PHARMACOKINETIC, BIOAVAILABILITY, AND FEASIBILITY STUDY OF ORAL VINORELBINE IN PATIENTS WITH SOLID TUMORS

Purpose: The feasibility of administering vinorelbine (Navelbine, Burr oughs Wellcome Co, Research Triangle Park, NC), a semisynthetic vinca alkaloid with broad activity, as a liquid-filled gelatin capsule wets evaluated in a bioavailability (F) and pharmacokinetic study. Patients and Methods: Each of 17 cancer patients had pharmacokinetic studies p erformed after receiving vinorelbine 30 mg/m(2) intravenously (IV), wh ich is the maximum-tolerated dose (MTD) for weekly IV administration, and twice after receiving the oral formulation at a nominal dose of 10 0 mg/m(2) Subsequently, these patients and 10 other subjects received the oral formulation at a dose of 100 mg/m(2)/wk to evaluate the feasi bility of chronic oral administration. Results: Plasma drug dispositio n was well described by a triphasic model. Mean central volume of dist ribution and steady-stare volume of distribution (Vss) were large (0.6 6 +/- 0.46 L/kg and 20.02 +/- 8.55 L/kg, respectively); the mean harmo nic terminal half-life (t(1/2)) was long (18 hours); and the high mean clearance (CI) rate (0,80 +/- 0.68 L/h/kg) approached hepatic blood f low. F was low (0.27 +/- 12), and absorption was rapid (mean time of m aximum plasma concentration [T-max], 0.91 +/- 0.22 hours). Absorption parameters after the first and second oral doses were similar, with me an F values of 0.27 +/- 0.14 and 0.25 +/- 0.11, respectively. Coeffici ents of variability (CVs) for F, maximum plasma concentration(C-max), and T-max were 32%, 42%, and 78%, respectively, indicating moderate in traindividual variability. The pharmacologic profile of this oral form ulation indicates that there is a large first-pass effect. Neutropenia was the principal toxicity of oral vinorelbine. Grade 3 or 4 neutrope nia occurred in 63% of patients, but only 11% developed neutropenia an d infection. Nausea, vomiting, and diarrhea were also common with oral administration, but these effects were rarely severe and could be ame liorated by using a divided-dose schedule and/or prophylactic antiemet ic and antidiarrheal agents. The mean nominal oral dose was 82 mg/m(2) , and the mean percentage of intended dose that was received was 92% A lthough dose escalations were permitted for negligible toxicity, doses were not escalated to greater than 100 mg/m(2)/wk in any patient. Vin orelbine given as a liquid-filled gelatin capsule at 100 mg/m(2) provi ded equivalent pharmacologic exposure as 30 mg/m(2) IV. Conclusion: Th e oral administration of vinorelbine, specifically a liquid-filled, so ft gelatin capsule, is a feasible route of administration. Weekly oral dosing at 100 mg/m(2) induces a consistent degree of myelosuppression , but the high frequency of grade 3 or 4 neutropenia, albeit brief and uncomplicated, warrants the recommendation of a slightly lower starti ng dose, ie, 80 mg/m(2)/d, for subsequent phase II evaluations, especi ally in heavily pretreated patients. (C) 1994 by American Society of C linical Oncology.