Olaparib in Subjects With Advanced Pancreatic Acinar Cell Carcinoma

Background: * Pancreatic Acinar Cell Carcinoma (PACC) is a rare pancreatic tumor, representing 0.5-1% of all pancreatic malignancies. * PACC is commonly advanced at presentation and median overall survival in this population is poor. * PACC is pathologically and biochemically distinct from pancreatic adenocarcinoma. * No clinical trials for PACC have ever been reported. * Patients are most commonly treated with combination regimens used for either pancreatic or colon adenocarcinoma with poor (approximately 30%) response rates in the first line setting. * PACC pathological specimens demonstrate evidence of high chromosomal instability, a hallmark of deoxyribonucleic acid (DNA) repair deficiency. * Data derived from ovarian and prostate cancer patients has demonstrated that mutations in DNA repair genes can define subgroups of cancer patients with distinct vulnerabilities to DNA damage response inhibitors. * Olaparib is a Poly-ADP ribose polymerase (PARP)-1 inhibitor that has been Food and Drug Administration (FDA) approved for the treatment of BReast CAncer genes 1 and 2 (BRCA)-mutant homologous recombination repair (HRR) deficient cancers. * As PACC has multiple hallmarks of homologous recombination repair (HRR) deficiency, we hypothesize that PACC will be sensitive to PARP inhibition with olaparib. * Pre-clinical modeling of PACC has been very limited with no currently available animal models or cell lines, which precludes testing this hypothesis in the laboratory setting. Objective: \- To assess the anti-tumor activity of single agent olaparib, a PARP inhibitor, in participants with advanced pancreatic acinar cell carcinoma (PACC) Eligibility: * Participants must have advanced previously treated PACC * Age \>=18 years * Adequate organ and bone marrow function Design: * This is a phase II, single arm, single center study of olaparib in participants with advanced previously treated PACC. * All participants will take olaparib by mouth twice daily for up to two years or until disease progression or intolerable side effects. * Participants will be assessed for safety (continuously) and efficacy (every 8 weeks). * Up to 13 evaluable participants will be enrolled.