Celgene announced today that it is teaming up with Acceleron on a new, early-stage approach to treating anemia, paying $25 million upfront and promising $217 million in milestones to partner on experimental drug ACE-536.

The deal builds on a pact the two biotechs already have in place for sotatercept (ACE-011), which dates back to 2008. And Celgene is taking an option on any other anemia drugs that Acceleron comes up with. In the pact Acceleron will be responsible for the Phase I and first Phase II study of ACE-536, with Celgene stepping in to run the second Phase II and Phase III. Acceleron will keep the U.S. co-promotion rights to ACE-536 in the deal, with a double-digit royalty stream due on worldwide sales.

“Celgene and Acceleron have a strong partnership that continues to advance innovative therapies in areas of great unmet medical need,” said Tom Daniel, the president of research for Celgene. “The work we will embark on with ACE-536 is a natural extension of our strong presence in hematology. We look forward to exploring the potential of ACE-536 for patients with anemia worldwide.”

ACE-536 is a protein therapeutic that inhibits members of the TGF-beta “superfamily” involved in erythropoiesis.