MDS with Isolated del(5q)

A 68-year-old woman presents with progressive fatigue and pallor over six months. CBC shows macrocytic anemia (Hb 8.2 g/dL, MCV 108 fL), WBC 4.2 with normal differential, and paradoxically elevated platelets at 620,000/µL. Bone marrow biopsy reveals hypercellular marrow with dysplastic erythroid and megakaryocytic lineages, <5% myeloblasts, and absent ring sideroblasts. Reticulocyte count is inappropriately low at 0.4%. Cytogenetic analysis demonstrates the karyotype marked **C** in the diagram. Which of the following is the MOST appropriate first-line pharmacological intervention for this patient?