Design, Synthesis, and Characterization of Brequinar Conjugates as Probes to Study DHODH Inhibition

Brequinar, a potent dihydroorotate dehydrogenase (DHODH) inhibitor, has been evaluated in multiple clinical trials as a potential treatment for cancer. To further understand brequinar‐based DHODH inhibition and DHODH′s therapeutic relevance in cancer, we have developed novel brequinar‐based probes. We disclose a 16‐step convergent synthesis of the first brequinar‐PROTAC and a four‐step approach towards the first mitochondrial‐directed brequinar probe. A PROTAC and mitochondria‐directed probe of brequinar both possess cytotoxicity that is superior to brequinar in a colony formation assay.