A vasodilator that blocks the activity of a protein called Rho kinase (ROCK) may be effective against difficult-to-treat types of leukemia.

Fasudil, which is approved in Japan and is undergoing clinical trials in the United States, has been used to dilate blood vessels in people who have suffered a stroke. The drug’s properties as a ROCK inhibitor caught the attention of researchers Reuben Kapur, PhD, and colleagues, who were studying the effects of mutations in several other proteins associated with difficult-to-treat leukemias.

The research focused on cells bearing oncogenic forms of two receptor proteins—KIT and FLT3—as well as BCR-ABL, a protein produced when parts of two chromosomes switch places. This abnormality is associated with chronic myelogenous leukemia. As the investigators reported in Cancer Cell, they found that blood-producing bone marrow cells with the mutations all had hyperactivated levels of ROCK. Using fasudil to slow the growth of those cells significantly prolonged the survival of laboratory mice with acute myeloid leukemia and myeloproliferative disease, which includes chronic myelogenous leukemia.

While acknowledging in a statement describing the study that the possible effectiveness of fasudil as an anti-leukemia agent has not been tested, “This drug could be fairly potent across the board with a lot of leukemias,” noted Kapur, the Frieda and Albrecht Kipp Professor of Pediatrics at the Indiana University School of Medicine in Indianapolis.

Kapur explained that targeting ROCK could be a more tolerable treatment than extensive chemotherapy for many older patients with leukemia.