Topical trial windows
Healing was assessed over 4 weeks in the first-in-man study and 13 weeks in Phase IIb.
Protocol / Research Dosing Guide
LL-37 Dosage Guide: Topical Trial Evidence, Reconstitution and Safety
An evidence-organized LL-37 reference that keeps the published topical wound-gel trials separate from the injectable schedules circulated in research communities.
Last reviewed September 16, 202618 minute readResearch information only
Level 4 — Early human trials (topical only)No human injection trialNot FDA approved
LL-37 Quick Start
LL-37 is the only cathelicidin the human body produces. It disrupts microbial membranes and also works as an immune signal, which is why it can both defend against microbes and amplify inflammation. The important boundary on this page is route: every published human trial applied LL-37 as a gel on a venous leg ulcer. Nothing published tests it as an injection.
Why researchers care
Wound healing, antimicrobial and anti-biofilm activity, immune signaling
Class
Human cathelicidin host-defense peptide, 37 amino acids, derived from hCAP-18
Route reported
Topical gel in published human trials; subcutaneous in community reports
Cycle length
2–4 week community blocks; no validated cycle for injection
Regulatory status
Not FDA approved; the synthetic drug candidate ropocamptide completed Phase IIb
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LL-37 Dosing Protocol and Schedule
The supplied source reports a community subcutaneous structure of roughly 100–250 mcg daily, with some write-ups citing up to 500 mcg, once daily and often five days per week for a two- to four-week block. It states plainly that no human trial supports the injectable route.
| Phase or study | Amount | Frequency / evidence |
|---|---|---|
| Community starting range | 100–200 mcg per day, subcutaneous | Community reported |
| Community upper range cited | Up to 500 mcg per day | Community reported |
| Community frequency | Once daily, often five days per week | Community reported |
| Community block length | 2–4 weeks, then a break | Community reported |
| Trial concentration | 0.5 mg/mL topical gel, twice weekly | Human trial |
| Trial concentration | 1.6 mg/mL topical gel, twice weekly | Human trial |
| Rest period for injection | Not established | Not established |
The two columns of evidence do not meet. Trial figures are wound-surface concentrations applied by clinical staff; the microgram figures are informal injectable practice with no trial behind them. In the trials the lowest concentration healed best, so higher is not better here.
LL-37 Supplies Needed
Neutral research-material planning only. This does not establish an appropriate amount or route.
Research planning item
Exact labeled research vial
Research planning item
Bacteriostatic water at a measured volume
Research planning item
U-100 insulin syringes
Research planning item
Alcohol prep swabs
Research planning item
Sharps container
Research planning item
Refrigeration for the prepared vial
Research planning item
Written concentration label with the preparation date
LL-37 Reconstitution Calculator
Vial-format concentration math
Concentration
2.5 mg/mL
Draw volume
0.1 mL
U-100 units
10
Mathematical draws
20
Arithmetic only. The entered amount is not a recommendation and does not establish suitability.
Best Time to Take LL-37: Morning or Night?
Morning or evening?
Not established. No study compared times of day.
Daily or spaced?
Community write-ups describe once daily, frequently five days on and two off. Trials dosed the gel twice weekly.
With food?
Not applicable to a topical or injected product.
Missed amount?
No validated replacement procedure exists for the injectable route.
LL-37 Route Comparison
| Format | What is reported | Evidence limit |
|---|---|---|
| Topical gel | 0.5, 1.6 and (first-in-man only) 3.2 mg/mL, twice weekly on the ulcer | The only route with randomized human evidence |
| Subcutaneous | 100–500 mcg daily in community write-ups | No published human injection study |
| Oral | Not viable; digested before absorption | No exposure data |
| Route conversion | Not established | Wound-surface concentration cannot be converted into an injected amount |
Routes and amounts are not interchangeable unless a verified study explicitly establishes a conversion.
LL-37 Half-Life and Dosing Frequency
| Measure | Finding | Evidence limit |
|---|---|---|
| Human plasma half-life | Not established in the sources reviewed | Do not infer frequency |
| Local persistence in a wound | Not characterized as a published figure | Trials measured healing, not exposure |
| Solution stability | LL-37 is degraded by proteases in solution | Cold, short storage is the reported handling practice |
| Community daily frequency | Not derived from pharmacokinetics | Not established |
LL-37 Dosage Chart
| Route | Amount | Frequency | Source | Human validation |
|---|---|---|---|---|
| Topical | 0.5 mg/mL | Twice weekly | Human trial | Best healing rate reported |
| Topical | 1.6 mg/mL | Twice weekly | Human trial | Effective but below the low concentration |
| Topical | 3.2 mg/mL | Twice weekly | First-in-man only | Not carried forward |
| Subcutaneous | 100–200 mcg | Once daily | Community report | No |
| Subcutaneous | Up to 500 mcg | Once daily | Community report | No |
Published study values describe those studies. Community-reported values are not validated dosing recommendations.
LL-37 Reconstitution Guide
Concentration: 2.5 mg/mL
| Entered amount | Volume | U-100 units |
|---|---|---|
| 0.25 mg | 0.1 mL | 10 units |
| 0.5 mg | 0.2 mL | 20 units |
| 0.75 mg | 0.3 mL | 30 units |
- 1.Confirm the exact quantity printed on the vial.
- 2.Choose and record the bacteriostatic water volume. 5 mg into 2 mL gives 2.5 mg/mL.
- 3.Clean the stopper with an alcohol swab.
- 4.Add the liquid slowly down the vial wall.
- 5.Swirl gently until clear; never shake.
- 6.Inspect for cloudiness, color or particles and discard anything that is not clear.
- 7.Label the vial with the concentration and the preparation date.
- 8.Refrigerate and use within a short window, since LL-37 degrades in solution.
Reconstitution does not establish identity, purity, sterility, stability, or an appropriate amount.
How LL-37 Works
Origin
LL-37 is cleaved from the precursor protein hCAP-18 and is the only human cathelicidin.
LL-37 Human Trials and FDA Status
Current status · verified September 16, 2026
Not FDA approved; the synthetic drug candidate ropocamptide completed Phase IIb
- A 2014 first-in-man randomized study in 34 patients tested topical 0.5, 1.6 and 3.2 mg/mL against placebo twice weekly, with the best healing rate at the lowest concentration.
- The HEAL LL-37 Phase IIb study in 148 patients tested topical 0.5 and 1.6 mg/mL over 13 weeks and reported it safe and well tolerated, with improved healing of large ulcers at the low concentration.
- No published human trial has tested subcutaneous or systemic LL-37.
- The drug candidate ropocamptide has not received marketing authorization; LL-37 sold as a research peptide is a different, research-use product.
Who Should Avoid LL-37?
This is an evidence-gap and precaution list, not an approved prescribing label.
Psoriasis, lupus or rosacea
LL-37 is implicated in the disease processes described in the literature
Pregnancy or breastfeeding
No safety data
People on immune-affecting medicines
No interaction data; requires clinician oversight
History of strong reactions to injected peptides
Mast-cell activation is a known LL-37 property
Children or adolescents
No established protocol
Expectation of treating systemic infection
No human evidence supports that use
LL-37 Side Effects, Risks and Safety
Injection-site redness, swelling, burning or itchingMost commonly reported
Important limitation: Consistent with mast-cell histamine release.
Flushing or warmthReported
Important limitation: Histamine-type response.
Inflammatory flare in autoimmune skin diseaseTheoretical
Important limitation: Based on disease-association research.
Topical tolerabilityHuman trial reported
Important limitation: Applies to the gel on skin, not to injection.
Long-term injectable safetyUnknown
Important limitation: No human safety database exists for injected LL-37.
Drug interactionsUnknown
Important limitation: No interaction studies.
LL-37 Timeline and Monitoring
Injectable timeline
Not established. Any promised week-by-week injectable result is unsupported.
Monitoring focus
Injection-site condition and any skin or inflammatory change.
Stopping signal
Persistent or spreading local reactions.
LL-37 Benefits and Results: What the Evidence Shows
| Claim | Evidence level | What research shows | Important limitation |
|---|---|---|---|
| Venous leg ulcer healing | Early human research | Two randomized topical trials | Topical route only |
| Antimicrobial activity | Laboratory | Membrane disruption and anti-biofilm work | No human infection outcome |
| Immune modulation | Preclinical | Signaling research | Direction of effect is context dependent |
| Systemic infection or Lyme disease | Not established | No human-trial support | Unsupported claim |
LL-37 Storage and Handling
Lyophilized powder
Freezer storage around -20 °C is the reported long-term condition.
Prepared vial
Refrigerated at 2–8 °C and used promptly; LL-37 is susceptible to proteolytic degradation in solution.
Light
Keep the vial out of light.
Appearance
A clear, colorless solution is expected. Cloudiness or particles mean discard.
LL-37 Troubleshooting
Cloudy or particle-filled solution
Discard it. Do not use a solution that is not clear.
Strong injection-site burning
This matches LL-37 mast-cell activity. Persistent reactions are a stop signal and warrant clinical review.
Draw volume looks too large
Use a smaller water volume for a more concentrated vial, then recheck the arithmetic.
Expecting the wound-trial result from an injection
The healing evidence is topical and does not transfer to injection.
A scheduled amount is missed
No validated missed-amount procedure exists.
LL-37 Comparisons
| Compound | Class or mechanism | Evidence | FDA status |
|---|---|---|---|
| LL-37 | Human cathelicidin host-defense peptide | Topical human trials | Antimicrobial: yes |
| BPC-157 | Soft-tissue recovery interest | Primarily preclinical | Antimicrobial: no |
| TB-500 | Tissue-repair interest | Primarily preclinical | Antimicrobial: no |
| KPV | Anti-inflammatory fragment interest | Primarily laboratory/preclinical | Antimicrobial: no |
LL-37 Frequently Asked Questions
What is LL-37?
The only cathelicidin antimicrobial peptide the human body makes, a 37-amino-acid host-defense peptide cut from hCAP-18.
Is LL-37 FDA approved?
No. The topical drug candidate ropocamptide completed Phase IIb but has not been approved or marketed.
What did the human trials actually test?
A gel applied to venous leg ulcers twice weekly at 0.5 and 1.6 mg/mL, not an injection.
Is there a validated injection dose?
No. The 100–500 mcg daily figures are community reports.
Does injecting it reproduce the wound-healing results?
There is no evidence that it does. The results belong to the topical, low-concentration setup.
What is its half-life?
Not established in the sources reviewed.
Why did the lowest concentration work best?
The trials reported the strongest healing rate at 0.5 mg/mL; the reason is not established, so more is not assumed to be better.
What side effects are reported with injection?
Mostly local: redness, swelling, itching or burning, consistent with mast-cell histamine release.
Can it treat Lyme disease or chronic infection?
No human-trial evidence supports that.
What does the calculator do?
Concentration and volume arithmetic only. It does not establish a dose.
Sources and Research
Coverage source
1. LL-37 protocol coverage source
Community subcutaneous structure, reconstitution math and page coverage; not primary evidence.
Open direct sourceHuman research
2. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers
Randomized first-in-man topical study; lowest concentration healed best.
Open direct sourceHuman research
3. HEAL LL-37 Phase IIb venous leg ulcer study
148-patient randomized topical trial over 13 weeks reporting safety and healing of large ulcers.
Open direct sourceLaboratory and review
4. Cathelicidin LL-37 in host defense and inflammatory disease
Mechanism and disease-association context including psoriasis, lupus and rosacea.
Open direct sourceMissing information flagged for review
- Validated human injection dose: Not established
- Human pharmacokinetics and half-life: Not established
- Validated cycle and rest period: Not established
- Compound-specific prepared-vial stability duration: Not established
- Long-term injectable safety: Not established
- Drug interaction data: Not established