A conjugate comprising a nucleoside ester of a steroid acid, said steroid acid having a cyclopentanophenanthrene carbon-carbon skeleton or a homolog thereof and containing up to a maximum of 40 carbon atoms and having at least one carboxylic group covalently bonded thereto, said ester exhibiting at least one activity selected from the group consisting of, (1) antiproliferative or antineoplastic activity induced by apoptosis as measured by activity against H9 cells, or (2) anti-HIV activity as measured by activity against T4 lymphocytes or a pharmaceutically acceptable salt, ester, derivative, metal complex, conjugate or prodrug thereof.