Abstract A8: Final results of a phase I dose escalation study of the safety and pharmacokinetics of foretinib administered orally daily to patients with solid tumors

Abstract

Abstract Foretinib is a potent, orally available, small-molecule inhibitor of MET and VEGFR2. Significant tumor cell growth inhibition was observed preclinically following treatment in multiple tumor models. Antitumor activity was observed in a previous phase I study in which foretinib was dosed intermittently on days 1–5 every 14 days. This phase I dose-escalation study to evaluate daily oral administration of foretinib was conducted in adults with solid tumors. Foretinib was orally administered until disease progression or toxicity mandated removal from the study. Dose-limiting toxicities (DLTs) that occurred during the first 28 days of treatment were used to determine the maximum tolerated dose (MTD). Safety, tolerability, pharmacodynamics (PD), and pharmacokinetics (PK) were evaluated. Tumor volume was assessed every 8 weeks by RECIST. A total of 37 patients (pts) were treated across 4 dose levels in the following order: 60 mg/d (6 pts), 80 mg/d (12 pts), 120 mg/d (3 pts), 100 mg/d (3 pts), and 80 mg/d (13 pts, PK expansion). Reported DLTs were hypertension and dehydration at 120 mg/d and diarrhea at 100 mg/d. The MTD of foretinib was determined to be 80 mg. With chronic dosing, 12 of 25 pts (48%) on 80 mg required a dose reduction to 60 mg between 21 days and 4 months on treatment. Frequent AEs associated with foretinib were hypertension (62%), fatigue (51%), nausea (43%), diarrhea (41%), proteinuria (30%), increased lactate dehydrogenase (27%), vomiting (24%), anorexia (22%), increased aspartate transaminase (19%), rash (16%), increased GGT (16%), and increased lipase (16%), primarily CTCAE grades 1 and 2. The foretinib plasma PK (at MTD) was characterized by a tmax of ≈4 hours, a steady-state oral clearance (CL/F) of ≈83 L/h, and ≈3.8-fold accumulation at steady state (achieved by ≈day 15). At steady state, values of Cmax and AUC0–24 were ≈45.7 ng/mL and ≈805 h · ng/mL, respectively, and the Cmin was ≈52% of Cmax. Plasma PD markers were measured during cycle 1 in 19 pts treated at the MTD. Shed Met (sMET) and VEGF showed increases, whereas sVEGFR2 showed a decrease. No pts had confirmed partial response or complete response, but stable disease (SD) (range, 2.1–18.1 months) was seen in 23 pts (74.2%). 11 pts had tumor regression from baseline, with tumor shrinkage ranging from 1%–21%. Disease progression was seen in 8 pts (25.8%). Overall, 35.5% of pts were event-free at 6 months, and 12.9% of pts (diagnoses included medullary thyroid, hepatocellular, and papillary renal cell carcinomas, and alveolar soft part sarcoma) were event-free at 12 months. 62% percent of pts withdrew due to progressive disease, 8% due to AEs, 5% due to death, and 24% due to consent withdrawal/investigator discretion/other. Foretinib can be safely administered at the oral daily dose of 80 mg (MTD); however, with chronic administration, dose reductions were not uncommon. The safety profile observed with daily dosing of foretinib is similar to that seen with intermittent dosing. Plasma PK results indicate that exposure to foretinib was well maintained over the daily dosing interval. PD results are similar to that seen with intermittent dosing and indicate that sMET, VEGF, and sVEGFR2 are promising markers for monitoring biological activity of foretinib. Prolonged SD and tumor regression in pts with various cancers suggest that foretinib has promise as an anticancer therapy. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A8.