Additional Study Information: This study is designed to test different doses of FLX475 to see if it is safe and to study how the drug is absorbed and how the human body gets rid of the drug. The study will test FLX475 alone and in combination with pembrolizumab, a drug already approved by the United States Food and Drug Administration (FDA) for the treatment of patients with certain types of cancers. Pembrolizumab also works to stimulate your immune system and is also known as a checkpoint inhibitor. The objective of the study is to assess the safety and activity of FLX475 alone and FLX475 in combination with pembrolizumab at different dosages in patients with different cancers.