Phase I clinical trial of 1-(2-[2-(4-pyridyl)-2-imidazoline-1-yl]-ethyl)-3-(4-carboxy-phenyl) urea (CGP 15720A).

A phase I clinical trial of the intravenous administration of a novel pyridyl imidazoline ethyl carboxy phenyl urea was carried out in 42 patients with advanced solid tumors. Five schedules were evaluated: I, daily X 5; II, daily X 10; III, daily X 15; IV, continuous infusion for 5 days; V, continuous infusion for 7 days. Toxicity was not seen in schedule I (maximum dose 3 g/m2/day) and was minimal in schedule IV (6 g/m2/day). In schedule II it was seen at 2 and 3 g/m2/day, in schedule III at 2 g/m2/day and in schedule V at 6 g/m2/day. Dose-limiting toxicity consisted of a syndrome of lethargy and fatigue. There were no definitely drug-related changes in hematologic or serum chemistry parameters. No responses were seen, but relief of pain in three patients with prostate cancer was noted. Pharmacokinetics indicate a short half-life, limited volume of distribution, and rapid renal clearance. The recommended dose for phase II studies is 3 g/m2/day X 10 or 2 g/m2/day X 15 days.