Abstract Pancreatic ductal adenocarcinoma (PDAC) is the 3rd leading cause of cancer death in the United States with a 5-year survival rate of only 7%. Early diagnosis is very difficult and thus 53% of PDAC patients are diagnosed after metastasis has already occurred with liver being the most frequently affected site. Therefore, it is urgent to understand the mechanism that leads to PDAC metastasis in liver in order to develop potential therapeutics. Research shows that environment that comprises the metastatic niche has unique features that facilitate tumor growth and chemoresistance. Differences between the tumor microenvironment (TME) of the primary site and the metastatic site may be a key reason why metastatic tumors are highly resistant to standard treatment. However, most current models only recreate the primary tumor environment, while a proper model which recapitulates the key features of the metastatic niche to study liver metastasis (LM) is still missing. To address this problem, we aim to design a biomimetic model that specifically recapitulates the liver premetastatic niche (PMN). Our 3D model accomplishes this by using 1) a collagen rich extracellular matrix (ECM) that mimics the metastatic site, 2) LM-derived fibroblasts, 3) and LM organoids derived from a mouse model of PDAC. Our preliminary results showed that primary PDAC organoids require CAFs derived from primary PDACs to exhibit chemoresistance. In contrast, LM organoids did not require primary CAFs to exhibit the same level of chemoresistance. This suggests that there are cell intrinsic factors that promote chemoresistance in LM organoid in addition to possible cell extrinsic factors from the PMN. In this research we investigate the role of LM-derived CAFs and PDAC-derived exosomes in liver PMN development and study their effect on growth and chemoresistance of LM organoids. Results of this research will help us to develop strategies specifically tailored to overcome the factors which promote chemoresistance in the PMN. Citation Format: Mahsa Pahlavan, Weikun Xiao, Flora Eun, Chang-Il Hwang, Reginald Hill. Development of a 3D biomimetic metastatic liver niche model for pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-123.