CYTARABINE IS AN ANTINEOPLASTIC, AND IS CYTOTOXIC TO A WIDE VARIETY OF PROLIFERATING MAMMALIAN CELLS IN CULTURE. IT EXHIBITS CELL PHASE SPECIFICIFY, PRIMARILY KILLING CELLS UNDERGOING DNA SYNTHESIS AND UNDER CERTAIN CONDITIONS BLOCKING THE PROGRESSION OF CELLS FROM THE G-1 PHASE TO THE S-PHASE. ALTHOUGH THE MECHANISM OF ACTION IS NOT COMPLETELY UNDERSTOOD. CYTARABINE ACTS THROUGH THE INHIBITION OF DNA POLYMERASE. IT ALSO HAS ANTIVIRAL AND IMMUNOSUPPRESSANT PROPERTIES.