A radioimmunotherapeutic drug for conditioning relapsed and refractory acute myeloid leukemia (AML) patients for a hematopoietic stem cell transplant has been granted orphan drug designation by the Food and Drug Administration.

Iomab-B is a radioimmunoconjugate consisting of the murine monoclonal antibody BC8 and an iodine-131 radioisotope. The Fred Hutchinson Cancer Research Center developed BC8 to target CD45, a panleukocytic antigen widely expressed on white blood cells. “When labeled with radioactive isotopes, BC8 carries radioactivity directly to the site of cancerous growth and bone marrow while avoiding effects of radiation on most healthy tissues,” says a statement from Actinium Pharmaceuticals, which would market the drug.

Iomab-B will be tested in a multicenter trial that will include 150 patients over age 55 with refractory and relapsed AML. “There has not been a new drug approved for relapsed and refractory AML patients over the age of 55 in decades and with Iomab-B being the only therapy of its kind, we are pleased to have achieved this important milestone,” Sandesh Seth, executive chairman of Actinium, said in the statement.