Gemcitabine and Nab-paclitaxel Combined With Momelotinib in Participants With Previously Untreated Metastatic Pancreatic Ductal Adenocarcinoma

Key Inclusion Criteria: * Presence of metastatic pancreatic adenocarcinoma plus 1 of the following: * Histological diagnosis of pancreatic adenocarcinoma confirmed pathologically, OR * Pathologist confirmed histological/cytological diagnosis of adenocarcinoma consistent with pancreas origin in conjunction with either: * The presence of a mass in the pancreas, OR * A history of resected pancreatic adenocarcinoma * Measurable disease per RECIST v1.1 * Adequate organ function defined as follows: * Total bilirubin ≤ 1.25 x upper limit of the normal range (ULN); aspartate transaminase (AST) and alanine transaminase (ALT) ≤ 3 x ULN * Absolute neutrophil count (ANC) \> 1500 cells/mm\^3, platelet \> 100,000 cells/mm\^3, hemoglobin \> 9 g/dL * Serum creatinine \< ULN OR calculated creatinine clearance (CrCl) of ≥ 60 ml/min * Eastern Cooperative Oncology Group (ECOG ) 0 or 1 * Modified Glasgow prognostic score (mGPS) of 1 or 2 at Screening (randomized phase only) Key Exclusion Criteria: * Neoadjuvant or adjuvant chemotherapy or chemoradiotherapy for pancreatic adenocarcinoma * Currently or previously treated with biologic, small molecule, immunotherapy, chemotherapy, or other agents for metastatic pancreatic carcinoma * Major surgery within 28 days of first dose of study drug * Minor surgical procedure(s) within 7 days of enrollment or not yet recovered from prior minor surgery (placement of central venous access device, fine needle aspiration, or endoscopic bil…