Gemcitabine and Leflunomide in Patients With Advanced Unresectable Pancreatic Cancer

PRIMARY OBJECTIVE: I. To evaluate the safety and tolerability of gemcitabine in combination with leflunomide and determine the recommended Phase 2 dose (RP2D) of the combination. SECONDARY OBJECTIVES: I. To evaluate the progression-free (PFS) and overall survival (OS). II. To evaluate the overall response rate (ORR), including confirmed and unconfirmed, complete and partial response and stable disease. III. To describe quality of life utilizing the Functional Assessment of Cancer Therapy: General (FACT-G) questionnaire. EXPLORATORY OBJECTIVES: I. To describe the pharmacokinetic profile of leflunomide when given in combination with gemcitabine. II. To examine the relationship between pharmacokinetics and disease progression. OUTLINE: Patients receive gemcitabine intravenously (IV) over 30 minutes on days 1, 8, and 15 of each cycle and leflunomide orally (PO) once daily (QD) on days -3 to -1 prior to cycle 1 and days 1-28 of each cycle thereafter. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients also receive cholestyramine PO three times a day (TID) for 11 days at the end of treatment in the absence of unacceptable toxicity. Patients also undergo computed tomography (CT), magnetic resonance imaging (MRI), or other imaging scans as clinically indicated throughout the study, as well as blood sample collection on study and during follow up. After completion of study treatment, patients are followed up at 30 days then up to 1 year.