This research study is being done to test the effectivenss and safety of an investigational treatment called LOXO-305. LOXO-305 is an investigational (or experimental) drug that may treat certain cancers like leukemia and lymphomas, including, mantle cell lymphoma (MCL). These cancers are dependent on or “addicted to” a protein made by the cancers called “BTK”. LOXO-305 is a “BTK inhibitor”—it is designed to block both normal and mutated forms of BTK in these cancers. Are you Eligible? (Inclusion Criteria) At least 18 years of age Able to swallow oral...