Results from a phase I/Ib trial of enzalutamide and gemcitabine and cisplatin in metastatic bladder cancer (mBC).

471Background: Novel targeted therapies are an unmet need in mBC. Androgen receptor (AR) is a rational target in BC and we conducted a phase 1/1b trial assessing safety and tolerability of AR antonist, enzalutamide (ENZ) in combination with gemcitabine and cisplatin (GC) in mBC. Methods: The dose escalation phase allowed patients with mBC regardless of the AR status (assessed on routine IHC) and dose expansion cohort allowed only AR+ pts. The dose escalation phase had 2 cohorts testing ENZ at doses of 80 and 160 mg respectively with GC (G 1000 mg/m2 on days 1, 8 and C 70 mg/m2 on day 1 every 21 days). After 6 cycles of ENZ+GC, pts. continued maintenance ENZ until disease progression. Primary objective was safety and tolerability of ENZ and GC. Secondary objectives were PFS, OS and objective tumor response. Exploratory objectives included evaluation of AR expression in tumor tissues and correlation with outcomes and CTC evaluation at baseline and prior to cycle 3, including AR expression in CTCs and correl...