Study Rationale:There is recent evidence that HIV protease inhibitors (HIV-PI) can improve pulmonary hemodynamics in experimental models of pulmonary arterial hypertension (PAH). There is also experimental evidence that both TLR4 and high mobility group box 1 (HMGB1) participate in the pathogenesis of experimental pulmonary hypertension. A recent high throughput screen for inhibitors of HMGB1 induced macrophage activation yielded HIV-protease inhibitors (PIs) as potent inhibitors of HMGB1 induced cytokine production. Based on the experimental evidence we propose a trial to determine whether HIV-PIs will alter the pathobiology of PAH.