LL-37 is a peptide the body makes, studied for how it interacts with microbes and immune cells. Much of the evidence is from cells and animals; human studies are limited. It's coming soon to Promise.
Coming soon
You are on the list. We will email you when LL-37 becomes available — and nothing else. Joining is not a medical request, and no prescription has been issued.
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LL-37 is coming soon to Promise. Add your email and we'll let you know when visits open.
A licensed provider reviews every request; not everyone qualifies.
Every treatment gets its own online clinical questionnaire — your history, medications, and goals.
A real person goes through your history and takes the time to get it right before anything is decided.
If a treatment isn't right for your history, you'll hear that plainly. That review is the whole point.
Made for your prescription by a licensed U.S. pharmacy and shipped in temperature-safe packaging.
Your care team checks in after it arrives. Adjust with your provider, or cancel at any time.
LL-37 is easy to find online and hard to trust there. Promise works the way medicine is supposed to work — a clinician decides, a licensed pharmacy fills, and someone stays accountable to you.
Prescribed for you specifically, after a real look at your health history — never pulled off a shelf.
Your prescription is compounded for you by a licensed U.S. pharmacy — not a mystery vial from an unregulated website.
Temperature-safe shipping, follow-up check-ins, and a care team that answers — before and after your medication arrives.
This peptide is studied for laboratory activity against microbes and for messages between immune cells. Those roles explain the research interest, without establishing a benefit from use in people.
Human research includes skin application trials. A larger placebo-controlled study missed its main goal; evidence from those trials does not establish results or safety for broader use.
When visits open, a licensed provider will review your history alongside the evidence and safety gaps, then decide whether a prescription is appropriate for you.
LL-37 is a peptide the body makes, studied for how it interacts with microbes and immune cells. Much of that work is in cells and animals. Human studies have tested it on the skin, but a larger venous leg ulcer trial missed its main goal.
This page explains the evidence and the safety questions before visits open. LL-37 is coming soon to Promise — add me to the list.
A peptide is a short chain of amino acids, the building blocks of proteins. This one has thirty-seven; the first two are leucine, which explains the letters and number in its name.
Cathelicidin is the family it belongs to, and humans have one member of that family. The peptide is cut from a larger starting protein called hCAP18. White blood cells and cells lining the skin and airways produce that starting material.
The fact that it exists in the body doesn't establish the safety of giving more of it as a medication. A normal role in immune defense and a useful prescription are separate questions.
The word antimicrobial means activity against microbes. In laboratory tests, the peptide has killed bacteria. Researchers also examine how it changes messages between immune cells.
That second role can cut both ways. In human-cell research, it bound DNA, the genetic material inside cells, and helped trigger immune alarm signals linked to psoriasis, a condition with inflamed patches of skin. Separate research found abnormal cathelicidin processing in rosacea, a condition with facial redness and inflammation, and examined that signaling in mice.
These are studies of disease biology, not evidence that adding the peptide helps someone with those conditions. An immune signal isn't automatically helpful just because it belongs to the body's defenses.
In 2014, a trial in 34 adults compared the peptide with a placebo, a comparison product without the peptide. Participants had hard-to-heal venous leg ulcers: open sores related to poor blood return through leg veins. Researchers studied direct skin application and reported changes in wound measurements that led to a larger trial.
The larger placebo-controlled trial, published in 2021 assigned 149 people to groups by chance; 148 received a study product or placebo. It found no significant difference in complete wound closure in the full study group. A finding in people with larger wounds came from an analysis done after the fact, so it needs confirmation.
A 2023 trial in 25 people with diabetic foot ulcers reported a difference in new tissue forming at the wound surface. It found no significant differences between groups in wound size or bacterial counts.
The route matters: these were topical studies, meaning applied to skin. They don't establish results or long-term safety for other ways of giving the peptide.
In its safety summary for cathelicidin, FDA flags possible unwanted immune reactions with certain ways of administering it. It also notes difficulties identifying the active ingredient and peptide impurities.
FDA also says nonclinical findings suggest harmful effects on male reproduction and tumor-promoting effects in some tissues. Nonclinical means research outside human trials. The agency says it lacks enough safety information to know whether giving this compound to people would cause harm.
A licensed provider may still prescribe — that decision is between you and your doctor.
Compounding means a pharmacy prepares medication for an individual patient. A compounded medication is different from an FDA-approved product: the formulation Promise will offer is not FDA-approved. Compounded medications are not reviewed by the FDA for safety, effectiveness, or quality. This page does not present the peptide as a replacement for care of an existing medical condition.
They sit in immune support, but they are different peptides. Thymosin Alpha-1 is studied for immune-cell communication, including T cells, cells that help coordinate immune responses. Cathelicidin research spans direct laboratory activity against microbes and skin immune messages.
KPV is a smaller peptide studied for inflammatory signaling in intestinal cells and mice. It is also coming soon to Promise. Each molecule has its own research and open questions; evidence for one does not carry over to the others.
When visits open, the process will start with its own LL-37 intake questionnaire. It will cover your health history, current medicines and supplements, and the reason for your request. The published safety concerns will be part of that discussion, alongside your existing care.
A licensed provider will review your answers and may ask for more information or decline. A prescription would be issued only after that review. If prescribed, a licensed U.S. pharmacy will compound and dispense the medication.
Your provider sets any protocol; Promise does not publish dosing. Follow-up check-ins from your care team will help revisit questions as they arise. Joining the list means hearing when visits open; it doesn't open a visit or create a prescription.
LL-37 is a peptide the body makes as part of its immune defenses. It contains thirty-seven amino acids, the building blocks of proteins, and belongs to the cathelicidin family. Researchers study its activity against microbes in laboratory tests and its role in immune-cell messages. Human trials have tested skin application, with mixed findings and unresolved safety questions.
Yes. When visits open, LL-37 will be prescribed by a licensed provider after a review of your health history and compounded for you by a licensed U.S. pharmacy. It will not be a product labeled for laboratory use. A prescription will depend on the provider deciding it is appropriate for you.
Starting a visit won't guarantee a prescription. When visits open, a licensed provider will review your health history, current medicines, and the reason for your request. The provider may ask for more information or decline. Joining the list now is simply a way to hear when visits open, rather than a medical evaluation.
No. LL-37 is not FDA-approved, and no FDA-approved product contains it. The formulation Promise will offer is a compounded medication, which is not reviewed by the FDA for safety, effectiveness, or quality. A prescription and a pharmacy preparing it do not change that status.
Not yet. LL-37 is coming soon to Promise — add me to the list on this page and we'll email you when visits open. It isn't available through Promise today. When visits open, there will be a medical review before any prescribing decision; the email list does not count as that review.
They are different peptides with different research histories. Thymosin Alpha-1 is studied for communication between immune cells, including T cells that help coordinate immune responses. LL-37 is a cathelicidin studied for direct activity against microbes in laboratory tests and for skin immune signaling. Findings for either compound cannot establish what the other will do in a person.
The human findings are mixed. A small early venous leg ulcer trial led to a larger placebo-controlled trial, which did not show an overall difference in its main wound-closure measure. A later small foot-ulcer trial reported a difference in new tissue at the wound surface without clear differences in wound size or bacterial counts. Skin application studies do not establish safety or results for broader use.
LL-37 sold online without a prescription is often labeled for laboratory use, with no prescribing provider, pharmacy dispensing for an individual patient, or care team following the person who uses it. When visits open through Promise, a licensed provider will decide whether to prescribe, a licensed U.S. pharmacy will compound and dispense the medication, and your care team will follow up. That process does not erase the evidence or safety gaps.
Other Immune Support options a provider may consider.
Immune Support
A 28-amino-acid peptide derived from prothymosin alpha and produced by the thymus, studied for T-cell maturation and immune signaling.
Requires an online medical evaluation. Prescribed only when a licensed provider determines it's appropriate.
Type a treatment, a goal, or a question.