Chidamide Combined With Clad/Gem/Bu With AutoSCT in R/R Diffuse Large B Cell Lymphoma

Study Groups: If you are found to be eligible to take part in this study, you will be enrolled in a group of at least 3 participants to begin receiving the study drugs. The dose of the study drugs you receive will depend on when you enrolled in this study. If no intolerable side effects occur in your group, researchers will continue to enroll participants at the next dose level until either the vorinostat reaches the dose level currently used alone without stem cell transplant, or the highest tolerable dose of this drug is found. The dose that you receive will remain the same throughout this study. You will be admitted to the hospital on Day -6. Study Drug Administration (for all patients): In stem cell transplant, the days before you receive your stem cells are called minus days. The day you receive the stem cells is called Day 0. The days after you receive your stem cells are called plus days. On Day -7, -4, 0, +3 , you will take chidamide by mouth. On Days -6, -5, -4, -3, and -2 you will receive cladribine by vein over 1/2 hours. On Day -6, -2, you will receive gemcitabine by vein over 3 1/2 - 4 1/2 hours. On Days -6, -5, -4, and -3, you will receive busulfan by vein over 3 hours. On Day -1, you will rest. On Day 0, you will receive your stem cells by vein over about 30-60 minutes. As part of standard care, you will receive G-CSF (filgrastim) as an injection just under your skin twice a day starting on Day +5 until your blood cell levels return to normal. Study Tests: On Day -1, you will have an electrocardiogram (ECG) to check your heart function. About 30-100 days after the transplant, you will have lung function tests. About 100 days after the transplant: Blood (about 4 teaspoons) will be drawn for routine tests. If the doctor thinks it is needed, you may have a bone marrow aspiration and biopsy to check the status of the disease. You will have a PET/CT scan of your whole body to check the status of the disease. Length of Study: As part of standard care, you will remain in the hospital for about 3-4 weeks after the transplant. After you are released from the hospital, you will continue as an outpatient for infections and transplant-related complications. You will be taken off study about 100 days after the transplant. You may be taken off study early if the disease gets worse, if intolerable side effects occur, or if you are unable to follow study directions. This is an investigational study. Chidamide, gemcitabine, busulfan, melphalan, and rituximab are all FDA approved and commercially available. The use of these study drugs in combination is investigational. Up to 93 patients will take part in this study.