Phase I study of tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide, NSC 286193)

A phase I trial of 2-beta-D-ribofuranosylthiazole-4-carboxamide (NCS 286193, tiazofurin) was conducted using a 5-day i.v. bolus schedule, every 21 days. Thirty one patients with advanced cancer were entered on the trial. A total of 106 cycles were administered with doses ranging from 550 to 2750 mg/m2. Concomitant administration of Allopurinol was necessary to prevent hyperuricemia. Tiazofurin was difficult to evaluate and many side effects were variable and sporadic. The dose limiting toxicities were nonhematologic consisting particularly of myalgias, headaches and general malaise. Other toxicities included nausea, vomiting, stomatitis, lethargy, sleeping difficulty, sinus bradycardia, skin rash, desquamation of the palms and soles, photophobias and burning of the eyes. Hematologic toxicity was mild and not dose related though it led to a neutropenic septic death in one patient at 2750 mg/m2. Anemia was documented in 60% of cycles. Biochemical abnormalities consisted of mild hyperglycemia, hyperuricemia and elevated skeletal creatinine phosphokinase levels which did not correlate with the incidence or degree of myalgias. Though some patients were able to tolerate higher doses, the recommended dose for phase 2 study is 1650 mg/m2. Further studies will be required to achieve a better understanding of this interesting drug.