 A polymer of fosfestrol, polydiethylstilbestrol phosphate, was developed as a long-acting estrogen for potential use in veterinary medicine, but was never marketed.Fosfestrol was first patented in 1941 and was mentioned in the literature by Huggins.Conjugated estrogens and diethylstilbestrol sulfate, which are water-soluble estrogens, were first reported to be effective in the treatment of prostate cancer via intravenous administration in 1952.