A phase I surrogate endpoint study of SU6668 in patients with solid tumors

Purpose. To evaluate the biologic effects of SU6668 in patients with solid tumors using comprehensive measures of pharmacokinetics (PK), functional imaging, and tissue correlative studies. Experimental design. Eligible patients with tumors accessible for core needle biopsy were treated with SU6668 at doses of 200 or 400 mg/m ²/day. Functional computed tomography (CT) scan and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were performed at baseline and repeated 4 weeks and 12 weeks after treatment for analysis of tumor angiogenesis. The PK was analyzed using a high-performance liquid chromatography assay. Tumor specimens obtained via core needle biopsy at baseline and 4 weeks later were analyzed for the biologic effects of SU6668. Results. Six of a total of seven patients received treatment for at least 3 months and underwent comprehensive correlative studies, including PK, imaging, and tissue biopsy. Functional CT showed that five of six patients had decreased blood flow in tumors in response to treatment, and DCE-MRI results indicated significant change of area under the signal intensity vs. time curve (AUC) and/or maximum slope (maximum rate of signal intensity change) in two of four patients evaluated with this technique. PK studies showed that the mean apparent oral clearance (Cl _oral) measured on day 1 was 6.3 ± 2.7 L/hr/m ², yielding a mean AUC of 16.6 ± 4.3 mg/L·hr. By day 22, the Cl _oral was 40% more than that observed on day 1. Conclusion. It is feasible to evaluate the biologic effects of antiangiogenic agents using comprehensive surrogate measures.