An ex vivo permissivity assay to assess replication of the oncolytic virus VSV-GP in patient-derived tumor samples.

The sparking interest in oncolytic viruses (OV) faces challenges in clinical translation due to limitations of pre-clinical models and the lack of predictive biomarkers for OV activity. Furthermore, functional assays which could determine permissivity of human tumors to OVs in a straightforward way are still lacking. Here, we present a novel ex vivo permissivity assay to precisely quantify replication of OVs in viable patient-derived tumors. As example, replication of reporter protein-expressing oncolytic VSV-GP variants was tracked via fluorescence, luminescence or qPCR across 133 patient-derived tumor samples (resection fragments/slices, biopsies) spanning more than 20 tumor entities. Based on the results of our comprehensive testing and by employing VSV-GP-NanoLuc-Katushka, we were able to establish a semi-automated permissivity assay with minimal hands-on time, allowing robust and real-time tracking of viral replication in patient-derived tumor samples. Given the urgent demand for innovative cancer treatments, this novel permissivity assay could be applied to select patients with tumors permissive to OV replication and might thus also show an enhanced clinical response.