ESR1 and neoplasm: Based on ERα degradation kinetic profile (internal in vitro data), subjects receiving a single dose of SAR439859 were scanned 4 h after dosing (Tmax for FES-PET imaging at tumor SAR439859 Cmax) to determine the pharmacodynamic relationship between SAR439859 dose and ERα occupancy in MCF7-Y537S tumor-bearing mice.