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2023 - Boronic Acid Transition State Inhibitors as Potent Inactivators of KPC and CTX-M β-Lactamases: Biochemical and Structural Analyses [Articolo su rivista]
Alsenani, Tahani A; Rodríguez, María Margarita; Ghiglione, Barbara; Taracila, Magdalena A; Mojica, Maria F; Rojas, Laura J; Hujer, Andrea M; Gutkind, Gabriel; Bethel, Christopher R; Rather, Philip N; Introvigne, Maria Luisa; Prati, Fabio; Caselli, Emilia; Power, Pablo; van den Akker, Focco; Bonomo, Robert A

Design of novel beta-lactamase inhibitors (BLIs) is one of the currently accepted strategies to combat the threat of cephalosporin and carbapenem resistance in Gram-negative bacteria. Boronic acid transition state inhibitors (BATSIs) are competitive, reversible BLIs that offer promise as novel therapeutic agents. In this study, the activities of two alpha-amido-beta-triazolylethaneboronic acid transition state inhibitors (S02030 and MB_076) targeting representative KPC (KPC-2) and CTX-M (CTX-M-96, a CTX-M-15-type extended-spectrum beta-lactamase [ESBL]) beta-lactamases were evaluated. The 50% inhibitory concentrations (IC(50)s) for both inhibitors were measured in the nanomolar range (2 to 135 nM). For S02030, the k(2)/K for CTX-M-96 (24,000 M-1 s(-1)) was twice the reported value for KPC-2 (12,000 M-1 s(-1)); for MB_076, the k(2)/K values ranged from 1,200 M-1 s(-1) (KPC-2) to 3,900 M-1 s(-1) (CTX-M-96). Crystal structures of KPC-2 with MB_076 (1.38-& ANGS; resolution) and S02030 and the in silico models of CTX-M-96 with these two BATSIs show that interaction in the CTX-M-96-S02030 and CTX-M-96-MB_076 complexes were overall equivalent to that observed for the crystallographic structure of KPC-2-S02030 and KPC-2-MB_076. The tetrahedral interaction surrounding the boron atom from S02030 and MB_076 creates a favorable hydrogen bonding network with S70, S130, N132, N170, and S237. However, the changes from W105 in KPC-2 to Y105 in CTX-M-96 and the missing residue R220 in CTX-M-96 alter the arrangement of the inhibitors in the active site of CTX-M-96, partially explaining the difference in kinetic parameters. The novel BATSI scaffolds studied here advance our understanding of structure-activity relationships (SARs) and illustrate the importance of new approaches to beta-lactamase inhibitor design.

2023 - Sulfonamidoboronic Acids as “Cross-Class” Inhibitors of an Expanded-Spectrum Class C Cephalosporinase, ADC-33, and a Class D Carbapenemase, OXA-24/40: Strategic Compound Design to Combat Resistance in Acinetobacter baumannii [Articolo su rivista]
Introvigne, Maria Luisa; Beardsley, Trevor J.; Fernando, Micah C.; Leonard, David A.; Wallar, Bradley J.; Rudin, Susan D.; Taracila, Magdalena A.; Rather, Philip N.; Colquhoun, Jennifer M.; Song, Shaina; Fini, Francesco; Hujer, Kristine M.; Hujer, Andrea M.; Prati, Fabio; Powers, Rachel A.; Bonomo, Robert A.; Caselli, Emilia

2021 - Straightforward synthesis of chiral non-racemic α-boryl isocyanides [Articolo su rivista]
Fini, Francesco; Zanni, Alessandro; Introvigne, Maria Luisa; Stucchi, Mattia; Caselli, Emilia; Prati, Fabio

A straightforward concise synthesis of chiral non-racemic aliphatic alpha-boryl isocyanides, relay intermediates for boron-based bioactive molecules in multicomponent reactions, is presented. The short synthetic sequence comprises as key steps copper-catalysed asymmetric borylation of imines, simultaneous nitrogen formylation/boron-protecting group interconversion and the final formamide dehydration reaction.

2020 - 1,2,3-Triazolylmethaneboronate: A Structure Activity Relationship Study of a Class of β-Lactamase Inhibitors against Acinetobacter baumannii Cephalosporinase [Articolo su rivista]
Caselli, E.; Fini, F.; Introvigne, M. L.; Stucchi, M.; Taracila, M. A.; Fish, E. R.; Smolen, K. A.; Rather, P. N.; Powers, R. A.; Wallar, B. J.; Bonomo, R. A.; Prati, F.

Boronic acid transition state inhibitors (BATSIs) are known reversible covalent inhibitors of serine β-lactamases. The selectivity and high potency of specific BATSIs bearing an amide side chain mimicking the β-lactam's amide side chain are an established and recognized synthetic strategy. Herein, we describe a new class of BATSIs where the amide group is replaced by a bioisostere triazole; these compounds were designed as molecular probes. To this end, a library of 26 α-triazolylmethaneboronic acids was synthesized and tested against the clinically concerning Acinetobacter-derived cephalosporinase, ADC-7. In steady state analyses, these compounds demonstrated Ki values ranging from 90 nM to 38 μM (±10%). Five compounds were crystallized in complex with ADC-7 β-lactamase, and all the crystal structures reveal the triazole is in the putative amide binding site, thus confirming the triazole-amide bioisosterism. The easy synthetic access of these new inhibitors as prototype scaffolds allows the insertion of a wide range of chemical groups able to explore the enzyme binding site and provides insights on the importance of specific residues in recognition and catalysis. The best inhibitor identified, compound 6q (Ki 90 nM), places a tolyl group near Arg340, making favorable cation-π interactions. Notably, the structure of 6q does not resemble the natural substrate of the β-lactamase yet displays a pronounced inhibition activity, in addition to lowering the minimum inhibitory concentration (MIC) of ceftazidime against three bacterial strains expressing class C β-lactamases. In summary, these observations validate the α-triazolylboronic acids as a promising template for further inhibitor design.

2020 - α-Triazolylboronic Acids: A Promising Scaffold for Effective Inhibitors of KPCs [Articolo su rivista]
Introvigne, M. L.; Taracila, M. A.; Prati, F.; Caselli, E.; Bonomo, R. A.

Boronic acids are known reversible covalent inhibitors of serine β-lactamases. The selectivity and high potency of specific boronates bearing an amide side chain that mimics the β-lactam's amide side chain have been advanced in several studies. Herein, we describe a new class of boronic acids in which the amide group is replaced by a bioisostere triazole. The boronic acids were obtained in a two-step synthesis that relies on the solid and versatile copper-catalyzed azide–alkyne cycloaddition (CuAAC) followed by boronate deprotection. All of the compounds show very good inhibition of the Klebsiella pneumoniae carbapenemase KPC-2, with Ki values ranging from 1 nM to 1 μM, and most of them are able to restore cefepime activity against K. pneumoniae harboring blaKPC-2. In particular, compound 1 e, bearing a sulfonamide substituted by a thiophene ring, proved to be an excellent KPC-2 inhibitor (Ki=30 nM); it restored cefepime susceptibility in KPC-Kpn cells (MIC=0.5 μg/mL) with values similar to that of vaborbactam (Ki=20 nM, MIC in KPC-Kpn 0.5 μg/mL). Our findings suggest that α-triazolylboronates might represent an effective scaffold for the treatment of KPC-mediated infections.