Selinexor and Lenalidomide for Consolidation and Maintenance Treatment in Multiple Myeloma Post-transplant

Inclusion Criteria: * Patients ≥18 years of age at time of enrollment. * Ability to understand and willingness to sign an IRB approved written informed consent document (or that of legally authorized representative, if applicable). * Histologically confirmed diagnosis of multiple myeloma that is symptomatic. Patients with multiple myeloma with local amyloid deposition in the bone marrow are eligible. * Patients must have undergone lenalidomide-based induction regimen. * Patient must have undergone AHCT within 80 to 140 days prior to C1D1 for MM. * Patient must be MRD-positive (per 10\^-5 threshold) using clonoSEQ MRD® assay on bone marrow biopsy prior to study enrollment. * Patient must have achieved very good partial response or better per IMWG response criteria prior to study enrollment. * Eastern Cooperative Oncology Group (ECOG) performance status and/or other performance status 0, 1, or 2. * Adequate organ function as defined below: * Absolute neutrophil count (ANC) ≥ 1.5 K/cumm. * Platelet count ≥ 100 K/cumm (patients for whom \<50% of bone marrow nucleated cells are plasma cells) or ≥50 K/cumm (patients for whom ≥50% of bone marrow nucleated cells are plasma cells).; platelet transfusions to help patients meet eligibility criteria are not allowed within 7 days before C1D1. * Hemoglobin ≥ 8.5 g/dL without blood transfusion within 7 days before C1D1. * Total bilirubin ≤ 1.5 x the upper limit of the normal range (ULN), patients with Gilbert's syndrome must have …