KPT-330 Plus RICE for Relapsed/Refractory Aggressive B-Cell Lymphoma

Inclusion Criteria: * Patients must have histologically confirmed aggressive B-cell non-Hodgkin lymphomas: * DLBCL including ABC, GCB or PMBCL subtypes * Double/triple hit lymphomas * Indolent lymphomas transformed to aggressive lymphomas * Follicular lymphomas grade 3B * Patients must have received at least two cycles of anthracycline based chemotherapy administered with curative intent and one of the following: * failed to have achieve at least a partial response after 2 or more cycles * failed to achieve a complete response after 6 or more cycles * progressed after an initial response * Patients must be age ≥18 years. * Patients must have at least one site of measurable disease, 1.5 cm in diameter or greater. * Patients must have ECOG performance status of 0-2. * Patients must have laboratory test results within these ranges: * Absolute neutrophil count ≥ 1500/mm³ * Platelet count ≥ 100,000/mm³ * Serum creatinine clearance ≥40 mL/min * Total bilirubin ≤ 1.5x ULN. Higher levels are acceptable if these can be attributed to active hemolysis or ineffective erythropoiesis. * AST (SGOT) and ALT (SGPT) ≤ 2x ULN * Women of childbearing potential must agree to use dual methods of contraception and have a negative serum pregnancy test prior to selinexor treatment. Male patients must use an effective barrier method of contraception if sexually active with a female of child-bearing potential. * Acceptable methods of contraception are condoms with contraceptive foam, oral, implantable or injectable contraceptives, contraceptive patch, intrauterine device, diaphragm with spermicidal gel, or a sexual partner who is surgically sterilized or post-menopausal. * For both male and female patients, effective methods of contraception must be used throughout the study and for three months following the last dose. * Patients must be able to understand and willing to sign a written informed consent document. * Patients must be able to adhere to the study visit schedule and other protocol requirements. * Patients must not have any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form. * Patients must not have any condition, including the presence of laboratory abnormalities, which places the subject at unacceptable risk if he/she were to participate in the study or confounds the ability to interpret data from the study. Exclusion Criteria: * Patients with hyperuricemia or other potential signs of tumor lysis syndrome * Patients with more than minimally symptomatic disease (i.e. \> grade 1), high tumor burden, or other indication for urgent treatment. * Patients who have had prior malignancies (other than B-cell lymphomas) for ≤5 years with exception of currently treated basal cell, squamous cell carcinoma of the skin, or carcinoma "in situ" of the cervix or breast. * Patients who have had other anti-cancer therapy, including radiation or experimental drug or therapy, within 28 days of enrollment. * Patients with known HIV, active hepatitis B, active hepatitis C. * Patients with known central nervous system involvement by lymphoma.