Modl-44. development of a novel, personalized drug sensitivity score to assess tumor killing and toxicity within an organotypic brain slice culture platform

Abstract Development of new therapeutics for clinical use requires balancing tumor killing and off-target toxicity to normal tissue. We have established an organotypic brain slice culture (OBSC) platform which enables us to assess both on- and off-target drug effects via engraftment, treatment, and analysis of cell lines and uncultured patient brain tumor tissue. We have used OBSCs to test seven cell lines, ten patient tissues, and normal brain tissue against a panel of eleven different therapeutics. To determine a normalized comparison among drugs of differing potencies, we have established a drug sensitivity score (DSS) which combines both direct tumor killing via bioluminescence imaging and off-target toxicity via propidium iodide staining. Our ability to define these values independently allows us to generate normalized therapeutic window ratios for each drug-tumor-OBSC interaction. From these results, 11 different parameters, including those commonly used to define drug activity such as IC10, IC50, and area under the curve, were assessed and combined into a single ranked score which combines more than 100 data points. This algorithm enables relative comparisons among tumor responses to several drugs with less bias toward more potent compounds which produce correspondingly high off-target toxicity. Trends across DSSs for every tumor indicate that we can calculate scores throughout the entire scoring range. While we find that patient tumor tissue is generally more sensitive to treatment than cell lines, there is still a wide distribution of patient tumor sensitivities among tumor types and therapeutics. Additionally, our DSS can detect differences in tumor sensitivity after a single gene alteration in RAD18. In summary, our DSS algorithm and scoring system provides a summarized, normalized way to assess both on-target killing and off-target toxicity, allowing more comprehensive comparisons of drugs with varying potency.