Phase I Study of the Safety, Tolerability, and Pharmacokinetics of Oral CP-868,596, a Highly Specific Platelet-Derived Growth Factor Receptor Tyrosine Kinase Inhibitor in Patients With Advanced Cancers

PURPOSE: This phase I, first-in-human study evaluated the safety, tolerability, pharmacokinetics, and maximum-tolerated dose (MTD) of an oral platelet-derived growth factor receptor inhibitor, CP-868,596. PATIENTS AND METHODS: Patients with advanced solid tumors were eligible. Dose escalations were performed in three groups with two formulations: uncoated on an empty stomach (UES), uncoated with food (UFED), and film-coated (FC) without food. Initial dose escalation in the UES group was followed by parallel escalations in the UFED and FC groups. RESULTS: Fifty-nine patients enrolled. CP-868,596 was escalated from 100 mg to 340 mg daily in the UES group, from 60 mg to 100 mg twice daily in the UFED group, and from 100 mg once daily to 140 mg twice daily in the FC group. MTDs were 200 mg daily in the UES group and 100 mg twice daily in the FC group; MTD was not reached at 100 mg twice daily in the UFED group. Dose-limiting toxicities included hematuria, increased gamma-glutamyltransferase or ALT, insomnia, and nausea/vomiting. Most treatment-related AEs were of grades 1 to 2 severity; nausea, vomiting, and diarrhea were reported most frequently. Administration with food generally improved tolerability. CP-868,596 was absorbed slowly; systemic exposure parameters appeared to increase greater than proportionally with dose. Mean serum concentrations exceeded the preclinically predicted minimal efficacious concentration (ie, 16 ng/mL) at all dosages. Food and film coating apparently increased interpatient variability of the maximum observed plasma concentration and the area under the concentration-time curve. No objective responses were reported, and eight patients achieved stable disease (mean duration, 5.7 months). CONCLUSION: CP-868,596 potentially demonstrated greater than dose-proportional pharmacokinetics. The recommended dosage of 100 mg twice daily with food was well tolerated. Additional development as a single agent in selected populations or in combination with chemotherapy in broader populations is warranted.