United Therapeutics Corp on Thursday signed a deal potentially worth up to $1.2 billion for the rights to develop and sell Arena Pharmaceuticals Inc's pulmonary arterial hypertension treatment, ralinepag.

The two companies said in a statement the deal for Arena's late-stage experimental treatment also includes milestone payments of up to $400 million based on certain regulatory events. 

Arena will receive low double-digit tiered royalties on annual net sales of ralinepag, the companies said.

(Reporting by Aakash Jagadeesh Babu in Bengaluru) ((Aakash.B@thomsonreuters.com; within the U.S. +16462238780, outside the U.S. +91 80 67491576; Reuters Messaging: Aakash.B.thomsonreuters.com@reuters.net))