Arena Pharmaceuticals, Inc. announced the initiation of a Phase 2 clinical study of ralinepag, a receptor agonist for non-prostanoid prostacyclin (IP) intended for the treatment of pulmonary arterial hypertension (PAH). The case-control study, randomized double-blind trial will last 22 weeks and will evaluate the hemodynamic effects, safety and tolerability of ralinepag on up to 60 patients with PAH. PAH is a progressive disease that can lead to heart failure and reduce life expectancy. Based on US data, it is estimated that the five-year survival from diagnosis of the disease is 57%. Ralinepag, orally available, in the phase 1 studies showed half-life of about 25 hours and was therefore suitable for one or two doses per day. The FDA has granted orphan drug status for the treatment of PAH.