Task: Translation
Input (Spanish): Los sistemas 2,4-diaminopteridinas, tales como aminopterina o metotrexato, son buenos agentes antitumorales ya que reducen la biosíntesis de purinas y pirimidinas al inhibir a la enzima
Output (English): The 2,4-diaminopteridine systems, such as aminopterin or methotrexate, are good antitumor agents since they reduce the biosynthesis of purines and pyrimidines by inhibiting the enzyme