184MO First-in-human phase I/IIa study of the first-in-class, next-generation CDK4-selective inhibitor PF-07220060 in combination with endocrine therapy (ET) in patients (pts) with HR+/HER2− metastatic breast cancer (mBC) who progressed on prior CDK4/6 inhibitors (CDK4/6i): Safety and efficacy update

PF-07220060 is a novel potent oral CDK4i with significant sparing of CDK6. Preliminary safety and dose escalation data from this phI/IIastudy were previously presented. Here we report updated safety and efficacy data in pts with HR+/HER2− mBC, who progressed on prior CDK4/6i and ET, treated with PF-07220060 + ET.