Brilanestrant (GDC-0810)

MCF-7 cells are trypsinized and washed twice in phenol red free RPMI containing 5% charcoal dextran stripped FBS with 20 mM HEPES and NEAA and adjusted to a concentration of 200000 cells per mL with the same medium. Next, 16 μL of the cell suspension (3200 cells) is added to each well of a poly-D-lysine coated 384-well plate, and the cells are incubated at 37℃ over 4 days to allow the cells to adhere and grow. On day 4, a 10-point, serial 1:5 dilution of Brilanestrant (GDC-0810) is added to the cells in 16 μL at a final concentration ranging from 10⁻⁵ M to 5.12 × 10⁻¹² M or 10⁻⁶ M to 5.12 × 10⁻¹³ M for fulvestrant. At 4 h post compound addition, the cells are fixed by adding 16 μL of 30% formalin to the 32 μL of cells and this compound (10% formalin final concentration) for 20 min. Cells are then washed twice with PBS Tween 0.1% and then permeabilized in PBS 0.1% Triton (50 μL/well) for additional 15 min. The PBS 0.1% triton is decanted, and the cells are washed: LI-COR blocking buffer (50 μL/well) was added, the plate is spun at 3000 rpm, and then the blocking buffer is decanted. Additional LI-COR blocking buffer (50 μL/well) is added, and the cells are incubated overnight at 4℃. The blocking buffer is decanted, and the cells are incubated overnight at 4℃ with SP1 anti-ER rabbit monoclonal antibody diluted 1:1000 in LI-COR blocking buffer/0.1% Tween-20. Wells, which are treated with blocking buffer with Tween but no antibody, are used as a background control. Wells are washed twice with PBS Tween 0.1% to remove free SP1 antibodies, and the cells are incubated at room temp for 60−90 min in LI-COR goat antirabbit IRDyeTM 800CW (1:1000) and DRAQ5 DNA dye diluted in LI-COR blocking buffer containing 0.1% Tween-20 and 0.01% SDS. Cells are then washed with 0.1%Tween-20/PBS three times. Plates are scanned on a LI-COR Odyssey infrared imaging system.