cationic antimicrobial peptide
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New antibiotics are needed against multidrug resistant Gram-negative pathogens that have compromised global health systems. Antimicrobial peptides are generally considered promising lead candidates for the next generation of antibiotics but have not fulfilled this expectation. Here we demonstrate activity of a cationic amphipathic undecapeptide (ChIP; Charge change Independent Peptide) against a wide panel of multidrug resistant Gram-negative pathogens. Importantly, the antimicrobial activity of ChIP is independent of the surface charge changes that confer colistin resistance through modification of Lipid A, while decreased activity of ChIP correlates with GlcN1 tri-acylation of Lipid A. In an in vivo peritonitis mouse model ChIP displays excellent activity against both colistin sensitive and resistant Escherichia coli and Acinetobacter baumannii strains.

The poor stability of antibacterial peptide to protease limits its clinical application. Among these limitations, trypsin mainly exists in digestive tract, which is an insurmountable obstacle to orally delivered peptides. OM19R is a random curly polyproline cationic antimicrobial peptide, which has high antibacterial activity against some gram-negative bacteria, but its stability against pancreatin is poor. According to the structure-activity relationship of OM19R, all cationic amino acid residues (l-arginine and l-lysine) at the trypsin cleavage sites were replaced with corresponding d-amino acid residues to obtain the designed peptide OM19D, which not only maintained its antibacterial activity but also enhanced the stability of trypsin. Proceeding high concentrations of trypsin and long-time (such as 10 mg/mL, 8 h) treatment, it still had high antibacterial activity (MIC = 16–32 µg/mL). In addition, OM19D also showed high stability to serum, plasma and other environmental factors. It is similar to its parent peptide in secondary structure and mechanism of action. Therefore, this strategy is beneficial to improve the protease stability of antibacterial peptides.

Background : In this first in human study, PLG0206, a novel engineered cationic antimicrobial peptide was evaluated for safety, tolerability and pharmacokinetics when intravenously administered as a single dose to healthy subjects. Methods : Six cohorts of 8 subjects received escalating single IV infusions of PLG0206 at 0.05, 0.125, 0.25, 0.5, or 1 mg/kg dose or placebo over 1-to-4-hours. Subjects were randomized to receive either PLG0206 (6 per cohort) or placebo (2 per cohort). Serial pharmacokinetic samples were taken prior to infusion and up to 48 hours post infusion. Safety and tolerability were assessed throughout the study. Results : The demographic characteristics of subjects were comparable between those treated with PLG0206 and placebo and between dose groups. The incidence of treatment emergent adverse events (TEAE) related to PLG0206 was low and most events were mild in severity and were similar between the PLG0206 treatment and placebo groups. The most common adverse events reported for PLG0206 were infusion related reactions, which were mitigated with increasing infusion time and volume. There were no serious adverse events (SAE), life-threatening events, or deaths throughout the study. IV PLG0206 exhibited linear pharmacokinetics over the dose range of 0.05 to 1.0 mg/kg. The median terminal half-life (t ½ ) ranged from 7.37 to 19.97 hours. Conclusion : Following a single IV infusion to healthy subjects, PLG0206 was safe and well tolerated and exhibited linear PK at doses ranging from 0.05 to 1 mg/kg. These findings support the ongoing development of IV PLG0206 as an antimicrobial agent.

Lactoferrin-binding protein B (LbpB) is a lipoprotein present on the surface of Neisseria that has been postulated to serve dual functions during pathogenesis in both iron acquisition from lactoferrin (Lf), and in providing protection against the cationic antimicrobial peptide lactoferricin (Lfcn). While previous studies support a dual role for LbpB, exactly how these ligands interact with LbpB has remained unknown. Here, we present the structures of LbpB from N. meningitidis and N. gonorrhoeae in complex with human holo-Lf, forming a 1:1 complex and confirmed by size-exclusion chromatography small-angle X-ray scattering. LbpB consists of N- and C-lobes with the N-lobe interacting extensively with the C-lobe of Lf. Our structures provide insight into LbpB’s preference towards holo-Lf, and our mutagenesis and binding studies show that Lf and Lfcn bind independently. Our studies provide the molecular details for how LbpB serves to capture and preserve Lf in an iron-bound state for delivery to the membrane transporter LbpA for iron piracy, and as an antimicrobial peptide sink to evade host immune defenses.

Abstract Background PLG0206 is a novel engineered cationic antimicrobial peptide being evaluated for treatment of prosthetic joint infections (PJI). This abstract presents the results from the first in human study to evaluate the safety, tolerability and pharmacokinetic (PK) profile of PLG0206 when administered as an intravenous (IV) infusion. Methods 6 cohorts of 8 participants were planned to receive escalating single 1-hour IV infusions of PLG0206 at 0.05, 0.125, 0.25, 0.5, 1, 2 and 3 mg/kg dose or placebo. Participants were randomized to receive either PLG0206 (6 per cohort) or placebo (2 per cohort). At each dose level, there were 2 sentinel participants (1 active, 1 placebo) who were dosed at least 48 hours in advance of the other participants in their group. Serial pharmacokinetic samples were taken prior to infusion and up to 48 post infusion. Safety and tolerability was assessed throughout the study. There was at least a 7-day period after dosing at each of the dose levels before dose escalation. Results PLG0206 was safe and well tolerated when administered to healthy volunteers at doses ranging from 0.05 and 1 mg/kg. Therapeutic exposures were achieved at 1 mg/kg. The 2 and 3 mg/kg cohorts were not studied. The incidence of treatment emergent adverse events related to study drug administration was low and most events mild (Grade 1) in severity and was similar between the PLG0206 treatment and placebo groups. There were no SAEs, life-threatening events or deaths throughout the study. IV PLG0206 exhibited linear PK over the dose range of 0.05 to 1.0 mg/kg. The median terminal half-life (t½) ranged from 7.37 to 19.97 hours. AUC0-∞ increased with increasing PLG0206 dose ranging between 1581.41 and 21141.52 ng.hr/mL. Cmax ranged between 256 and 2653 ng/mL. The mean apparent volume of distribution (Vz) increased was between 25.49 and 94.2 L, mean clearance (CL) were similar across all and ranged from 2.42 to 4.18 L/hour. Conclusion Following single IV infusion to healthy volunteers, PLG0206 was safe and well tolerated at doses ranging from 0.05 to 1 mg/kg. IV PLG0206 exhibits linear PK over the dose range. These findings support the ongoing development of IV PLG0206 and will inform dosing regimens in future studies to investigate its utility as an antimicrobial agent. Disclosures David Huang, MD, PhD, Peptilogics (Employee) Despina Dobbins, BS, Peptilogics (Employee) Parviz Ghahramani, PhD, PharmD, MSc, MBA, Peptilogics (Consultant) Jonathan Steckbeck, PhD, Peptilogics (Employee)

Abstract Background PLG0206 is a novel engineered cationic antimicrobial peptide being evaluated for treatment of prosthetic joint infections (PJI). This study evaluated the rapid bactericidal activity of PLG0206 to decrease biofilm and planktonic bacteria on ex vivo infected prosthesis following removal from patients with chronic PJI. Methods De-identified infected prosthetics were removed from nine patients with PJI, despite chronic suppressive oral antibiotics, during a 2-stage revision procedure. Removed prosthetics were then submersed ex vivo to an expected clinical exposure of PLG0206, 1 mg/mL, for ~15 minutes. Upon completion of the 15-minute exposure, the treated explant was placed into buffer and sonicated. The sonication solution was then plated for bacterial analysis including colony forming unit (CFU) enumeration. Remaining explanted implants from the same patient served as a control and was processed similarly but without exposure to PLG0206. Results As shown in the Table, both Gram-positive and Gram-negative bacteria were identified from removed prosthetics during a 2-stage revision procedure of chronic PJI. Eight of ten infected prosthetics treated ex vivo to PLG0206 1 mg/mL were sterilized (No. 1-5, 8-10). Of the two infected prosthetics that were not sterilized (No. 6 and 7), one was polymicrobial (No. 6) and the other was monomicrobial (No. 7). Collectively, infected prosthetics exposed to PLG0206 demonstrated a mean 4log10 reduction (range 2 to 7). Summary of culture and CFU log reduction among infected prosthetics exposed and not exposed to PLG0206 Table: Summary of culture and CFU log reduction among infected prosthetics exposed and not exposed to PLG0206 Conclusion Overall, these findings support the ongoing development of PLG0206 as a local irrigation solution at 1 mg/mL concentration in the wound cavity for 15 minutes in patients undergoing treatment of a PJI occurring after total knee arthroplasty. Disclosures David Huang, MD, PhD, Peptilogics (Employee) Nicholas Pachuda, DPM, Peptilogics (Employee) Despina Dobbins, BS, Peptilogics (Employee) Jonathan Steckbeck, PhD, Peptilogics (Employee) Kenneth Urish, MD, PhD, Peptilogics (Grant/Research Support)

Abstract Background PLG0206 is a novel engineered cationic antimicrobial peptide being evaluated for treatment of prosthetic joint infections. In this study, the activity of PLG0206 was evaluated by broth microdilution against 104 isolates of Staphylococcus epidermidis, 53 other coagulase-negative staphylococci (CoNS), 3 S. aureus, and 66 Gram-negative isolates consisting of Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii. Methods Imipenem, levofloxacin, tigecycline, linezolid, vancomycin, oxacillin, ceftazidime, colistin, and amikacin were tested as comparators. Testing was conducted in accordance with guidelines from the Clinical and Laboratory Standards Institute (CLSI; M7 and M100). Test organisms consisted of reference strains from the American Type Culture Collection, the Centers for Disease Control Antibiotic Reference Bank and clinical isolates from the Micromyx repository. The media employed for testing in the broth microdilution MIC assay for all organisms were cation-adjusted Mueller Hinton Broth and for PLG0206 only included RPMI-1640 medium supplemented with 0.002% P-80. Results Activity of PLG0206 in RPMI against CoNS, S. aureus, and resistant Gram-negative* pathogens are shown in Table. Activity of PLG0206 in RPMI against CoNS, S. aureus and resistant Gram-negative* pathogens Activity of PLG0206 in RPMI against CoNS, S. aureus and resistant Gram-negative* pathogens Conclusion PLG0206 was found to have potent antimicrobial activity when evaluated in RPMI against S. epidermidis, CoNS non-epidermidis, S. aureus, Enterobacterales, P. aeruginosa, and A. baumannii, including isolates with multi-drug resistance. Disclosures David Huang, MD, PhD, Peptilogics (Employee) Jonathan Steckbeck, PhD, Peptilogics (Employee) Chris Pillar, PhD, Micromyx (Employee) Bev Murray, BS, Micromyx (Employee) David Huganfel, BS, Micromyx (Employee) Dean Shinabanger, PhD, Micromyx (Employee)

Percutaneous implants are widely used in clinical practice. However, infection is the main clinical problem of percutaneous implants. Titanium dioxide nanotubes are suitable for forming coatings on complex surfaces such as implants. HHC-36, a cationic antimicrobial peptide, has been identified to have a strong broad-spectrum antibacterial effect. In the present study, we use poly D,L-lactic acid (PDLLA) and poly lactic-co-glycolic acid (PLGA) coating to build HHC-36 sustained-release system on the surface of titanium dioxide nanotubes. The titanium specimens were anodized coated with HHC-36-PDLLA/PLGA. The morphology and surface elemental distribution of the specimens were evaluated. Besides, results in the present study demonstrated that with antibacterial peptide HHC-36 sustained-release coating, titanium dioxide nanotubes maintain effective drug release for 15 days in vitro, and show significant antibacterial activity. The proliferation of Staphylococcus aureus can be effectively inhibited by PDLLA/PLGA-HHC-36 coated titanium dioxide nanotube. In addition, PDLLA-HHC-36 and PLGA-HHC-36 coating was demonstrated to be biocompatible and antibacterial in vivo. These findings demonstrated that HHC-36 coated titanium nanotube could improve antibacterial potential of percutaneous implants, and indicated a novel and efficient strategy in preventing bacterial infection of percutaneous implants.

AbstractWound infections are still problematic in many cases and demand new alternatives for current treatment strategies. In recent years, biomaterials-based wound dressings have received much attention due to their potentials and many studies have been performed based on them. Accordingly, in this study, we fabricated and optimized an antibacterial chitosan/silk fibroin (CS/SF) electrospun nanofiber bilayer containing different concentrations of a cationic antimicrobial peptide (AMP) for wound dressing applications. The fabricated CS/SF nanofiber was fully characterized and compared to the electrospun silk fibroin and electrospun chitosan alone in vitro. Then, the release rate of different concentrations of peptide (16, 32, and 64 µg/ml) from peptide-loaded CS/SF nanofiber was investigated. Finally, based on cytotoxic activity, the antibacterial activity of scaffolds containing 16 and 32 µg/ml of the peptide was evaluated against standard and multi-drug resistant strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa isolated from burn patients. The peptide-loaded CS/SF nanofiber displayed appropriate mechanical properties, high water uptake, suitable biodegradation rate, a controlled release without cytotoxicity on Hu02 human foreskin fibroblast cells at the 16 and 32 µg/ml concentrations of peptide. The optimized CS/SF containing 32 μg/ml peptide showed strong antibacterial activity against all experimental strains from standard to resistance. The results showed that the fabricated antimicrobial nanofiber has the potential to be applied as a wound dressing for infected wound healing, although further studies are needed in vivo.