Novel phosphate-bearing prodrugs of sulfonyl hydrazines have the formula presented below. Pharmaceutical compositions and uses thereof in the treatment of cancer are claimed. The aforementioned prodrugs include enantiomers, stereoisomers and tautomers thereof, as well as pharmaceutically acceptable salts or solvates and metabolites from all stages. The aforementioned prodrugs are preferentially activated in hypoxic tumors and can be given either alone, or in combination with other anticancer agents or with phototheraphy or radiotherapy. ##STR00001## where R is C.sub.1-C.sub.10 alkyl or haloalkyl; R' and R'' are each independently C.sub.1-C.sub.10 alkyl; R.sup.1 is CH.sub.3; and X is O; or a pharmaceutically acceptable salt, solvate, polymorph or metabolite thereof.