FDA approves Pfizer's Bosulif pill for patients with rare leukemia

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.

BOSULIF (bosutinib) Indication and Important Safety Information

BOSULIF is indicated for the treatment of adult patients with chronic, accelerated, or blast phase Ph+ CML with resistance, or intolerance to prior therapy.

Contraindication: Hypersensitivity to BOSULIF. Anaphylactic shock occurred in less than 0.2 percent of treated patients.

Gastrointestinal Toxicity: Diarrhea, nausea, vomiting and abdominal pain have been observed. Median time to onset for diarrhea was two days, median duration was one day and median number of episodes per patient was three. Monitor and manage patients using standards of care, including antidiarrheals, antiemetics, and/or fluid replacement. Withhold, dose reduce, or discontinue BOSULIF as necessary.

Myelosuppression: Thrombocytopenia, anemia and neutropenia have been observed. A complete blood count should be performed weekly for the first month and then monthly or as clinically indicated. Withhold, dose reduce, or discontinue BOSULIF as necessary.

Hepatic Toxicity: Twenty percent of patients experienced an increase in either ALT or AST. Liver enzyme elevation usually occurs early in treatment. Perform monthly hepatic enzyme tests for the first three months and as clinically indicated. In patients with transaminase elevations, monitor liver enzymes more frequently. Drug induced liver injury has occurred. Withhold, dose reduce, or discontinue BOSULIF as necessary.