Rituximab for Treatment of Systemic Sclerosis-Associated Pulmonary Arterial Hypertension (SSc-PAH)

This prospective, double-blind, placebo-controlled, multi-center, randomized trial will evaluate the effect of rituximab on disease progression in subjects with SSc-PAH receiving concurrent stable-dose standard medical therapy with a prostanoid, endothelin receptor antagonist, and/or phosphodiesterase 5 (PDE-5) inhibitor. The study will focus on assessment of clinical response and safety measures longitudinally. In addition, the effects of treatment with rituximab on the underlying immune mechanisms associated with B-cell dysregulation and pathogenic autoantibody response in this disease will be investigated. 1000 mg of rituximab or placebo will be administered as two IV infusions given two weeks apart. Clinical assessments and sample collection will occur at monthly visits through Week 48. If a participant has not recovered B cells by Week 48, B cell studies will be conducted quarterly until reconstitution is documented or for 2 years after initial treatment. This trial will include a sub-study, entitled "Right Ventricular Response to Rituximab in Systemic Sclerosis-Associated Pulmonary Arterial Hypertension - A Magnetic Resonance Imaging Sub-study" (RESTORE Sub-study). The objective of the RESTORE sub-study is to evaluate the therapeutic effect of rituximab on the right ventricle of patients with SSc-PAH. Changes in right ventricular end diastolic volume index (RVEDVI) and stroke volume (SV) determined by cardiac MRI will be used as surrogates of right ventricle function and prognosis. Enrollment for the RESTORE sub-study will parallel that of main trial. Twenty patients from each treatment arm, distributed among all participating sites, will be recruited for this sub-study. Each patient will be studied at baseline (i.e. prior to initiation of study drug) and after 24 weeks or at time of discontinuation. In addition to the data collection and testing specified in the main trial, participants in RESTORE will undergo comprehensive cardiac MRI evaluation. All main trial study inclusion and exclusion criteria apply, as well as additional exclusion criteria that pertain only to the RESTORE sub-study: 1) known hypersensitivity to Gadolinium; 2) inability to tolerate or cooperate with MRI; 3) morbid obesity; and 4) presence of metallic objects or pacemakers.