Cathelicidin LL-37, hCAP-18 fragment, ropocamptide
The only cathelicidin humans make: a 37-amino-acid peptide cut from a larger protein (hCAP-18) in white blood cells and skin. It kills bacteria and other microbes, signals immune cells and takes part in wound repair.
Category 2 is FDA’s list of bulk substances that may present significant safety risks in compounding. The 503A bulks list adds substances that pharmacies may compound with. Advisory committee votes are advice; FDA makes the final decision. Sport status follows the WADA Prohibited List in force since January 1, 2026; athletes should confirm with their anti-doping organization. Checked October 5, 2026. Status of every compound.
LL-37 is the 37-amino-acid peptide cut from hCAP-18, the only cathelicidin humans make. It breaks up the outer membranes of bacteria, and in cell and animal work it also signals through FPR2, a receptor on immune cells and blood vessel lining, drawing cells into a wound and prompting new vessels. The same signaling, when skin levels run high, is tied to the inflammation of rosacea and psoriasis.
AnimalMainly from cell and animal studies; not shown in people.
No human study has measured what it does inside the body: the trials put it on ulcers or into tumors. Its effects on healthy tissue, and over time, are unknown.
Grönberg 2014
Applied to venous leg ulcers twice weekly for 4 weeks at 0.5, 1.6 or 3.2 mg/mL; 0.5 mg/mL did best and 3.2 mg/mL no better than placebo.
HEAL LL-37, 2021
Phase 2b: 0.5 or 1.6 mg/mL on leg ulcers, with compression bandaging; no benefit over placebo overall.
NCT02225366
Injected into melanoma skin tumors at 250–500 mcg per tumor weekly, for up to 8 weeks (3 patients treated).
No set cycle, shown over 26 weeks
The ways LL-37 is most often run, each tagged with where it comes from.
34 people. Healing rate about 6× placebo at 0.5 mg/mL and 3× at 1.6 mg/mL; the Phase 2b follow-up in 148 people didn’t confirm a benefit overall.
New healing tissue (granulation) grew more than with placebo, but bacteria counts and inflammation markers didn’t fall more (Miranda 2023).
Early dose-finding study. Only 3 patients were treated and one stopped for lack of benefit; results exist only on the trial registry.
Trials applied it directly to cleaned ulcers or injected it into skin tumors. Community use is injection under the skin, rotating sites.
No published guidance. Skip the missed dose and resume the usual schedule; don’t double up.
Mean ulcer area fell 68% at 0.5 mg/mL and 50% at 1.6 mg/mL, with healing rates about 6× and 3× placebo (Grönberg 2014, 34 people).
TrialIn 148 people, healing was no better than placebo overall; a later analysis found benefit only in large ulcers (10 cm² or more).
TrialGranulation tissue grew more than with placebo at every weekly check (p=0.006–0.037).
TrialNo local or whole-body safety concerns in the ulcer trials (2014, 2021)
These trials put it on wounds; injected use hasn’t been studied for safety.
Possible immune reaction to injected peptide (FDA concern)
Stop and get care for hives, swelling or trouble breathing.
Skin flare in rosacea or psoriasis (theoretical: high LL-37 levels are linked to both)
Stop if a rash or flare appears.
Injection-site redness or soreness (any injected peptide)
Rotate sites. Spreading redness, heat or pus needs medical care.
Hives, face or throat swelling or trouble breathing; fever with a hot, spreading red injection site; or a new or changing skin lump.
No product label covers LL-37, so these come from human studies and from precautions based on how it works. Most important first.
Trial: seen in human studies, or a group those studies left out. Precaution: follows from how it works or from a related drug, and hasn’t been tested. This isn’t a complete list: a pharmacist or doctor can check a specific medicine or condition.
Usually run on its own.
4 key published human studies, with how many people took part. Animal studies aren’t listed here.
Healing was no better than placebo in the whole group; a post hoc look found significant improvement only in ulcers of 10 cm² or more. Both strengths were well tolerated.
Mahlapuu et al., Wound Repair Regen 2021, PMID 34687253
Healing-rate constants were about 6× (p=0.003) and 3× (p=0.088) placebo at 0.5 and 1.6 mg/mL, with mean ulcer area down 68% and 50%; 3.2 mg/mL did no better than placebo; no safety concerns.
Grönberg et al., Wound Repair Regen 2014, PMID 25041740
The granulation index rose more than with placebo on days 7, 14, 21 and 28 (p=0.031, 0.009, 0.006, 0.037), but IL-1α, TNF-α and bacterial counts didn’t fall more.
Miranda et al., Arch Dermatol Res 2023, PMID 37480520
Only 3 patients were treated; one stopped for lack of efficacy, no serious adverse events were reported, and the response data posted to the registry are unclear.
Posted registry results, NCT02225366
All human exposure has been local. A 34-person dose-finding trial treated leg ulcers for 4 weeks; the 148-person Phase 2b treated them for 13 weeks and found no benefit overall; a small trial treated diabetic foot ulcers; three melanoma patients had it injected into tumors. The serious events in the Phase 2b were judged unrelated to it. Nothing systemic has been measured.
| Vial | Water | Common dose | Draw | Strength | Action |
|---|---|---|---|---|---|
| 5 mg | 2 mL | – | – | 2.5 mg/mL |
Every compound side by side: the half-life chart and the storage chart.
The only cathelicidin humans make: a 37-amino-acid peptide cut from a larger protein (hCAP-18) in white blood cells and skin. It kills bacteria and other microbes, signals immune cells and takes part in wound repair.
LL-37 is the 37-amino-acid peptide cut from hCAP-18, the only cathelicidin humans make. It breaks up the outer membranes of bacteria, and in cell and animal work it also signals through FPR2, a receptor on immune cells and blood vessel lining, drawing cells into a wound and prompting new vessels. The same signaling, when skin levels run high, is tied to the inflammation of rosacea and psoriasis. No human study has measured what it does inside the body: the trials put it on ulcers or into tumors. Its effects on healthy tissue, and over time, are unknown.
Not approved as a drug in the US or EU. Nomination withdrawn, so no longer in FDA Category 2 (April 2026), and not on the July 2026 advisory committee agenda. FDA had cited possible immune reactions, too little human safety data, and lab and animal findings of harm to male reproduction and of tumor promotion in some tissues.
From human studies (Grönberg 2014): Applied to venous leg ulcers twice weekly for 4 weeks at 0.5, 1.6 or 3.2 mg/mL; 0.5 mg/mL did best and 3.2 mg/mL no better than placebo. Phase 2b: 0.5 or 1.6 mg/mL on leg ulcers, with compression bandaging; no benefit over placebo overall (HEAL LL-37, 2021). These are the amounts sources reference, not recommendations.
No product label covers LL-37, so these come from human studies and from precautions based on how it works. Anyone with cancer, or cancer within five years: The ulcer trials excluded malignant disease unless in remission five years; in lab work it makes some cancer cells grow or move, and FDA cited tumor promotion in animals. Anyone injecting it: No human study has given it by injection into the body, and FDA cited possible immune reactions and too little human safety data. Pregnancy or breastfeeding: Excluded from the ulcer trials, which required contraception or post-menopausal status, and no human safety data cover it. The “Who should avoid it” section lists 3 more groups.
Before mixing: Freezer (about −20 °C) for long-term storage. After mixing: Fridge (2–8 °C); use within about 4 weeks. This is common practice; no product label covers it.
Probably. Not named on the 2026 list. It has no approval from any health authority, so it falls under S0 (non-approved substances), banned at all times.
Yes. The human studies section lists 4 published studies. Among them, from 2021: Healing was no better than placebo in the whole group; a post hoc look found significant improvement only in ulcers of 10 cm² or more. Both strengths were well tolerated.
For the protocol details
For how it works, who should avoid it and the limits of the evidence