Budotitane [cis-diethoxybis(1-phenylbutane-1,3-dionato)titanium (IV)] is a novel inorganic metal complex. Preclinical studies in established screening models indicate considerable antitumor activity. We have performed a clinical Phase I and pharmacokinetic trial with budotitane administered as i.v. infusion twice weekly. The starting dose of 100 mg/m2 was derived from a prior single dose Phase I study. Eighteen patients with solid tumors refractory to all other known treatment modalities were entered. 17 patients had received prior chemotherapy. Dose levels ranged from 100 mg/m2 to 230 mg/m2, with a total of 122 budotitane infusions administered. Neither leuko- nor thrombocytopenia were observed. 2/5 pts at 180 mg/m2 and 2/4 pts at 230 mg/m2 developed a 3-fold increase of reticulocytes without signs of hemolysis or bleeding. Nonhematologic toxicity was moderate at doses of < or = 180 mg/m2. Fifteen patients reported loss of taste at the day of infusion. At 230 mg/m2, 2/4 pts developed WHO grade 3 cardiac arrhythmias with polytope premature ventricular beats and nonsustained ventricular tachycardia. A limited pharmacokinetic analysis was performed at dose levels 180 mg/m2 and 230 mg/m2. At 180 mg/m2, Cmax was 2.9 +/- 1.2 microg/ml, t1/2 78.7 +/- 24.4 h, Cltot 25.3 +/- 4.6 ml/min and AUC 203 +/- 71.5 h x microg/ml. At 230 mg/m2, Cmax was 2.2 +/- 0.8 microg/ml, t1/2 59.3 +/- 12.1 h, Cltot 44.9 +/- 23.6 ml/min and AUC was 183 +/- 90.4 h x microg/ml. No objective tumor response was observed. We conclude that the maximum tolerated dose of budotitane administered twice weekly is 230 mg/m2, the dose limiting toxicity is cardiac arrhythmia. Further evaluation of the nature of the cardiac toxicities observed is warranted. Using this schedule, 180 mg/m2 is a safe dose for subsequent clinical studies.