Plerixafor and Cemiplimab in Metastatic Pancreatic Cancer

Inclusion Criteria: Age ≥18 years. * Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 * Have histologically or cytologically-proven ductal pancreatic cancer. * Have metastatic disease. * Have documented radiographic disease progression after previous systemic chemotherapy given in a neoadjuvant, adjuvant, locally advanced or metastatic setting. * Patients with the presence of at least one measurable lesion. * Willing to have to a tumor biopsy. * Life expectancy of greater than 3 months. * Patients must have adequate organ and marrow function defined by study - specified laboratory tests. * Woman of childbearing potential must have a negative pregnancy test and follow contraceptive guidelines as defined per protocol. * Men must use acceptable form of birth control while on study. * Ability to understand and willingness to sign a written informed consent document. Exclusion Criteria: * Known history or evidence of brain metastases. * Had chemotherapy, radiation, or steroids within 14 days prior to study treatment. * Have received any investigational drugs, a live vaccine, any allergen hyposensitization therapy, growth factors or major surgery within 28 days prior to study treatment. * Require any antineoplastic therapy. * Had surgery within 28 days of dosing of investigational agent. * Has received any prophylactic vaccine within 14 days of first dose of study drug. * History of prior treatment with anti-CXCR4. * Have used any systemic steroids within 14 days of study treatment. * Patients receiving growth factors including, but not limited to, granulocyte-colony stimulating factor (G-CSF), Granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin, within 14 days of study drug administration. * Hypersensitivity reaction to any monoclonal antibody. * Evidence of clinical or radiographic ascites. * Have clinically significant and/or malignant pleural effusion. * Patient with uncontrolled intercurrent illness including, but not limited to, uncontrolled infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Has an active known or suspected autoimmune disease. * Prior tissue or organ allograft or allogeneic bone marrow transplantation. * All toxicities attributed to prior anti-cancer therapy other than alopecia and fatigue must have resolved to grade 1 (National Cancer Institute Common Terminology Criteria for Adverse Events \[CTCAE\], version 5) or baseline before administration of study drug. * Infection with HIV or hepatitis B or C at screening. * Patient has a pulse oximetry of \<92% on room air. * Patient is on supplemental home oxygen. * Has uncontrolled intercurrent acute or chronic medical illness or any use of illicit drugs or substance abuse. * Patient is unwilling or unable to follow the study schedule for any reason. * Woman who are pregnant or breastfeeding. * Have rapidly progressing disease, as judged by the investigator. * History of significant, recurrent, unexplained postural hypotension in the last 6 months.