FDA Approves Pfizer Drug For Rare Blood Cancer

WASHINGTON (AP) - The Food and Drug Administration on Tuesday approved a new Pfizer drug to treat a rare form of blood and bone marrow cancer that causes a buildup of unhealthy white blood cells.

Pfizer's Bosulif is a daily pill to treat chronic myeloid leukemia patients who carry a specific genetic variation. The disease is one of four types of the blood cancer, and accounts for about 15 percent of leukemia cases.

The disease, which usually affects seniors, causes the bone marrow to produce unhealthy white blood cells that do not grow and die like normal cells. Instead, the cells buildup in the bone marrow and crowd out healthy cells that are needed to fight off infections.

Bosulif works by blocking an enzyme called tyrosine kinase that triggers the production of unhealthy cells. The FDA approved the pill for patients with a genetic mutation, known as the Philadelphia chromosome, who do not respond to other cancer therapies, including Novartis' Gleevec.

An estimated 5,430 patients will be diagnosed with chronic myelogenous leukemia this year, according to the FDA. The agency cleared the drug under its orphan drug program, which provides financial incentives for the development of drugs for rare diseases.

The FDA approved Bosulif based on a Pfizer study showing 34 percent of patients treated with the drug responded within the first six months of treatment. In patients previously treated with Gleevec, 33 percent had blood counts that returned to a normal range within 48 weeks. Fifty five percent of patients achieved normal blood counts with no evidence of leukemia within that same timeframe.

The most common side effects seen in patients included diarrhea, nausea, abdominal pain, rash and fever.