FDA approves Bosulif to treat chronic myelogenous leukemia

FDA approves new orphan drug for chronic myelogenous leukemia

The U.S. Food and Drug Administration today approved Bosulif (bosutinib) to treat chronic myelogenous leukemia (CML), a blood and bone marrow disease that usually affects older adults.

An estimated 5,430 men and women will be diagnosed with CML in 2012. Most people with CML have a genetic mutation, called the Philadelphia chromosome, which causes the bone marrow to make an enzyme called tyrosine kinase. This enzyme triggers the development of too many abnormal and unhealthy white blood cells called granulocytes. Granulocytes fight infection.

Bosulif is intended for patients with chronic, accelerated or blast phase Philadelphia chromosome positive CML who are resistant to or who cannot tolerate other therapies, including imatinib. Bosulif works by blocking the signal of the tyrosine kinase that promotes the development of abnormal and unhealthy granulocytes.

"With the approval of tyrosine kinase inhibitors, we are seeing improvements in the treatment of CML based on a better understanding of the molecular basis of the disease," said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research. "These improvements have been observed in chronic and accelerated phases of CML."

Other drugs recently approved by FDA to treat various forms of CML include imatinib (2001), dasatinib (2006) and nilotinib (2007).

The safety and effectiveness of Bosulif was evaluated in a single clinical trial that enrolled 546 adult patients who had chronic, accelerated or blast phase CML. All patients had disease that progressed after treatment with imatinib or imatinib followed by dasatinib and/or nilotinib, or who could not tolerate the side effects of prior therapy. All patients in the trial were treated with Bosulif.

In patients with chronic phase CML, efficacy was determined by the number of patients who experienced a major cytogenetic response (MCyR) within the first 24 weeks of treatment. Results showed 34 percent of patients who had been previously treated with imatinib achieved MCyR after 24 weeks. Of the patients who achieved MCyR at any time, 52.8 percent had their response last at least 18 months. Among patients previously treated with imatinib followed by dasatinib and/or nilotinib, about 27 percent achieved MCyR within the first 24 weeks of treatment. Of those who achieved MCyR at any time, 51.4 percent had their MCyR last at least nine months.

In patients with accelerated CML previously treated with at least imatinib, 33 percent had their blood counts that returned to normal range (complete hematologic response) and 55 percent achieved normal blood counts with no evidence of leukemia (overall hematologic response) within the first 48 weeks of treatment. Meanwhile, 15 percent and 28 percent of patients with blast phase CML achieved complete hematologic response and overall hematologic response, respectively.

The most common side effects observed in those receiving Bosulif were diarrhea, nausea, a low level of platelets in the blood (thrombocytopenia), vomiting, abdominal pain, rash, low red blood cell count (anemia), fever and fatigue.

Bosulif is marketed by New York City-based Pfizer.