RecruitingPhase 2Drug trialA Phase 2 Study to Evaluate the Safety and Efficacy of Pacritinib in Relapsed or Refractory Waldenström MacroglobulinemiaThis study is being done to examine the safety and effectiveness of pacritinib as a possible treatment for participants with Waldenström macroglobulinemia (WM). The name of the study drug involved in this study is: -Pacritinib (a type of kinase inhibitor)