This trial will have 3 parts plus screening and follow-up parts:~Parts A and B: Participants will either be included in part A or B. Each is a 24-week double-blind (this means none of the participants, doctors, or other trial staff will know what treatment each participant took) part where participants will receive either dupilumab or a placebo (a placebo looks like a trial drug but does not have any medicine in it).~Part C: 28-week extension part that will include participants from parts A and B and all participants will receive dupilumab
The study is researching an experimental drug called dupilumab. The study is focused on participants with active eosinophilic gastritis (EoG) with or without eosinophilic duodenitis (EoD). Participants with EoD only are not eligible for enrollment. EoG and EoD are uncommon, persistent, allergic/immune diseases in which eosinophils (a type of white blood cell) gather in large numbers in the stomach and small intestine and cause inflammation and damage.~The aim of the study is to evaluate the effect of dupilumab on relieving EoG (with or without EoD) symptoms and reducing inflammation in the stomach and, if applicable, small intestine in adults and adolescents aged 12 years and older, compared to placebo.~The study is looking at several other research questions, including:~What side effects may happen from taking the study drug~How much study drug is in your blood at different times~Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects)~Exploratory research to better understand the study drug and EoG with or without EoD and related diseases.