This study has three parts, called screening, treatment, and follow up. During screening, doctors will check if a person can join the study. If eligible, participants will take a study medicine called NX 5948 by mouth once every day. The medicine is taken in cycles that last 28 days.

People will keep taking the medicine as long as it is helping and side effects are manageable. Treatment may stop if the cancer gets worse, side effects become too severe, or the study ends. After treatment stops, participants will continue to be followed by the study team so doctors can check their health over time.

This study is for people who have a blood cancer called chronic lymphocytic leukemia or small lymphocytic lymphoma. Their cancer has come back or did not get better after treatment. They must have already been treated with two types of cancer medicines that target cancer cells in different ways, called BTK inhibitors and BCL 2 inhibitors. Researchers want to study new treatment options for people whose cancer has not responded to these earlier therapies.

People can join this study if they are 18 years old or older and have a blood cancer called chronic lymphocytic leukemia or small lymphocytic lymphoma that has come back or did not get better after treatment. Their diagnosis must be confirmed by laboratory tests. They must have already received two types of cancer medicines called BTK inhibitors and BCL 2 inhibitors. They must also have cancer that can be seen and measured on a scan, such as a lymph node that is larger than 1.5 centimeters.

The purpose of this study is to find out if a new medicine called NX 5948 is safe and works well for adults who have a blood cancer called chronic lymphocytic leukemia or small lymphocytic lymphoma. These cancers have come back or did not get better after earlier treatments. Researchers want to see if this new medicine can help treat the cancer and improve health.