ASCT Combined With BCMA CAR-T and GPRC5D/CD3 BiTEs Maintenance for Transplant-Eligible Ultra-High-Risk Multiple Myeloma

Inclusion Criteria: 1. Age ≥ 18 years and ≤ 70 years. 2. Participants with documented newly-diagnosed multiple myeloma according to IMWG diagnostic criteria. 3. Measurable disease at screening, defined as: Serum M-protein level ≥1.0 g/dL or urine M-protein level ≥200 mg/24 hours; or Light chain MM without measurable disease in serum or urine: serum Ig free-light chain (FLC) ≥10 mg/dL and abnormal serum Ig kappa lambda FLC ratio. 4. Patients deemed eligible for high-dose chemotherapy with ASCT. 5. Presence of at least one of the following ultra-high-risk features: a. Double-hit multiple myeloma, defined as the presence of at least two of the following high-risk cytogenetic abnormalities: t(4;14), t(14;16), deletion 1p, gain 1q, MYC rearrangement, deletion 17p, or TP53 mutation; b. Presence of extramedullary soft tissue plasmacytomas; c. Circulating plasma cells ≥2% in peripheral blood. 6. Tumor cells were BCMA and GPRC5D positive. 7. Serum total bilirubin \<2 x upper limit of normal (ULN), serum AST and ALT \<3 x ULN, creatinine clearance ≥ 30mL/min (Cockroft-Gault formula). 8. Informed Consent/Assent: All subjects have the ability to understand and the willingness to sign a written informed consent. Exclusion Criteria: 1. Active amyloidosis. 2. Central nervous system involvement. 3. Prior BCMA-targeted therapy or CAR-T therapy. 4. Active hepatitis B or hepatitis C virus infection. 5. Known HIV infection. 6. Life expectancy \<6 months. 7. Woman who are pregnant or breastfeeding. 8. Evidence of uncontrolled dysfunction of heart, lung, brain, and other important organs. 9. Any other conditions that are not eligible for the trial in the judgement of the principal investigator.