United Therapeutics Corporation (Nasdaq: UTHR) today announced the closing of the transactions contemplated by its license agreement with Arena Pharmaceuticals, Inc. (Nasdaq: ARNA). 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.