The US Food and Drug Administration approved Bosulif as treatment for a rare disease, found in older adults, which attacks the blood and bone marrow and is known as chronic myelogenous leukemia (CML).

Approximately 5,430 people will be diagnosed with CML in 2012. The majority of people with CML have the Philadelphia chromosome, a genetic mutation where the bone marrow produces an enzyme called tyrosine kinase. This enzyme sparks excess creation of unhealthy and irregular white blood cells named granulocytes, which fight infection.

Bosulif is aimed towards patients with chronic, accelerated, and blast phase (extremely high levels of granulocytes) Philadelphia chromosome positive CML and who are also not responding to other therapies. Bosulif works by obstructing the tyrosine kinase signal that helps produce the abnormal 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.

The FDA has approved other drugs such as imanitib, dasatinib, and nilotinib to treat many forms of CML. Bosulif was evaluated in a single clinical trial that included 546 adult patients who have chronic, accelerated, or blast phase CML. All patients in the study had CML that continued to progress after being treated with imanitib and dasatinib and/or nilotinib, or could not tolerate side effects of these treatments. Participants were all given Bosulif.

The effectiveness of Bosulif was determined by the amount of patients who experienced a major cytogenetic response (MCyR) within the first 24 weeks of treatment for chronic level CML. Findings showed patients who previously used imanitib reached MCyR after the initial 24 weeks. 52.8 percent of the patients who achieved MCyR at any time had a response that lasted 18 months or longer. Of the patients who were previously treated using imatinib, followed by dasatinib and/or nilotinib, 27 percent reached MCyR within 24 weeks. Among those who achieved MCyR at anytime, 51.4 percent had a response that lasted nine months or longer.

Of those patients with accelerated CML previously treated with at least imatinib, 33 percent had their blood counts return to normal, while 55 percent reached normal blood counts with no evidence of leukemia within the beginning 48 weeks of treatment. In addition, 15 percent of participants with blast phase CML achieved normal blood counts, while 28 percent achieved normal blood counts with no evidence of leukemia.

Common side effects seen associated with Bosulif are diarrhea, nausea, low levels of platelets in the blood, abdominal pain, anemia, vomiting, fever, and fatigue.

Written by Kelly Fitzgerald