BTK and B-cell chronic lymphocytic leukemia: Eligible patients were exposed to either one to two prior lines of therapy (CLL/SLL eligible after frontline covalent BTK inhibitor after fifth study amendment) with endpoints of maximum tolerated dose (MTD) (phase 1) and ORR (phase 2).17,21 Pirtobrutinib was well tolerated at all dose levels, with no dose-limiting toxicities.