GDC-0032 (taselisib) has greater selectivity for mutant PI3Kα isoforms and is effective in inhibiting proliferation of p110α-mutant breast cancer cell lines in vitro and the growth of human breast cancer xenograft models harboring PIK3CA mutations in vivo (Dickler et al., 2018; Juric et al., 2017; Ndubaku et al., 2013). Here, PIK3CA is linked to breast cancer.