This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Targeted Anticancer Drugs and Immunosuppressants, Subject name: Pharmacology
A 23-year-old female underwent kidney transplantation. After 8 days, she suffered from acute humoral rejection. She was successfully managed with tacrolimus and one more drug that suppressed B and T lymphocytes. Drug which target both B and T lymphocytes inhibiting de novo synthesis of purines is? 
Select and explain. 
A. Cyclophosphamide, B. Mycophenolate mofetil, C. Methotrexate, D. Prednisone
B: Mycophenolate mofetil
Answer: B: Mycophenolate mofetil 
Explanation: Mycophenolic acid is formed from mycophenolate mofetil. It inhibits inosine monophosphate dehydrogenase, the rate limiting enzyme in the de novo pathway of purine synthesis. This action suppresses both B and T-lymphocytes.