Chemo- and Radioprotection: Clinical Trials Combining WR-2721 with Cisplatin and Cyclophosphamide

WR-2721 [S-2-(3-aminopropylamino) ethyl-phosphorothioic acid] was one of the most effective and least toxic of over a thousand sulfhydryl radioprotectors tested. Yuhas and Storer first reported that WR-2721 could increase the radiation resistance of murine skin and bone marrow by factors of 2.5 and 2.7, respectively, without increasing the radiation resistance of the animals’ solid mammary tumors. (Yuhas 1980a) Preclinical data on WR-2721 have been expanded to include five additional species, 11 additional normal tissues, and 16 additional transplanted or spontaneous tumors. Differential protection in favor of normal tissues has resulted in little or no protection in the majority of experimental tumors. The basic proposal that WR-2721 can improve the effectiveness of solid tumor radiotherapy remains intact, except that it does not protect the central nervous system (Coleman et al. 1989; Yuhas 1980a).