Pre-transplant Purging and Post-transplant MRD-guided Maintenance Therapy With Elranatamab in Patients With High-risk Multiple Myeloma

To learn if giving elranatamab before and after an autologous stem cell transplant (ASTC) can help to control newly diagnosed, high-risk MM. An ASTC is a type of transplant in which a person's own stem cells are collected, preserved, and returned to them.

Inclusion Criteria: 1. Transplant eligible patients with newly diagnosed multiple myeloma (NDMM). 2. High-risk multiple myeloma\* 3. Participants with disease response ≥ PR to induction therapy 4. Age ≥ 18 and ≤ 75. Non-English-speaking participants are eligible. 5. Karnofsky performance status ≥70 (Appendix A). 6. Adequate liver function (total bilirubin ≤1.5X ULN; ALT ≤2.5 X ULN) 7. Estimated creatinine clearance ≥40 mL/min. Creatinine clearance may be calculated using Cockcroft-Gault, estimated glomerular filtration rate (Modification of Diet in Renal Disease \[MDRD\]), or Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula). \* 8. Participant agrees to not donate blood while taking lenalidomide and for 28 days after stopping lenalidomide. 9. Participant agrees to enroll in the lenalidomide REMS program. 10. Women of child-bearing potential (WOCPB) must abstain from heterosexual intercourse or agree to use a contraceptive method that is highly effective (with a failure rate of \1 year. * Participants who have been amenorrhoeic for \