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A newly designed Pt(ii)–NHC complex shows potent activity against the Gram-positive S. aureus pathogen. Further investigation reveals biofilm inhibition, in vivo activity inside mammalian cells, and combinatorial antimicrobial activity with FDA-approved drugs.

Copper Pyrithione, [Cu(PyS)2] has shown excellent biological activity against cancer cells and bacterial cells, however, it has extremely low aqueous solubility, limiting its applicability. Herein, we report a series of PEG-substituted pyrithione copper(II) complexes with significantly increased aqueous solubility. While long PEG chains lead to a decrease in bioactivity, the addition of short PEG chains leads to improved aqueous solubility with retention of activity. One novel complex, [Cu(PyS1)2], has particularly impressive anticancer activity, surpassing that of the parent complex.

A cationic amphiphilic peptide effectively prevents the aggregation of soluble Aβ42 and also disintegrates matured fibrils into soluble precursors. In addition, the peptide also rescues cells from the toxicity of Aβ42.

Background: Drug repurposing is a viable approach to expediting the tedious conventional drug discovery process, given rapidly increasing bacterial resistance. In this context, we have repurposed pyrvinium pamoate (PP) for its antibacterial activity against Staphylococcus aureus. Methods: US FDA-approved non-antibiotics were screened against clinically relevant bacterial pathogens to identify antibacterials. The hits were further evaluated utilizing a variety of preclinical parameters, following which in vivo efficacy was estimated in isolation and in combination in a murine neutropenic thigh infection model. Result: The screening identified PP exhibiting potent activity against S. aureus along with concentration-dependent killing. PP also showed a post-antibiotic effect of >22 h and significantly eradicated preformed S. aureus biofilms and intracellular S. aureus at 1× and 5× MIC, respectively. PP synergized with levofloxacin both in vitro and in vivo, resulting in ∼1.5 and ∼0.5 log10 CFU/g reduction against susceptible and resistant S. aureus infections, respectively, as compared with untreated control. Conclusion: Pyrvinium potentiates levofloxacin against levofloxacin-resistant S. aureus.

Background: In the authors' previous study, 4-(2-((3-methyl-4-oxo-2-thioxo/dioxothiazolidin-5-ylidene) methyl) hydrazineyl) benzonitriles were found to demonstrate potent antibacterial activity against Acinetobacter baumannii. Interestingly, the aforementioned compounds contain a 4-cyanophenylhydrazine motif. Materials & methods: Intrigued by this observation, the authors focused on preparing a library of 4-cyanophenylhydrazine derivatives and studied their detailed antibacterial potential. Results: This study led to the identification of a 4-cyanophenylhydrazine with potent inhibitory activity against carbapenem-resistant A. baumannii BAA-1605, with minimum inhibitory concentration (MIC) of 0.25 μg/ml and highest selectivity index of 640. The compound also demonstrated potent inhibition against multidrug-resistant A. baumannii isolates (MIC: 0.25–1 μg/ml). Conclusion: The identified 4-cyanophenylhydrazine compound exhibited synergistic activity with amikacin, tobramycin and polymyxin B against carbapenem-resistant A. baumannii BAA-1605.

Discovery of novel antibiotics targeting multidrug-resistant (MDR) pathogens such as A. baumannii is an urgent, unmet medical need. Our work has highlighted the potential of this unique scaffold to annihilate MDR A. baumannii alone and in combination with amikacin both in vitro and in animals, that too without inducing resistance. Further in depth analysis identified central metabolism to be a putative target. Taken together, these experiments lay down the foundation for effective management of infections caused due to highly MDR pathogens.

During tuberculosis (TB) infection caused by Mycobacterium tuberculosis (Mtb), a sub-population of mycobacteria can enter a non-replicating persistent state that is not susceptible to most frontline TB drugs, resulting in phenotypic antimicrobial resistance (AMR), which contributes to an extended duration of TB therapy, frequent non-compliance and disease relapse. Recent clinical trial data indicated that inclusion of the fluoroquinolone Moxifloxacin (MXF) led to a shortening of TB treatment from 6-months to 4-months. MXF, however, has limited efficacy on Mtb persisting in a hypoxic environment. Here, we report a prodrug approach significantly enhancing lethality of MXF against non-replicating hypoxic Mtb while retaining its effectiveness against replicating Mtb. Since hypoxia is associated with a reductive environment and induces the expression of reductive enzymes such as nitroreducatases (NTRs) in Mtb, we designed and synthesized a library of nitroaryl and nitroheteroaryl conjugates of MXF. After optimization of several factors, including reduction potential, rate, and efficiency of drug release, as well as selectivity, we identified 2-nitrothiazole-derivative as a prodrug that is rapidly and nearly quantitatively converted to MXF in the presence of NTR. Biochemical studies supported by computational data reveal a rate-limiting influence of electron transfer in the mechanistic pathway for activation of the nitroaryl group, a key step in prodrug activation leading to drug release. The potency of lead prodrug against replicating bacteria in both cellular and animal model studies, and mode of action is nearly identical to MXF with significantly higher lethality against non-replicating Mtb than MXF. The prodrug showed improved accumulation of MXF inside non-replicating Mtb when compared with MXF alone, likely due to the ability of prodrug to enhance accumulation of MXF within non-replicating Mtb. Hence, together, the newly developed 2-nitrothiazole-prodrug is rapidly, efficiently, and selectively cleaved under reductive conditions to produce the active drug and had superior permeability and accumulation in non-replicating Mtb, which likely contributes to its increased efficacy. This proof-of-concept study supports prodrug approaches with a focus on improving accumulation of the active drug within non-replicating pathogens as a strategy to address phenotypic AMR.

With growing concerns regarding target residue mutation hovering over established anti-TB pharmacophores, it is imperative to have reserve chemotypes at our disposal to curb unrestrained spread of tuberculosis. In this context, we herein present the synthesis and bio-evaluation of a library of new nitrobenzothiazinone (BTZ) congeners comprising 2-mercapto/amino-benzothiazinone tethered 1,2,3-triazole hybrids as antitubercular agents. In preliminary screening, 10 out of 37 compounds displayed substantial in vitro potency against Mtb H37Rv (MIC 0.5–8 μg mL(−1)). Structural optimization of the initial hit 5o (MIC 0.5 μg mL(−1)) led to identification of linker variants 9a, 9b, 9c, and 9d exhibiting potent anti-TB activity (MIC 0.03–0.12 μg mL(−1)). When tested against Vero cells to determine their selectivity index (SI), these compounds displayed no appreciable cytotoxicity (SI >80). Further studies on activity against drug resistant (DR) Mtb indicated these compounds to be equally potent (MIC 0.03–0.25 μg mL(−1)). The in silico covalent docking study suggested a similar polar interaction to that of PBTZ169 with an additional and contrasting side chain interaction at the active site of Mtb DprE1 target protein. Further, the time kill kinetic study found compounds 9a and 9d to be demonstrating bactericidal efficacy, completely eliminating bacilli in 7 days at 10× MIC. The most promising compound 9d, considering its potent anti-TB activity (MIC 0.06 μg mL(−1) against drug susceptible Mtb and MIC 0.06–0.25 μg mL(−1) against DR Mtb) along with a broad therapeutic index (SI >640) demonstrating a comparable concentration dependent bactericidal efficacy to that of RIF, holds a significant edge to be translated into a potent anti-Mtb agent.

To target antimicrobial resistance, 4-nitroisobenzofuran-1(3H)-one (IITK2020), is presented as an exclusive inhibitor of S. aureus including drug-resistant S. aureus clinical strains, that prevents peptidoglycan biosynthesis.

Chemical investigation of roots of the plant, Rubia cordifolia Linn, led to the isolation of an undescribed anthraquinone, cordifoquinone R, determined as 1,2-dihydroxy-6-methoxyanthracene-9,10-dione (6) based on the 1D and 2D NMR analyses and HRESIMS. Ten other known compounds viz.1,4-dihydroxy-2-methoxyanthracene-9,10-dione (1), rubiadin (2), xanthopurpurin (3), 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone (4), alizarin (5), β-sitosterol glucoside (7), scopoletin (8), oleanolic acid, (9), pomolic acid (10), queretaroic acid (11) were also isolated. Out of these compounds, 4, 10, and 11 are first reported from this plant species. Compounds 2, 3, 6, 7, and 10 showed activity in the range of 16-32 µg/ml against S. aureus ATCC 29213.

Antimicrobial resistance (AMR) has been increasing unrelentingly worldwide, thus negatively impacting human health. The discovery and development of novel antibiotics is an urgent unmet need of the hour. However, it has become more challenging, requiring increasingly time-consuming efforts with increased commercial risks. Hence, alternative strategies are urgently needed to potentiate the existing antibiotics. In this context, short cationic peptides or peptide-based antimicrobials that mimic the activity of naturally occurring antimicrobial peptides (AMPs) could overcome the disadvantages of AMPs having evolved as potent antibacterial agents. Besides their potent antibacterial efficacy, short peptide conjugates have also gained attention as potent adjuvants to conventional antibiotics. Such peptide antibiotic combinations have become an increasingly cost-effective therapeutic option to tackle AMR. This Review summarizes the recent progress for peptide-based small molecules as promising antimicrobials and as adjuvants for conventional antibiotics to counter multidrug resistant (MDR) pathogens.

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA) are primary causes of skin and soft tissue infections worldwide. To address the emergency caused due to increasing multidrug-resistant (MDR) bacterial infections, a series of novel fluoro and trifluoromethyl-substituted salicylanilide derivatives were synthesized and their antimicrobial activity was investigated. MIC data reveal that the compounds inhibited S. aureus specifically (MIC 0.25–64 µg/mL). The in vitro cytotoxicity of compounds with MIC

Artocarpus hirsutus Lam., or wild jack, a perennial tree of the Western Ghats of peninsular India, serves as a rich source of flavonoids. The indigenous knowledge of this multipurpose flora chronicles the efficient property of its bark as a natural treatment for various skin infections. Herein, we describe a rational explanation of this traditional knowledge via a broader evaluation of inhibitory activity of one of its phytoconstituents, cudraflavone C (Cud C), a prenyl flavone isolated from stem bark against diverse multidrug-resistant Staphylococcus aureus along with decidedly potent synergy combinations with a standard drug, gentamycin, especially against gentamycin-resistant S. aureus NRS 10119. Cud C exhibited equipotent MIC (4 μg/mL) against a varied array of MDR strains comprising MRSA, VRSA, and VRE and was nontoxic toward eukaryotic cells with a sizable selectivity index (SI 25-50). Cud C displayed concentration-dependent bactericidal activity against planktonic cells, an excellent biofilm disruption property exceeding that of levofloxacin and vancomycin against preformed S. aureus biofilm, and an enhanced capability to kill intracellular S. aureus more potently than vancomycin, thus exemplifying its position as an antibacterial lead candidate. In addition, S. aureus was unable to generate resistance to Cud C even after exposure for more than 40 days, whereas it generated resistance to levofloxacin within ∼20 days of exposure. Therefore, the naturally occurring prenylflavone Cud C can be accounted for as one of the reasons for the reported antibacterial properties of the bark of A. hirsutus. Taken together, detailed biological studies propose that Cud C can be considered as an effective antibacterial drug candidate against MDR S. aureus, which is fast becoming a significant threat to public health worldwide.

In our continued efforts to find potential chemotherapeutics active against drug-resistant (DR) Mycobacterium tuberculosis (Mtb), causative agent of Tuberculosis (TB) and to curb the current burdensome treatment regimen, herein we describe the synthesis and biological evaluation of urea and thiourea variants of 5-phenyl-3-isoxazolecarboxylic acid methyl esters as promising anti-TB agent. Majority of the tested compounds displayed potent in vitro activity not only against drug-susceptible (DS) Mtb H37Rv but also against drug-resistant (DR) Mtb. Cell viability test against Vero cells deemed these compounds devoid of significant toxicity. 3,4-Dichlorophenyl derivative (MIC 0.25 µg/mL) and 4-chlorophenyl congener (MIC 1 µg/mL) among urea and thiourea libraries respectively exhibited optimum potency. Lead optimization resulted in the identification of 1,4-linked analogue of 3,4-dichlorophenyl urea derivative demonstrating improved selectivity. Further, in silico study complemented with previously proposed prodrug like attributes of isoxazole esters. Taken together, this molecular hybridization approach presents a new chemotype having potential to be translated into an alternate anti-Mtb agent.

The genus

An amyloid-β inspired biocompatible short peptide amphiphile (sPA) molecule was used for controlled and targeted delivery of bioactive silver nanoparticles via transforming sPA nanostructures. Such sPA-AgNPs hybrid structures can be further used to develop antibacterial materials to combat emerging bacterial resistance. Due to the excellent antibacterial activity of silver, the growth of clinically relevant bacteria was inhibited in the presence of AgNPs-sPA hybrids. Bacterial tests demonstrated that the high biocompatibility and low cytotoxicity of the designed sPA allow it to work as a model drug delivery agent. It therefore shows great potential in locally addressing bacterial infections. The results of our study suggest that these nanodevices have the potential to trap and then engage in the facile delivery of their chemical payload at the target site, thereby working as potential delivery materials. This system has potential therapeutic value for the treatment of microbiota triggered progression of neurodegenerative diseases.

Stimuli-responsive self-destructing soft structures serve as versatile hosts for the encapsulation of guest molecules. A new paradigm for H2S-responsive structures, based on a modified tripeptide c...

We report here a concise route to synthesize various stereoisomers of tetrahydrofuran amino acids (TAAs) and the synthesis of TAA-containing linear cationic dodecapeptides. Some of these linear peptides show slightly better antimicrobial activities than their tetra- and octameric congeners, but no activity against Mycobacterium tuberculosis, for which octapeptides exhibited by far the best results; this implies that antibacterial activity is dependent on the length of these linear peptides. All the dodecapeptides described here were found to be toxic in nature against Vero cells. The study helps to delineate the optimal length of this series of linear peptides and select potential leads in the development of novel cationic peptide-based antibiotics. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Vancomycin is a standard drug for the treatment of multidrug-resistant Gram-positive bacterial infections. Albeit, development of resistance (VRE, VRSA) and its inefficacy against persistent infections is a demerit. It is also intrinsically inactive against Gram-negative bacteria. Herein, we report a vancomycin derivative, VanQAmC10, that addresses these challenges. VanQAmC10 was rapidly bactericidal against carbapenem-resistant A. baumannii (6 log10 CFU/mL reduction in 6 h), disrupted A. baumannii biofilms, and eradicated their stationary phase cells. In MRSA infected macrophages, the compound reduced the bacterial burden by 1.3 log10 CFU/mL while vancomycin exhibited a static effect. Further investigation indicated that the compound, unlike vancomycin, promoted the intracellular degradative mechanism, autophagy, in mammalian cells, which may have contributed to its intracellular activity. The findings of the work provide new perspectives on the field of glycopeptide antibiotics.

Background The dearth of antimicrobials to treat MDR infections has led to search for novel moieties with potent activity. The most suitable compounds have been derived from mainly natural sources. In this context, the current study focused on identification and determination of antistaphylococcal activity of malabaricone B (MB), one of the naturally abundant secondary metabolites (malabaricones A–D) present in the Myristicaceae family. Malabaricones have previously been reported to possess various biological activities including antimicrobial activity but prospects of its effective utilization against Staphylococcus aureus infections in particular have not been explored in detail to the best of our knowledge. Methods Malabaricones (A–D) were screened against an ESKAPE pathogen panel via broth microdilution assays. The hit compounds were then tested against Vero cells via MTT assays to determine their selectivity index. As the next step, their activity against clinical drug-resistant strains was evaluated. Further, time–kill kinetics against S. aureus were determined along with the ability to synergize with approved drugs via chequerboard assays, which was further validated via combination time–kill kinetics assays. The hit compound's in vitro post-antibiotic effect (PAE) and propensity to generate resistance to S. aureus was determined. Its activity against intracellular S. aureus in a J774 macrophage model of infection and ability to eradicate pre-formed S. aureus biofilms in vitro was ascertained. Finally, the hit compound's in vivo efficacy was determined in a murine neutropenic S. aureus thigh infection model. Results Amongst the hits identified, MB demonstrated a potent in vitro antistaphylococcal profile including equipotent activity against clinical MDR S. aureus and Enterococcus sp. with MIC 1–2 mg/L. MB exhibited concentration-dependent bactericidal activity with complete killing at 5 × MIC within 15 min of exposure with no regrowth up to 24 h. MB also displayed PAE of ∼22 h at 10 × MIC. It also has very low propensity for generation of resistance to S. aureus ATCC 29213. MB significantly eradicated pre-formed S. aureus biofilms and reduced intracellular S. aureus in the J774 macrophage infection model as well. MB strongly synergized with gentamicin at 1 × MIC in vitro with complete killing at 24 h as compared with untreated S. aureus. MB also possessed significant in vivo activity against S. aureus at 50 mg/kg BID dose with ∼0.5 log10 cfu/g reduction in thigh compared with untreated mice. Conclusions MB demonstrates the potential to be further developed for infections caused by S. aureus owing to its excellent in vitro and in vivo activity.

In pursuit of potent anti-TB agents active against drug resistant tuberculosis (DR-TB), herein we report synthesis and bio-evaluation of a new series of isoxazole-carboxylic acid methyl ester based 2-substituted quinoline derivatives. Preliminary evaluation indicated selectivity towards Mtb H37Rv, with no inhibition of non-tubercular mycobacterial (NTM)bacterial pathogen panel. Out of 36 synthesized compounds, majority exhibited substantial inhibition of Mtb H37Rv (MIC 0.5-8 μg/mL). Cell viability test against Vero cells revealed no significant cytotoxicity. Further, screening against drug resistant strains (DR-Mtb) found hit compound displaying promising potency (MIC 1-4 μg/mL). Structure optimization of the hit led to the identification of lead compound demonstrating potent inhibition of both drug-susceptible Mtb (MIC 0.12 μg/mL) and drug-resistant Mtb (MIC 0.25-0.5 μg/mL) along with a high selectivity index (SI)80. Taken together, with appreciable selectivity and potent activity, these chemotypes show prospect to be turned into a potential anti-TB candidate.

Antimicrobial resistance is a serious challenge to modern medicine. Besides imposing high financial burden, multidrug resistant infections are directly responsible for high morbidity and mortality. Even though a number of antibiotics are currently available to treat infections caused by ESKAPE organisms, more and more bacterial strains are becoming resistant to these drugs. Prevailing circumstances pose an urgent unmet need for the development of newer antimicrobials to treat the infections caused by MDR organisms. Rhodanine and structurally related 5-membered heterocycles possess wide range of pharmacological activities. A number of these derivatives have shown good to potent inhibition against various microorganisms. They are reported to alter the function of DNA gyrase B, metallo-β-lactamases, penicillin binding protein (PBP), Mur ligases, RNA polymerase, Enoyl ACP reductases, 1-deoxy-d-xylulose-5-phosphate reductoisomerase. etc which are vital in bacterial growth, survival and replication. In this study, we have generated a library of Rhodanine and related 5 membered heterocyclic derivatives and screened them against a panel of pathogens. Among all the compounds, 2a-i, 3a-b, 3g, 4, 6b-c, 6e, 6g, 12a-b and 14b-c have demonstrated good to moderate inhibition against S. aureus (MIC 0.125-8 μg/mL). Further, compound 17b demonstrated moderate activity against A. baumannii (MIC 8 μg/mL). In addition, compounds 2a, 2e, 4, 6c, 6g and 14b have shown good to mild inhibition against MDR S. aureus including VRSA (MIC 0.5-16 μg/mL) with good selectivity index 20-1600. In addition, compound 2e inhibited the growth gradually after 6 h in time kill kinetic studies and not antagonized with the tested FDA approved drugs.

Background Antimicrobial resistance is a growing menace, claiming millions of lives all over the world. In this context, drug repurposing is one approach gaining interest as a suitable alternative to conventional drug discovery and development. Methods Whole-cell assays were used to screen FDA-approved drugs to identify novel antimicrobial agents active against bacterial pathogens. Following identification of nitazoxanide, its various characteristics, such as antimicrobial activity against MDR isolates, time–kill kinetics, ability to synergize with approved drugs, antibiofilm activity and ability to generate resistance in Staphylococcus aureus, were determined, followed by determination of its in vivo potential against MDR S. aureus. Results Nitazoxanide demonstrated a potent in vitro antistaphylococcal profile, including equipotent activity against clinical drug-resistant S. aureus and Enterococcus spp. Nitazoxanide exhibited concentration-dependent killing, significantly eradicated preformed S. aureus biofilm and S. aureus did not generate resistance to it. Nitazoxanide strongly synergized with linezolid both in vitro and in vivo against linezolid-susceptible and -resistant S. aureus, displaying superior activity to untreated control and drug-alone treatment groups. Conclusions Nitazoxanide can be utilized in combination with linezolid against infections caused by linezolid-resistant S. aureus as it exhibits strong synergism in vitro and in vivo.

A facile method was developed for the synthesis of quinazolinone derivatives in a one-pot condensation reaction via in situ amine generation using ammonia as the amine source and with the formation of four new C–N bonds in good to excellent yields. With the optimised method, we synthesized a library of piperazine linked quinazoline derivatives and the synthesized compounds were evaluated for their inhibitory activity against Mycobacterium tuberculosis. The compounds 8b, 8e, 8f, 8m, 8n and 8v showed potent anti-mycobacterial activity with MIC values of 2–16 μg mL−1. All the synthesized compounds follow Lipinski's rules for drug likeness.

A series of new fluoroquinolone analogs (3-18) were prepared, in three steps, by substituting chloro esters and esters with cyclic amines on the C-7 endo-nortropine derivatives of difluoroquinolone acid. All the synthesized compounds displayed good MIC against the Staphylococcus aureus when initially screened for Escherichia coli, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. The molecules were further evaluated for their antibacterial activity against fluoroquinolone-resistant strains of S. aureus and for cytotoxic assay. Based on the results, five of the sixteen compounds displayed the potential to be developed further for treatment against fluoroquinolone-resistant strains of S. aureus.

Background Antimicrobial resistance is an urgent threat affecting healthcare systems worldwide. Identification of novel molecules capable of escaping current resistance mechanisms and exhibiting potent activity against highly drug-resistant strains is the unmet need of the hour. Methods Whole cell growth inhibition assays were used to screen and identify novel inhibitors. The hit compounds were tested against Vero cells to determine the selectivity index, followed by time-kill kinetics against Staphylococcus aureus. The ability of disulfiram to synergize with several approved drugs utilized for the treatment of S. aureus was determined using fractional inhibitory concentration indexes, followed by its ability to decimate staphyloccocal infections ex vivo. Finally, the in-vivo potential of disulfiram was determined in a neutropenic murine model of S. aureus infection. Results The screening showed that disulfiram has equipotent antibacterial activity against S. aureus, including clinical drug-resistant strains (minimum inhibitory concentration 8–16 mg/L). Disulfiram exhibited concentration-dependent bactericidal activity (∼7 log10 colony-forming units/mL reduction), synergized with linezolid and gentamycin against S. aureus, eradicated staphylococcal biofilms (64-fold better than vancomycin), decimated intracellular S. aureus better than vancomycin, exhibited longer post antibiotic effect than vancomycin, and reduced bacterial counts in murine thigh as well as vancomycin at 50 mg/kg. Conclusion Taken together, disulfiram exhibits all the characteristics required for repurposing as an antibacterial targeting staphylococcal infections.

Green and facile synthesis of 24 tryptanthrin-thiopyrano[2,3-b]indole hybrid molecules is described (i) by a thermal one-pot multi-component strategy, (ii) using ammonium acetate in solvent-free conditions at 100 °C and (iii) by electrochemical method at room temperature. The in vitro antibacterial activities of compounds were evaluated against bacterial pathogen panel including clinically relevant highly drug-resistant MRSA/VRSA isolates, which led to the identification of nitro-substituted hybrid molecule 4c as being the most potent molecule against S. aureus ATCC 29213 with a high selectivity index. Upon further analysis, 4c exhibited concentration dependent bactericidal activity with a long PAE (post-antibiotic effect) and synergized with linezolid against S. aureus. From the in vitro metabolic stability assay (using rat liver microsomes) it was found that 4c has half-life of120 min. The co-crystallographic studies indicated that amino group in compound 4c is the potential binding site. From all the studies, it was clear that compound 4c exhibits all the hallmarks for positioning it as a novel anti-staphylococcal therapeutic option.

Zaire ebolavirus has been responsible for several catastrophic outbreaks with a high mortality rate. Unfortunately, there were no approved therapies or vaccines to treat or prevent infections caused by Ebola virus (EBOV) or other filoviruses. Atoltivimab/ maftivimab/odesivimab (Inmazeb) is the first Food and Drug Administration (FDA)-approved treatment for Zaire ebolavirus infection in adult and pediatric patients, including neonates born to a mother who is reverse transcription polymerase chain reaction (RT-PCR)-positive for Zaire ebolavirus infection. The efficacy of Inmazeb has been established in vivo and it has successfully completed a phase I clinical trial in healthy individuals with no drug-related adverse effects. Additionally, Inmazeb has displayed significant reduction in mortality in the PALM (PAmoja tuLinde Maisha) trial, when compared with the control arm receiving ZMapp. Inmazeb has received orphan drug designation from both the U.S. FDA and the European Medicines Agency (EMA).

The quinoline moiety remains a privileged antitubercular (anti-TB) pharmacophore, whereas 8-nitrobenzothiazinones are emerging potent antimycobacterial agents with two investigational candidates in the clinical pipeline. Herein, we report the synthesis and bioevaluation of 30 piperazinyl-benzothiazinone-based quinoline hybrids as prospective anti-TB agents. Preliminary evaluation revealed 24/30 compounds exhibiting substantial activity (minimum inhibitory concentration [MIC] = 0.06-1 µg/ml) against Mycobacterium tuberculosis (Mtb) H37Rv. Cytotoxicity analysis against Vero cells found these to be devoid of any significant toxicity, with the majority displaying a selectivity index of80. Furthermore, potent nontoxic compounds, when screened against clinical isolates of drug-resistant Mtb strains, demonstrated equipotent inhibition with MIC values of 0.03-0.25 µg/ml. A time-kill study identified a lead compound exhibiting concentration-dependent bactericidal activity, with 10× MIC completely eliminating Mtb bacilli within 7 days. Along with acceptable aqueous solubility and microsomal stability, the optimum active compounds of the series manifested all desirable traits of a promising antimycobacterial candidate.

Ever increasing drug resistance has become an impeding threat that continues to hamper effective tackling of otherwise treatable tuberculosis (TB). Such dismal situation necessitates identification and exploration of multitarget acting newer chemotypes with bactericidal efficacy as a priority, that could efficiently hinder uncontrolled spread of TB. In this context, herein we present design, synthesis and bio-evaluation of chalcone tethered bezoxazole-2-amines as promising anti-TB chemotypes. Preliminary screening of 24 compounds revealed initial hits 3,4,5-trimethoxyphenyl and 5-nitrofuran-2-yl derivative exhibiting selective inhibition of Mycobacterium tuberculosis (Mtb) H37Rv. Further, structural optimization of hit compounds generated 12 analogues, amongst which 5-nitrofuran-2-yl derivatives displayed potent inhibition of not only drug-susceptible (DS) Mtb but also clinical isolates of drug-resistant (DR) Mtb strains equipotently. Moreover, cell viability test against Vero cells found these compounds with favourable selectivity. Time kill analysis led to the identification of the lead compound (E)-1-(4-((5-chlorobenzo[d]oxazol-2-yl)amino)phenyl)-3-(5-nitrofuran-2-yl)prop-2-en-1-one, that demonstrated bactericidal killing of Mtb bacilli. Together with acceptable microsomal stability, the lead compound of the series manifested all desirable traits of a promising antitubercular agent.

Fluoroquinolones (FQs) are among the front-line antibiotics used to treat severe infections caused by Gram-negative bacteria. However, recently, due to toxicity concerns, their use has been severely restricted. Hence, efforts to direct delivery of this antibiotic specifically to bacteria/site of infection are underway. Here, we report a strategy that uses a bacterial enzyme for activation of a prodrug to generate the active antibiotic. The ciprofloxacin-latent fluorophore conjugate 1, which is designed as a substrate for nitroreductase (NTR), a bacterial enzyme, was synthesized. Upon activation by NTR, release of Ciprofloxacin (CIP) as well as a fluorescence reporter was observed. We provide evidence for the prodrug permeating bacteria to generate a fluorescent signal and we found no evidence for activation in mammalian cells supporting selectivity of activation within bacteria. As a testament to its efficacy, 1 was found to have potent bactericidal activity nearly identical to CIP and significantly reduced the bacterial burden in a neutropenic mouse thigh infection model, again, at comparable potency with CIP, a clinically used FQ. Thus, together, we have developed a small molecule that facilitates bacteria-specific fluoroquinolone delivery.

Nosocomial infections arising from opportunistic pathogens, such as Staphylococcus aureus, are growing unabated, compounded by the rapid emergence of antimicrobial resistance. Herein, we demonstrate a new molecular design that exhibits excellent activity against multidrug-resistant S. aureus with no cytotoxicity and resensitizes fluoroquinolones (FQ) towards FQ-resistant methicillin-resistant S. aureus strains, with DNA gyrase B as the likely molecular target as determined by molecular dynamics (MD) simulations.

Occurrence of infections due to the drug resistant Staphylococcus aureus is on rise necessitating the need for rapid development of new antibacterial agents. In our present work, a series of new 3-phenylquinazolin-4(3H)-one derivatives were designed, synthesized and evaluated for their antibacterial activity against ESKAP (E. coli, S. aureus, K. pneumoniae, A. baumannii, P. aeroginosa) pathogen panel and pathogenic mycobacterial strains. The study revealed that compounds 4a, 4c, 4e, 4f, 4g, 4i, 4o and 4p exhibited selective and potent inhibitory activity against Staphylococcus aureus with MIC values in the range of 0.125–8 µg/mL. Further, the compounds 4c, 4e and 4g were found to be non toxic to Vero cells (CC50 = >10–>100 µg/mL) and exhibited favourable selectivity index (SI = 40–>200). The compounds 4c, 4e and 4g also showed potent inhibitory activity against various MDR-S. aureus including VRSA. The promising results obtained indicated the potential use of the above series of compounds as promising antibacterial agents for the treatment of multidrug resistant Staphylococcus aureus infections.

Drug resistant bacteria pose a major health concern and affect a large section of global population. Antibacterial drug discovery has stagnated owing to multiple factors including unattractive returns for major pharmaceutical companies. Thus, discovery of effective antibacterial drugs against drug-resistant bacteria is an urgent unmet need affecting healthcare systems globally. In this study, fluorine-containing 2,3-diarylquinolines (4a-l) and non-fluorinated analog 4m were synthesized utilizing environmentally benign chemistry of arenediazonium salts and arynes for regioselective installation of aryl groups at C-2 and C-3 positions, respectively. In vitro antibacterial evaluation against various Gram-negative and Gram-positive bacteria revealed inhibitory activity of majority of these compounds against Gram-positive S. aureus ATCC 29213. Compounds 4e, 4i, 4j and 4l were most potent inhibitors with MIC values of 10.95−24.0 µM. None of the compounds inhibited Gram-negative bacteria. 4e, 4i and 4l also displayed low levels of cytotoxicity against Vero cells, therefore, offering high safety profiles. Importantly, 4e, 4i and 4l exhibited equipotent inhibition of Methicillin and Vancomycin-resistant S. aureus, rendering them potential hits for further development. Molecular docking studies with topoisomerase II DNA gyrase demonstrated significant interactions of these inhibitors with target protein, which provided valuable insights into their potent antibacterial activity.

The discovery and clinical utilization of antibiotics is one of the most important breakthroughs that has revolutionized medical science and significantly contributed to saving millions of lives. However, due to irrational, rampant misuse of antibiotics along with poor patient compliance has led to current state of almost entering postantibiotic era because of a phenomenon called antimicrobial resistance (AMR). Furthermore, the problem has become compounded due to the dearth of novel and effective antibacterials being discovered and developed owing to a multitude of factors, including ever increasing costs of discovery and development as well as complex and costly clinical trials for regulatory approval. As a result of this, recent reports suggest an estimated death toll of 700,000 deaths each year attributable to AMR along with future projected deaths reaching ∼10 million by 2050. Thus new policies to invigorate antibiotic discovery and development are required to avoid postantibiotic era.

Sarecycline hydrochloride (Seysara) is a novel, narrow-spectrum tetracycline derivative approved by the U.S. Food and Drug Administration (FDA) in October 2018 for the treatment of inflammatory non-nodular moderate to severe acne vulgaris. It was initially developed by Paratek Pharmaceuticals, Inc. (U.S.) and Allergan plc (U.S.), which later was acquired by Almirall S.A. (Barcelona, Spain). Almirall S.A. obtained U.S. FDA approval of oral sarecycline tablets under the trade name Seysara. Sarecycline exhibits antibacterial activity against important skin/soft tissue pathogens with targeted activity against Cutibacterium acnes--an anaerobic Gram-positive bacterium linked with acne lesions--and also exerts anti-inflammatory effects as do other tetracyclines used in the treatment of acne vulgaris. Interestingly, unlike the broad-spectrum tetracyclines, sarecycline is less potent against aerobic Gram-negative bacilli and anaerobic bacteria associated with endogenous intestinal microbial flora. This provides it with a more specific antibacterial spectra with lower chances of adverse off-target antibacterial effects, thus making it a promising choice of treatment over others in its class. It has also demonstrated low propensity to resistance as compared with other tetracyclines and is also active against tetracycline-resistant Staphylococcus aureus as well as erythromycin- and clindamycin-resistant C. acnes strains. Sarecycline has successfully undergone numerous phase I, phase II and three phase III studies establishing it as a well-tolerated once-daily oral drug available as a tablet for the treatment of patients 9 years of age or above.