This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Leukemia, Subject name: Medicine
Drug of choice in chronic myeloid leukemia: 
Select and explain. 
A. ImitanibMesylate, B. Fludarabine, C. Cladribine, D. Pentostatin
A: ImitanibMesylate
Answer: A: ImitanibMesylate 
Explanation: Ans.(a) Imatinib mesylateRef: Harrison 19th ed. / 102e-3* Imatinib mesylate is an inhibitor of tyrosine kinase which is used for treatment of the following cancers# Chronic myeloid leukemia# Gastro-intestinal stromal tumors# Systemic mastocytosis