“The drug powering this breakthrough is actually very old. Cyclophosphamide was first developed in the 1950s for chemotherapy. Fifty years later, researchers at Johns Hopkins began studying whether it could be repurposed to prevent a common and sometimes deadly complication of bone-marrow transplants called graft-versus-host disease, where the donor’s white blood cells—which form the recipient’s new immune system—attack the rest of the body as foreign. The bigger the mismatch between donor and recipient, the more likely this was to happen. Cyclophosphamide worked stunningly well against graft-versus-host disease: The drug cut rates of acute and severe complications by upwards of 80 percent.

Cyclophosphamide has now enabled more patients than ever to get bone-marrow transplants —more than 7,000 last year, according to NMDP. (Bone-marrow transplant is still used as an umbrella term, though many of these procedures now use cells collected from the blood rather than bone marrow, which can be done without surgery. Both versions are also known, more accurately, as hematopoietic or blood stem-cell transplants.) The field has essentially surmounted the problem of matching donors, a major barrier to transplants, Ephraim Fuchs, an oncologist at Johns Hopkins University, told me. Fuchs couldn’t remember the last time a patient failed to get a blood stem-cell transplant because they couldn’t find a donor.”

From The Atlantic.