A 62-year-old man presents with bone pain, anemia (Hb 8.2 g/dL), and elevated serum creatinine. Serum protein electrophoresis shows an M-spike of 4.2 g/dL. Bone marrow biopsy confirms >30% plasma cells. He is newly diagnosed with multiple myeloma and is eligible for autologous stem cell transplantation. What is the drug of choice for induction therapy in this patient?