Effect of the radioprotective drugs MEA, DMSO, and WR-2721 on tumor control and skin tolerance in the rat.

Mercaptoethylamine (MEA), dimethylsulfoxide (DMSO), and S-2-(3-aminopropylamino)ethylphosphorothioate (WR-2721) were tested for their protective effects against single and fractionated doses of 250 kv X-rays. Acute and late skin reactions and control of the BA-1112 rhabdomyosarcoma were examined in protected and unprotected WAG/Rij rats. All drugs protected skin in both single and fractionated treatment regimens, with MEA giving the most protection and DMSO the least. DMSO and WR-2721 protected tumors against single doses of radiation, and all three drugs tested protected tumors against fractionated irradiation. As a result, only single-fraction treatments of MEA-protected animals showed therapeutically favorable differential protection.