United Therapeutics Corporation announced the closing of the transactions contemplated by its license agreement with Arena Pharmaceuticals, Inc. Under the agreement, United Therapeutics acquired exclusive, worldwide rights to develop and manufacture the Phase 3 investigational drug candidate ralinepag, a next-generation, oral, selective and potent prostacyclin receptor agonist in development for the treatment of pulmonary arterial hypertension (PAH). Upon closing, United Therapeutics paid Arena $800 million. Arena is also entitled to potential milestone payments of up to $400 million based on the achievement of certain regulatory events as well as low double-digit tiered royalties on annual net sales of ralinepag products.