Study of CPI-0209 in patients with advanced tumors.

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. The patients were from the phase 1 portion of the phase 1/2 study of CPI-0209 in patients with advanced tumors (clinicaltrials.gov identifier: NCT04104776). Phase 1 was a 7-cohort dose escalation study in patients receiving CPI-0209 once daily at doses between 50 and 375 mg. All patients gave informed consent and the trial was conducted in accordance with the Declaration of Helsinki.