Changes from baseline in phospho-AKT and Ki-67 levels following treatment with alpelisib plus letrozole or placebo plus letrozole. A, phospho-AKT level at baseline and Cycle 1 Day 15 for each patient; B, mean percentage change from baseline in phospho-AKT level at Cycle 1 Day 15; C, mean percentage change from baseline in phospho-AKT level at end of treatment; D, Ki-67 level at baseline and Cycle 1 Day 15 for each patient; E, mean percentage change from baseline in Ki-67 level at Cycle 1 Day 15; F, mean percentage change from baseline in Ki-67 level at end of treatment.