A Study to Assess the Efficacy and Safety of Efgartigimod in Adult Patients With Primary Immune Thrombocytopenia (ITP).

Inclusion criteria:

• Ability to understand the requirements of the trial, to provide written informedconsent (including consent for the use and disclosure of research-related healthinformation), and to comply with the trial protocol procedures (including requiredtrial visits).

• Male or female patient aged ≥18 years.

• Confirmed ITP diagnosis, at least 3 months before randomization and according to theAmerican Society of Hematology Criteria, and no known other etiology forthrombocytopenia.

• Diagnosis supported by a response to a prior ITP therapy (other than thrombopoietinreceptor agonists [TPO-RAs]), in the opinion of the investigator.

• Mean platelet count of <30×10E9/L from 2 counts: 1 platelet count collected duringthe screening period and the predose platelet count on the day of randomization.

• At the start of the trial, the patient is either on concurrent ITP treatment(s) andhas received at least 1 prior therapy for ITP in the past, or the patient is not ontreatment for ITP but has received at least 2 prior treatments for ITP. Patientsreceiving permitted concurrent ITP treatment(s) at baseline, must have been stablein dose and frequency for at least 4 weeks prior to randomization.

• Women of childbearing potential must have a negative serum pregnancy test at thescreening visit and a negative urine pregnancy test at baseline before trialmedication (infusion) can be administered.

• Women of childbearing potential should use a highly effective or acceptable methodof contraception during the trial and for 90 days after the last administration ofthe IMP.

Exclusion criteria:

• ITP/thrombocytopenia associated with another condition, eg, lymphoma, chroniclymphocytic leukemia, viral infection, hepatitis, induced or alloimmunethrombocytopenia, or thrombocytopenia associated with myeloid dysplasia.

• Use of certain medications before the start of the studies (more details in theprotocol)

• Patients who have a history of malignancy, including malignant thymoma, ormyeloproliferative or lymphoproliferative disorders, unless deemed cured by adequatetreatment with no evidence of recurrence for ≥3 years before screening. Patientswith completely excised non-melanoma skin cancer (such as basal cell carcinoma orsquamous cell carcinoma) or cervical carcinoma in situ would be permitted at anytime.

• Uncontrolled hypertension, defined as a repeated elevated blood pressure exceeding 160 mmHg (systolic) and/or 100 mmHg (diastolic) despite appropriate treatments.

• History of any major thrombotic or embolic event within 12 months prior torandomization.

• History of coagulopathy or hereditary thrombocytopenia or a family history ofthrombocytopenia.

• History of a recent or planned major surgery (that involves major organs eg, brain,heart, lung, liver, bladder, or gastrointestinal tract) within 4 weeks ofrandomization.

• Positive serum test at screening for an active viral infection with any of thefollowing conditions: Hepatitis B virus (HBV), Hepatitis C virus (HCV), Humanimmunodeficiency virus (HIV)

• Clinical evidence of significant unstable or uncontrolled acute or chronic diseasesother than ITPdespite appropriate treatments which could put the patient at unduerisk.

• Patients with known medical history of hypersensitivity to any of the ingredients ofthe IMP.

• Patients who previously participated in a clinical trial with efgartigimod and havereceived at least 1 administration of the IMP.

• Pregnant or lactating females. More details in the protocol