Phase I trial of tiazofurin administered by i.v. bolus daily for 5 days, with pharmacokinetic evaluation.

Tiazofurin is a novel C-nucleoside with significant antitumor activity in murine tumor models. In a phase I clinical trial, patients received tiazofurin by bolus iv infusion daily for 5 days. Six doses ranging from 550 to 4100 mg/m2/day were evaluated. Thirty-one treatment courses were initiated in 21 patients. Tiazofurin induced multiple, transient toxic effects at all but the lowest dose level, and treatment interruption was a common result. Nine of 28 treatment courses initiated at doses greater than or equal to 1100 mg/m2/day were interrupted at less than 5 days; only five of eight courses initiated at 1100 mg/m2/day were completed. Symptoms leading to treatment interruption included headache, nausea and emesis, and lethargy and malaise. Other significant, transient toxic effects included skeletal muscle injury manifest as pain, weakness, or serum biochemical abnormalities; mucocutaneous effects; and mental or mood changes. One case each of transient pericarditis and fatal cardiomyopathy occurred at the highest dose. Myelosuppression was observed but was transient and not dose limiting. In addition to leukopenia and thrombocytopenia, unexpected declines in serum hemoglobin were observed, although these were of uncertain significance. Tiazofurin induced significant increases in uric acid production which could be reversed with coadministration of allopurinol. Pharmacokinetic analysis revealed tiazofurin plasma elimination to be at least biphasic, with a beta-half-time of 4.2 hours; most of an injected dose could be recovered from the urine as unaltered compound within 24 hours. From this study we conclude that an appropriate dose for phase II trials with this schedule is less than or equal to 1000 mg/m2/day. The schedule may be a difficult one for clinical evaluation of antitumor activity, however, because of the possibility of frequent treatment interruption due to multiple systemic toxic effects.

Phase I study of taxol using a 5-day intermittent schedule.

Taxol is a plant product derived from the western yew, Taxus brevifolia. We have conducted a phase I clinical study of Taxol used intravenously daily for 5 days at 3-week intervals. The starting dose was 5 mg/m2 daily, and the highest dose used was 40 mg/m2 daily for 5 days. The daily dosage of Taxol was mixed in 250 mL of intravenous fluid and infused over a period of 1 hour. A total of 20 patients with metastatic solid tumors refractory to standard therapy received 45 courses of therapy. Taxol was generally well tolerated and caused no significant nausea or vomiting. A mild degree of diarrhea was reported by six patients, and a moderate degree of stomatitis at the higher dose levels developed in four patients. All patients treated in the dosage range of 20 mg/m2 to 40 mg/m2 experienced nearly complete alopecia. Myelosuppression, predominantly in the form of leukopenia, was the dose-limiting toxicity. The nadir of leukopenia was reached between days 8 and 12 followed by complete recovery between days 15 and 21. Leukopenia was first observed following the Taxol dosage level of 20 mg/m2/d, was moderately severe at the dosage level of 30 mg/m2/d, and was severe at the dosage level of 40 mg/m2/d. No objective tumor regression was observed. A starting dosage level of 30 mg/m2/d for 5 days is recommended for phase II trials using this schedule.