Although neutropenia was observed with palazestrant monotherapy in this study, results from 2 separate phase 1b/2 studies showed that combination of full-dose palazestrant with palbociclib [34] or with ribociclib [35, 36] was feasible in patients with advanced or metastatic ER+/HER2− breast cancer. The gene discussed is ESR1; the disease is breast cancer.