from the two leucine residues at the start of its sequence. It is made by neutrophils, epithelial cells, and other tissues as part of the body's first line of defense against infection.

As a host-defense peptide, LL-37 does two jobs at once: it can kill microbes directly and it helps orchestrate the immune and repair response around a wound. It is not an FDA-approved drug. In the United States it is available only as a pharmacy-compounded preparation under physician supervision, and its clinical use is best described as investigational — the mechanistic rationale is strong, but published human data remain limited.

How LL-37 works

LL-37's direct antimicrobial action comes from its structure: it is a cationic, amphipathic peptide that is drawn to the negatively charged membranes of bacteria, fungi, and some enveloped viruses, where it inserts and disrupts the membrane, killing the microbe. This broad, membrane-level mechanism is one reason resistance to it is uncommon.

Beyond killing microbes, LL-37 acts as a signaling molecule. It recruits immune cells (chemotaxis), promotes angiogenesis — the growth of new blood vessels — and drives re-epithelialization and closure at a wound site [3][4]. Importantly, its immunomodulatory role is genuinely dual: depending on concentration and context it can either dampen or amplify inflammation. That same versatility means dysregulated LL-37 has been implicated in inflammatory skin and autoimmune conditions such as rosacea, psoriasis, and lupus — a nuance we take seriously rather than gloss over [2].

What LL-37 is used for

What the evidence shows

LL-37 is one of the most thoroughly characterized human antimicrobial peptides at the laboratory level. Its structure, membrane-disrupting mechanism, and broad activity against microbes are well established, as is its identity as the sole human cathelicidin [1][2].

Preclinical and cell-based work supports a role in healing: LL-37 promotes angiogenesis in vivo and accelerates wound closure and re-epithelialization in laboratory and animal models [3][4]. Reduced LL-37 levels have been observed in chronic wounds, which is part of the rationale for studying it therapeutically.

What is missing is the same thing missing for most compounded peptides: large, well-controlled human trials establishing efficacy and long-term safety for the uses patients ask about. LL-37 also carries a genuine two-sided story — the very activity that makes it a host-defense and repair peptide has been tied to inflammatory and autoimmune disease when it is dysregulated. We present both sides honestly, because the science does.

Dosing & administration context

In clinical use, LL-37 is typically administered by subcutaneous injection, with the specific dose expressed in micrograms and the schedule set as a short, monitored course. Because it is a compounded preparation and human dosing standards are not established by regulatory approval, protocols vary and are individualized.

The dose, route, frequency, and duration are decisions for the prescribing physician based on your goals, history, and response — which is why we frame this as clinical context rather than a self-dosing guide. LL-37 sourced outside a licensed pharmacy (research-only vials, gray-market powders) offers no assurance of identity, purity, or sterility, and given this peptide's inflammatory potential that uncertainty matters more, not less.

LL-37 is not an FDA-approved medication, and its therapeutic use is investigational. Content on this page is clinical context for physician-supervised, pharmacy-compounded use — not a dosing guide or a substitute for medical advice.

Safety & side effects

Human safety data for therapeutic LL-37 are limited, so we take a conservative posture. The most specific consideration is its dual immunomodulatory nature: because dysregulated LL-37 has been associated with inflammatory skin and autoimmune conditions, we screen for those histories before prescribing and monitor closely during a course.

As with any injected peptide, local injection-site reactions are the most common expected effect. The overarching safety principle is source control — a preparation from a licensed 503A or 503B compounding pharmacy is a fundamentally different risk profile than a research vial of unknown origin.

How Strong Health prescribes LL-37

At Strong Health, LL-37 is prescribed only after a physician evaluation that includes a careful review of your immune and inflammatory history — a step that matters more for this peptide than for most, given its links to autoimmune and inflammatory disease. It is dispensed exclusively through licensed 503A or 503B compounding pharmacies under physician orders; we do not sell or recommend research-only product.

We treat LL-37 as investigational and set expectations accordingly. Your physician defines the protocol, watches for any inflammatory response, reviews how you respond at scheduled intervals, and adjusts or stops treatment based on real outcomes rather than on the promise of the mechanism alone.

Available in person at our Miami (Brickell) clinic and via telehealth across our service areas.

Frequently asked questions