This clinical trial is focused on studying a condition known as Primary Immune Thrombocytopenia (ITP). ITP is a disorder that can lead to easy or excessive bruising and bleeding, resulting from unusually low levels of platelets, which are cells that help blood clot. The study will evaluate a treatment called efgartigimod, which is given through an intravenous (IV) infusion. Efgartigimod is designed to help manage the symptoms of ITP by potentially increasing platelet counts in the blood.

The purpose of this study is to assess how effective and safe efgartigimod is compared to a placebo. Participants in the study will be randomly assigned to receive either efgartigimod or a placebo, which is a substance with no active medication. The study will begin with a phase where neither the participants nor the researchers know who is receiving the actual treatment or the placebo. This is followed by an open-label phase where all participants will receive efgartigimod. The study will monitor participants over a period to see how well the treatment controls the disease by measuring platelet counts and observing any side effects.

Throughout the study, participants will have regular visits to check their platelet levels and overall health. The goal is to determine if efgartigimod can help maintain platelet counts at a safe level, reducing the risk of bleeding and improving the quality of life for those with ITP. The study will also look at how long it takes for the treatment to start working and how long the effects last. This research aims to provide valuable information on a new potential treatment option for people living with Primary Immune Thrombocytopenia.