A phase I study of intravenous oncolytic reovirus type 3 dearing in patients with advanced cancer

Purpose: To determine the safety and feasibility of daily i.v. administration of wild-type oncolytic reovirus (type 3 Dearing) to patients with advanced cancer, assess viral excretion kinetics and antiviral immune responses, identify tumor localization and replication, and describe antitumor activity. Experimental Design: Patients received escalating doses of reovirus up to 3 × 10¹⁰ TCID₅₀ for 5 consecutive days every 4 weeks. Viral excretion was assessed by reverse transcription-PCR and antibody response by cytotoxicity neutralization assay. Pretreatment and post-treatment tumor biopsies were obtained to measure viral uptake and replication. Results: Thirty-three patients received 76 courses of reovirus from 1 × 10 ⁸ for 1 day up to 3 × 10¹⁰ TCID₅₀ for 5 days, repeated every four weeks. Dose-limiting toxicity was not seen. Common grade1 to 2 toxicities included fever, fatigue, and headache, which were dose and cycle independent. Viral excretion at day 15 was not detected by reverse transcription-PCR at 25 cycles and only in 5 patients at 35 cycles. Neutralizing antibodies were detected in all patients and peaked at 4 weeks. Viral localization and replication in tumor biopsies were confirmed in 3 patients. Antitumor activity was seen by radiologic and tumor marker (carcinoembryonic antigen, CA19.9, and prostate-specific antigen) evaluation. Conclusions: Oncolytic reovirus can be safely and repeatedly administered by i.v. injection at doses up to 3 × 10¹⁰ TCID₅₀ for 5 days every 4 weeks without evidence of severe toxicities. Productive reoviral infection of metastatic tumor deposits was confirmed. Reovirus is a safe agent that warrants further evaluation in phase II studies.