Xenograft of bladder cancer cell line HT1376 were treated with or without EZH2 inhibitors before subject to RNA-seq

Advanced bladder cancer remains a difficult cancer to treat, and for the majority of patients, current standard treatments ultimately prove ineffective.  These tumors frequently harbor mutations in the BAF complex subunit ARID1A, which has been reported to confer sensitivity to EZH2 inhibition in several tumor types.  Here we describe the generation of CPI-0209, a best-in-class, orally available EZH2 inhibitor.  We show that mutant bladder cancer lines harboring ARID1A loss of function (LOF) mutations are preferentially sensitive to inhibition of EZH2. Treatment with CPI-0209 not only elicits a significant monotherapeutic response in ARID1A mutant models, it also outperforms cisplatin and improves response in chemo-resistant models. These findings shine light on new therapeutic opportunities for patients with advanced urothelial carcinoma.