A Phase I Dose Escalation Study of Once-Weekly Oral Administration of Docetaxel as ModraDoc001 Capsule or ModraDoc006 Tablet in Combination with Ritonavir

Purpose: Oral bioavailability of docetaxel is poor. Absorption could be improved by development of pharmaceutical formulations based on docetaxel solid dispersions, denoted ModraDoc001 capsule and ModraDoc006 tablet (both 10 mg) and coadministration of ritonavir, an inhibitor of CYP3A4 and P-glycoprotein. In this study, the safety, MTD, recommended phase II dose (RP2D), pharmacokinetics, and preliminary antitumor activity of oral docetaxel combined with ritonavir in a once-weekly continuous schedule was investigated. Patients and Methods: Patients with metastatic solid tumors were included. Dose escalation was performed using a classical 3+3 design. Pharmacokinetic sampling was performed for up to 48 hours after drug administration. Safety was evaluated using CTCAE v3.0. Antitumor activity was assessed according to RECIST v1.0. Results: Sixty-seven patients were treated at weekly docetaxel dosages ranging from 30 to 80 mg in combination with 100- or 200-mg ritonavir. Most common toxicities were nausea, vomiting, diarrhea and fatigue, mostly of grade 1-2 severity. No hypersensitivity reactions were observed. The area under the plasma concentration-time curve (AUC(0-48)) of docetaxel at the RP2D of once-weekly 60-mg ModraDoc001 capsule with 100-mg ritonavir was 1,000 +/- 687 ng/mL/hour and for once-weekly 60-mg ModraDoc006 tablet with 100-mg ritonavir, the AUC(0-48) was 1,790 +/- 819 ng/mL/hour. Nine partial responses were reported as best response to treatment. Conclusions: Oral administration of once-weekly docetaxel as ModraDoc001 capsule or ModraDoc006 tablet in combination with ritonavir is feasible. The RP2D for both formulations is 60-mg ModraDoc with 100-mg ritonavir. Antitumor activity is considered promising.