Sotatercept (ACE-011) With Lenalidomide or Pomalidomide and Dexamethasone in Relapsed/Refractory Multiple Myeloma

It is possible that the combination of lenalidomide, dexamethasone and ACE 011 may reduce or prevent the growth of cancer cells along with improving anemia and bone lesions that sometimes occur in people with multiple myeloma. This current study is the first study combining ACE 011 with lenalidomide. In this research study, the investigators are looking for the highest dose of ACE 011 that can be given with lenalidomide and dexamethasone. The investigators will also begin to collect information about the effect of the combination of ACE 011, lenalidomide and dexamethasone on multiple myeloma.