Hematologic Malignancies USMLE Step 1 Practice Question

A 41-year-old woman presents to the emergency department with a 2-week history of progressive fatigue, spontaneous ecchymoses, and epistaxis. Her husband notes she has had several episodes of gingival bleeding while brushing her teeth. Vital signs are stable. Physical examination reveals petechiae on bilateral lower extremities, gingival erythema with active bleeding, and no hepatosplenomegaly. Laboratory results are as follows: WBC 8,200/µL, hemoglobin 7.2 g/dL, platelets 18,000/µL, PT 18 seconds (normal 11-13.5), PTT 52 seconds (normal 25-35), fibrinogen 95 mg/dL (normal 200-400), and D-dimer 8.2 µg/mL (normal <0.5). Peripheral blood smear shows abnormal promyelocytes with abundant azurophilic granules and multiple Auer rods in most blast cells. Flow cytometry confirms CD33+, CD13+, HLA-DR negative blasts. Which of the following is the most appropriate initial pharmacologic intervention?