A Phase I study of intravenous (IV) bolus 4'-O-tetrahydropyranyladriamycin (Pirarubicin) was done in 55 patients in good performance status with refractory tumors. Twenty-six had minimal prior therapy (good risk), 23 had extensive prior therapy (poor risk), and six had renal and/or hepatic dysfunction. A total of 167 courses at doses of 15 to 70 mg/m2 were evaluable. Maximum tolerated dose in good-risk patients was 70 mg/mz, and in poor-risk patients, 60 mg/m2. The dose-limiting toxic effect was transient noncumulative granulocytopenia. Granulocyte nadir was on day 14 (range, 4-22). Less frequent toxic effects included thrombocytopenia, anemia, nausea, mild alopecia, phlebitis, and mucositis. Myelosuppression was more in patients with hepatic dysfunction. Pharmacokinetic analyses in 21 patients revealed Pirarubicin plasma T ' /z a (+SE) of 2.5 f 0.85 minutes, TB l/z of 25.6 rt 6.5 minutes, and T y of 23.6-t 7.6 hours. The area under the curve was 537-t 149 ng/ml X hours, volume of distribution (V,) 3504 t 644 l/mz, and total clearance ((21,) was 204 + 39.3 l/hour/mz. Adriamycinol, doxorubicin, adriamycinone, and tetrahydropyranyladriamycinol were the metabolites detected in plasma and the amount of doxorubicin was I 10% of the total metabolites. Urinary excretion of Pirarubicin in the first 24 hours was I 10%. Activity was noted in mesothelioma, leiomyosarcoma, and basal cell carcinoma. The recommended starting dose for Phase I1 trials is 60 mg/m2 IV bolus every 3 weeks. Cancer 66:2082-2091,1990. IRARUBICIN (4'-0-tetrahydropyranyladriamycin) is a P synthetic analog of doxorubicin (Adriamycin). ' Pi-rarubicin (THP-Adriamycin) exhibited similar or greater antitumor activity than doxorubicin in experimental tu