The purpose of this study is to find out if study drug, botensilimab, when given in combination with chemotherapy consisting of nab-paclitaxel + gemcitabine, can help patients with metastatic pancreatic cancer. Botensilimab has not been approved by US Food and Drug Administration (FDA). Nab-paclitaxel + gemcitabine is an approved chemotherapy combination for pancreatic cancer, but they are not FDA approved to treat pancreatic cancer that has progressed after receiving initial treatment. This trial consists of two parts (Part 1 and Part 2). All visits and procedures are the same in both parts...