Vascular endothelial growth factor receptor tyrosine kinase inhibitors: PTK787/ZK 222584.

PTK787/ZK 222584 (PTK/ZK) is an oral potent and selective inhibitor of the vascular endothelial growth factor (VEGF)-mediated Flt-1 and KDR receptor tyrosine kinases. PTK/ZK has been shown to reduce growth and microvasculature in subcutaneously implanted human tumor xenografts in nude mice. A clinical difficulty in evaluating angiogenesis inhibitors has been the usefulness of conventional study endpoints. Therefore, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been studied as a pharmacodynamic marker of efficacy of PTK/ZK. Phase I studies are under way evaluating the optimum dose and schedule of oral PTK/ZK administered continuously to patients with advanced cancers of types known to overexpress VEGF. To date, particularly in patients with liver metastases from colorectal cancer treated with PTK/ZK, DCE-MRI has been a useful predictor of the biological response of VEGF-receptor inhibition. Toxicities have been manageable and have included lightheadedness, ataxia, nausea, vomiting, and hypertension. Stabilization of disease for >/= 6 months has been seen in heavily pretreated patients receiving PTK/ZK at higher doses. Preliminary data suggest that PTK/ZK can be administered safely on a continuous daily dosing schedule, efficacy data look promising, and DCE-MRI correlates with biological response. DCE-MRI will be used to guide dose optimization of PTK/ZK and perhaps of other angiogenesis inhibitors in future studies.