This is a Phase II non-randomized, single arm, open label study of abemaciclib in combination with pembrolizumab in patients with unresectable or metastatic gastric, gastroesophageal junction, or esophageal adenocarcinoma who have received at least two lines of prior therapy. Treatment will be administered in 21-day cycles. Pembrolizumab will be administered intravenously (IV) at a dose of 200 mg on day 1 of each cycle. Abemaciclib will be taken orally twice a day on each day of the cycle, 150 mg per dose. Treatment will continue until disease progression or development of unacceptable toxicities.
This study will test the combination of abemaciclib with pembrolizumab in patients with gastric, gastroesophageal junction, or esophageal adenocarcinoma that is metastatic or cannot be surgically removed, and who have progressed on, or were unable to tolerate, at least 2 earlier courses of treatment for their advanced disease.