Study Design:This is a single center open label phase 0 study to evaluate the effect of SQV +RIT in patients with IPAH. Subjects with IPAH(N=20) will be enrolled into a study, which will be divided into 3 cohorts and entail the administration of HIV protease inhibitors in three doses. The first cohort (n=3) will receive a starting dose of SQV 0.3 mg/kg twice daily in combination with RIT 0.03 mg/kg twice daily. If the first dose is well-tolerated, the second cohort (n= 3 ) with IPAH will be given doses of SQV 3 mg/kg and RIT 0.3 mg/kg twice daily. If the second dose is well-tolerated, the last cohort (n= 14 ) with IPAH will be given doses of SQV 15 mg/kg and RIT 1.5 mg/kg twice daily.