This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cytotoxic Anticancer Drugs, Subject name: Pharmacology
Pentostatin acts by inhibiting: 
Select and explain. 
A. RNA dependent DNA polymerase, B. Aldolase, C. Adenosine deaminase, D. Adenylyl cyclase
C: Adenosine deaminase
Answer: C: Adenosine deaminase 
Explanation: * Pentostatin and cilastatin are not statins i.e. these do not act by inhibiting HMG-CoA reductase. * Pentostatin acts by inhibiting adenosine deaminase. * It is used for the treatment of hairy cell leukemia. * Drug of choice for hairy cell leukemia is cladribine.