The present invention is directed to novel dipeptide thereof, represented by the general Formula I: ##STR1## where R.sub.1 -R.sub.3, X and Y are defined herein. The present invention also relates to the discovery that compounds having Formula I are potent inhibitors of caspases and apoptotic cell death. Therefore, the inhibitors of this invention can retard or block cell death in a variety of clinical conditions in which the loss of cells, tissues or entire organs occurs.