This study focuses on patients who have pancreatic cancer that cannot be removed with surgery and who have already received standard of care treatment (including IV chemotherapy). The purpose of the study is to determine whether the use of an investigational drug called NanoPac helps kill cancer cells in patients with pancreatic cancer. Researchers also aim to identify the dose of NanoPac that is best tolerated and causes the least side effects when injected directly into the tumor in the pancreas. NanoPac is made of very small particles of another drug called paclitaxel, which is a chemotherapy drug approved by the U.S. Food and Drug Administration for other types of cancer. The use of Nanopac in this study is investigational.