Optimization of Pyrrolamide Topoisomerase II Inhibitors Toward Identification of an Antibacterial Clinical Candidate (AZD5099)

AZD5099 (compound <b>63</b>) is an antibacterial agent that entered phase 1 clinical trials targeting infections caused by Gram-positive and fastidious Gram-negative bacteria. It was derived from previously reported pyrrolamide antibacterials and a fragment-based approach targeting the ATP binding site of bacterial type II topoisomerases. The program described herein varied a 3-piperidine substituent and incorporated 4-thiazole substituents that form a seven-membered ring intramolecular hydrogen bond with a 5-position carboxylic acid. Improved antibacterial activity and lower in vivo clearances were achieved. The lower clearances were attributed, in part, to reduced recognition by the multidrug resistant transporter Mrp2. Compound <b>63</b> showed notable efficacy in a mouse neutropenic Staphylococcus aureus infection model. Resistance frequency versus the drug was low, and reports of clinical resistance due to alteration of the target are few. Hence, <b>63</b> could offer a novel treatment for serious issues of resistance to currently used antibacterials