An Open-Label Trial of Losartan Potassium in Participants With Eosinophilic Esophagitis (EoE)

Inclusion Criteria: * Written informed consent/assent * Confirmed, active EoE (at Screening or within 12 weeks prior to enrollment) * Does or does not have diagnosis of a connective tissue disorder (CTD) * Has been on a high dose of proton pump inhibitor (PPI) for at least 8 weeks prior to a diagnostic endoscopy of EoE without histologic resolution (i.e., ≥ 15 eosinophils/HPF). * Maintain the same diet, swallowed steroid and PPI therapies throughout the duration of the study * Female participants must be either: 1. Of non-childbearing potential (pre-menarchal or surgically sterile with documentation). OR 2. Have a negative urine pregnancy test at screening and at each monthly study visit. Exclusion Criteria: * Any past or planned cardiac surgery. * An aortic root Z-score ≥ 3.0 on a previous echocardiogram. * Intolerance to Losartan * A mean blood pressure measurement (both systolic and diastolic) at screening that is below the 2nd percentile for his/her age * Renal dysfunction * Another disorder that causes esophageal eosinophilia (e.g., hypereosinophilic syndrome, Churg Strauss vasculitis, eosinophilic granuloma, or a parasitic infection). * A diagnosis of hepatic insufficiency (e.g., liver failure, history of liver transplantation or persistent liver transaminase elevation). * A history of abnormal gastric or duodenal biopsy or documented gastrointestinal disorders (e.g., Celiac Disease, Crohn's disease or Helicobacter pylori infection), not including chronic gastritis, chronic duodenitis, mucosal eosinophilia or other eosinophilic gastrointestinal disorders (EGIDs). * Use of anti-immunoglobulin (Ig)E monoclonal antibody (mAb), anti-tumor necrosis factor (TNF) mAb, anti-IL-5 agents, or anti-IL-13 within 6 months prior to study entry * Use of methotrexate, cyclosporine, interferon α, or other systemic immunosuppressive or immunomodulating agents within 3 months prior to the screening visit. * A stricture during endoscopy procedure that prevents passage of the endoscope * Taking or is planning to take an angiotensin receptor blocker (ARB), angiotensin-converting enzyme inhibitor (ACEI), beta blocker (BB), or calcium-channel blocker therapy at the screening visit or at any time during the study or has been taking any of these medications for 3 months prior to the screening visit. * Taking or planning to take hydrochlorothiazide, digoxin, warfarin, cimetidine, phenobarbital, rifampin, or fluconazole. * Taking or planning to take potassium supplements or salt substitutes containing potassium. * A female participant who is pregnant or nursing or, if of childbearing potential, is not using a medically accepted, effective method of birth control (e.g., condom, oral/injectable/subcutaneous contraceptive, intrauterine device, or sexual abstinence). * Participated/participating in any investigative drug or device study within 30 days prior to study entry. * Participated/participating in any investigative biologics study within 3 months prior to study entry. * Unable to be confirmed, active EoE (at Screening or within 12 weeks prior to enrollment)