ABSTRACTDespite routine use of platinum-based chemotherapeutics across diverse cancer types, there remains a need to improve efficacy and patient selection for treatment. A multi-omic assessment of five human bladder cancer cell lines and their chemotherapy resistant derivatives, coupled with whole-genome CRISPR screens were used to identify puromycin- sensitive aminopeptidase, NPEPPS, as a novel functional driver of treatment resistance to cisplatin. Depletion of NPEPPS resulted in enhanced cellular cisplatin import, sensitization of resistant cancer cells to cisplatin in vitro and in vivo. Pharmacologic inhibition of NPEPPS with tosedostat in cells and in chemoresistant, patient-derived tumor organoids improved response to cisplatin. Depletion of LRRC8A and LRRC8D, two subunits of the volume regulated anion channel (VRAC), a known importer of intracellular cisplatin, enhanced resistance to cisplatin. Linking NPEPPS function to VRAC cisplatin import supports NPEPPS as a driver of cisplatin resistance and by virtue of clinically available inhibitors, the potential for rapid clinical translation.HIGHLIGHTS∙CRISPR screens with multi-omics identify NPEPPS as a driver of cisplatin resistance∙NPEPPS depletion in multiple bladder cancer models enhances cisplatin sensitivity∙LRRC8A and LRRC8D loss increase resistance to cisplatin in CRISPR screens∙Unique resource of functional and multi-omic data is provided to the community