Development and evaluation of 2,4-disubstituted-5-aryl pyrimidine derivatives as antibacterial agents.

Designing novel candidates as potential antibacterial scaffolds has become crucial due to the lack of new antibiotics entering the market and the persistent rise in multidrug resistance. Here, we describe a new class of potent antibacterial agents based on a 5-aryl-N2,N4-dibutylpyrimidine-2,4-diamine scaffold. Structural optimization focused on the 5-aryl moiety and the bioisosteric replacement of the side chain linker atom. Screening of the synthesized compounds focused on a panel of bacterial strains, including gram-positive Staphylococcus aureus strains (Newman MSSA, methicillin- and vancomycin-resistant), and the gram-negative Escherichia coli (ΔAcrB strain). Several compounds showed broad-spectrum antibacterial activity with compound 12, bearing a 4-chlorophenyl substituent, being the most potent among this series of compounds. This frontrunner compound revealed a minimum inhibitory concentration (MIC) value of 1 µg/mL against the S. aureus strain (Mu50 methicillin-resistant S. aureus/vancomycin-intermediate S. aureus) and an MIC of 2 µg/mL against other tested strains. The most potent derivatives were further tested against a wider panel of bacteria and evaluated for their cytotoxicity, revealing further potent activities toward Streptococcus pneumoniae, Enterococcus faecium, and Enterococcus faecalis. To explore the mode of action, compound 12 was tested in a macromolecule inhibition assay. The obtained data were supported by the safety profile of compound 12, which possessed an IC50 of 12.3 µg/mL against HepG2 cells. The current results hold good potential for a new class of extended-spectrum antibacterial agents.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Modification of the benzenoid part.

Bacterial resistance to currently used antibiotics demands the development of novel antibacterial agents with good safety margins and sufficient efficacy against multi-drug resistant isolates. We have previously described the synthesis of N-butyl-2-(butylthio)quinazolin-4-amine (I) as an optimized hit with broad-spectrum antibacterial activity and low cytotoxicity. In addition, we have identified a potential growing vector for this series of compounds. Herein, we describe further hit optimization which includes systematic diversifications of both the benzenoid part and the substituents at position 6 and 7 of compound I. Growing of the molecule beside the core modifications yielded several compounds with remarkable anti(myco)bacterial activity against a panel of pathogenic bacteria, including drug-resistant strains. Compound 12 showed a 2-4 fold improvement in activity than I against S. aureus Newman, S. pneumoniae DSM-20566 and E. faecalis DSM-20478. The compounds also showed a good safety profile towards human HepG2 cells.

From EGFR kinase inhibitors to anti-inflammatory drugs: Optimization and biological evaluation of (4-(phenylamino)quinazolinyl)-phenylthiourea derivatives as novel NF-κB inhibitors.

The transcription factor NF-κB is a pivotal mediator of chronic inflammatory and autoimmune diseases. Based on our previously published dual EGFR/NF-κB inhibitors, we designed and synthesized new thiourea quinazoline derivatives that retained only the NF-κB inhibitory activity. Several congeners displayed a strong suppression of NF-κB activity in a reporter gene assay, yet low cytotoxicity, and were further evaluated in differentiated macrophage-like THP-1 cells. The compounds exhibited a strong inhibition of IL-6 and, less potently, of TNFα release, which was accompanied by a selective induction of macrophage cell death. The mode of action was investigated with a selected inhibitor, 18, revealing that the translocation of p65/RelA to the nucleus but not its release from the IκB complex was inhibited. Eventually, 18 was identified as the first small molecule inhibitor affecting only the phosphorylation of p65-Ser468 but not of Ser536, which may be causally related to the retention of NF-κB in the cytoplasm. Altogether, our novel NF-κB inhibitors seem applicable for the suppression of cytokine release and the additional selective depletion of activated macrophages in various inflammatory diseases.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Optimization of the 2,4-substituents.

The emergence of bacterial resistance has triggered a multitude of efforts to develop new antibacterial agents. There are many compounds in literature that were reported as potent antibacterial agents, however, they lacked the required safety to mammalian cells or no clear picture about their toxicity profile was presented. Inspired by discovered hit from our in-house library and by previously reported 2,4-diaminosubstituted quinazolines, we describe the design and synthesis of novel 2,4-disubstituted-thioquinazolines (3-13 and 36), 2-thio-4-amino substituted quinazolines (14-33) and 6-substituted 2,4-diamonsubstituted quinazolines (37-39). The synthesized compounds showed potent antibacterial activity against a panel of Gram-positive, efflux deficient E.coli and Mycobacterium smegmatis. The panel also involved resistant strains including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis and vancomycin-resistant Enterococcus faecium, in addition to Mycobacterium smegmatis. The newly synthesized compounds revealed MIC values against the tested strains ranging from 1 to 64 µg/mL with a good safety profile. Most of the 2-thio-4-amino substituted-quinazolines showed significant antimycobacterial activity with the variations at position 2 and 4 offering additional antibacterial activity against the different strains. Compared to previously reported 2,4-diaminosubstituted quinazolines, the bioisosteric replacement of the 2-amino with sulfur offered a successful approach to keep the high antibacterial potency while substantially improving safety profile as indicated by the reduced activity on different cell lines and a lack of hemolytic activity.

Expanding the Myxochelin Natural Product Family by Nicotinic Acid Containing Congeners.

Myxobacteria represent a viable source of chemically diverse and biologically active secondary metabolites. The myxochelins are a well-studied family of catecholate-type siderophores produced by various myxobacterial strains. Here, we report the discovery, isolation, and structure elucidation of three new myxochelins N1-N3 from the terrestrial myxobacterium Corallococcus sp. MCy9049, featuring an unusual nicotinic acid moiety. Precursor-directed biosynthesis (PDB) experiments and total synthesis were performed in order to confirm structures, improve access to pure compounds for bioactivity testing, and to devise a biosynthesis proposal. The combined evaluation of metabolome and genome data covering myxobacteria supports the notion that the new myxochelin congeners reported here are in fact frequent side products of the known myxochelin A biosynthetic pathway in myxobacteria.

Cystobactamid 507: Concise Synthesis, Mode of Action, and Optimization toward More Potent Antibiotics.

Lack of new antibiotics and increasing antimicrobial resistance are among the main concerns of healthcare communities nowadays, and these concerns necessitate the search for novel antibacterial agents. Recently, we discovered the cystobactamids-a novel natural class of antibiotics with broad-spectrum antibacterial activity. In this work, we describe 1) a concise total synthesis of cystobactamid 507, 2) the identification of the bioactive conformation using noncovalently bonded rigid analogues, and 3) the first structure-activity relationship (SAR) study for cystobactamid 507 leading to new analogues with high metabolic stability, superior topoisomerase IIA inhibition, antibacterial activity and, importantly, stability toward the resistant factor AlbD. Deeper insight into the mode of action revealed that the cystobactamids employ DNA minor-groove binding as part of the drug-target interaction without showing significant intercalation. By designing a new analogue of cystobactamid 919-2, we finally demonstrated that these findings could be further exploited to obtain more potent hexapeptides against Gram-negative bacteria.

Design and synthesis of novel quinazoline derivatives and their evaluation as PI3Ks inhibitors.

The aim of this work was to synthesize 4-acetamido-, 4-amino- and 4-oxo-6-substituted aminoquinazolines and to evaluate them as phosphoinositide 3-kinases (PI3Ks) inhibitors. The respective chemotype was designed based on combining the structural features of two previously reported scaffolds acting as potent PI3Kγ inhibitors, which are quinazoline derivatives and amino-heterocyclic derivatives. In vitro enzymatic assay at 10 µM against all the eight human PI3K isoforms showed that an unsubstituted benzamide group at position 6 and an acetyl group at N(4) gave the best inhibitory activity on PI3Kγ. Interestingly, compounds 5a and 5e showed a significant, inhibitory effect on Class II PI3K-C2γ. This is of high value since there are very few inhibitors for this isoform reported in the literature.

Evaluation of serum irisin level and severity of erectile dysfunction in diabetic males: a cross sectional prospective study.

BACKGROUND: Irisin is an exercise-induced myokine that alleviates endothelial dysfunction and reduces insulin resistance in type 2 diabetes mellitus (T2DM). The current study aimed to assess the serum level of irisin in T2DM men with erectile dysfunction (ED) compared to T2DM patients with normal erectile function and healthy controls, as well as investigate the association between serum irisin level and the severity of ED in T2DM patients. PATIENTS AND METHODS: A cross-sectional study was conducted on 90 males, divided into three groups: 32 T2DM patients with ED, 24 T2DM patients without ED, and 34 healthy controls. Socio-demographic characteristics and scores of the validated Arabic version of the international Index of Erectile Function-5 (ArIIEF-5), Generalized Anxiety Disorder-7 (GAD-7) and Patient Health Questionnaire-9 (PHQ-9) were obtained. Furthermore, routine laboratory tests employed for diabetes monitoring and serum levels of total testosterone and irisin were assessed within these groups. RESULTS: T2DM men with ED had significantly lower serum levels of irisin and testosterone, as well as a lower ArIIEF-5 score, but their GAD-7 and PHQ-9 scores were significantly higher than those without ED or controls (p < 0.001). Among T2DM men, serum irisin levels positively associated with ArIIEF-5 scores and serum testosterone (r = 0.413, p = 0.002; r = 0.936, p < 0.001, respectively) but negatively associated with glycosylated hemoglobin levels (r = -0.377, p = 0.004). Multivariate regression analysis to predict ED in T2DM patients found that GAD-7 score was the only most significant predictor for ED (ꞵ = - 1.176, standard error = 0.062, p < 0.001). CONCLUSION: The current study had demonstrated that irisin positively correlated with the ArIIEF-5 and serum testosterone but negatively correlated with HbA1c in T2DM men. Nevertheless, further validation of these findings is necessary through cohort studies.

Effect of COVID-19 on sexual and reproductive functions of Egyptian males following recovery: A cross sectional study.

INTRODUCTION: We aimed to assess the sexual and the reproductive functions in males post COVID-19 infection in Beni-Suef Governorate. METHODS: One hundred men were recruited in the current study. All participants were assessed by the Arabic validated version of the International Index of the Erectile Function 5 (ArIIEF-5), semen analysis, and Hospital Depression and Anxiety Scale (HADS). Finally, morning testosterone serum level was measured. RESULTS: There were significant decreases in the sperm total motility, the ArIIEF-5 score, and serum total testosterone in the post COVID-19 patients after 3 months when compared to the controls. However, there were significant increases in the sperm total motility, the ArIIEF-5 score, and serum total testosterone in the post COVID-19 patients after 6 months group when compared to the post COVID-19 patients after 3 months group. Moreover, there was a significant increase in the HADS score in the post COVID-19 patients after 3 months when compared to the controls. In contrast, there was a significant decrease in the HADS score in the post COVID-19 patients after 6 months when compared to the post COVID-19 patients after 3 months. CONCLUSION: Our study had shown temporary impairment of sexual and reproductive functions in post COVID-19 convalescent males especially after 6 months from the onset of the infection.

Correlation between Serum Levels of Nitric Oxide and Adropin and Erectile Dysfunction in Males with Nonalcoholic Fatty Liver Disease: An Observational Study.

The current study aimed to evaluate the serum levels of nitric oxide (NO) and adropin in males with non-alcoholic fatty liver disease (NAFLD) induced erectile dysfunction (ED) and NAFLD patients without ED and controls. The current study selected 165 participants from the hepatology department from November 2021 to November 2022. The patients were either suffering from NAFLD with normal liver functions or non-alcoholic steatohepatitis with abnormal liver functions. They were diagnosed by abdominal ultrasonography. Participants were evaluated using the validated Arabic version of the International Index of Erectile Function (ArIIEF-5), the Arabic form of the Generalized Anxiety Disorder-7 (GAD-7) questionnaire and the Patient Health Questionnaire-9 (PHQ-9). Noteworthy, there were significant positive correlations between ArIIEF-5 score, NO, adropin and total testosterone (r = 0.380, p = 0.001; r = 0.507, p = < 0.001; r = 0.246, p = 0.038, respectively). Meanwhile, there were significant negative correlations between ArIIEF-5 score, creatinine, duration of the disease and scores of GAD-7 and PHQ-9 (r = -0.656, p = < 0.001; r = -0.368, p = 0.002; r = -0.663, p = < 0.001; r = -0.248, p = 0.037, respectively). Finally, a linear regression analysis revealed that GAD-7, creatinine, and adropin were the only strong independent predictors of ArIIEF-5, as the 95% confidence interval in the form of upper and lower bounds was -0.349, -0.843, p < 0.001, -6.507, -18.402, p < 0.001, 0.476, 0.117, and p 0.002, respectively. Impaired NO and adropin levels play a potential role in the development of ED in patients with NAFLD.

Nanoparticles in liposomes: a platform for increased antibiotic selectivity in multidrug resistant bacteria in respiratory tract infections.

Antibiotic resistance is a cause of serious illness and death, originating often from insufficient permeability into gram-negative bacteria. Nanoparticles (NP) can increase antibiotic delivery in bacterial cells, however, may as well increase internalization in mammalian cells and toxicity. In this work, NP in liposome (NP-Lip) formulations were used to enhance the selectivity of the antibiotics (3C and tobramycin) and quorum sensing inhibitor (HIPS-1635) towards Pseudomonas aeruginosa by fusing with bacterial outer membranes and reducing uptake in mammalian cells due to their larger size. Poly (lactic-co-glycolic) acid NPs were prepared using emulsion solvent evaporation and incorporated in larger liposomes. Cytotoxicity and uptake studies were conducted on two lung cell lines, Calu-3 and H460. NP-Lip showed lower toxicity and uptake in both cell lines. Then formulations were investigated for suitability for oral inhalation. The deposition of NP and NP-Lip in the lungs was assessed by next generation impactor and corresponded to 75% and 45% deposition in the terminal bronchi and the alveoli respectively. Colloidal stability and mucus-interaction studies were conducted. NP-Lip showed higher diffusion through mucus compared to NPs with the use of nanoparticle tracking analyzer. Moreover, the permeation of delivery systems across a liquid-liquid interface epithelial barrier model of Calu-3 cells indicated that NP-Lip could cause less systemic toxicity upon in-vivo like administration by aerosol deposition. Monoculture and Pseudomonas aeruginosa biofilm with Calu-3 cells co-culture experiments were conducted, NP-Lip achieved highest toxicity towards bacterial biofilms and least toxicity % of the Calu-3 cells. Therefore, the NP- liposomal platform offers a promising approach for enhancing antibiotic selectivity and treating pulmonary infections.

Hit optimization by dynamic combinatorial chemistry on Streptococcus pneumoniae energy-coupling factor transporter ECF-PanT.

Herein, we present the first application of target-directed dynamic combinatorial chemistry (tdDCC) to the whole complex of the highly dynamic transmembrane, energy-coupling factor (ECF) transporter ECF-PanT in Streptococcus pneumoniae. In addition, we successfully employed the tdDCC technique as a hit-identification and -optimization strategy that led to the identification of optimized ECF inhibitors with improved activity. We characterized the best compounds regarding cytotoxicity and performed computational modeling studies on the crystal structure of ECF-PanT to rationalize their binding mode. Notably, docking studies showed that the acylhydrazone linker is able to maintain the crucial interactions.

Discovery and optimization of thiazole-based quorum sensing inhibitors as potent blockers of Pseudomonas aeruginosa pathogenicity.

Pseudomonas aeruginosa causes life-threatening infections especially in hospitalized patients and shows an increasing resistance to established antibiotics. A process known as quorum sensing (QS) enables the pathogen to collectively adapt to various environmental conditions. Disrupting this cell-to-cell communication machinery by small-molecular entities leads to a blockade of bacterial pathogenicity. We aim to devise QS inhibitors acting on the PA-specific PQS QS system via the signal-molecule receptor and transcriptional regulator PqsR (MvfR). In this manuscript, we describe the further optimization of PqsR inverse agonists by broadening the structural space of a previously described triazole-bearing lead compound and arriving at highly potent thiazole derivatives with activities against P. aeruginosa virulence factor pyocyanin in the nanomolar range. All new derivatives were profiled regarding biological activity as well as in vitro ADMET parameters. Additionally, we assessed safety-pharmacology characteristics of the two most promising compounds both bearing a 3-chloro-4-isopropoxyphenyl motive. Demonstrating an overall favorable profile, our new PqsR inverse agonists represent a valuable addition as optimized lead compounds, enabling preclinical development of P. aeruginosa-specific pathoblockers.

Two natural compounds as potential inhibitors against the Helicobacter pylori and Acinetobacter baumannii IspD enzymes.

In a vast majority of bacteria, protozoa and plants, the methylerythritol phosphate (MEP) pathway is utilized for the synthesis of isopentenyl diphosphate (IDP) and dimethylallyl diphosphate (DMADP), which are precursors for isoprenoids. Isoprenoids, such as cholesterol and coenzyme Q, play a variety of crucial roles in physiological activities, including cell-membrane formation, protein degradation, cell apoptosis, and transcription regulation. In contrast, humans employ the mevalonate (MVA) pathway for the production of IDP and DMADP, rendering proteins in the MEP pathway appealing targets for antimicrobial agents. This pathway consists of seven consecutive enzymatic reactions, of which 4-diphosphocytidyl-2C-methyl-D-erythritol synthase (IspD) and 2C-methyl-D-erythritol 2,4-cyclodiphosphate synthase (IspF) catalyze the third and fifth steps, respectively. In this study, we characterized the enzymatic activities and protein structures of Helicobacter pylori IspDF and Acinetobacter baumannii IspD. Then, using the direct interaction-based thermal shift assay, we conducted a compound screening of an approved drug library and identified 27 hit compounds potentially binding to AbIspD. Among them, two natural products, rosmarinic acid and tanshinone IIA sodium sulfonate, exhibited inhibitory activities against HpIspDF and AbIspD, by competing with one of the substrates, MEP. Moreover, tanshinone IIA sodium sulfonate also demonstrated certain antibacterial effects against H. pylori. In summary, we identified two IspD inhibitors from approved ingredients, broadening the scope for antibiotic discovery targeting the MEP pathway.

Towards Translation of PqsR Inverse Agonists: From In Vitro Efficacy Optimization to In Vivo Proof-of-Principle.

Pseudomonas aeruginosa (PA) is an opportunistic human pathogen, which is involved in a wide range of dangerous infections. It develops alarming resistances toward antibiotic treatment. Therefore, alternative strategies, which suppress pathogenicity or synergize with antibiotic treatments are in great need to combat these infections more effectively. One promising approach is to disarm the bacteria by interfering with their quorum sensing (QS) system, which regulates the release of various virulence factors as well as biofilm formation. Herein, this work reports the rational design, optimization, and in-depth profiling of a new class of Pseudomonas quinolone signaling receptor (PqsR) inverse agonists. The resulting frontrunner compound features a pyrimidine-based scaffold, high in vitro and in vivo efficacy, favorable pharmacokinetics as well as clean safety pharmacology characteristics, which provide the basis for potential pulmonary as well as systemic routes of administration. An X-ray crystal structure in complex with PqsR facilitated further structure-guided lead optimization. The compound demonstrates potent pyocyanin suppression, synergizes with aminoglycoside antibiotic tobramycin against PA biofilms, and is active against a panel of clinical isolates from bronchiectasis patients. Importantly, this in vitro effect translated into in vivo efficacy in a neutropenic thigh infection model in mice providing a proof-of-principle for adjunctive treatment scenarios.

Sorbent extraction behavior of cesium and strontium from nitric acid solutions using a new high thermal stability material.

In this study a new low-cost carbonaceous material was prepared from husks of opuntia-ficus-indica as a starting material (precursor) which was accomplished by chemical activation route using H3PO4 impregnation. The material has been identified by different analytical tools. The sorption performance of Cs(I) and Sr(II) from HNO3 solutions was examined through batch system. Variations of the distribution coefficients (Kd) as a function of HNO3 concentration in the range 0.001-5.0 M were presented. Some of separation probabilities were suggested. The results attained signals that the Sr(II) selectivity is higher than that of Cs(I) at high molarities. The retention capacity (qe) of Cs(I) and Sr(II) ions increased with growing temperature. The capacities at 0.001 M HNO3 are 34 and 108 mg/g for Cs(I) and Sr(II), respectively. Whereas, at 2.0 M HNO3 capacities were about 4 and 37 mg/g for each of Cs(I) and Sr (II), respectively. This studies demonstrates that the prepared carbonaceous sorbent is an economically effective sorbent for retention of Cs(I) and Sr(II) species from HNO3 solutions. Cs(I) and Sr(II) removal potential was tested from simulated low- and intermediate-level radioactive waste samples.

NanoTafla Nanocomposite as a Novel Low-Cost and Eco-Friendly Sorbent for Strontium and Europium Ions.

Now the wide use of nanooxides is attributed to their remarkable collection of properties. Nanocomposites have an impressive variety of important applications. A thermal decomposition approach provides a more optimistic method for nanocrystal synthesis due to the low cost, high efficiency, and expectations for large-scale production. Therefore, in this study a new eco-friendly nanooxide composite with sorption characteristics for europium (Eu(III)) and strontium (Sr(II)) was synthesized by a one-step thermal treatment process using earth-abundant tafla clay as a starting material to prepare a modified tafla (M-Taf) nanocomposite. The synthesized nancomposite was characterized by different techniques before and after sorption processes. Different factors that affected the sorption behavior of Eu(III) and Sr(II) in aqueous media by the M-Taf nanocomposite were studied. The results obtained illustrated that the kinetics of sorption of Eu(III) and Sr(II) by the M-Taf nanocomposite are obeyed according to the pseudo-second order and controlled by a Langmuir isotherm model with maximum sorption capacities (Q max) of 25.5 and 23.36 mg/g for Eu(III) and Sr(II), respectively. Also, this novel low-cost and eco-friendly sorbent has promising properties and can be used to separate and retain some radionuclides in different applications.

Structure-Guided Optimization of Small-Molecule Folate Uptake Inhibitors Targeting the Energy-Coupling Factor Transporters.

Here, we report on a potent class of substituted ureidothiophenes targeting energy-coupling factor (ECF) transporters, an unexplored target that is not addressed by any antibiotic in the market. Since the ECF module is crucial for the vitamin transport mechanism, the prevention of substrate uptake should ultimately lead to cell death. By utilizing a combination of virtual and functional whole-cell screening of our in-house library, the membrane-bound protein mediated uptake of folate could be effectively inhibited. Structure-based optimization of our hit yielded low-micromolar inhibitors, whereby the most active compounds showed in addition potent antimicrobial activities against a panel of clinically relevant Gram-positive pathogens without significant cytotoxic effects.

Dislocation of Total Hip Replacement in Femoral Neck Fracture: Do Surgical Approach and Dual Mobility Implant Matter?

INTRODUCTION: Total hip replacement (THR) in the neck of femur fracture in the elderly is associated with a higher risk of dislocation compared to hemiarthroplasty of hip or total hip replacement in the native hip. There is uncertainty regarding combining surgical approach, femoral head size, and the usage of single bearing or dual mobility to reduce the risk of dislocation. This study looks into the bearing of the prosthesis for posterior or lateral surgical hip approach as well as their head size to give a stable hip to these vulnerable groups of patients. METHODS: Initial data were collected retrospectively from February 2017 till May 2019 from the electronic records database and clinical notes. Patients included in the study had a femoral neck fracture (age >60 years) who underwent a total hip replacement. Subsequent data were collected prospectively from June 2019 to July 2020. RESULTS: High rate of dislocation was found with posterior approach and single bearing prosthesis. However, if dual mobility prosthesis was used while using the posterior approach the dislocation rate was very low. Also, with lateral approach and single bearing prosthesis using large femoral head size, the dislocation rate was negligible. CONCLUSIONS: We recommend a dual mobility prosthesis for posterior approach THR and lateral approach with single-bearing hip replacement with large size femoral head. The dislocation rate is low using this principle irrespective of the surgical approach.

Targeting the IspD Enzyme in the MEP Pathway: Identification of a Novel Fragment Class.

The enzymes of the 2-C-methylerythritol-d-erythritol 4-phosphate (MEP) pathway (MEP pathway or non-mevalonate pathway) are responsible for the synthesis of universal precursors of the large and structurally diverse family of isoprenoids. This pathway is absent in humans, but present in many pathogenic organisms and plants, making it an attractive source of drug targets. Here, we present a high-throughput screening approach that led to the discovery of a novel fragment hit active against the third enzyme of the MEP pathway, PfIspD. A systematic SAR investigation afforded a novel chemical structure with a balanced activity-stability profile (16). Using a homology model of PfIspD, we proposed a putative binding mode for our newly identified inhibitors that sets the stage for structure-guided optimization.