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The U.S. Food and Drug Administration has expanded the approved use of Imbruvica (ibrutinib) to treat patients with chronic lymphocytic leukemia who have received at least one previous therapy.

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The drug blocks Bruton's tyrosine kinase (BTK), which has been shown to inhibit malignant B-cell survival. The drug was also approved in November to treat patients with mantle cell lymphoma who had received at least one prior therapy (OT 12/10/13 issue). Both approvals were granted under the agency's accelerated approval process.


"The FDA completed its review of Imbruvica's new indication under the agency's accelerated approval process, which played a vital role in rapidly making this new therapy available to those who need it most," Richard Pazdur, MD, Director of the FDA's Office of Hematology and Oncology Products, said in a news release.


The accelerated approval program allows the FDA to approve a drug to treat a serious disease based on clinical data showing that the drug has an effect on a surrogate endpoint that is reasonably likely to predict a clinical benefit to patients. The program provides earlier patient access to promising new drugs while the company conducts confirmatory clinical trials.


According to estimates from the National Cancer Institute, 15,680 Americans were diagnosed with CLL in 2013, 4,580 Americans died from the disease, and it is the most common type of leukemia.


The approval of Imbruvica for CLL is based on a trial of 48 patients previously treated for the disease. On average, the patients were diagnosed with CLL 6.7 years prior to the study, and had received four prior therapies. The patients received a 420 milligram orally administered dose until the treatment reached an unacceptable toxicity or the disease progressed.


Results showed that nearly 58 percent of the participants had their cancer shrink, and the duration of response (at the time of the study) ranged from 5.6 to 24.2 months. An improvement in survival or disease-related symptoms has not been established.


The most common side effects observed in the study included thrombocytopenia, diarrhea, bruising, neutropenia, anemia, upper respiratory tract infection, fatigue, musculoskeletal pain, rash, pyrexia, constipation, peripheral edema, arthralgia, nausea, stomatitis, sinusitis, and dizziness.


Imbruvica is manufactured by Pharmacyclics, Inc.