Discovery of Tetracyclic Derivatives as Highly Potent, Selective, and Bioavailable PKMYT1 Inhibitors for Cancer Therapy

PKMYT1 represents a promising therapeutic target for CCNE1-amplified cancers due to its synthetic lethal relationship with CCNE1. By leveraging a structure-based drug design strategy, we successfully developed a series of novel, highly potent and selective PKMYT1 inhibitors. Notably, compound <b>20</b> exhibited potent antiproliferative activity in CCNE1-amplified cell lines while showing minimal effects on their wild-type counterparts, along with exceptional selectivity across a broad kinase panel. Moreover, its favorable pharmacokinetic properties contributed to robust antitumor efficacy in an HCC1569 xenograft model. Furthermore, two prodrug derivatives of compound <b>20</b> were designed to improve aqueous solubility, achieving dose-proportional systemic exposure in rats during dose-escalation preclinical toxicity studies. Additionally, the combination of prodrug <b>22</b> with Trodelvy^Ⓡ, a TROP2 ADC, demonstrated synergistic antitumor activity in triple-negative breast cancer MDA-MB-231 xenograft models.