Thymosin alpha-1, KPV, LL-37, BPC-157 and VIP are sold for colds, long COVID, leaky gut and colitis. Most of what they do to immune cells was shown in mice or in a dish. When they were tested on patients with hepatitis, sepsis, colitis or chronic ulcers, the largest trials found the smallest effects.
Open the immune target mapSolid green means a randomized trial in people. Pale green means a small human study. Brown means animals only, and dashed means cells in a dish. Switch to the cell view to see every peptide that acts on macrophages, T cells or the gut lining.
Tap any cell to switch to the cell view.
No effect on these cells has been measured in people. See the clinical results below.
Grade A means an approved drug or several randomized trials; grade D means animal or cell data only. The squares show each record's key studies: green ones were done in people, brown ones in animals or cells.
A 28-amino-acid thymus peptide sold as Zadaxin in dozens of countries for hepatitis B; not approved in the US, mixed trial results.
A 28-amino-acid gut and nerve peptide that relaxes blood vessels and calms inflammation; approved only in an erectile dysfunction injection.
An 11-amino-acid piece of erythropoietin that does not raise red blood cells, tested in small trials for nerve pain and nerve loss.
A nine-amino-acid hormone made by the thymus that needs zinc to work; tested in 1980s autoimmune trials, never approved.
A 37-amino-acid antimicrobial peptide your skin and white blood cells already make. Human trials tested it mainly as an ulcer cream.
A five-amino-acid ghrelin-receptor agonist that releases growth hormone. Its only efficacy trial, for post-surgery gut paralysis, failed.
Short 2-4 amino acid peptides plus a thymus extract from one Russian institute, each tied to an organ; evidence is mostly in-house.
A 15-amino-acid synthetic peptide studied mostly in rats for tendon, muscle and gut healing. Human data is a handful of tiny pilot studies.
A 3-amino-acid tail of the hormone alpha-MSH that calmed colitis and skin inflammation in mice. No human study exists.
Every human trial cited on this page, plotted by how many people took part and what it found. Tap a dot for the details, or browse by condition below. Small trials found benefits; most large trials found none.
28-day deaths 23.4% vs 24.1% on placebo in 22 ICUs. No secondary outcome differed.
Sepsis is the best test of an immune drug: deaths are common and easy to count.
TESTS, Wu et al., BMJ
28-day deaths 23.4% vs 24.1% on placebo in 22 ICUs. No secondary outcome differed.
SourceETASS, Wu et al., Critical Care
28-day deaths 26.0% vs 35.0%, a borderline result in a single-blind trial.
SourceGiven as an enema to 53 adults with ulcerative colitis. Scores fell on both drug and placebo with no clear difference. The healing claims come from rats.
Calmed colitis in mice when added to drinking water. Nobody knows how much survives stomach acid in a person.
Gut nerves release it to pull water into the bowel. Given as a drug, it caused diarrhea in about a third of trial patients.
Restarted the bowel faster after surgery in rats. In 114 patients after bowel surgery it did not beat placebo.
Gut and skin cells make LL-37 to kill bacteria. Taking extra has not been tested for any gut condition.
Swipe the table sideways to see all six columns.
| Peptide | What it acts on | Best human evidence | Status | WADA | Main route |
|---|---|---|---|---|---|
| Thymosin Alpha-1 | TLR9 and TLR2 on dendritic cells | Many RCTs; the two largest were negative | Approved outside US | Not named; approved abroad, so outside S0 | Subcutaneous injection |
| VIP (Vasoactive Intestinal Peptide) | VPAC1 and VPAC2 on immune, gut and muscle cells | ED trials behind a UK license; COVID trials negative | Approved outside US | Not named on the list | Intracavernous injection (approved, with phentolamine) |
| ARA-290 | Innate repair receptor on injured tissue | Four small 28-day RCTs in nerve damage | Research chemical | Prohibited under S2 as a repair-receptor agonist | Subcutaneous injection |
| Thymulin | Immature T cells and macrophages; needs zinc | Two 1980s RCTs: arthritis positive, MS negative | Research chemical | Covered by S0 (unapproved substances) | Subcutaneous injection (1980s human trials, rodent studies) |
| LL-37 | Bacterial membranes; FPR2 on immune and vessel cells | Three ulcer-cream RCTs; the largest missed its goal | Research chemical | Covered by S0 (unapproved substances) | Topical (wound cream or solution) |
| Ipamorelin | Ghrelin receptor (GH release, gut movement) | One 114-patient RCT for gut paralysis, negative | Research chemical | Prohibited at all times (S2) | Intravenous infusion (in studies) |
| Khavinson Peptide Bioregulators | Claimed to bind DNA; no defined receptor | Open-label studies from the developers' institute | Approved outside US | Not named; unapproved synthetics may fall under S0 | Intramuscular injection (Thymalin, research use of synthetic peptides) |
| BPC-157 | No confirmed receptor | One colitis RCT, abstract only, no clear effect | In clinical trials | Named under S0, prohibited at all times | Subcutaneous injection |
| KPV | NF-kB inside gut cells, entering through PepT1 | None. Mouse colitis studies only | Research chemical | Covered by S0 (unapproved substances) | Oral |
Want two of these next to each other on every field? Open the compare tool.
These are claims you will see in clinic marketing and on forums that no human study supports yet. Each one is a gap in the research, not proof that the peptide fails.
Every trial enrolled patients with a disease. Not one measured colds, infections or recovery in healthy adults.
There are no controlled trials of thymosin alpha-1 or VIP in any of these.
Gut permeability has never been measured in a human study of either one.
Nobody has measured how much oral KPV or oral BPC-157 reaches the colon or the blood.
The evidence is one 20-patient study with no control group, run by the clinic that created the protocol.
Thymosin alpha-1 safety data stop at about 12 months. KPV has no repeat-dose toxicity data at all.
Not FDA-approved; sold as Zadaxin in about 35 other countries. FDA advisers voted 17 to 4 against compounding it in 2024.
WADA: Not named; approved abroad, so outside S0Not FDA-approved. In FDA Category 1, so pharmacies may compound it for an individual prescription while FDA reviews it.
WADA: Not named on the listInvestigational, stalled after phase 2. No legal compounding path in the US.
WADA: Prohibited under S2 as a repair-receptor agonistNever approved. No legal compounding path in the US.
WADA: Covered by S0 (unapproved substances)Never approved anywhere. Off FDA Category 2 since April 2026 but still not eligible for compounding; an FDA advisory review is due by February 2027.
WADA: Covered by S0 (unapproved substances)Never approved. On FDA Category 2; advisers voted 0 to 12 against compounding it in 2024.
WADA: Prohibited at all times (S2)Thymalin and Thymogen are registered medicines in Russia only. The organ-named peptides are sold as supplements there.
WADA: Not named; unapproved synthetics may fall under S0Never approved. FDA advisers voted 8 to 6 in July 2026 to allow compounding for ulcerative colitis. No rule has been published.
WADA: Named under S0, prohibited at all timesNever approved. FDA advisers voted 8 to 6 in July 2026 to allow compounding. The vote is advisory and no rule has been published.
WADA: Covered by S0 (unapproved substances)Each peptide page has a table of the doses used in published trials and on approved labels, with a source for every row. Those tables open with a free account.
Create a free accountOne email when an immune or gut peptide trial reads out or the FDA rules on KPV, BPC-157 or LL-37 compounding. Human evidence first, sources linked.