Antiviral activity of Vigna radiata extract against feline coronavirus in vitro.

Feline infectious peritonitis (FIP) is a fatal illness caused by a mutated feline coronavirus (FCoV). This disease is characterized by its complexity, resulting from systemic infection, antibody-dependent enhancement (ADE), and challenges in accessing effective therapeutics. Extract derived from Vigna radiata (L.) R. Wilczek (VRE) exhibits various pharmacological effects, including antiviral activity. This study aimed to investigate the antiviral potential of VRE against FCoV, addressing the urgent need to advance the treatment of FIP. We explored the anti-FCoV activity, antiviral mechanism, and combinational application of VRE by means of in vitro antiviral assays. Our findings reveal that VRE effectively inhibited the cytopathic effect induced by FCoV, reduced viral proliferation, and downregulated spike protein expression. Moreover, VRE blocked FCoV in the early and late infection stages and was effective under in vitro ADE infection. Notably, when combined with VRE, the polymerase inhibitor GS-441524 or protease inhibitor GC376 suppressed FCoV more effectively than monotherapy. In conclusion, this study characterizes the antiviral property of VRE against FCoV in vitro, and VRE possesses therapeutic potential for FCoV treatment.

Microwave-Assisted Atom Transfer Radical Cyclization in the Synthesis of 3,3-Dichloro-γ- and δ-Lactams from N-Alkenyl-Tethered Trichloroacetamides Catalyzed by RuCl2(PPh3)3 and Their Cytotoxic Evaluation.

An expeditious synthesis of γ- and δ-lactams from tethered alkenyl trichloroacetamides in the presence of 5% of RuCl2(PPh3)3 is reported. In this investigation we have demonstrated that microwave activation significantly enhances reaction rates, leading to the formation of the corresponding lactams in yields ranging from good to excellent. Thus, we have been able to prepare a wide range of lactams, including indole and morphan bicyclic scaffolds, where the corresponding reactions were completely diastereoselective. This process was successfully extended to α,α-dichloroamides without affecting either their yield or their diastereoselectivity. Some of the lactams prepared in this work were evaluated for their hemolytic and cytotoxic responses. All compounds were found to be non-hemolytic at the tested concentration, indicating their safety profile in terms of blood cell integrity. Meanwhile, they exhibited interesting cytotoxicity responses that depend on both their lactam structure and cell line. Among the molecules tested, γ-lactam 2a exhibited the lowest IC50 values (100-250 µg/mL) as a function of its cell line, with promising selectivity against squamous carcinoma cells (A431) in comparison with fibroblasts (3T3 cell line).

Discovery of a Bacterial Hydrazine Transferase That Constructs the N-Aminolactam Pharmacophore in Albofungin Biosynthesis.

Structural motifs containing nitrogen-nitrogen (N-N) bonds are prevalent in a large number of clinical drugs and bioactive natural products. Hydrazine (N2H4) serves as a widely utilized building block for the preparation of these N-N-containing molecules in organic synthesis. Despite its common use in chemical processes, no enzyme has been identified to catalyze the incorporation of free hydrazine in natural product biosynthesis. Here, we report that a hydrazine transferase catalyzes the condensation of N2H4 and an aromatic polyketide pathway intermediate, leading to the formation of a rare N-aminolactam pharmacophore in the biosynthesis of broad-spectrum antibiotic albofungin. These results expand the current knowledge on the biosynthetic mechanism for natural products with N-N units and should facilitate future development of biocatalysts for the production of N-N-containing chemicals.

In Silico Analysis: Anti-Inflammatory and α-Glucosidase Inhibitory Activity of New α-Methylene-γ-Lactams.

The research about α-methylene-γ-lactams is scarce; however, their synthesis has emerged in recent years mainly because they are isosters of α-methylene-γ-lactones. This last kind of compound is structurally most common in some natural products' nuclei, like sesquiterpene lactones that show biological activity such as anti-inflammatory, anticancer, antibacterial, etc., effects. In this work, seven α-methylene-γ-lactams were evaluated by their inflammation and α-glucosidase inhibition. Thus, compounds 3-methylene-4-phenylpyrrolidin-2-one (1), 3-methylene-4-(p-tolyl)pyrrolidin-2-one (2), 4-(4-chlorophenyl)-3-methylenepyrrolidin-2-one (3), 4-(2-chlorophenyl)-3-methylenepyrrolidin-2-one (4), 5-ethyl-3-methylene-4-phenylpyrrolidin-2-one (5), 5-ethyl-3-methylene-4-(p-tolyl)pyrrolidin-2-one (6) and 4-(4-chlorophenyl)-5-ethyl-3-methylenepyrrolidin-2-one (7) were evaluated via in vitro α-glucosidase assay at 1 mM concentration. From this analysis, 7 exerts the best inhibitory effect on α-glucosidase compared with the vehicle, but it shows a low potency compared with the reference drug at the same dose. On the other side, inflammation edema was induced using TPA (12-O-tetradecanoylphorbol 13-acetate) on mouse ears; compounds 1-7 were tested at 10 µg/ear dose. As a result, 1, 3, and 5 show a better inhibition than indomethacin, at the same doses. This is a preliminary report about the biological activity of these new α-methylene-γ-lactams.

Isolation, Identification and Chemical Modification of Bufadienolides from Bufo melanostictus Schneider and Their Cytotoxic Activities against Prostate Cancer Cells.

The traditional Chinese medicine toad venom (Venenum bufonis) has been extensively used to treat various diseases, including cancers, in China and other Southeast Asian countries. The major constituents of toad venom, e.g., bufadienolides and alkaloids, exhibit broad-spectrum pharmacological effects in cancers. Herein, two new bufadienolides (1 and 2), along with eleven known compounds (3-13) were successfully isolated from Bufo melanostictus Schneider. Their structures were elucidated by extensive spectroscopic data and X-ray diffraction analysis. Furthermore, four lactam derivatives were synthesized through the transformation of bufadienolides lactones. The inhibitory effects of these compounds against human prostate cancer cell lines PC-3 and DU145 were evaluated. The outcomes indicated a notable trend, with a substantial subset displaying nanomolar range IC50 values against PC-3 and DU145 cells, underscoring their pronounced cytotoxicity. Moreover, a noteworthy distinction surfaces, wherein lactones consistently outperformed their lactam counterparts, further validating their heightened potency for the treatment of prostate cancer. This study contributes significant preclinical evidence substantiating the therapeutic viability of bufadienolides and toad venom as intervention strategies for prostate cancer.

Effectiveness of nirmatrelvir-ritonavir versus azvudine for adult inpatients with severe or critical COVID-19.

BACKGROUND: In China, both nirmatrelvir-ritonavir (Paxlovid) and azvudine have been granted approval to treat adult SARS-CoV-2-infected patients with moderate symptoms. Information about the clinical effect of the two available agents among inpatients with severe or critical COVID-19 is scarce. PURPOSE: To compare the clinical outcomes of Paxlovid and azvudine among adult inpatients with severe or critical COVID-19. METHOD: We conducted a retrospective cohort study in two large medical centres after the epidemic control measures were lifted in China. A new propensity score matched-inverse probability of treatment weighting cohort was constructed to evaluate the in-hospital all-cause mortality, hospital length of stay, Sequential Organ Failure Assessment (SOFA) score and safety. RESULTS: A total of 955 individuals were in the cohort. The antiviral therapy strategies were decided by the senior physician and the supplies of the pharmacy. A total of 451 patients were in the Paxlovid group, and 504 patients were in the azvudine group. Compared with Paxlovid, the effects of azvudine on in-hospital all-cause mortality were not significantly different, and the OR (95% CI) was 1.084 (0.822 to 1.430), and the average hospital length of stay of patients discharged alive was also similar in the azvudine group, and the difference (day) and (95% CI) was 0.530 (-0.334 to 1.393). After 7 days of therapy, the degree of decline in the SOFA score was greater in the Paxlovid group than in the azvudine group (p<0.001). The change in glomerular filtration rate was not significantly different (p=0.824). CONCLUSION: Paxlovid and azvudine had similar effectiveness on in-hospital all-cause mortality and hospital length of stay. Compared with the azvudine group, after 7 days of therapy, the degree of decline in SOFA score was significantly higher in the Paxlovid group. These findings need to be verified in larger prospective studies or randomised controlled trials.

Proof-of-concept studies with a computationally designed Mpro inhibitor as a synergistic combination regimen alternative to Paxlovid.

As the SARS-CoV-2 virus continues to spread and mutate, it remains important to focus not only on preventing spread through vaccination but also on treating infection with direct-acting antivirals (DAA). The approval of Paxlovid, a SARS-CoV-2 main protease (Mpro) DAA, has been significant for treatment of patients. A limitation of this DAA, however, is that the antiviral component, nirmatrelvir, is rapidly metabolized and requires inclusion of a CYP450 3A4 metabolic inhibitor, ritonavir, to boost levels of the active drug. Serious drug-drug interactions can occur with Paxlovid for patients who are also taking other medications metabolized by CYP4503A4, particularly transplant or otherwise immunocompromised patients who are most at risk for SARS-CoV-2 infection and the development of severe symptoms. Developing an alternative antiviral with improved pharmacological properties is critical for treatment of these patients. By using a computational and structure-guided approach, we were able to optimize a 100 to 250 µM screening hit to a potent nanomolar inhibitor and lead compound, Mpro61. In this study, we further evaluate Mpro61 as a lead compound, starting with examination of its mode of binding to SARS-CoV-2 Mpro. In vitro pharmacological profiling established a lack of off-target effects, particularly CYP450 3A4 inhibition, as well as potential for synergy with the currently approved alternate antiviral, molnupiravir. Development and subsequent testing of a capsule formulation for oral dosing of Mpro61 in B6-K18-hACE2 mice demonstrated favorable pharmacological properties, efficacy, and synergy with molnupiravir, and complete recovery from subsequent challenge by SARS-CoV-2, establishing Mpro61 as a promising potential preclinical candidate.

Navigating resistance to ALK inhibitors in the lorlatinib era: a comprehensive perspective on NSCLC.

INTRODUCTION: The emergence of anaplastic lymphoma kinase (ALK) rearrangements in non-small cell lung cancer (NSCLC) has revolutionized targeted therapy. This dynamic landscape, featuring novel ALK inhibitors and combination therapies, necessitates a profound understanding of resistance mechanisms for effective treatment strategies. Recognizing two primary categories - on-target and off-target resistance - underscores the need for comprehensive assessment. AREAS COVERED: This review delves into the intricacies of resistance to ALK inhibitors, exploring complexities in identification and management. Molecular testing, pivotal for early detection and accurate diagnosis, forms the foundation for patient stratification and resistance management. The literature search methodology involved comprehensive exploration of Pubmed and Embase. The multifaceted perspective encompasses new therapeutic horizons, ongoing clinical trials, and their clinical implications post the recent approval of lorlatinib. EXPERT OPINION: Our expert opinion encapsulates the critical importance of understanding resistance mechanisms in the context of ALK inhibitors for shaping successful treatment approaches. With a focus on molecular testing and comprehensive assessment, this review contributes valuable insights to the evolving landscape of NSCLC therapy.

Adaptative Strategy of Immunosuppressive Drugs Dosage Adjustments When Combined With Nirmatrelvir/Ritonavir in Solid Organ Transplant Recipients With COVID-19.

Nirmatrelvir/ritonavir is a promising option for preventing severe COVID-19 in solid organ transplant recipients with SARS-CoV-2 infection. However, concerns have arisen regarding potential drug interactions with calcineurin inhibitors (CNI). This two-phase multicentre retrospective study, involving 113 patients on tacrolimus and 13 on cyclosporine A, aimed to assess the feasibility and outcomes of recommendations issued by The French societies of transplantation (SFT) and pharmacology (SFPT) for CNI management in this context. The study first evaluated adherence to recommendations, CNI exposure, and clinical outcomes. Notably, 96.5% of patients on tacrolimus adhered to the recommendations, maintaining stable tacrolimus trough concentrations (C0) during nirmatrelvir/ritonavir treatment. After reintroduction, most patients experienced increased C0, with 42.9% surpassing 15 ng/mL, including three patients exceeding 40 ng/mL. Similar trends were observed in cyclosporine A patients, with no COVID-19-related hospitalizations. Moreover, data from 22 patients were used to refine the reintroduction strategy. Modelling analyses suggested reintroducing tacrolimus at 50% of the initial dose on day 8, and then at 100% from day 9 as the optimal approach. In conclusion, the current strategy effectively maintains consistent tacrolimus exposure during nirmatrelvir/ritonavir treatment, and a stepwise reintroduction of tacrolimus may be better suited to the low CYP3A recovery.

LTK mutations responsible for resistance to lorlatinib in non-small cell lung cancer harboring CLIP1-LTK fusion.

The CLIP1-LTK fusion was recently discovered as a novel oncogenic driver in non-small cell lung cancer (NSCLC). Lorlatinib, a third-generation ALK inhibitor, exhibited a dramatic clinical response in a NSCLC patient harboring CLIP1-LTK fusion. However, it is expected that acquired resistance will inevitably develop, particularly by LTK mutations, as observed in NSCLC induced by oncogenic tyrosine kinases treated with corresponding tyrosine kinase inhibitors (TKIs). In this study, we evaluate eight LTK mutations corresponding to ALK mutations that lead to on-target resistance to lorlatinib. All LTK mutations show resistance to lorlatinib with the L650F mutation being the highest. In vitro and in vivo analyses demonstrate that gilteritinib can overcome the L650F-mediated resistance to lorlatinib. In silico analysis suggests that introduction of the L650F mutation may attenuate lorlatinib-LTK binding. Our study provides preclinical evaluations of potential on-target resistance mutations to lorlatinib, and a novel strategy to overcome the resistance.

Synthesis of Asp-based lactam cyclic peptides using an amide-bonded diaminodiacid to prevent aspartimide formation.

Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a ß-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cyclo[Lys9,Asp13] KIIIA7-14 and 1Y.

A combination of nirmatrelvir and ombitasvir boosts inhibition of SARS-CoV-2 replication.

Antiviral therapeutics are highly effective countermeasures for the treatment of coronavirus disease 2019 (COVID-19). However, development of resistance to antivirals undermines their effectiveness. Combining multiple antivirals during patient treatment has the potential to overcome the evolutionary selective pressure towards antiviral resistance, as well as provide a more robust and efficacious treatment option. The current evidence for effective antiviral combinations to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication is limited. Here, we demonstrate a combination of nirmatrelvir with ombitasvir, to jointly bring about potent inhibition of SARS-CoV-2 replication. We developed an in vitro 384- well plate cytopathic effect assay for the evaluation of antiviral combinations against Calu-3 cells infected with SARS-CoV-2 and found, that a combination of ombitasvir and nirmatrelvir was synergistic; thereby decreasing the nirmatrelvir IC50 by approx. 16-fold. The increased potency of the nirmatrelvir-ombitasvir combination, over nirmatrelvir alone afforded a greater than 3 log10 reduction in viral titre, which is sufficient to fully prevent the detection of progeny SARS-CoV-2 viral particles at 48 h post infection. The mechanism of this potentiated effect was shown to be, in-part, due to joint inhibition of the 3-chymotrypsin-like protease via a positive allosteric modulation mechanism.

A case report of drug interaction between co-packaged nirmatrelvir-ritonavir and tacrolimus causing hyponatremia in a lung transplant recipient.

BACKGROUND: Coronavirus disease 2019 (COVID-19) infection in lung transplant recipients can be lethal owing to the use of immunosuppressants. Antiviral agents may be administered to these patients. Co-packaged nirmatrelvir-ritonavir is a new agent currently being used in combination. CASE PRESENTATION: In this report, we present a case of a 64-year-old woman, a lung transplant recipient, who experienced hyponatremia and showed a high serum tacrolimus concentration following the administration of the co-packaged nirmatrelvir-ritonavir combination. CONCLUSION: Although the nirmatrelvir-ritonavir and tacrolimus combination is not contraindicated, other treatment strategies should be considered first, if available, and the dose of tacrolimus should be reduced when using the nirmatrelvir-ritonavir combination. In cases where combination therapy is necessary, serum tacrolimus levels should be closely monitored in lung transplant recipients. Documentation of more such reports is important to identify drug interactions between nirmatrelvir-ritonavir and other agents, with the aim of preventing severe adverse effects.

Preclinical evaluation of the SARS-CoV-2 Mpro inhibitor RAY1216 shows improved pharmacokinetics compared with nirmatrelvir.

Although vaccines are available for SARS-CoV-2, antiviral drugs such as nirmatrelvir are still needed, particularly for individuals in whom vaccines are less effective, such as the immunocompromised, to prevent severe COVID-19. Here we report an α-ketoamide-based peptidomimetic inhibitor of the SARS-CoV-2 main protease (Mpro), designated RAY1216. Enzyme inhibition kinetic analysis shows that RAY1216 has an inhibition constant of 8.4 nM and suggests that it dissociates about 12 times slower from Mpro compared with nirmatrelvir. The crystal structure of the SARS-CoV-2 Mpro:RAY1216 complex shows that RAY1216 covalently binds to the catalytic Cys145 through the α-ketoamide group. In vitro and using human ACE2 transgenic mouse models, RAY1216 shows antiviral activities against SARS-CoV-2 variants comparable to those of nirmatrelvir. It also shows improved pharmacokinetics in mice and rats, suggesting that RAY1216 could be used without ritonavir, which is co-administered with nirmatrelvir. RAY1216 has been approved as a single-component drug named 'leritrelvir' for COVID-19 treatment in China.

Conjugation to Native and Nonnative Triscatecholate Siderophores Enhances Delivery and Antibacterial Activity of a ß-Lactam to Gram-Negative Bacterial Pathogens.

Developing new antibiotics and delivery strategies is of critical importance for treating infections caused by Gram-negative bacterial pathogens. Hijacking bacterial iron uptake machinery, such as that of the siderophore enterobactin (Ent), represents one promising approach toward these goals. Here, we report a novel Ent-inspired siderophore-antibiotic conjugate (SAC) employing an alternative siderophore moiety as the delivery vector and demonstrate the potency of our SACs harboring the ß-lactam antibiotic ampicillin (Amp) against multiple pathogenic Gram-negative bacterial strains. We establish the ability of N,N',N''-(nitrilotris(ethane-2,1-diyl))tris(2,3-dihydroxybenzamide) (TRENCAM, hereafter TC), a synthetic mimic of Ent, to facilitate drug delivery across the outer membrane (OM) of Gram-negative pathogens. Conjugation of Amp to a new monofunctionalized TC scaffold affords TC-Amp, which displays markedly enhanced antibacterial activity against the gastrointestinal pathogen Salmonella enterica serovar Typhimurium (STm) compared with unmodified Amp. Bacterial uptake, antibiotic susceptibility, and microscopy studies with STm show that the TC moiety facilitates TC-Amp uptake by the OM receptors FepA and IroN and that the Amp warhead inhibits penicillin-binding proteins. Moreover, TC-Amp achieves targeted activity, selectively killing STm in the presence of a commensal lactobacillus. Remarkably, we uncover that TC-Amp and its Ent-based predecessor Ent-Amp achieve enhanced antibacterial activity against diverse Gram-negative ESKAPE pathogens that express Ent uptake machinery, including strains that possess intrinsic ß-lactam resistance. TC-Amp and Ent-Amp exhibit potency comparable to that of the FDA-approved SAC cefiderocol against Gram-negative pathogens. These results demonstrate the effective application of native and appropriately designed nonnative siderophores as vectors for drug delivery across the OM of multiple Gram-negative bacterial pathogens.

Contributions of Hyperactive Mutations in Mpro from SARS-CoV-2 to Drug Resistance.

The appearance and spread of mutations that cause drug resistance in rapidly evolving diseases, including infections by the SARS-CoV-2 virus, are major concerns for human health. Many drugs target enzymes, and resistance-conferring mutations impact inhibitor binding or enzyme activity. Nirmatrelvir, the most widely used inhibitor currently used to treat SARS-CoV-2 infections, targets the main protease (Mpro) preventing it from processing the viral polyprotein into active subunits. Our previous work systematically analyzed resistance mutations in Mpro that reduce binding to inhibitors; here, we investigate mutations that affect enzyme function. Hyperactive mutations that increase Mpro activity can contribute to drug resistance but have not been thoroughly studied. To explore how hyperactive mutations contribute to resistance, we comprehensively assessed how all possible individual mutations in Mpro affect enzyme function using a mutational scanning approach with a fluorescence resonance energy transfer (FRET)-based yeast readout. We identified hundreds of mutations that significantly increased the Mpro activity. Hyperactive mutations occurred both proximal and distal to the active site, consistent with protein stability and/or dynamics impacting activity. Hyperactive mutations were observed 3 times more than mutations which reduced apparent binding to nirmatrelvir in recent studies of laboratory-grown viruses selected for drug resistance. Hyperactive mutations were also about three times more prevalent than nirmatrelvir binding mutations in sequenced isolates from circulating SARS-CoV-2. Our findings indicate that hyperactive mutations are likely to contribute to the natural evolution of drug resistance in Mpro and provide a comprehensive list for future surveillance efforts.

In vitro activity of cefiderocol against European Pseudomonas aeruginosa and Acinetobacter spp., including isolates resistant to meropenem and recent ß-lactam/ß-lactamase inhibitor combinations.

Carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter spp. represent major threats and have few approved therapeutic options. Non-|fermenting Gram-negative isolates were collected from hospitalized inpatients from 49 sites in 6 European countries between 01 January 2020 and 31 December 2020 and underwent susceptibility testing against cefiderocol and ß-lactam/ß-lactamase inhibitor combinations. Meropenem-resistant (MIC >8 mg/L), cefiderocol-susceptible isolates were analyzed by PCR, and cefiderocol-resistant isolates were analyzed by whole-genome sequencing to identify resistance mechanisms. Overall, 1,451 (950 P. aeruginosa; 501 Acinetobacter spp.) isolates were collected, commonly from the respiratory tract (42.0% and 39.3%, respectively). Cefiderocol susceptibility was higher than |ß|-|l|a|c|t|a|m|/|ß|-|l|a|c|t|a|mase| inhibitor combinations against P. aeruginosa (98.9% vs 83.3%-91.4%), and P. |aeruginosa resistant to meropenem (n = 139; 97.8% vs 12.2%-59.7%), ß-lactam/ß-lactamase inhibitor combinations (93.6%-98.1% vs 10.7%-71.8%), and both meropenem and ceftazidime-avibactam (96.7% vs 5.0%-||45.0%) or |ceftolozane-tazobactam (98.4% vs 8.1%-54.8%), respectively. Cefiderocol and sulbactam-durlobactam susceptibilities were high against Acinetobacter spp. (92.4% and 97.0%) and meropenem-resistant Acineto|bacter |spp. (n = 227; 85.0% and 93.8%) but lower against sulbactam-durlobactam- (n |= 15; 13.3%) and cefiderocol- (n = 38; 65.8%) resistant isolates, respectively. Among meropenem-resistant P. aeruginosa and Acinetobacter spp., the most common ß-||lactamase genes were metallo-ß-lactamases [30/139; blaVIM-2 (15/139)] and oxacillinases [215/227; blaOXA-23 (194/227)], respectively. Acquired ß-lactamase genes were identified in 1/10 and 32/38 of cefiderocol-resistant P. aeruginosa and Acinetobacter spp., and pirA-like or piuA mutations in 10/10 and 37/38, respectively. Conclusion: cefiderocol susceptibility was high against P. aeruginosa and Acinetobacter spp., including meropenem-resistant isolates and those resistant to recent ß-lactam/ß-lactamase inhibitor combinations common in first-line treatment of European non-fermenters. IMPORTANCE: This was the first study in which the in vitro activity of cefiderocol and non-licensed ß-lactam/ß-lactamase inhibitor combinations were directly compared against Pseudomonas aeruginosa and Acinetobacter spp., including meropenem- and ß-lactam/ß-lactamase inhibitor combination-resistant isolates. A notably large number of European isolates were collected. Meropenem resistance was defined according to the MIC breakpoint for high-dose meropenem, ensuring that data reflect antibiotic activity against isolates that would remain meropenem resistant in the clinic. Cefiderocol susceptibility was high against non-fermenters, and there was no apparent cross resistance between cefiderocol and ß-lactam/ß-lactamase inhibitor combinations, with the exception of sulbactam-durlobactam. These results provide insights into therapeutic options for infections due to resistant P. aeruginosa and Acinetobacter spp. and indicate how early susceptibility testing of cefiderocol in parallel with ß-lactam/ß-lactamase inhibitor combinations will allow clinicians to choose the effective treatment(s) from all available options. This is particularly important as current treatment options against non-fermenters are limited.

Activity of cefiderocol and innovative ß-lactam/ß-lactamase inhibitor combinations against isogenic strains of Escherichia coli expressing single and double ß-lactamases under high and low permeability conditions.

OBJECTIVES: To analyse the impact of the most clinically relevant ß-lactamases and their interplay with low outer membrane permeability on the activity of cefiderocol, ceftazidime/avibactam, aztreonam/avibactam, cefepime/enmetazobactam, cefepime/taniborbactam, cefepime/zidebactam, imipenem/relebactam, meropenem/vaborbactam, meropenem/xeruborbactam and meropenem/nacubactam against recombinant Escherichia coli strains. METHODS: We constructed 82 E. coli laboratory transformants expressing the main ß-lactamases circulating in Enterobacterales (70 expressing single ß-lactamase and 12 producing double carbapenemase) under high (E. coli TG1) and low (E. coli HB4) permeability conditions. Antimicrobial susceptibility testing was determined by reference broth microdilution. RESULTS: Aztreonam/avibactam, cefepime/zidebactam, cefiderocol, meropenem/xeruborbactam and meropenem/nacubactam were active against all E. coli TG1 transformants. Imipenem/relebactam, meropenem/vaborbactam, cefepime/taniborbactam and cefepime/enmetazobactam were also highly active, but unstable against most of MBL-producing transformants. Combination of ß-lactamases with porin deficiency (E. coli HB4) did not significantly affect the activity of aztreonam/avibactam, cefepime/zidebactam, cefiderocol or meropenem/nacubactam, but limited the effectiveness of the rest of carbapenem- and cefepime-based combinations. Double-carbapenemase production resulted in the loss of activity of most of the compounds tested, an effect particularly evident for those E. coli HB4 transformants in which MBLs were present. CONCLUSIONS: Our findings highlight the promising activity that cefiderocol and new ß-lactam/ß-lactamase inhibitors have against recombinant E. coli strains expressing widespread ß-lactamases, including when these are combined with low permeability or other enzymes. Aztreonam/avibactam, cefiderocol, cefepime/zidebactam and meropenem/nacubactam will help to mitigate to some extent the urgency of new compounds able to resist MBL action, although NDM enzymes represent a growing challenge against which drug development efforts are still needed.

New polycyclic tetramate macrolactams with antimycobacterial activity produced by marine-derived Streptomyces sp. KKMA-0239.

During our screening for anti-mycobacterial agents against Mycobacterium avium complex (MAC), two new polycyclic tetramate macrolactams (PTMs), named hydroxycapsimycin (1) and brokamycin (2), were isolated along with the known PTM, ikarugamycin (3), from the culture broth of marine-derived Streptomyces sp. KKMA-0239. The relative structures of 1 and 2 were elucidated by spectroscopic data analyses, including 1D and 2D NMR. Furthermore, the absolute configuration of 1 was confirmed by a single-crystal X-ray diffraction analysis. Compounds 2 and 3 exhibited moderate antimycobacterial activities against MAC, including clinically isolated drug-resistant M. avium.