Satralizumab in the Treatment of Pulmonary Arterial Hypertension (SATISFY-JP Trial)

Inclusion Criteria: 1. Patients whose age at the time of consent acquisition is between 20 and 80 years old. 2. Patients who have been diagnosed with pulmonary arterial hypertension (PAH) and fall into one of the following among the first group of the clinical classification of pulmonary hypertension (Nice Classification, 2018) Idiopathic pulmonary arterial hypertension (IPAH) Hereditary pulmonary arterial hypertension (HPAH) Drug/toxin-induced pulmonary arterial hypertension Pulmonary arterial hypertension associated with connective tissue disease Pulmonary arterial hypertension associated with congenital heart disease (only after repair surgery) 3. Patients in the World Health Organization (WHO) Functional Classification (FC) I, II, or III. 4. Patients with immune responsive-phenotype 5. Patients with a 6-minute walking distance of 150 to 600 meters at screening. 6. Patients whose resting hemodynamic values within 30 days prior to enrollment meet all of the following Mean pulmonary artery pressure (mPAP) is 25 mmHg or higher PVR is higher than 4 Wood units 7. Patients who are using up to three PAH drugs and have not changed the dosage and administration for at least 90 days prior to enrollment 8. Patients who are receiving home oxygen therapy under the same conditions for at least 30 days prior to enrollment 9. Patients who have given written consent for the study Exclusion Criteria: 1. Patients with a history of severe allergy to any of the components of the study drug. 2. Patients who have received IL-6 inhibitors (tocilizumab, sarilumab, etc.) in the past or are currently receiving them at the time of screening. 3. Patients with infectious diseases such as pneumonia or tuberculosis during the screening period. 4. Patients with pulmonary artery wedge pressure (PAWP) greater than 15 mmHg on the last right heart catheterization performed during the screening period. 5. Patients who are using epoprostenol (intravenous) or treprostinil (intravenous or subcutaneous) and cannot discontinue. 6. Patients who are currently participating in other clinical trials or clinical studies. Or, patients who have participated in other clinical trials/trials prior to participation in this study and whose adverse events, if any, have occurred during the period of participation and have not been confirmed to have resolved or stabilized 7. Pregnant women or lactating patients. 8. Patients who are unable to consent to contraception from the time of obtaining consent until at least 3 months after the last dose of the study drug 9. Patients who have received a live vaccine within 6 weeks prior to enrollment 10. Patients who are positive for HIV-1 antibody, HIV-2 antibody, HTLV-1 antibody, HBs antigen, or HCV antibody. 11. Patients with active or recurrent bacterial, viral, fungal, or mycobacterial infections, or with other infectious diseases 12. Patients who have been hospitalized or developed an infection requiring intravenous administration of an infectious agent within 4 weeks prior to the baseline visit or an infection requiring oral administration of an infectious agent within 2 weeks prior to the baseline visit. 13. Patients who are receiving steroids at a dose higher than 10 mg/day of prednisone (PSL) equivalent. 14. Patients with a history of malignancy, including solid tumors, hematologic malignancies, and intraepithelial carcinomas, within the past 5 years. 15. Patients who are judged to lack the capacity to consent. 16. Other patients who are judged by the investigator to be unsuitable for the study.