Proof of Concept Study of IMMUNOadsorption Therapy in Patients With Idiopathic Pulmonary Arterial Hypertension

Inclusion Criteria: * Able to understand and willing to sign the Informed Consent Form * age \> 18 and \< 80 years at time of informed consent * Idiopathic pulmonary arterial hypertension diagnosed by right heart catheter * WHO functional classification III * Application of conventional IPAH therapy, which has been stable for the prior 8 weeks * Able to perform a 6-minute-walk test (MWT) * Negative pregnancy test (β-HCG) at the start of the trial and appropriate contraception throughout the trial for women with child-bearing potential. Exclusion Criteria: * Pregnancy and/or lactation * PAH of any cause other than permitted in the inclusion criteria, e.g. concomitantly to portal hypertension, complex congenital heart disease, reversed shunt, HIV infection, suspected pulmonary veno-occlusive disease * Contraindication for right heart catheterization * Any change in disease-targeted therapy within 8 weeks prior to inclusion * Walking impairment due to causes other than IPAH that would preclude performance of a 6MWT * Any patient who has received any investigational medication within 8 weeks prior to the start of this trial or who is scheduled to receive another investigational drug during the course of the trial between visits V1 and V9 * Known intolerance to immunoadsorption in general or to one of the excipients (e.g. sheep antibodies or agarose) or other supporting agents * Hemoglobin concentration of \< 75% below the lower limit of normal * Systolic blood pressure \< 85 mmHg * Lack of compliance or other similar reason that, in the judgment of the Investigator, precludes satisfactory participation in the trial * Concurrent severe or uncontrolled medical disease (i.e. uncontrolled diabetes, congestive heart failure, myocardial infarction within 6 months prior to the study, unstable and uncontrolled hypertension, chronic renal disease, or active uncontrolled generalized viral, bacterial and/ or mycotic infection) which by assessment of the treating Investigator could compromise patients safety or participation in the study * Drug or alcohol abuse within the last 5 years * Hypercoagulability * Known severe immunodeficiency (e.g. AIDS) * Severe lung disease: FEV1/FVC \< 50%, total capacity \< 60% of normal value * Indications that prohibit transient anticoagulation using Heparin and/or ACD-A-solutions