Testing the Safety of Anti-Cancer Drug, CX-5461 (Pidnarulex), in Treating Lymphoma With Specific Changes in the MYC Gene

This study is testing the safety of a drug called CX-5461 (pidnarulex) in adults with aggressive B-cell lymphomas — specifically those with certain changes in a gene called MYC — whose cancer has come back or stopped responding to at least two prior treatments. **You may be eligible if...** - You are 18 or older - You have been diagnosed with double-expressor lymphoma, high-grade B-cell lymphoma with MYC and BCL2/BCL6 changes, or Burkitt lymphoma - You have received at least two prior treatments for DLBCL (or at least one for Burkitt lymphoma) and no standard treatment options remain effective - Your blood counts and organ function are in acceptable range - If HIV-positive, your viral load must be undetectable on effective treatment **You may NOT be eligible if...** - You have cancer spread to the brain (CNS lymphoma) - You have a heart rhythm problem causing prolonged QT interval - You are taking strong CYP3A4-interacting medications that cannot be stopped - You are pregnant or breastfeeding - You have uncontrolled serious illness Talk to your doctor to see if this trial is right for you.