Abstract B74: A phase I trial and viral clearance study of reovirus (Reolysin) in children with relapsed or refractory extra-cranial solid tumors: A Children's Oncology Group phase I consortium report
Authors: Kolb Edward A. , Sampson Valerie B. , Stabley Deborah , Walter Alexa , Cripe Timothy P. , Hingorani Pooja , Ahern Charlotte Hsieh , Ingle Ashish M. , Weigel Brenda J. , Blaney Susan B. 
Published: May 2015

Purpose: Reovirus (Respiratory Enteric Orphan virus) Serotype 3 – Dearing Strain is a naturally occurring, ubiquitous, non-enveloped human virus. Reovirus has been shown to replicate specifically in, and be cytopathic to, transformed cells possessing an activated Ras signaling pathway. We conducted a Phase I trial of Reolysin, a manufactured, purified reovirus, in children with relapsed or refractory extracranial solid tumors to define a maximum tolerated or recommended phase 2 dose (PP2D), as well as its toxicities and pharmacokinetic properties.

Experimental Design: Reovirus was administered intravenously, daily for 5 consecutive days every 28 days for up to 12 cycles. Using a 3+3 design, two planned dose levels were evaluated: 3 x 108 TCID50/kg (∼60% of the adult dose) and 5 x 108 TCID50/kg. The cohort was expanded at the RP2D to obtain additional single agent safety and viral clearance data. Additionally, a 3rd cohort received the RP2D ( 5 x 108 TCID50/kg Reolysin) plus oral cyclophosphamide (50 mg/m2/day x 21 days). Twice weekly quantitative real time PCR of reovirus genomic RNA from serum, stool and saliva, and antiviral immune response by ELISA was evaluated after the first two courses.

Results: Twenty-nine patients were enrolled, one was subsequently found to be ineligible. Of the 28 eligible patients, 5 are not evaluable (one is still on study) for dose-limiting toxicity (DLT). Six evaluable patients were enrolled on dose level 1; one with extensive pulmonary metastases experienced grade 5 respiratory failure attributed to their underlying disease. Given the severity of the event, the cohort was expanded to six without further DLTs. None of the six evaluable patients enrolled on dose levels 2 and 3, respectively, had a DLT. One patient in the single agent expansion cohort experienced a grade 5 thromboembolic event, grade 4 hypokalemia, grade 3 hypocalcemia, grade 4 hypophosphatemia, grade 3 hyponatremia, and grade 3 hypoalbuminemia possibly attributed to the Reolysin. With twice weekly monitoring by quantitative real time PCR, the median time to a clear the reovirus viremia was 6.5 days. Seven patients were viremic beyond the five days of therapy. No patient had detectable virus in their serum beyond day 17. Only one patient had detectable viral RNA in saliva or stool (day 6 in saliva). Four patients receiving the RP2D had stable disease at the end of one cycle, all others had progressive disease. All patients developed an anti-reovirus antibody during the first cycle of treatment. In three patients receiving a second cycle of reovirus, peak viral levels were reduced relative to cycle 1. There were no objective responses.

Conclusions: Reovirus at a dose of 5 x 108 TCID50/kg daily for 5 days is well tolerated alone and in combination with oral cyclophosphamide. Virus is cleared rapidly from the serum of most patients, even when given with cyclophosphamide, and shedding in stool and saliva is not seen.

Citation Format: Edward A. Kolb, Valerie B. Sampson, Deborah Stabley, Alexa Walter, Timothy P. Cripe, Pooja Hingorani, Charlotte Hsieh Ahern, Ashish M. Ingle, Brenda J. Weigel, Susan B. Blaney. A phase I trial and viral clearance study of reovirus (Reolysin) in children with relapsed or refractory extra-cranial solid tumors: A Children's Oncology Group phase I consortium report. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B74.