Inclusion Criteria:

• written informed consent obtained
• male or female patients aged 5 to 18 years at time of screening
• of non-childbearing potential, of childbearing potential and willing to use specific barrier methods outlined in the protocol
• confirmed active eosinophilic esophagitis (at Screening or within six weeks prior to Baseline Visit) as defined by esophageal mucosal eosinophils greater than or equal to 24 per hpf (400X magnification)
• within the week prior to dosing, patient has one of the following symptoms of moderate (or worse) severity: vomiting, regurgitation (acid taste or feeling material movement upward, abdominal, chest pain/heartburn (burning or pain behind the sternum), or difficulty swallowing
• been on a therapeutic dose of PPIs (with or without histamine H2 receptor antagonists)for at least four weeks without resolution of symptoms, or by negative pH probe (with or without having failed a course of PPIs)

Exclusion Criteria:

• another disorder that causes esophageal eosinophilia (e.g.,HES,Churg Strauss vasculitis, EG, or a parasitic infection)
• history of abnormal gastric or duodenal biopsy or documented GI disorders (e.g.,Celiac Disease, Crohn's disease or Helicobacter pylori infection)
• history of the following GI surgeries:fundoplication, gastric surgery or surgery for intestinal atresia -use of systemic immunosuppressive or immunomodulating agents (anti- immunoglobulin E [IgE] mAb, methotrexate, cyclosporin, interferon α, or anti tumor necrosis factor [TNF] mAb) within six months prior to study entry.
• received attenuated live attenuated vaccines (e.g., measles, mumps, rubella [MMR], Bacille Calmette Guerin [BCG],varicella, Flumist or polio) within three months prior to study entry.
• use of swallowed inhaled corticosteroids for the treatment of EE within one month prior to study entry. Note: Inhaled and nasal corticosteroids for the treatment of asthma and allergies, respectively, are permitted provided that the dose remains the same during the study
• a stricture on endoscopy that prevents passage of the endoscope
• participation in any investigational drug or device study within 30 days prior to study entry.
• female subjects who are pregnant or nursing.
• concurrent infection or disease that may preclude assessment of eosinophilic esophagitis.
• concurrent immunodeficiency (human immunodeficiency [HIV], or acquired immunodeficiency syndrome [AIDS] or congenital immunodeficiency).