Immune & defense Antimicrobial 'protegrin' peptidomimetic
Murepavadin
Regulatory status
Status at a glance
503A compounding status
Not nominated
We found no pending nomination for the 503A bulks list. Unless the substance has another legal pathway (for example, a USP monograph or use in an FDA-approved drug), 503A pharmacies generally may not compound with it.
- FDA approval
- Not FDA-approved for any use
- 503B outsourcing
- Not determined
- Anti-doping (WADA)
- Not on the WADA Prohibited List
- DEA schedule
- Not a controlled substance
About peptide status
Most peptides discussed here are not FDA-approved for any use, and products labeled “research use only” are not for human use. Removal from Category 2 does not authorize compounding. PCAC votes are non-binding recommendations; FDA and HHS make the final decisions.
This is not medical or legal advice, and we do not publish dosing, sourcing or reconstitution information. Talk with a licensed clinician before using any peptide.
If you think you are having a medical emergency, call 911.
Key takeaway
Murepavadin is an investigational antimicrobial peptidomimetic that targets a protein unique to Pseudomonas aeruginosa, developed by Polyphor for serious lung infections. Its intravenous Phase 3 program was halted after an unexpected rate of kidney injury, and later inhaled development did not mature. As of 2026 it is not approved.
At a glance
- FDA status
- Investigational antimicrobial peptidomimetic, not approved by the FDA
- Target
- Pseudomonas aeruginosa, including drug-resistant strains
- Intravenous program
- Phase 3 halted for kidney toxicity
- Inhaled program
- Later development did not advance
- Evidence strength
- Low research
Summary
Murepavadin is an investigational peptidomimetic antibiotic built to target Pseudomonas aeruginosa. Learn how it works and why its Phase 3 program halted.
What is murepavadin?
Murepavadin is an experimental antibiotic built as a protegrin-derived peptidomimetic, a cyclized peptide-like molecule. It was developed by Polyphor (later Spexis) specifically against Pseudomonas aeruginosa, a bacterium that causes serious hospital and lung infections and is often resistant to other drugs. It was studied intravenously for hospital- and ventilator-associated pneumonia and later explored as an inhaled formulation. It is investigational and not approved.
How does it work?
Murepavadin acts through a species-specific, non-lytic mechanism. It targets LptD, an outer-membrane protein that Pseudomonas aeruginosa needs to transport and assemble lipopolysaccharide, a building block of its outer membrane. Disrupting LptD impairs the bacterium's outer-membrane construction and kills it.
In the laboratory, it was active against multidrug-resistant and even colistin-resistant strains. This describes the mechanism, separate from the safety outcome below.
Is it FDA-approved?
Safety note
Status: Investigational antimicrobial peptidomimetic, not approved by the FDA
Category: In clinical trials · Primary body area: Immune & defense
No. Murepavadin is investigational and not approved. Its intravenous Phase 3 program was halted, and the company that developed it was later restructured, leaving no active development.
What does the research show?
Editor’s note
Evidence strength: Low research (2 human · 0 animal/cell studies)
The pivotal intravenous Phase 3 program was halted for kidney toxicity with no positive confirmatory efficacy data, and inhaled development did not mature.
The pivotal program was stopped for safety.
| Program | Population | Outcome |
|---|---|---|
| Phase 1 study, indexed on PubMed | Healthy volunteers | Characterized the drug's intravenous pharmacokinetics and early safety |
| Phase 3 PRISM program, which followed | Patients with pneumonia | Closed in 2019 after a higher-than-expected incidence of acute kidney injury in the murepavadin group; enrollment had already been suspended |
A review summarizes the drug's novel class and antibacterial profile. There is no positive confirmatory efficacy trial, and the IV program ended on a safety signal.
Sources: a Phase 1 pharmacokinetic and safety study (Wach et al., Antimicrobial Agents and Chemotherapy, 2018, DOI: 10.1128/AAC.02355-17) and a review of murepavadin (Martin-Loeches et al., Expert Review of Anti-infective Therapy, 2018, DOI: 10.1080/14787210.2018.1441024), both indexed on PubMed; and reporting on the Phase 3 program closure. This document is educational, is not medical advice or a health claim, and is not an offer to sell any product.
Registered human trials
2 registered human trials on ClinicalTrials.gov that we reviewed
Sources
- [1]
- [2]
Compare every peptide’s status in the peptide regulatory status database
More for Immune & defense
View all immune & defense peptides →- In clinical trials Immune & defense
Aviptadil
Aviptadil is a synthetic form of vasoactive intestinal peptide (VIP), a signaling molecule that acts on lung receptors, and it has been studied mainly for severe COVID-19 respiratory failure. In the NIH-funded TESICO trial of 461 patients, aviptadil did not beat placebo on the 90-day recovery scale (odds ratio 1.11, 95% CI 0.80 to 1.55, p = 0.54). Ninety-day mortality was 38% with aviptadil versus 36% with placebo (p = 0.78), and the trial stopped early for futility. As of 2026 it is not FDA-approved for any use.
- FDA-approved Immune & defense
Cyclosporine
Cyclosporine (also spelled ciclosporin; brands include Sandimmune, Neoral, and the eye drop Restasis) is a cyclic peptide from a fungus that suppresses the immune system, and it transformed organ transplantation when it arrived in the 1980s. It works by blocking the activation of T cells. It has been FDA-approved in the U.S. since 1983, is available in oral, intravenous, and eye-drop forms, and carries boxed warnings for the systemic versions.
- FDA-approved Immune & defense
Enfuvirtide
Enfuvirtide (formerly sold as Fuzeon) is a peptide HIV drug that blocks the virus from entering CD4 immune cells, the first of the so-called fusion inhibitors. It was used in treatment-experienced patients whose virus is no longer controlled by other antiretrovirals. It was FDA-approved in the U.S. in 2003, but Fuzeon was discontinued there in February 2025.
- Not FDA-approved Immune & defense
Ll-37
LL-37 is the body's natural antimicrobial "host-defense" peptide, intensely studied as part of the immune system and sold on the "research peptide" market for antimicrobial and immune support. Its biology is well described, but there is no approved product and no human efficacy evidence for the injected wellness use, and its effects are context-dependent. As of 2026 it is not FDA-approved.
- In clinical trials Immune & defense
Nangibotide
Nangibotide is an investigational peptide that inhibits the inflammatory receptor TREM-1, developed by Inotrem as an intravenous treatment for septic shock. Its Phase 2b trial did not meet its primary endpoint, though a signal appeared in a subgroup of patients with high levels of a related biomarker. As of 2026 it is not approved.
- FDA-approved Immune & defense
Polymyxin-B-Colistin
Polymyxin B and colistin (colistin is also called polymyxin E) are older cyclic lipopeptide antibiotics that have returned to use as last-resort treatments for multidrug-resistant Gram-negative infections. They punch holes in the bacterial outer membrane but carry meaningful kidney and nerve toxicity. Both have long been FDA-approved in the U.S. and are reserved for serious infections with few other options.