Synergistic Effect of Vedolizumab and Pentoxifylline

Inclusion Criteria: * Patients with active Crohn's disease (CD) defined by blood lab values, stool markers, abnormal MR enterography imaging, or colonoscopic findings * Patients who are good candidates to start standard dosing of vedolizumab * Patients who have not used an off-label or investigational drug for CD in the 8 weeks prior to screening * Patients who have met the washout period of 8 weeks for infliximab, 4 weeks for certolizumab pegol, and 2 weeks for adalimumab if there is a history of anti-TNF exposure and 8 weeks if there is a history of exposure to natalizumab * Oral aminosalicylates are allowed during the study, provided that the dose has been stable for at least 2 weeks prior to screening * Oral corticosteroids are allowed provided that the dose is prednisone ≤40 mg/day or equivalent and/or budesonide ≤9mg/day and has been stable for at least 2 weeks prior to screening * Patients are able to discontinue thiopurines (azathioprine and 6-mercaptopurine) or methotrexate upon initiation of vedolizumab * Rectal therapies, narcotics, anti-diarrheals, probiotics, and antibiotics will be permitted at investigator discretion Exclusion Criteria: * Contraindications or history of allergy to PTX * Known interaction of PTX with patient's current medications * Use of an off-label or investigational drug for CD in the 8 weeks prior to first VDZ infusion * Pregnancy * GFR \<30 at any time in the 6 months prior to first infusion of VDZ * Documented cirrhosis * Age \<18 or \>80 years old * Contraindication to colonoscopy at 24 week study time-point