Timothy Yap, MBBS, PhD, FRCP, University of Texas MD Anderson Cancer Center, Houston, TX, provides an overview of the results of a first-in-human Phase I/IIa dose-escalation/expansion study of the first-in-class CDK2/4/6 inhibtior PF-06873600 alone or with endocrine therapy in patients with breast or ovarian cancer. In this study it was found that PF-3600 can be combined with endocrine therapy with a manageable safety profile and demonstrates promising preliminary antitumor activity in heavily pretreated patients. This interview took place at the San Antonio Breast Cancer Symposium 2021 in San Antonio.