Drug: Q4W GMA301 IV injections (300 mg) Drug: Q4W GMA301 IV injections (600 mg) Drug: Q4W GMA301 IV injections (1000 mg) Drug: Q4W GMA301 IV injections (1800 mg) Other: Q4W placebo IV injections
A Randomized, Placebo-Controlled, Double-blind, Dose Escalation Study to Assess Safety, Efficacy and Pharmacokinetics of GMA301 Injection in Subjects with Pulmonary Arterial Hypertension