The Neutrally Charged Diarylurea Compound PQ401 Kills Antibiotic-Resistant and Antibiotic-Tolerant Staphylococcus aureus

Abstract

Resistance or tolerance to traditional antibiotics is a challenging issue in antimicrobial chemotherapy. Moreover, traditional bactericidal antibiotics kill only actively growing bacterial cells, whereas nongrowing metabolically inactive cells are tolerant to and therefore “persist” in the presence of legacy antibiotics. Here, we report that the diarylurea derivative PQ401, previously characterized as an inhibitor of the insulin-like growth factor I receptor, kills both antibiotic-resistant and nongrowing antibiotic-tolerant methicillin-resistant Staphylococcus aureus (MRSA) by lipid bilayer disruption. PQ401 showed several beneficial properties as an antimicrobial lead compound, including rapid killing kinetics, low probability for resistance development, high selectivity to bacterial membranes compared to mammalian membranes, and synergism with gentamicin. In contrast to well-studied membrane-disrupting cationic antimicrobial low-molecular-weight compounds and peptides, molecular dynamic simulations supported by efficacy data demonstrate that the neutral form of PQ401 penetrates and subsequently embeds into bacterial lipid bilayers more effectively than the cationic form. Lastly, PQ401 showed efficacy in both the Caenorhabditis elegans and Galleria mellonella models of MRSA infection. These data suggest that PQ401 may be a lead candidate for repurposing as a membrane-active antimicrobial and has potential for further development as a human antibacterial therapeutic for difficult-to-treat infections caused by both drug-resistant and -tolerant S. aureus. IMPORTANCE Membrane-damaging antimicrobial agents have great potential to treat multidrug-resistant or multidrug-tolerant bacteria against which conventional antibiotics are not effective. However, their therapeutic applications are often hampered due to their low selectivity to bacterial over mammalian membranes or their potential for cross-resistance to a broad spectrum of cationic membrane-active antimicrobial agents. We discovered that the diarylurea derivative compound PQ401 has antimicrobial potency against multidrug-resistant and multidrug-tolerant Staphylococcus aureus. PQ401 selectively disrupts bacterial membrane lipid bilayers in comparison to mammalian membranes. Unlike cationic membrane-active antimicrobials, the neutral form of PQ401 rather than its cationic form exhibits maximum membrane activity. Overall, our results demonstrate that PQ401 could be a promising lead compound that overcomes the current limitations of membrane selectivity and cross-resistance. Also, this work provides deeper insight into the design and development of new noncharged membrane-targeting therapeutics to combat hard-to-cure bacterial infections.

EML webinar overview: Simulation-assisted discovery of membrane targeting nanomedicine

“…We find that both the bending energy and the lipid-inclusion line tension contribute a negative energy variation during the pore growth process, thereby facilitating the pore growth. Following this discovery, it is also shown that smaller vesicles have lower energy barrier for rupture since their high curvature leads to higher bending energy, a conclusion in line with the experimental observations [31]. Such size effect can potentially be utilized to understand the recently developed antiviral agent by Cho et al [19] with a strong sizebased selectivity.…”

“…The above studies demonstrated that modelling and simulation can predict the ability of molecular agents to selectively penetrate into lipid membranes of pathogen, providing a theoretical basis to understand membrane activity and selectivity of membrane active nanomedicine. However, we also found that, while some molecular agents (such as PQ401) can penetrate into the mammalian-mimetic membrane, they do not disrupt mammalian-mimetic GUVs and red blood cells [31]. This observation suggests that penetration is only the first and necessary step, but not sufficient for the final rupture of the lipid membrane.…”

Diarylureas: Repositioning from Antitumor to Antimicrobials or Multi-Target Agents against New Pandemics

“…Unlike other well-studied membrane-disrupting cationic antimicrobial low-molecular-weight antimicrobials, maximum membrane activity was shown by PQ401 in its neutral form rather than its cationic form. PQ401 also showed efficacy in both the Caenorhabditis elegans and Galleria mellonella models of MRSA infection [ 62 ]. A series of the diarylureas was synthesized and screened for antimicrobial activity against Gram positive and negative bacteria and fungi.…”

New Antimicrobial Bioactivity against Multidrug-Resistant Gram-Positive Bacteria of Kinase Inhibitor IMD0354

“…We identified several bioactive compounds, of which biological activities have been previously determined [ 20 ]. For example, the selective retinoic acid receptor γ (RARγ) agonist CD437 and CD1530 [ 19 ], the selective peroxisome proliferator-activated receptor γ (PPARγ)-agonist nTZDpa [ 21 ], the anti-parasite drug bithionol [ 22 ], and insulin-like growth factor receptor inhibitor PQ401 [ 23 ]. Each show promising antimicrobial potency against multidrug-resistant Gram-positive pathogens and their persister cells.…”

“…Each show promising antimicrobial potency against multidrug-resistant Gram-positive pathogens and their persister cells. Considering that many hit compounds are excluded for further investigation due to their in vivo inactivity and toxicity, bioactive compound hits in particular have a high potential to become lead compounds because their in vivo efficacy and in vivo toxicity have been previously proven in several animal models [ 21 , 22 , 23 ]. Therefore, we further investigated other bioactive compound hits.…”