This is a single-center, prospective, controlled study with one eltrombopag treatment group and 2 control groups, one on standard steroid treatment, and another one untreated.

The aim of the study is to determine the effect of Thrombopoietin Receptor (MPL) agonists on shear-induced platelet activation.

STUDY DESIGN:

Single-center (Medical University Vienna), prospective, controlled study. Patients will be recruited at the Division of Haematology and Haemostaseology at the Medical University in Vienna, one eltrombopag treatment group and 2 control groups, one on standard steroid treatment, another one untreated.

AIM OF THE STUDY:

To determine the effect of MPL agonists on shear-induced platelet activation. Data obtained from patients treated with eltrombopag shall be compared to those from untreated patients and patients on steroids. These investigations will extend previous studies that investigated platelet function without in vitro activation in patients receiving eltrombopag.

PATIENTS:

Trial Population:

Total number of patients n=34: 12 on eltrombopag, 12 on corticosteroids and 10 without treatment will be included in this trial.

Treatment with eltrombopag or corticosteroids. Eltrombopag starting dose: 25 mg/day, increased as needed (to 50 mg or maximum 75 mg once daily) every 2 weeks to reach a platelet count between 50,000-100000/µL and tapering the dosis if platelet count >= 100,000/µL. Afterwards, if platelet count stable (tolerance +/- 20%), platelet control every 4 weeks, otherwise weekly.

Prednisolone starting dose: 1 mg/kg/day to reach a platelet count between 50,000-100,000 /µL tapering of the dosage if platelet count >= 100,000/µL.

Laboratory Investigations:

In the eltrombopag group and in the newly treated prednisolone group platelet counts and platelet function tests will be performed at planned visits.

In patients who are on continuous corticosteroids (part of control group I) and untreated patients (control group II), which have a platelet count between 50,000 and 100,000/µL platelet counts, reticulated platelets, platelet function tests and platelet antibodies will be studied at entry and after 4 weeks (+ 5 days).

Inclusion Criteria (for all groups):

• Male and female patients with an established chronic autoimmune thrombocytopenia (cAITP)
• Age ≥ 18 and ≤ 90 years
• Females, if not pregnant, not nursing and consenting to perform safe anti-contraception
• Written consent before any study related procedure

Inclusion Criteria (for patients treated with eltrombopag):

• Platelet count < 50,000 /µL at screening
• At least one prior alternative cITP therapy

Inclusion Criteria (for patients treated with corticosteroids - Control group 1):

• Platelet count < 50,000 /µL in history
• At least 50% of the patients should have < 50,000 /µL at inclusion and should be followed for 3 months

Inclusion Criteria (for patients untreated - Control group 2):

• Platelet count < 50,000 /µL in history
• At screening platelet count between 50,000 and 100,000 /µL

Exclusion Criteria (for all patients):

• History of venous or arterial thromboembolism or stroke
• Known coronary heart disease or cardiac arrythmias
• Known HIV or Hepatitis C infection
• Impaired liver function defined as elevated ALT > 1.5 UNL, bilirubin more than ULN, albumin less than normal value
• Prothrombin time less than normal value
• Elevated creatinine level (> 1.3 ULN)
• Unable/unwilling to follow protocol
• Previous or active malignancy
• Patients who have been included in any other study with eltrombopag any time before
• Patients treated with another investigational product within the last 3 months