Phase I clinical and pharmacokinetic study of PTK/ZK, a multiple VEGF receptor inhibitor, in patients with liver metastases from solid tumours

The family of VEGF receptors are important mediators of angiogenesis, which is essential for tumour growth and metastasis. PTK/ZK is a multiple VEGF receptor inhibitor that blocks the activity of all known VEGF receptor tyrosine kinases. This phase I/II trial evaluated the safety, pharmacokinetics and efficacy of PTK/ZK in patients with liver metastases from solid tumours. Patients were administered oral PTK/ZK monotherapy once daily at doses of 300-1200 mg/day in 28-day cycles until unacceptable toxicity or tumour progression occurred. Twenty-seven patients were enrolled and treatment with PTK/ZK was generally well tolerated. The most frequently reported adverse events were fatigue, nausea, dizziness, and vomiting (mostly National Cancer Institute Common Toxicity Criteria grade 1 or 2). The area under the concentration-time curve (AUC) of PTK/ZK increased between 300 and 1000 mg/day with no further increase from 1000 to 1200 mg/day; the AUC decreased by 50% between day 1 and day 15. The DCE-MRI showed a statistically significant early reduction of tumour blood supply (measured as Ki) at day 2 at doses ⩾750 mg/day. Disease progression was significantly correlated with percent change from baseline Ki. Thirteen patients had stable disease for at least two cycles (56 days). Median overall survival was 11.8 months (95% CI = 6.6, 17.1 months). Long-term therapy with PTK/ZK demonstrated predictable pharmacokinetics, was safe and feasible in patients with metastatic disease, and showed promising clinical activity. The minimum biologically active dose was established at 750 mg/day whereas the recommended dose for phase III studies is 1200 mg/day.