CYTOSINE ARABINOSIDE IS AN ANTINEOPLASTIC, AND 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.I. 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.