Meropenem-ANT3310, a unique ß-lactam-ß-lactamase inhibitor combination with expanded antibacterial spectrum against Gram-negative pathogens including carbapenem-resistant Acinetobacter baumannii.

ANT3310 is a novel broad-spectrum diazabicyclooctane serine ß-lactamase inhibitor being developed in combination with meropenem (MEM) for the treatment of serious infections in hospitalized patients where carbapenem-resistant Gram-negative pathogens are expected. In this study, we evaluated the in vitro antibacterial activity of MEM in the presence of ANT3310 at 8 µg/mL against global clinical isolates that included Acinetobacter baumannii (n = 905), carbapenem-resistant Enterobacterales (CRE), carrying either oxacillinase (OXA) (n = 252) or Klebsiella pneumoniae carbapenemase (KPC) (n = 180) carbapenemases, and Pseudomonas aeruginosa (n = 502). MEM was poorly active against A. baumannii, as were MEM-vaborbactam, ceftazidime-avibactam, aztreonam-avibactam, cefepime-taniborbactam, cefepime-zidebactam, and imipenem-relebactam (MIC90 values of ≥32 µg/mL). On the other hand, MEM-ANT3310 displayed an MIC90 value of 4 µg/mL, similar to that observed with sulbactam-durlobactam, a drug developed to specifically treat A. baumannii infections. ANT3310 (8 µg/mL) additionally restored the activity of MEM against OXA- and KPC-producing CREs decreasing MEM MIC90 values from >32 µg/mL to 0.25 and 0.5 µg/mL, respectively. The combination of 8 µg/mL of both MEM and ANT3310 prevented growth of 97.5% of A. baumannii and 100% of OXA- and KPC-positive CREs, with ~90% of P. aeruginosa isolates also displaying MEM MICs ≤8 µg/mL. Furthermore, MEM-ANT3310 was efficacious in both thigh and lung murine infection models with OXA-23 A. baumannii. This study demonstrates the potent in vitro activity of the MEM-ANT3310 combination against both carbapenem-resistant A. baumannii and Enterobacterales clinical isolates, a key differentiator to other ß-lactam/ß-lactamase combinations.

Novel Specific Metallo-ß-Lactamase Inhibitor ANT2681 Restores Meropenem Activity to Clinically Effective Levels against NDM-Positive Enterobacterales.

The global dissemination of metallo-ß-lactamase (MBL)-producing carbapenem-resistant Enterobacterales (CRE) is a serious public health concern. Specifically, NDM (New Delhi MBL) has been a major cause of carbapenem therapy failures in recent years, particularly as effective treatments for serine-ß-lactamase (SBL)-producing Enterobacterales are now commercially available. Since the NDM gene is carried on promiscuous plasmids encoding multiple additional resistance determinants, a large proportion of NDM-CREs are also resistant to many commonly used antibiotics, resulting in limited and suboptimal treatment options. ANT2681 is a specific, competitive inhibitor of MBLs with potent activity against NDM enzymes, progressing to clinical development in combination with meropenem (MEM). Susceptibility studies have been performed with MEM-ANT2681 against 1,687 MBL-positive Enterobacterales, including 1,108 NDM-CRE. The addition of ANT2681 at 8 µg/ml reduced the MEM MIC50/MIC90 from >32/>32 µg/ml to 0.25/8 µg/ml. Moreover, the combination of 8 µg/ml of both MEM and ANT2681 inhibited 74.9% of the Verona integron-encoded MBL (VIM)-positive and 85.7% of the imipenem hydrolyzing ß-lactamase (IMP)-positive Enterobacterales tested. The antibacterial activity of MEM-ANT2681 against NDM-CRE compared very favorably to that of cefiderocol (FDC) and cefepime (FEP)-taniborbactam, which displayed MIC90 values of 8 µg/ml and 32 µg/ml, respectively, whereas aztreonam-avibactam (ATM-AVI) had a MIC90 of 0.5 µg/ml. Particularly striking was the activity of MEM-ANT2681 against NDM-positive Escherichia coli (MIC90 1 µg/ml), in contrast to ATM-AVI (MIC90 4 µg/ml), FDC (MIC90 >32 µg/ml), and FEP-taniborbactam (MIC90 >32 µg/ml), which were less effective due to the high incidence of resistant PBP3-insertion mutants. MEM-ANT2681 offers a potential new therapeutic option to treat serious infections caused by NDM-CRE.

Discovery of a Novel Metallo-ß-Lactamase Inhibitor That Potentiates Meropenem Activity against Carbapenem-Resistant Enterobacteriaceae.

Infections caused by carbapenem-resistant Enterobacteriaceae (CRE) are increasingly prevalent and have become a major worldwide threat to human health. Carbapenem resistance is driven primarily by the acquisition of ß-lactamase enzymes, which are able to degrade carbapenem antibiotics (hence termed carbapenemases) and result in high levels of resistance and treatment failure. Clinically relevant carbapenemases include both serine ß-lactamases (SBLs; e.g., KPC-2 and OXA-48) and metallo-ß-lactamases (MBLs), such as NDM-1. MBL-producing strains are endemic within the community in many Asian countries, have successfully spread worldwide, and account for many significant CRE outbreaks. Recently approved combinations of ß-lactam antibiotics with ß-lactamase inhibitors are active only against SBL-producing pathogens. Therefore, new drugs that specifically target MBLs and which restore carbapenem efficacy against MBL-producing CRE pathogens are urgently needed. Here we report the discovery of a novel MBL inhibitor, ANT431, that can potentiate the activity of meropenem (MEM) against a broad range of MBL-producing CRE and restore its efficacy against an Escherichia coli NDM-1-producing strain in a murine thigh infection model. This is a strong starting point for a chemistry lead optimization program that could deliver a first-in-class MBL inhibitor-carbapenem combination. This would complement the existing weaponry against CRE and address an important and growing unmet medical need.

Substituted α-mercaptoketones, new types of specific neprilysin inhibitors.

New neprilysin inhibitors containing an α-mercaptoketone HSC(R1R2)CO group, as zinc ligand were designed. Two parameters were explored for potency optimization: the size of the inhibitor which could interact with the S1, S1' or S2' domain of the enzyme and the nature of the substituents R1, R2 of the mercaptoketone group. Introduction of a cyclohexyl chain in R1, R2 position and a (3-thiophen)benzyl group in position R3 (compound 12n) yielded to the most potent inhibitor of this series with a Ki value of 2±0.3nM. This result suggests that this new inhibitor interacts within the S1, S1' domain of NEP allowing a pentacoordination of the catalytic Zn2+ ion by the mercaptoketone moiety.

Chemical Optimization of Selective Pseudomonas aeruginosa LasB Elastase Inhibitors and Their Impact on LasB-Mediated Activation of IL-1ß in Cellular and Animal Infection Models.

LasB elastase is a broad-spectrum exoprotease and a key virulence factor of Pseudomonas aeruginosa, a major pathogen causing lung damage and inflammation in acute and chronic respiratory infections. Here, we describe the chemical optimization of specific LasB inhibitors with druglike properties and investigate their impact in cellular and animal models of P. aeruginosa infection. Competitive inhibition of LasB was demonstrated through structural and kinetic studies. In vitro LasB inhibition was confirmed with respect to several host target proteins, namely, elastin, IgG, and pro-IL-1ß. Furthermore, inhibition of LasB-mediated IL-1ß activation was demonstrated in macrophage and mouse lung infection models. In mice, intravenous administration of inhibitors also resulted in reduced bacterial numbers at 24 h. These highly potent, selective, and soluble LasB inhibitors constitute valuable tools to study the proinflammatory impact of LasB in P. aeruginosa infections and, most importantly, show clear potential for the clinical development of a novel therapy for life-threatening respiratory infections caused by this opportunistic pathogen.

Synthesis and biological activities of topopyrones.

Structure-activity studies were employed to investigate the stabilization of DNA-topoisomerases I and II covalent binary complexes by topopyrone analogues. The synthesis of five new topopyrone derivatives and study of their ability to stabilize DNA-topoisomerase I and DNA-topoisomerase II covalent binary complexes are described. The biochemical assays suggest that the orientation of the fused 1,4-pyrone ring and halogen substituents contribute importantly to the overall potency of the topopyrones as topoisomerase poisons.

Virtual Screening Approach to Identifying a Novel and Tractable Series of Pseudomonas aeruginosa Elastase Inhibitors.

Novel therapies are required to treat chronic bacterial infections in cystic fibrosis (CF) sufferers. The most common pathogen responsible for these infections is Pseudomonas aeruginosa, which persists within the lungs of CF sufferers despite intensive antibiotic treatment. P. aeruginosa elastase (also known as LasB or pseudolysin) is a key virulence determinant that contributes to the pathogenesis and persistence of P. aeruginosa infections in CF patients. The crucial role of LasB in pseudomonal virulence makes it a good target for the development of an adjuvant drug for CF treatment. Herein we discuss the discovery of a new series of LasB inhibitors by virtual screening and computer assisted drug design (CADD) and their optimization leading to compounds 29 and 39 (K i = 0.16 µM and 0.12 µM, respectively).

Synthesis and evaluation of verticipyrone analogues as mitochondrial complex I inhibitors.

Verticipyrone has recently been isolated from the culture broth of Verticillium sp. and shown to inhibit NADH fumarate reductase, as well as NADH oxidoreductase (complex I) of the mitochondrial electron transport chain. In order to assess the structural elements in verticipyrone essential for complex I inhibitor, 15 structural analogues were prepared and analyzed for their effects on mitochondrial NADH oxidoreductase and NADH oxidase activities. Also measured were the abilities of several of the analogues to inhibit respiration as judged by a shift to glycolysis, and to inhibit the growth of several mammalian cell lines. The nature of the pyrone ring was shown to be important to potency of inhibition, as was the length and nature of substituents in the side chain of the analogues.

ANT2681: SAR Studies Leading to the Identification of a Metallo-ß-lactamase Inhibitor with Potential for Clinical Use in Combination with Meropenem for the Treatment of Infections Caused by NDM-Producing Enterobacteriaceae.

The clinical effectiveness of the important ß-lactam class of antibiotics is under threat by the emergence of resistance, mostly due to the production of acquired serine- (SBL) and metallo-ß-lactamase (MBL) enzymes. To address this resistance issue, multiple ß-lactam/ß-lactamase inhibitor combinations have been successfully introduced into the clinic over the past several decades. However, all of those combinations contain SBL inhibitors and, as yet, there are no MBL inhibitors in clinical use. Consequently, there exists an unaddressed yet growing healthcare problem due to the rise in recent years of highly resistant strains which produce New Delhi metallo (NDM)-type metallo-carbapenemases. Previously, we reported the characterization of an advanced MBL inhibitor lead compound, ANT431. Herein, we discuss the completion of a lead optimization campaign culminating in the discovery of the preclinical candidate ANT2681, a potent NDM inhibitor with strong potential for clinical development.

Discovery of ANT3310, a Novel Broad-Spectrum Serine ß-Lactamase Inhibitor of the Diazabicyclooctane Class, Which Strongly Potentiates Meropenem Activity against Carbapenem-Resistant Enterobacterales and Acinetobacter baumannii.

The diazabicyclooctanes (DBOs) are a class of serine ß-lactamase (SBL) inhibitors that use a strained urea moiety as the warhead to react with the active serine residue in the active site of SBLs. The first in-class drug, avibactam, as well as several other recently approved DBOs (e.g., relebactam) or those in clinical development (e.g., nacubactam and zidebactam) potentiate activity of ß-lactam antibiotics, to various extents, against carbapenem-resistant Enterobacterales (CRE) carrying class A, C, and D SBLs; however, none of these are able to rescue the activity of ß-lactam antibiotics against carbapenem-resistant Acinetobacter baumannii (CRAB), a WHO "critical priority pathogen" producing class D OXA-type SBLs. Herein, we describe the chemical optimization and resulting structure-activity relationship, leading to the discovery of a novel DBO, ANT3310, which uniquely has a fluorine atom replacing the carboxamide and stands apart from the current DBOs in restoring carbapenem activity against OXA-CRAB as well as SBL-carrying CRE pathogens.

SAR Studies Leading to the Identification of a Novel Series of Metallo-ß-lactamase Inhibitors for the Treatment of Carbapenem-Resistant Enterobacteriaceae Infections That Display Efficacy in an Animal Infection Model.

The clinical effectiveness of carbapenem antibiotics such as meropenem is becoming increasingly compromised by the spread of both metallo-ß-lactamase (MBL) and serine-ß-lactamase (SBL) enzymes on mobile genetic elements, stimulating research to find new ß-lactamase inhibitors to be used in conjunction with carbapenems and other ß-lactam antibiotics. Herein, we describe our initial exploration of a novel chemical series of metallo-ß-lactamase inhibitors, from concept to efficacy, in a survival model using an advanced tool compound (ANT431) in conjunction with meropenem.

Synthesis of new sulfonate and phosphonate derivatives for cation-independent mannose 6-phosphate receptor targeting.

The cation-independent mannose 6-phosphate receptor (CI-M6PR) is essential for the endocytosis of proteins bearing the mannose 6-phosphate (M6P) recognition marker. This study described the synthesis of M6P and M6S analogs presenting greater affinity for CI-M6PR than their natural compounds. Moreover, the finding of their lack of cytotoxicity for human cells and of their increased stability in human serum supports the high potential of these isosteric derivatives in therapies requiring CI-M6PR targeting.

Novel calcium sensing receptor ligands: a patent survey.

INTRODUCTION: In the parathyroid gland, the calcium sensing receptor responds to small changes in circulating levels of Ca(2+), and consequently stimulates or inhibits the secretion of parathyroid hormone (PTH). Thus, ligands potentiating the action of calcium (calcimimetics) lead to decreased PTH secretion and can thus be useful for the treatment of hyperparathyroidism. On the other hand, ligands which antagonize the action of calcium (calcilytics) stimulate PTH secretion, favoring bone tissue regeneration. AREAS COVERED: This review first discusses the rapid development of calcimimetics (only one of which has been approved for the treatment of hyperparathyroidism) followed by that of calcilytics (none of which has as yet been approved for the treatment of osteoporosis). Peer-reviewed articles generated by these patents are also surveyed. EXPERT OPINION: The rapid progress in developing a clinically approved calcimimetic has not been matched by an identical success in finding an orally available calcilytic useful for the treatment of osteoporosis. However, the growing importance of osteoporosis as a debilitating disease is a stimulating factor in discovering such compounds.

Synthesis and biological evaluation of cyclic nitrogen mustards based on carnitine framework.

Two series of cyclic nitrogen mustards structurally related to L-carnitine have been prepared. The cytotoxic activity of these compounds was evaluated by using Chlorambucil as a reference. In accordance with earlier report, the cytotoxicity is in direct correlation with the lipophilicity of the introduced alkyl chains. Among the cyclic nitrogen mustards synthesized, the most cytotoxic compounds were the one acylated with a palmitoyl side chain, which showed activities comparable to that of Chlorambucil.