Non-β-lactam inhibitors targeting KPC-2 β-lactamase: Structural insights and rational design strategies to combat antimicrobial drug resistance.

Antimicrobial resistance poses a major global health challenge. Among the clinically significant mechanisms of bacterial resistance, mutational changes in KPC-2 β-lactamase represent a major threat to the therapeutic efficacy of β-lactam antibiotics. The widespread dissemination of KPC-2 has severely compromised the effectiveness of carbapenems, which are often considered antibiotics of last resort. Conventional β-lactamase inhibitors (e.g., clavulanic acid, sulbactam, and tazobactam) exhibit poor inhibitory activity against KPC-2, highlighting the urgent need for structurally distinct non-β-lactam inhibitors. This review critically discusses the rational design, mechanisms of action, and structure-activity relationships (SAR) of non-β-lactam KPC-2 β-lactamase inhibitors, including diazabicyclooctanes (DBOs), boronic acid (BA)-based inhibitors, and emerging scaffolds. The 3-D structural architecture of KPC-2 binding pocket is used to elucidate the key pharmacophoric features responsible for inhibitor binding and activity, including interactions with Ser70, the oxyanion hole, the Ω-loop, and the Thr235/Thr237 carboxylate-binding pocket. The review also provides a comparative mechanistic analysis of β-lactam and non-β-lactam inhibitors, emphasizing their SAR and emerging rational strategies for the design of novel broad-spectrum non-β-lactam β-lactamase inhibitors (BLIs). Furthermore, the impact of resistance-associated mutations on inhibitor binding is discussed to provide insights into the rational design of next-generation, potent BLIs.