Current standard-of-care systemic therapy options for locally advanced and metastatic bladder cancer (BC), which are predominantly based on cisplatin-gemcitabine combinations, are limited by significant treatment failure rates and frailty-based patient ineligibility. We previously addressed the urgent clinical need for better-tolerated BC therapeutic strategies using a drug screening approach, which identified outstanding antineoplastic activity of clofarabine in preclinical models of BC. To further assess clofarabine as a potential BC therapy component, we conducted head-to-head comparisons of responses to clofarabine versus gemcitabine in preclinical in vitro and in vivo models of BC, complemented by in silico analyses. In vitro data suggest a distinct correlation between the two antimetabolites, with higher cytotoxicity of gemcitabine, especially against several nonmalignant cell types, including keratinocytes and endothelial cells. Accordingly, tolerance of clofarabine (oral or intraperitoneal application) was distinctly better than for gemcitabine (intraperitoneal) in patient-derived xenograft models of BC. Clofarabine also exhibited distinctly superior anticancer efficacy, even at dosing regimens optimized for gemcitabine. Neither complete remission nor cure, both of which were observed with clofarabine, were achieved with any tolerable gemcitabine regimen. Taken together, our findings demonstrate that clofarabine has a better therapeutic window than gemcitabine, further emphasizing its potential as a candidate for drug repurposing in BC. PATIENT SUMMARY: We compared the anticancer activity of clofarabine, a drug used for treatment of leukemia but not bladder cancer, and gemcitabine, a drug currently used for chemotherapy against bladder cancer. Using cell cultures and mouse models, we found that clofarabine was better tolerated and more efficacious than gemcitabine, and even cured implanted tumors in mouse models. Our results suggest that clofarabine, alone or in combination schemes, might be superior to gemcitabine for the treatment of bladder cancer.

Center for Cancer Research and Comprehensive Cancer Center Medical University of Vienna Vienna Austria

Center for Cancer Research and Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria

Department of Pathology Medical University of Vienna Vienna Austria

Department of Pathology Medical University of Vienna Vienna Austria; Department of Pathology Tenon Hospital Sorbonne University Paris France

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Weill Cornell Medical College New York NY USA; Department of Urology University of Texas Southwestern Dallas TX USA; Department of Urology 2nd Faculty of Medicine Charles University Prague Czech Republic; Division of Urology Department of Special Surgery Jordan University Hospital The University of Jordan Amman Jordan; Research Center for Evidence Medicine Urology Department Tabriz University of Medical Sciences Tabriz Iran; Karl Landsteiner Institute of Urology and Andrology Vienna Austria

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