This clinical trial is studying the safety and potential anti-tumor activity of an investigational drug called ARV-393 in patients diagnosed with advanced Relapsed/Refractory non-Hodgkin's lymphoma (R/R NHL) to determine if ARV-393 may be a possible treatment option. ARV-393 is thought to work by breaking down a protein present in many types of non-Hodgkins lymphomas, which may prevent, slow or stop tumor growth. This is the first time ARV-393 will be used by people. The investigational drug will be given as an oral tablet.