In search of safer marrow transplants

From Atlanta, at a meeting of the American Society of Hematology

A bone marrow transplant preceded by destruction of one’s own bone marrow with radiation or chemotherapy is a bleak prospect for a leukemia patient. Although the procedure can be lifesaving, it carries toxicity risks and weakens the patient. That’s why people with autoimmune diseases rarely get a marrow transplant—even though it’s potentially curative.

Scientists have now devised a synthetic antibody called ACK2 that targets a protein displayed on the surface of marrow cells and destroys them without radiation or chemo. These marrow cells, also called hematopoietic stem cells, can develop into various immune cells. In autoimmune diseases, some of them run amok and orchestrate tissue damage.

When researchers gave ACK2 to mice, it wiped out roughly 98 percent of the animals’ marrow cells with few side effects. After the ACK2 had cleared from the animals’ blood, the researchers gave them healthy donor marrow cells, which developed into a nondefective immune system.

Immunologist Agnieszka Czechowicz of Stanford University School of Medicine and her colleagues found that treating mice with ACK2 left prominent niches in bone marrow where replacement cells could grow. She doesn’t envision ACK2 as a treatment for leukemia patients since it doesn’t specifically target cancer cells. But it might benefit people with noncancerous immune disorders such as type 1 diabetes, multiple sclerosis, or sickle cell disease, Czechowicz says.