LL-37

LL-37 is a chain of 37 amino acids that the human body makes ^[14]. Amino acids are the building blocks of proteins. LL-37 is part of the skin's first defense against germs ^[14]. White blood cells and the lining of some organs make it too ^[19]. It kills some germs and also steers the immune system ^[19].

FDA calls it cathelicidin LL-37 ^[1]. It is part of no FDA-approved drug and has no official US quality standard ^[5]. A drug company has tested it as a treatment for leg sores, under the name ropocamptide ^[11]. Doctors in one US study injected it into melanoma, a skin cancer ^{[14] [15]}.

LL-37 is in limbo: FDA lists it among the Category 2 substances whose nominations were withdrawn, and it has not added it to Category 1 ^{[1] [2]}. That is not approval, and it does not make compounding lawful. Checked 23 October 2026.

Category 2 is FDA's list of substances that raise significant safety concerns. Category 1 is the list of substances under evaluation, which pharmacies may use while FDA reviews them ^[3]. In April 2026, the groups that nominated LL-37 withdrew, so it came off Category 2 ^{[1] [7]}. Taking a substance off Category 2 does not by itself let pharmacies use it ^[8].

FDA says its Pharmacy Compounding Advisory Committee will discuss LL-37 at a meeting before the end of February 2027 ^{[4] [9]}. FDA has posted no date for that meeting and no review of LL-37 for it ^[4]. The committee gives advice only. FDA decides by writing a rule, after public comment ^{[7] [20]}.

Until FDA acts, a pharmacy that makes LL-37 is outside federal law ^{[3] [5]}. In 2020, FDA warned a compounder that LL-37 was not eligible for compounding ^[5]. The same year, that compounding pharmacy pleaded guilty to distributing unapproved new drugs, LL-37 among them ^[6].

The evidence grade is limited-human: three trials in people put LL-37 on skin sores, and their results are mixed ^{[10] [11] [12]}. FDA says it lacks the safety information to know whether LL-37 would harm people ^[1]. The body makes its own LL-37, and some studies only measure how much of it a person has ^{[12] [19]}. A level found in the body does not show that taking LL-37 helps.

Leg sores: in a 2014 trial, 34 adults with hard-to-heal leg ulcers had LL-37 or a placebo, a dummy treatment, put on the wound ^[10]. Two of the three LL-37 groups healed faster than the placebo group ^[10]. A larger 2021 trial in 148 adults found no clear benefit over placebo across the whole group ^[11]. A later look found a gain in people with large sores, and the authors say a new trial must test that ^[11]. People in both trials tolerated LL-37 on the skin well ^{[10] [11]}.

Foot sores: in a 2023 trial in Jakarta, adults with diabetes and mildly infected foot sores used LL-37 cream or a placebo cream ^{[12] [13]}. New healing tissue grew faster with LL-37, but germs on the wound did not drop more than with placebo ^[12].

Shots: one small US study injected LL-37 into melanoma tumors in the skin ^[15]. A 2018 report describes a 63-year-old woman whose injected tumors shrank. About 45 days in, she grew many skin growths, which went away after the shots stopped ^[14].

Animals and cells: in diabetic mice, LL-37 helped wounds close ^[16]. In mice with ovarian tumors, blocking the body's own LL-37 slowed tumor growth ^[17]. In lab dishes, LL-37 made human cells grow faster ^[18]. A 2010 review says LL-37 seems to feed some cancers and hold back others ^[19].

There is no legal way to get LL-37 in the US today ^{[2] [5]}. No approved drug contains it. A pharmacy may use a substance with no official quality standard only if it is in an approved drug or on the federal list. LL-37 is neither ^{[3] [5]}. FDA could add it by writing a rule after its committee meets ^{[4] [7]}.

No trial that gives LL-37 is open now. Of the two registry records that give it, one study is complete and the other has an unknown status ^{[13] [15]}. Any open trial would appear in the trials block below, with the date the official registry was last checked.

Pharmacies are the one channel for LL-37 that federal records name ^{[5] [6]}. In 2020, FDA warned a compounder that its LL-37 products did not meet the rules for compounding ^[5]. The same year, that compounding pharmacy pleaded guilty to distributing unapproved new drugs, LL-37 among them ^[6]. It agreed to give up its 2019 sales of those products ^[6].

With a product made outside the rules, nobody checks what is in it the way FDA checks an approved drug. FDA warns that LL-37 products may hold impurities and may set off the immune system ^[1]. We found no federal record that names LL-37 sold by websites or clinics, so this page does not describe those channels.