Purpose
Reovirus is a naturally occurring human virus that is cytopathic to malignant cells possessing an activated Ras signaling pathway. We conducted a phase I trial of Reolysin, a manufactured, proprietary isolate of purified reovirus, in children with relapsed/refractory extracranial solid tumors to define the recommended phase 2 dose (RP2D), toxicities and pharmacokinetic properties when administered as a single agent or in combination with cyclophosphamide.
Experimental Design
Reolysin was administered intravenously for 5 consecutive days, every 28 days. Using a 3 + 3 design, the following dose levels were evaluated: 3 × 108 Tissue Culture Inhibitory Dose 50% (TCID50)/kg; 5 × 108 TCID50/kg (maximum dose was 3 × 1010 TCID50); and 5 × 108 TCID50/kg plus oral cyclophosphamide (50 mg/m2/day × 21 days).
Results
Twenty-nine patients were enrolled; 28 were eligible and 24 were evaluable for toxicity and response. There were no hematologic dose-limiting toxicities. Grade 5 respiratory failure and a Grade 5 thromboembolic event were reported, both in the setting of progressive disease. The median time to clear the reovirus viremia was 6.5 days. Eight of twenty-four patients were viremic beyond the five days of therapy, all were negative by day 17. No patient had detectable viral RNA in saliva or stool. There were no objective responses.
Conclusions
Reolysin at a dose of 5 × 108 TCID50/kg daily for 5 days was well tolerated in children alone and in combination with oral cyclophosphamide. Virus was cleared rapidly from the serum and shedding in stool and salivawas not detectable.
