• Documented informed consent by the participant

• Willingness to provide tissue and blood samples for correlative studies

• Age: \>= 18 years

• Eastern Cooperative Oncology Group (ECOG) performance status =\< 1

• Must have a confirmed histologic or cytologic diagnosis of advanced unresectable pancreatic ductal adenocarcinoma (PDA)

• Must have received at least 16 weeks of 1st or 2nd line therapy and achieved partial response or stable disease (by computed tomography \[CT\] or magnetic resonance imaging \[MRI\]) with no signs of progression within 30 days before start of treatment

• Last chemotherapy treatment must be within 30 days prior to start of treatment

• No prior therapy with an anti-PD-1, anti-PD-L1, or anti PD L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (e.g., CTLA-4, OX 40, CD137)

• Measurable or evaluable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1. Lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions

• Participants must have recovered from all adverse events (AEs) due to previous therapies to =\< grade 1 or baseline, with the following exception: participants with =\< grade 2 neuropathy are eligible

‣ Note: Participants who have entered the follow-up phase of an investigational study may participate as long as it has been 4 weeks after the last dose of the previous investigational agent

• A male participant must agree to use a contraception of this protocol during the treatment period and for at least 90 days after the last dose of study treatment and refrain from donating sperm during this period

• A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies:

‣ Not a woman of childbearing potential (WOCBP) OR

⁃ Females of child-bearing potential must be willing to use effective contraception during study and for 30 days after the last dose

• Hemoglobin \>= 9.0 g/dL or \>= 5.6 mmol/L. Criteria must be met without erythropoietin dependency and without packed red blood cell (pRBC) transfusion within last 2 weeks (performed within 14 days prior to day 1)

• Absolute neutrophil count (ANC) \>= 1,500/mm\^3 (performed within 14 days prior to day 1)

• Platelets \>= 100,000/mm\^3 (performed within 14 days prior to day 1)

• Total serum bilirubin =\< 1.5 x upper limit of normal (ULN) OR direct bilirubin =\< ULN for participants with total bilirubin levels \> 1.5 x ULN (performed within 14 days prior to day 1)

• Aspartate Aminotransferase =\< 1.5 x ULN or =\< 3 x ULN with liver metastases (performed within 14 days prior to day 1)

• Alanine aminotransferase (ALT) =\< 1.5 x ULN or =\< 3 x ULN with liver metastases (performed within 14 days prior to day 1)

• Creatinine =\< 1.5 x ULN OR calculated creatinine clearance \>= 30 mL/min for participant with creatinine levels \>1.5 x institutional ULN (performed within 14 days prior to day 1)

• International normalized ratio (INR) or prothrombin time (PT) =\< 1.5 x ULN unless participant is receiving anticoagulant therapy as long as PT or activated partial thromboplastin time (aPTT) is within therapeutic range of intended use of anticoagulants (performed within 14 days prior to day 1)

• aPTT =\< 1.5 x ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulants (performed within 14 days prior to day 1)

• Women of childbearing potential (WOCBP): negative urine or serum pregnancy test

‣ If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required