The invention is directed to 5-amino-3-(3′-deoxy-&bgr;-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2,7-dione prodrugs, whose metabolized parent compound has immunomodulatory activity. The invention also relates to the therapeutic use of such prodrugs and pharmaceutical compositions thereof in treating disease states associated with abnormal cell growth, such as cancer.