Not approved; the FDA flags tumor and reproduction findingsThe FDA writes that for cathelicidin LL-37, "nonclinical research findings suggest detrimental effects on male reproduction and that this drug can be protumorigenic in some tissues," and that it "lacks sufficient safety-related information … to know whether the drug would cause harm when administered to humans".[3] This page does arithmetic and reports the record; it does not suggest amounts.
What is the LL-37 peptide?
LL-37 is the active end of human cathelicidin, a protein of the innate immune system: the last 37 amino acids of hCAP18, released when the protein is cut.[16] Its name comes from its two leading leucines and its length.
- Sequence
- LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES, 37 residues (cathelicidin residues 134–170)[16]
- Formula and weight
- C205H340N60O53, 4,493 g/mol[17]
- Our engine
- C205H340N60O53, 4,493.3 g/mol average, 4,490.58 monoisotopic
- Other names
- Cathelicidin LL-37, CAP18, ropocamptide (its INN)[17]
- Peptide or protein?
- 37 amino acids, just under the 40 at which U.S. drug law would call it a protein[15]
Paste the sequence into the peptide molecular weight calculator with no modifications and the formula matches PubChem. LL-37 is one of the longest chains the calculator can handle from a plain sequence; see what are peptides for where it sits among the rest.
LL-37's FDA status
LL-37 has no approval and no orphan designation; it spent two and a half years on the FDA's Category 2 safety list before the nomination was withdrawn in April 2026, and the FDA says it still intends to consult its advisory committee about it.[1][2][4]
| Date | What happened |
|---|---|
| Sept 29, 2023 | Added to 503A Category 2, substances raising "significant safety risks"[4] |
| Apr 15, 2026 | FDA announces removal "after seven calendar days"[4] |
| Apr 22, 2026 | Removed because the nomination was withdrawn; moved to the "nominated but withdrawn" safety table[4][3] |
| Before end of Feb 2027 | FDA "intends to consult the PCAC … regarding the potential inclusion of Cathelicidin LL-37 on the 503A bulks list"[4]; the meeting page lists LL-37 first on its agenda[5] |
| Oct 30, 2026 | Not covered by the HHS enforcement-discretion policy[6] |
- What the FDA wrote. Besides the tumor and male-reproduction findings, it cites immune-reaction risk "for certain routes of administration" and difficulty characterizing the ingredient.[3]
- Enforcement. A 2020 warning letter listed LL-37 among substances a pharmacy's compounded products were "not eligible" to use.[7]
- No meeting notice yet. As of November 14, 2026 no Federal Register notice has set a date, and the FDA's own meeting page says the time and location "will be scheduled in the coming months".[5]
- LL-37 is not alone on the agenda. The same meeting will consider five bulk substances.[5]
| Substance | Covered here? |
|---|---|
| Cathelicidin (LL-37) | This page |
| GHK-Cu | GHK-Cu page |
| Dihexa acetate | No page; not a measured search term here |
| Melanotan II | MT2 page |
| Mechano growth factor, pegylated (PEG-MGF) | No page; not a measured search term here |
Three of the five have pages on this site, so whatever the committee recommends, the legal status page and the status table will change on the day the minutes appear.
A withdrawn nomination does not make a substance legal to compound; are peptides legal? explains why.
What the LL-37 trials found
Every human trial of LL-37 put it on the skin or into a tumor, and the largest and best-controlled one, a 148-patient phase 2b study in venous leg ulcers, found no significant benefit.[9]
| Trial | Design and people | Route | Reported |
|---|---|---|---|
| Grönberg 2014[8] | First-in-man randomized, double-blind, placebo-controlled; 34 with hard-to-heal venous leg ulcers | Topical, twice weekly for 4 weeks | Healing rate about 6 times placebo at the lowest strength (p = 0.003); the highest strength matched placebo. "No safety concerns" |
| Mahlapuu 2021 (HEAL LL-37)[9] | Phase 2b, double-blind, placebo-controlled; 148 with venous leg ulcers | Topical, with compression | No significant benefit in the full population; a post hoc signal only in wounds of 10 cm² or more. "Well tolerated and safe" |
| Miranda 2023[10] | Randomized, double-blind, controlled; mildly infected diabetic foot ulcers | Topical cream, twice weekly for 4 weeks | Better granulation on days 7–28; inflammatory markers and bacterial counts not improved |
| NCT02225366[11] | Phase 1/2 at MD Anderson; 4 enrolled | Injected into melanoma skin metastases, weekly | No serious adverse events posted; other events included squamous cell carcinoma and actinic keratosis, one each |
- The dose-response was backwards. In the first trial the lowest strength healed best and the highest matched placebo, which is why the phase 2b tested the two lower strengths.[8][9]
- A published case. A patient in the melanoma trial developed multiple wart-like, keratoacanthoma-like skin lesions about 45 days in; they cleared within two months of stopping.[12]
- Nothing systemic. No trial of LL-37 injected under the skin or into a muscle was found.[11]
Read together with the FDA's tumor note, the melanoma trial's skin findings are the part of this record a reader should weigh most carefully.[3][12] See also are peptides safe?
LL-37 and sport
WADA's 2026 list does not name LL-37.[13] It has no approval anywhere, so the S0 class for non-approved substances would appear to cover it, though WADA has not said so. From January 1, 2027, USADA says "peptides" in general are named under S0.[14] More on are peptides banned in sports?
LL-37 weight math
At 4,493 g/mol, LL-37 is the heaviest peptide on this site after cagrilintide: 1 mg is only 222.6 nmol, about a fifth as many molecules as 1 mg of a short peptide like DSIP.
| Vial + liquid | mg/mL | mcg per unit | nmol per unit | Units per 100 mcg |
|---|---|---|---|---|
| 2 mg + 1 mL | 2 | 20 | 4.45 | 5 |
| 2 mg + 2 mL | 1 | 10 | 2.23 | 10 |
| 5 mg + 1 mL | 5 | 50 | 11.13 | 2 |
| 5 mg + 2 mL | 2.5 | 25 | 5.56 | 4 |
| 10 mg + 1 mL | 10 | 100 | 22.26 | 1 |
| 10 mg + 2 mL | 5 | 50 | 11.13 | 2 |
Topical trial strengths are written as mg/mL rather than as a dose, and the arithmetic for that is the same concentration math the dosage calculator uses: milligrams divided by millilitres.
Other peptide pages
The peptides most often looked up alongside this one. Each page gives that peptide's FDA status, compounding status and published human evidence, with sources; the status table has all 23 in one place.
- BPC-157Not approved 15-amino-acid peptide. Human data: a few tiny, uncontrolled studies.
- TB-500Not approved A 7-amino-acid fragment of thymosin beta-4. No human trials of TB-500 itself.
- BPC-157 + TB-500 blendNot approved Two peptides in one vial: the arithmetic of a fixed ratio.
- GHK-CuNot approved Copper peptide. Studied on skin; injectable use has no published trials.
- KPVNot approved Lys-Pro-Val tripeptide. No human data by any route.
- TesamorelinFDA-approved Egrifta SV and Egrifta WR. Labeled doses, diluents and volumes.
Frequently asked questions
Is LL-37 FDA-approved?
What is LL-37 used for in research?
Does LL-37 work for wound healing?
What are the safety concerns with LL-37?
Sources
- openFDA Drugs@FDA searches for thymalfasin, thymosin, kisspeptin, emideltide, hexarelin, examorelin, GHRP, cathelicidin and Zadaxin (no match)
- Search orphan drug designations and approvals (thymalfasin: 4 designations; kisspeptin, hexarelin, emideltide, cathelicidin: none)
- Certain bulk drug substances for use in compounding that may present significant safety risks
- Bulk drug substances nominated for use in compounding under section 503A (category lists)
- February 2027 meeting of the Pharmacy Compounding Advisory Committee (agenda: cathelicidin LL-37, GHK-Cu, dihexa acetate, melanotan II, pegylated mechano growth factor)
- Enforcement discretion policy regarding 503A compounding using certain peptide bulk drug substances (91 FR 68526)
- Warning letter: Tailor Made Compounding LLC
- Grönberg A et al. Topical LL-37 in hard-to-heal venous leg ulcers: first-in-man RCT (Wound Repair Regen 2014;22:613–621)
- Mahlapuu M et al. HEAL LL-37: phase 2b RCT of topical LL-37 in venous leg ulcers (Wound Repair Regen 2021;29:938–950)
- Miranda E et al. LL-37 cream in mildly infected diabetic foot ulcers: RCT (Arch Dermatol Res 2023;315:2623–2633)
- NCT02225366: intratumoral injections of LL37 for melanoma (phase 1/2, results posted)
- Dolkar T et al. Verrucous lesions after intratumoral LL-37 (J Cutan Pathol 2018;45:539–544)
- World Anti-Doping Code: Prohibited List 2026
- Athlete advisory: what's new on the 2027 WADA Prohibited List
- 21 CFR 600.3(h)(6): definition of a protein
- UniProt P49913: cathelicidin antimicrobial peptide (LL-37 = residues 134–170)
- PubChem CID 16198951: LL-37 (ropocamptide)