Dose escalation and pharmacodynamic study of intravenous adminstration of Reolysin, a live replication competent RNA virus in patients with advanced solid tumors

Abstract

3583 Background: Reolysin is reovirus serotype 3 - Dearing strain, a double-stranded replication- competent RNA non-enveloped icosahedral virus. It induces cytopathic and anti-cancer effects in cells with an activating mutation in the ras proto-oncogene. Methods: This was a single center dose escalation trial of Reolysin administered intravenously every four weeks in doses ranging from 1X108 to 3X1010 tissue culture infective dose (TCID)50. Serum for neutralizing antibody, and serum, stool, saliva, and urine for viral shedding were collected. Tumor samples were analyzed for activating mutations in the ras and braf oncogenes. Results: Eighteen patients received 27 doses of Reolysin in 6 dose cohorts accomplishing a 300 fold dose escalation without a protocol-defined dose limiting toxicity. Drug related grade 2 toxicities included fatigue and fever (1 patient each). All patients developed neutralizing antibody during the course of the study. Viral shedding was observed in 6 patients [urine (5), serum (4), saliva (3), and stool (2)]. One patient with anthracycline and taxane refractory breast cancer experienced a partial response (PR) and her tumor had a mutation in the ras oncogene. Biopsy from a chest wall mass showed evidence of necrosis and viral replication by electron microscopy. The overall clinical benefit rate was 45% and appeared higher in patients with viral shedding (67%) than those without (33%). Conclusions: Reolysin administered as a one hour infusion on a monthly schedule is safe and well-tolerated even in multiple doses. Reolysin has anti-tumor activity as a single agent warranting further evaluation, including in combination with chemotherapy. Viral shedding may suggest intrapatient replication yielding a benefit and should be studied carefully in future studies. [Table: see text]