LL-37: Legal Status, Studies and Safety

Legal status of LL-37

Under FDA review

LL-37 is waiting for an FDA advisory committee review planned before the end of February 2027 ^{[13] [3]}. Until FDA acts, it cannot be legally compounded ^[9].

FDA status

FDA removed it from Category 2 in April 2026 because the nominators withdrew their nominations ^[7]. That removal did not make it legal to compound ^[9]. FDA now lists it as "nominated but withdrawn," which is outside every category ^[4]. It is not in Category 1 and is not on the 503A bulks list, so a 503A pharmacy may not lawfully compound it today ^[1]. FDA says it has too little safety information, and nonclinical findings suggest harm to male reproduction ^[4].

Advisory committee

Not yet reviewed. It is one of five peptides FDA plans to bring to the committee: GHK-Cu, LL-37, dihexa, Melanotan II and PEG-MGF ^[13]. That review is expected before the end of February 2027 ^{[13] [3]}. No date had been set as of Oct 16, 2026 ^[3].

FDA-approved products

None. We found no FDA-approved drug that contains LL-37.

Sports (WADA)

LL-37 is not named on the 2026 list ^[11]. The list's S0 class covers substances with no approval by any government health authority for human use ^[11]. Whether that class covers LL-37 is a judgment call, so athletes should ask their anti-doping agency before use.

What happens next

FDA plans to bring it to its Pharmacy Compounding Advisory Committee before the end of February 2027, according to law firm reports ^{[13] [3]}. No meeting date had been set as of Oct 16, 2026 ^[3]. Even a favorable vote would not be binding. FDA would still have to act through rulemaking or another formal step ^[10].

Checked against FDA sources on Oct 24, 2026. We update this box when FDA acts. Report a change: [email protected].

What LL-37 is

FDA's lists call it cathelicidin LL-37 ^[4]. Researchers who tested it on leg ulcers describe it as "the human synthetic peptide LL-37" ^[5]. Online sellers market it for immune support and healing. None of those products has been reviewed by FDA ^[1].

Where LL-37 sits with FDA

FDA put LL-37 in Category 2, its significant-safety-risk group, in September 2023 ^[6]. In April 2026, after the nominators withdrew, FDA took it out of Category 2 along with 11 other peptides ^[7]. That did not make it legal: a 503A pharmacy may compound only from ingredients with a USP or NF monograph, those in approved drugs, or those on the bulks list, and LL-37 is none of these ^{[8] [1] [9]}.

FDA's advisory committee page lists one upcoming meeting, before the end of February 2027, on LL-37, GHK-Cu, dihexa acetate, Melanotan II and PEG-MGF ^[2]. Even a favorable vote there would be nonbinding; FDA would then need a rule, a Category 1 listing or enforcement discretion ^[10]. For the six peptides that won votes in July 2026, FDA had taken none of those steps by mid-October ^[3].

One small human trial, on leg ulcers

The human study we found is a 2014 first-in-human trial by Grönberg and colleagues in 34 people with hard-to-heal venous leg ulcers ^[5]. LL-37 was applied to the wound, not injected. After a placebo run-in, people got one of three strengths or placebo for four weeks ^[5]. The two lower strengths were reported to heal faster than placebo; the highest strength showed no difference from placebo ^[5]. The authors reported no local or whole-body safety concerns ^[5].

That is one small, short trial of a skin treatment. It says nothing about injecting LL-37 for immunity or infections. For another peptide sold for immune support, see thymosin alpha-1, which FDA advisers voted down in 2024.

FDA's male reproduction finding

On its safety page, FDA writes that "nonclinical research findings suggest detrimental effects on male reproduction" and that the safety information it has is insufficient ^[4]. Nonclinical means animal or lab work, not human data. It is still the clearest specific warning FDA has posted about LL-37, and it is one of the questions the 2027 review is likely to weigh.

Sports: not named, still a question

You will not find LL-37 on WADA's 2026 list ^[11]. Because no health authority we know of has approved it as a medicine, the open question is S0, WADA's class for non-approved substances ^[11]. Only your anti-doping organization can rule on that.

Getting LL-37 legally

"Research use only" labels do not make a product legal to use; FDA has said so in warning letters ^[12]. See our peptide FDA status tracker, the other 2027 review candidates GHK-Cu and dihexa, BPC-157, the legal peptide price tracker, FDA warning letters and wellness injections.

Dated changes for LL-37

• Apr 22, 2026: The removal took effect around this date. FDA now lists it as nominated but withdrawn, which does not allow compounding ^{[4] [9]}.
• Apr 21, 2026: A law firm report said the advisory committee will meet before the end of February 2027 to review it and four other peptides ^[13].
• Apr 15, 2026: FDA gave seven days' notice that it would remove 12 peptides, including this one, from Category 2 because the nominators withdrew ^[7].
• Sep 29, 2023: FDA placed it in Category 2, citing significant safety risks ^[6].

The other substances on FDA's February 2027 review list with their own pages: GHK-Cu, dihexa and Melanotan II. Already voted on in July 2026: TB-500 and KPV.

How we check

Two kinds of sources back this page: FDA's own lists and meeting pages, rechecked Oct 24, 2026 ^{[1] [4] [2]}, and the 2014 trial, whose abstract we read through Europe PMC because PubMed blocked our reader ^[5]. Sellers are not linked. Details of our process: editorial standards.