A Phase 1 Clinical Study of Temsirolimus (CCI-779) in Japanese Patients with Advanced Solid Tumors

Temsirolimus (CCI-779) is a novel inhibitor of the mammalian target of rapamycin. This Phase 1 study was aimed at investigating the maximum-tolerated dose, toxicity, pharmacokinetics and antitumor activity in Japanese patients with advanced solid tumors. Temsirolimus was given as a 30 min intravenous infusion once a week. Patients with solid tumors not amenable to standard forms of treatment were eligible. Dose escalation of temsirolimus was planned from 15, 45, 80 to 165 mg/m(2). The pharmacokinetics of temsirolimus and sirolimus in whole blood were examined for cycles 1, 2, 4 and 5 of treatment. Ten patients (median age 60.5 years; range 41-69 years) with advanced solid tumors were enrolled. Their primary cancers were renal cell carcinoma (five patients), lung cancer (three patients) and colorectal cancer (two patients). The major toxicities were hypophosphatemia diarrhea, hyperglycemia, stomatitis, pyrexia, elevated aspartate aminotransferase, rash, reduced neutrophil count, elevated alanine aminotransferase, anorexia, hypertriglyceridemia and somnolence. Two of three patients who received temsirolimus 45 mg/m(2) developed dose-limiting toxicities of Grade 3 stomatitis (one patient) and Grade 3 diarrhea (two patients). The maximum-tolerated dose was 15 mg/m(2). The peak blood concentrations of temsirolimus and sirolimus, a major active metabolite, increased in a dose-dependent manner. The area under the concentration-versus-time curve of sirolimus, but not temsirolimus, increased in a dose-dependent manner. The recommended dose for Phase 2 clinical studies of temsirolimus in Japanese patients with advanced solid tumors is 15 mg/m(2) intravenously once a week.