Phase I clinical studies with WR-2721.

Toxicity studies of S-2-(3 aminopropylamino)-ethylphosphorothioic acid (WR-2721) access patients in remission following radiation therapy. The dose has been escalated from 25 to 250 mg/m2 without significant symptoms. Inconsistent variation in the systolic blood pressure in some patients has been observed over an 8-10-point range without producing any symptoms. The variation could be within the patient's normal range. However, tests are planned to rule out cardiac toxicity or peripheral vascular reaction. Combining WR-2721 with conventional radiotherapy is contemplated by intravenous injection of the drug 20-30 minutes before irradiation. This will start as weekly injections, and the number of weekly injections will be increased progressively. Animal studies suggest that the level already safely reached could give significant protection to the normal tissues without protecting tumor.