Mocetinostat for patients with previously treated, locally advanced/metastatic urothelial carcinoma and inactivating alterations of acetyltransferase genes

BACKGROUND: The authors evaluated mocetinostat (a class I/IV histone deacetylase inhibitor) in patients with urothelial carcinoma harboring inactivating mutations or deletions in CREB binding protein [CREBBP] and/or E1A binding protein p300 [EP300] histone acetyltransferase genes in a single-arm, open-label phase 2 study. METHODS: Eligible patients with platinum-treated, advanced/metastatic disease received oral mocetinostat (at a dose of 70 mg 3 times per week [TIW] escalating to 90 mg TIW) in 28-day cycles in a 3-stage study (ClinicalTrials.gov identifier NCT02236195). The primary endpoint was the objective response rate. RESULTS: ] after TIW dosing of 0.2 ng/mL/mg). CONCLUSIONS: To the authors' knowledge, the current study represents the first clinical trial using genomic-based selection to identify patients with urothelial cancer who are likely to benefit from selective histone deacetylase inhibition. Mocetinostat was associated with significant toxicities that impacted drug exposure and may have contributed to modest clinical activity in these pretreated patients. The efficacy observed was considered insufficient to warrant further investigation of mocetinostat as a single agent in this setting.