BETHESDA, MD 05 September 2012—Pfizer Inc. on September 4 announced the approval of bosutinib, a tyrosine kinase inhibitor, as a second-line agent for the treatment of chronic myelogenous leukemia (CML) in adults.

Labeling (PDF) for the drug states that it is indicated for use in patients with chronic, accelerated, or blast phase Philadelphia chromosome-positive CML who did not tolerate other therapy or whose illness did not respond to past treatment.

Bosutinib oral tablets will be marketed under the brand name Bosulif. A Pfizer spokeswoman said the company expects the product to be available within the next few weeks.

According to FDA, bosutinib was approved on the basis of results of efficacy data from 503 patients with CML who had previously been treated with imatinib, a tyrosine kinase inhibitor. Some patients had also been treated with a second tyrosine kinase inhibitor—either dasatinib or nilotinib.

About a third of clinical trial participants with chronic-phase CML who had previously been treated with imitinib alone had achieved a major cytogenetic response (MCR) after 24 weeks of bosutinib therapy, according the labeling. Among patients who had been treated previously with two tyrosine kinase inhibitors, 27% achieved an MCR at week 24.

The labeling states that 55% of clinical trial participants with active-phase CML had a complete hematologic response or had returned to chronic-phase CML by week 48 of bosutinib therapy. In patients with blast-phase CML, 28% achieved this level of response by week 48 of bosutinib therapy.

The recommended dosage of bosutinib is 500 mg taken once daily with food. Treatment should continue until the disease progresses or the therapy becomes intolerable.

The most common adverse events associated with bosutinib therapy in clinical trials were diarrhea, nausea, vomiting, abdominal pain, thrombocytopenia, anemia, rash, fever, and fatigue.

Gastrointestinal toxicity during bosutinib treatment should be managed using antidiarrheals, antiemetics, fluid replacement, and other standard remedies, according to the labeling.

Patients should undergo weekly blood counts for the first month of bosutinib therapy and then monthly or as needed thereafter. If myelosuppression occurs, it may be necessary to interrupt or discontinue bosutinib therapy or reduce the dosage as is described in a table in the drug's labeling.

Concomitant use of bosutinib and strong or moderate P-glycoprotein inhibitors and strong or moderate inhibitors or inducers of cytochrome P-450 isoenzymes 3A should be avoided, according to the labeling.

Bosutinib will be available in 100-mg tablets packaged in bottles of 120 each and 500-mg tablets in bottles of 30 each. The bottles should be stored at controlled room temperature.