ALPINE: Maintenance Letrozole/Abemaciclib

This is a phase 2, single arm trial of maintenance letrozole/abemaciclib after carboplatin/paclitaxel chemotherapy with or without anti-PD-(L)1 blockade in patients with advanced or recurrent estrogen receptor (ER) positive (ER+), mismatch repair proficient (MMRP), tumor protein p53 (TP53) wild-type endometrial cancer. The U.S. Food and Drug Administration (FDA) has not approved abemaciclib or letrozole for endometrial cancer but they have been approved for other uses. The research study procedures include screening for eligibility, study treatment visits, X-rays, Computerized Tomography (CT) scans, Magnetic Resonance Imaging (MRI) scans, Positron Emission Tomography (PET) scans, blood tests, and electrocardiograms (EKGs). Participants will be administered study drugs for up to 2 years and will be followed for 3 years after completing study treatment. It is expected that about 32 people will take part in this research study. Eli Lilly is supporting this research study by providing funding and the study drug abemaciclib.