Pharmacogenomic characterisation of a large collection of primary cell lines identifies novel therapeutic options for pleural mesothelioma

Background: Pleural mesothelioma (PM) urgently requires novel effective treatments. Drug repurposing is a relevant strategy to discover new therapeutic options among well-known drugs used in clinical practice. This study aimed to identify new therapies in the context of molecular heterogeneity of PM. Methods: We performed a multi-omics study of the largest cohort of patient-derived primary PM cell lines (n=58) to date, using whole exome sequencing, RNA sequencing and methylome analysis. We also conducted a large-scale drug screening of over 1300 compounds on a subset of cell lines (n=11), as well as an extension screen (n=48) for selected drugs of interest. The best candidates were validated using 3D culture and mouse models. Results: We demonstrated that the molecular landscape of the cell lines cohort recapitulates the main findings in tumours and revealed new specific features of PM. The large-scale drug screening and subsequent validations highlighted notably strong sensitivity to entinostat and fluvastatin. Importantly, both compounds displayed same efficacy in 2D and 3D culture models and single treatment prolonged survival in vivo similarly or even better than standard chemotherapy. Strikingly, combining entinostat treatment with anti-PD1 led to cures in some mice and immunized them against tumour cells. Conclusions: Among several candidates, we identified entinostat, notably in combination with immune checkpoint inhibitor, and to a lesser extent fluvastatin, as promising therapeutic options for patients. We believe our study provides a valuable resource that could contribute to advances in the field and warrants further clinical investigation. 58 patient-derived primary pleural mesothelioma cell lines were analyzed either with the Infinium HumanMethylation450 Beadchip (Illumina) or with the Infinium MethylationEPIC BeadChip Kit (Illumina) or both after bisulfite conversion of 500 ng of genomic DNA using the Zymo EZ DNA Methylation Kit (Ozyme)