CDK4 and breast cancer: A phase 1/2 trial evaluating inavolisib, an investigational PI3Kα‐selective inhibitor, in combination with fulvestrant, recently showed a favourable safety profile compared to other agents of the same class and an encouraging preliminary anti‐tumour activity with an overall response rate (ORR) of 25% and a clinical benefit rate (CBR, defined as the sum of complete response, partial response and stable disease > 6 months) of 49% in a similar population of patients with PIK3CA‐mutated HR+/HER2−–BC following progression on ET and CDK4/6i.52