Structure–Activity Relationship Studies of Acetazolamide-Based Carbonic Anhydrase Inhibitors with Activity against Neisseria gonorrhoeae

Neisseria gonorrhoeae is an urgent threat to public health in the United States and around the world. Many of the current classes of antibiotics to treat N. gonorrhoeae infection are quickly becoming obsolete due to increased rates of resistance. Thus, there is a critical need for alternative antimicrobial targets and new chemical entities. Our team has repurposed the FDA-approved carbonic anhydrase inhibitor scaffold of acetazolamide to target N. gonorrhoeae and the bacteria’s essential carbonic anhydrase, NgCA. This study established both structure–activity and structure–property relationships that contribute to both antimicrobial activity and NgCA activity. This ultimately led to molecules 20 and 23, which displayed minimum inhibitory concentration values as low as 0.25 μg/mL equating to an 8- to 16-fold improvement in antigonococcal activity compared to acetazolamide. These analogues were determined to be bacteriostatic against the pathogen and likely on-target against NgCA. Additionally, they did not exhibit any detrimental effects in cellular toxicity assays against both a human endocervical (End1/E6E7) cell line or colorectal adenocarcinoma cell line (Caco-2) at concentrations up to 128 μg/mL. Taken together, this study presents a class of antigonococcal agents with the potential to be advanced for further evaluation in N. gonorrhoeae infection models.