A Study to Assess the Efficacy and Safety of Efgartigimod IV in Adult Participants With Primary Immune Thrombocytopenia

To join this study, you need to be at least 18 years old. You must also have had primary ITP for more than a year and have a low platelet count. In the past, you should have tried at least one common ITP treatment (like steroids, IVIg, or other specific medicines) and it didn't work well enough.

There are also some reasons why you might not be able to join. For instance, if you have other serious health problems or a different type of ITP (not primary ITP), or if you have certain related conditions like another serious autoimmune disease or a current severe bleeding problem, you wouldn't be able to take part.

If you decide to take part, you'll first have a screening period of up to two weeks to make sure the study is right for you. If you qualify, you'll be randomly assigned to one of two groups: either you'll receive efgartigimod, or you'll receive a placebo (a dummy medicine). You won't know which one you're getting, and neither will your study doctor, during this 'double-blind' period, which lasts up to 24 weeks.

After this initial phase, everyone will then receive efgartigimod for about 52 weeks. If you and your doctor agree, you might continue receiving efgartigimod for another 52 weeks. Throughout the study, you'll have regular visits to the clinic for check-ups, blood tests, and to receive your study medication, which will be given as an IV (into a vein). After all the treatment periods, there will be a follow-up period of about eight weeks where you won't be taking the study drug. The total time you'd be involved in the study could be up to 138 weeks (roughly 2.5 years).