Pilot Dose Escalation Trial of Stereotactic Body Radiation Therapy (SBRT) in Combination With GC4419 in Pancreatic Cancer

Inclusion Criteria: 1. Cytologic or biopsy confirmed adenocarcinoma of the pancreatic head, body or tail 2. Disease that is appropriate for SBRT by virtue of being: a. Locally advanced and technicallyunresectable, as determined by a pancreaticobiliary surgeon as part of a multidisciplinary review at the investigative site, including multi-phasic CT demonstrating: i.Greater than 180 degree tumor involvement of the superior mesenteric artery ii. Greater than 180 degree tumor involvement of the celiac axis, including major branches of the celiac axis that render it unresectable (e.g. common hepatic artery). iii. Tumor involvement of the first branch of the SMA that is not surgically reconstructible iv. Long segment involvement of the superior mesenteric vein/portal vein or hepatic artery that is not surgically reconstructible b. Potentially resectable, but patient is judged not a candidate for surgery, after multidisciplinary review at the investigative site; c. Potentially resectable, but the patients refuses surgery and is considered an acceptable candidate for SBRT after multidisciplinary review at the investigative site; d. "Borderline" resectable, as determined by multidisciplinary review, including absence of distant lymphadenopathy and the primary tumor characterized by one of more of the following: i. A tumor-vessel interface (TVI) with the mesenteric vein (SMV) or portal vein (PV) measuring ≥180° of the circumference of either vein's wall or short-segment occlusion of either vein with a normal vein above or below the obstruction amenable to reconstruction; ii. Any TVI with the common hepatic artery (CHA) with normal artery proximal and distal to the TVI amenable to reconstruction; iii. A TVI with the superior mesenteric artery (SMA) measuring \<180° of the circumference of the vessel wall 3. Pancreatic tumor size and limited bowel involvement by tumor must be judged acceptable for SBRT at the discretion of the treating investigator 4. No evidence of distant metastasis either prior to or after induction chemotherapy. 5. Completion of at least 3 months of standard induction chemotherapy for LAPC, which should consist of either FOLFIRINOX, gemcitabine or nab-paclitaxel or another standard combination of induction chemotherapy agents 6. Patient must have metal stent in place if duodenal stent is required. If patient has plastic stent, this must be replaced prior to radiation. 7. Ability to understand and follow the breathing instructions involved in the respiratory gating procedure or to tolerate compression sufficient to reduce fiducial motion to \<= 5mm. 8. Age 18 years or older 9. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (0, 1 or 2) 10. Adequate hematologic function as indicated by i. Absolute neutrophil counts (ANC) ≥ 1,500/mm3 ii. Hemoglobin (Hgb) ≥ 8.0 g/dL iii. Platelet count ≥ 75,000/mm3 11. Adequate renal and liver function as indicated by: i. Creatinine ≤ 1.5 x upper-normal limit (ULN) ii. Total bilirubin ≤ 1.5 x upper-normal limit (ULN) iii. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 x ULN iv. Alkaline phosphatase ≤ 2.5 x ULN 12. Properly obtained written informed consent Exclusion Criteria: 1. Prior radiation therapy to the abdomen that would overlap with treatment field 2. Prior surgical resection of pancreatic tumor 3. Receiving any approved or investigational anti-cancer agent other than those provided for in this study 4. Uncontrolled or active gastric or duodenal ulcer disease within 30 days of enrollment 5. Visible invasion of tumor into the lumen of the bowel or stomach on endoscopy (Note: Radiological infiltration into bowel is allowed, unless deemed clinically unsafe.) 6. Residual or ongoing ≥ Grade 3 non-hematologic toxicity from chemotherapy 7. Contraindication to IV contrast 8. Concurrent participation in another interventional clinical trial or use of another investigational agent within 30 days of study entry Note: Patients who are participating in non-interventional clinical trials (e.g., QOL, imaging, observational, follow-up studies, etc.) are eligible, regardless of the timing of participation. 9. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, renal failure, cardiac arrhythmia, or psychiatric illness that would limit compliance with treatment 10. Second primary malignancy within the last 5 years, unless treated definitively and with low risk of recurrence in the judgment of the treating investigator 11. Known history of HIV or active hepatitis B/C (patients who have been vaccinated for hepatitis B and do not have a history of infection are eligible) 12. Female patients who are pregnant or breastfeeding 13. Women of child-bearing potential who are unwilling or unable to use an acceptable method of birth control to avoid pregnancy for the entire study period and for 30 days after the last dose of GC4419. This includes any woman who has experienced menarche but has not undergone successful surgical sterilization or is not postmenopausal (defined as amenorrhea for at least 12 consecutive months, or women on hormone replacement therapy with serum FSH levels greater than 35 mIU/mL. A negative urine or serum pregnancy test must be obtained within 14 days prior to the start of study therapy in all women of child-bearing potential. 14. Male subjects who are unwilling or unable to use an acceptable method of birth control to avoid pregnancy for the entire study period and for up to 90 days after the last dose of GC4419 are excluded. 15. Requirement for concurrent treatment with nitrates or other drugs that may, in the judgment of the treating investigator, create a risk for a precipitous decrease in blood pressure. 16. Medical history that includes any condition, or requires the use of concomitant medications which, in the investigator's judgment, are associated with or create a risk of increased carotid sinus sensitivity, symptomatic bradycardia, or syncopal episodes.