The purpose of this study is to determine the synergistic effect and clinical benefits of vedolizumab and pentoxifylline in the management of patients with inflammatory bowel disease.

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