Purpose: A Phase I trial was performed to determine the dose-limiting toxicity and maximum tolerated dose, and to describe the pharmacokinetics of the alkyl-lysophospholipid, ilmofosine, when administered as a weekly 2-h infusion in patients with solid tumors. Experimental Design: Thirty-nine patients were entered into a trial of ilmofosine administered weekly for 4 weeks followed by a 2-week rest period. Dose escalation occurred in 10 levels from 12 to 650 mg/m 2 . Results: Thirty-six patients

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... were evaluable for toxicity. The median number of cycles per patient was 1 (range, 1-4). Dose-limiting gastrointestinal toxicity occurred at 650 mg/m 2 with grade 3 nausea in two patients and grade 3 vomiting and diarrhea in one patient. Grade 2 diarrhea was observed in four of six patients treated at 550 mg/m 2 . In addition, two patients treated at 550 mg/m 2 and two patients treated at 650 mg/m 2 experienced a decline in performance status of two or more levels that was determined to be due to treatment. There were no tumor responses. Stabilization of disease for at least 8 weeks occurred in six patients. Plasma concentrations of ilmofosine and its sulfoxide metabolite were evaluated by high-pressure liquid chromatography. The elimination of both compounds was biexponential with terminal half-lives of ϳ40 h for ilmofosine and 48 h for the sulfoxide. The area under the concentration-time curve was dose-proportional for each compound, and there was no evidence of saturable kinetics. Conclusions: The dose-limiting toxicity of ilmofosine is gastrointestinal and the recommended dose for Phase II trials is 450 mg/m 2 as a 2-h weekly infusion. The relatively long half-life of ilmofosine and its active metabolite support the use of this intermittent schedule.