Abstract Pancreatic ductal adenocarcinoma (PDAC) is clinically still treated as a single disease. We have generated patient-derived models representing the recently identified quasi-mesenchymal, classical and exocrine-like PDAC subtypes, and report a two-marker set facilitating patient stratification by immunohistochemistry. The subtypes show significant differences in overall survival and drug sensitivity, with the exocrine-like subtype being resistant to the tyrosine kinase inhibitors erlotinib, dasatinib, as well as the chemotherapeutic paclitaxel. Highly expressed cytochrome P450 3A5 (CYP3A5) actively metabolizes these compounds in the exocrine-like subtype, and pharmacological or shRNA-mediated CYP3A5 inhibition sensitizes tumor cells in vivo. Additionally, we investigated the transcriptional network underlying the subtype-specific CYP3A5 expression. Hence, these data show that exocrine-like PDAC adopts a highly effective detoxification mechanism akin to that of hepatocytes. High expression of CYP3A5 in other tumor entities suggests this pathway as an important target to overcome drug resistance and to predict response to therapy with small molecule drugs. Citation Format: Elisa M. Noll, Elisa M. Noll, Christian Eisen, Christian Eisen, Elisa Espinet, Elisa Espinet, Albrecht Stenzinger, Wilko Weichert, Martin R. Sprick, Andreas Trumpp, Andreas Trumpp. CYP3A5 mediates resistance to small molecule inhibitors in a subtype of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr IA22.