Phosphorodiamidate derivatives of e.g. gemcitabine are provided for use in treating cancer. In one embodiment, the two amidate motifs each comprises NR′R″ where R′ is H and R″ is CR5R6CO2R7, where R6 is H, R5 is the side chain, including H and C1, of a naturally occurring alpha amino acid, and R7 is branched or unbranched, substituted or unsubstituted, acyclic or cyclic alkyl, including t-butyl-CH2-, benzyl and C3 to C6 cycloalkyl. Formula (I).
