Background: Ridaforolimus is an inhibitor of mTOR with evidence of antitumor activity in an I.V. formulation. This multicenter, open-label, 3+3 design nonrandomized, dose-escalation, phase I/IIa trial was conducted to determine the safety, pharmacokinetic (PK) and pharmacodynamic parameters, maximum tolerated dose, and antitumor activity of oral ridaforolimus. Patients and methods: Patients with metastatic or unresectable solid tumors refractory to therapy were eligible. Seven different continuous and intermittent dosing regimens were examined. Results: One hundred and forty-seven patients were enrolled in this study among which 85 were patients with sarcoma. Stomatitis was the most common DLT observed. The dosing regimen, 40 mg QD × 5 days/week, provided the best combination of cumulative dose, dose density, and cumulative exposure, and was the recommended dosing regimen for subsequent clinical development. PK was nonlinear, with less than proportional increases in day-1 blood AUC0-∞ and Cmax, particularly with doses >40 mg. The terminal half-life estimate of ridaforolimus (QD × 5 40 mg) was 42.0 h, and the mean half-life ∼30-60 h. The clinical benefit rate, (complete response, partial response, or stable disease for ≥4 months was 24.5 for all patients and 27.1 for patients with sarcoma. Conclusion: Oral ridaforolimus had an acceptable safety profile and exhibited antitumor activity in patients with sarcoma and other malignancies. ClinicalTrials.gov Identifier: NCT00112372.
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