Given the increased use of CDK inhibitors in standard of care protocols and the limited activity of selective FGFR inhibitors in FGFR1-amplified breast cancer in basket trials, based on the safety and pharmacodynamic data found on this study, the combination could be further evaluated in molecularly selected patients the moment there is a compelling clinical/preclinical rationale supporting a specific target niche. This evidence concerns the gene FGFR1 and breast cancer.