This invention relates to pharmaceutical formulations and formulation strategies of protides (phosphoramidate derivatives of nucleosides) and, in particular, protides useful in the treatment of cancer, such as NUC-3373 (5-fluoro-2′-deoxyuridine-5′-O-[1-naphthyl (benzoxy-L-alaninyl)] phosphate) and NUC-7738 (3′-deoxyadenosine-5′-O-[phenyl(benzyloxy-L-alaninyl)] phosphate). In particular, the invention relates to formulations that comprise a polar aprotic solvent, for example, dimethyl acetamide (DMA).