Currently, there are at least 18 different CDK4/6 inhibitors being tested in over 100 clinical trials against various tumour types (for reviews see (Asghar et al, 2015; O'Leary et al, 2016; Klein et al, 2018; Alvarez‐Fernandez & Malumbres, 2020; Yuan et al, 2021)). The gene discussed is CDK4; the disease is neoplasm.