CDK4 and breast cancer: Another study is “TAS-116 plus palbociclib in breast and Rb-null cancer”, which is a preclinical phase 1 study investigating the combination therapy of heat shock protein 90 (Hsp90) inhibitor TAS-116 and cyclin-dependent kinase 4/6 inhibitor palbociclib in the treatment of breast cancer and retinoblastoma-null cancer (Clinical trial—NCT05655598).