Patients with recurrent, persistent and/or metastatic estrogen receptor-positive rare ovarian cancer, who failed one line of platinum based chemotherapy for advanced or recurrent disease, will be included in this study. One cohort will include low-grade serous or endometrioid epithelial ovarian cancer and another cohort will include adult type granulosa cell tumors. The results of large randomized phase 3 trials of the combination of an aromatase inhibitor combined with a CDK4/6 inhibitor in hormone sensitive, HER2 negative breast cancer can form the basis for a trial with this drug combination in hormone sensitive rare ovarian cancer. The aim is to increase the response rate to aromatase inhibitors and the duration of response in this study population with limited therapeutic options, monitor the quality of life and explore the (epi)genomic signatures that correlate with response or endocrine resistance. Abemaciclib will be supplied as capsules administered orally, 150 mg every 12 hours (Q12H) on Days 1 to 28 of a 28-day cycle, plus letrozole 2.5 mg OD Days 1 to 28 of a 28-day cycle.
The purpose of this study is to assess the efficacy and safety of abemaciclib and letrozole for treatment of estrogen receptor-positive rare ovarian cancer.