A group of new compounds, N-(all-trans-Retinoyl)-L-cysteic acid, N-(13-cis-Retinoyl)-L-cysteic acid, N-(all-trans-Retinoyl)-L-cysteinesulfinic acid, N-(13-cis-Retinoyl)-L-cysteinesulfinic acid, N-(all-trans-Retinoyl)-L-homocysteic acid, N-(13-cis-Retinoyl)-L-homocysteic acid, and sodium salts of these compounds, including sodium salts of their esters and amides, is shown to exhibit therapeutic effects per se, and which compounds in combination with cytotoxic compounds, such as docetaxel, paclitaxel, doxorubicin and mitoxantrone, exhibit a synergistic effect. These compounds make it possible to manufacture new formulations of poorly soluble pharmaceutical compounds, and the present invention discloses a process of manufacturing water-soluble formulations of such compounds, exemplified by docetaxel, and paclitaxel, exhibiting enhanced pharmacological activity, and formulations of water-soluble pharmaceuticals exemplified by doxorubicin and mitoxantrone, exhibiting improved therapeutic efficacy.