Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, USA.
Antimicrob Agents Chemother. 2012 Jul;56(7):3556-62. doi: 10.1128/AAC.06263-11. Epub 2012 Apr 9.
Resistance to trimethoprim (TMP) resulting from point mutations in the enzyme drug target dihydrofolate reductase (DHFR) drives the development of new antifolate inhibitors effective against methicillin-resistant Staphylococcus aureus (MRSA). For the past several years we have used structure-based design to create propargyl-linked antifolates that are highly potent antibacterial agents. In order to focus priority on the development of lead compounds with a low propensity to induce resistance, we prospectively evaluated resistance profiles for two of these inhibitors in an MRSA strain. By selection with the lead inhibitors, we generated resistant strains that contain single point mutations F98Y and H30N associated with TMP resistance and one novel mutation, F98I, in DHFR. Encouragingly, the pyridyl propargyl-linked inhibitor selects mutants at low frequency (6.85 × 10(-10) to 1.65 × 10(-9)) and maintains a low MIC (2.5 μg/ml) and a low mutant prevention concentration (1.25 μg/ml), strongly supporting its position as a lead compound. Results from this prospective screening method inform the continued design of antifolates effective against mutations at the Phe 98 position. Furthermore, the method can be used broadly to incorporate ideas for overcoming resistance early in the development process.
由于酶药物靶标二氢叶酸还原酶 (DHFR) 中的点突变导致对甲氧苄啶 (TMP) 的耐药性，推动了新的抗叶酸抑制剂的开发，这些抑制剂对耐甲氧西林金黄色葡萄球菌 (MRSA) 有效。在过去的几年中，我们一直使用基于结构的设计来创建与丙炔基相连的抗叶酸药物，这些药物是非常有效的抗菌剂。为了优先开发不易诱导耐药性的先导化合物，我们前瞻性地评估了两种抑制剂在 MRSA 菌株中的耐药谱。通过用先导抑制剂进行选择，我们生成了含有与 TMP 耐药相关的单点突变 F98Y 和 H30N 的耐药菌株，以及 DHFR 中的一个新突变 F98I。令人鼓舞的是，吡啶基丙炔基连接的抑制剂以低频率（6.85×10(-10) 至 1.65×10(-9)) 选择突变体，并保持低 MIC（2.5μg/ml）和低突变预防浓度（1.25μg/ml），强烈支持其作为先导化合物的地位。这种前瞻性筛选方法的结果为设计针对 Phe 98 位置突变的有效抗叶酸药物提供了信息。此外，该方法可以广泛用于在开发过程的早期纳入克服耐药性的想法。
