Ibrutinib in Treating Patients With Relapsed or Refractory Classical Hodgkin Lymphoma

Inclusion Criteria * Patients with relapsed or refractory classical HL who have previously received autologous stem cell transplant and/or allogeneic stem cell transplant. Patients must have received prior autologous stem cell transplant at least 12 weeks (3 months) before the first dose of ibrutinib and/or allogeneic stem cell transplant must have been completed at least 6 months prior to the first dose of Ibrutinib. OR * Patients with relapsed or refractory HL who have failed at least 2 lines of prior therapy and are not eligible for autologous stem cell transplant due to: * Inability to achieve a CR or PR prior to transplant * Age or comorbid conditions * Inability to collect stem cells * Completion of any prior treatment with radiation, chemotherapy, biologics, and/or other investigational agents at least 4 weeks prior to the first dose of ibrutinib. Patients must have completed any prior immunotherapy (e.g., rituximab or PD-1 inhibition) or antibody drug conjugate therapy (e.g. brentuximab vedotin) at least 4 weeks prior to the first dose of ibrutinib in the absence of clear disease progression. * Prior treatment with at least 2 lines of therapy for HL including brentuximab vedotin. In those patients who cannot receive brentuximab vedotin, treatment with 2 prior therapeutic regimens is sufficient. * Fluorodeoxyglucose (FDG)-avid disease by PET and measurable disease of at least 1.5 cm in minimum dimension by CT scan with contrast, as assessed by the site radiolog…