A phase I study of bevacizumab in children with refractory solid tumors: A Children’s Oncology Group study

Abstract

9017 Background: Bevacizumab is a humanized monoclonal antibody targeting the vascular endothelial growth factor (VEGF-A) that has demonstrated significant growth inhibition in several pre-clinical models of pediatric solid tumors. However, the agent has never been tested in pediatric patients. Methods: A phase I dose escalation study in children with refractory solid tumors was conducted to define the dose limiting toxicities (DLTs), and to determine the pharmacokinetics (PK) and recommended phase II dose of bevacizumab administered by IV infusion every 2 weeks in 28-day cycles. Cohorts were enrolled at dose levels of 5, 10, and 15 mg/kg; the final dose level was expanded to include at least 3 children <6 years of age. Serial blood samples were collected for PK, plasma VEGF concentration, and circulating mature and progenitor endothelial cells (CECs/CEPs). Results: 20 patients (10 male), median age 13 yrs (range 1–21), were enrolled at dose levels 5 (n=3), 10 (n=3), and 15 (n=14) mg/kg. 18 patients were fully evaluable for toxicity (one withdrew consent prior to treatment and the second was removed for rapid disease progression). A total of 67 cycles were administered with a median of 3 per patient (range 1–16). Treatment was well tolerated and no DLTs were observed. Only one grade 3 toxicity, lymphopenia, was attributed to drug. Non-dose limiting, grade 1–2 toxicities included infusional reaction (n=3), rash (n=3), mucositis (n=2), and proteinuria (n=3). There was no hypertension, hemorrhage or thrombosis reported. There were no partial or complete responses; 3 pts with Ewings and 2 pts with soft tissue sarcoma had disease stabilization for > 3 months. The serum exposure to bevacizumab as measured by AUC appeared to increase in proportion to dose. The median clearance of bevacizumab was 4.1 ml/day/kg (range 3.2–15.9), and the median T1/2 was 11.8 days (range 3.9–14.6). In some patients, a rapid rate of rise in plasma VEGF, increase in mature CECs or decrease in CEPs was observed. Conclusion: Bevacizumab at doses up to 15mg/kg every two weeks is well tolerated in children with solid tumors. No significant financial relationships to disclose.