Phase I clinical trial of weekly iv 2,3-dihydro-1H-imidazo[1,2-b]pyrazole (IMPY)

In a phase I trail, 2,3-dihydro-1H-imidazo[1,2-b]pyrazole was administered iv weekly at doses ranging from 0.1 to 3.0 g/m²/wk to patients with refractory metastatic solid tumors. Although gastrointestinal toxicity was tolerable and neither granulocyte nor platelet toxicity was seen, significant dose-limiting hemolysis was encountered at doses of 1.5 g/m²/wk. While no definite tumor regressions were seen in the 32 patients evaluable for response, two patients (squamous cell carcinoma of lung and tonsil) had clinically useful improvement.