The U.S. Food and Drug Administration has expanded the approved use of Imbruvica (ibrutinib) to treat patients with chronic lymphocytic leukemia (CLL) who carry a deletion in chromosome 17 (17p deletion), which is associated with poor responses to standard treatment for CLL. Imbruvica received a breakthrough therapy designation for this use.
The FDA is also approving new labeling to reflect that Imbruvica's clinical benefit in treating CLL has been verified. In February 2014, Imbruvica received accelerated approval to treat CLL based on its effect on overall response rate. New clinical trial results examining progression-free survival and overall survival have confirmed the drug's clinical benefit.
A type of non-Hodgkin lymphoma, CLL is a rare blood and bone marrow disease that usually gets worse slowly over time, causing a gradual increase in white blood cells called B lymphocytes, or B cells. The National Cancer Institute estimates that 15,720 Americans will be diagnosed and 4,600 will die from CLL in 2014. Imbruvica works by blocking the enzyme that allows cancer cells to grow and divide.
"We continue to see advances in the availability of therapies to treat chronic lymphocytic leukemia, especially for difficult-to-treat patient populations," said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research. "Imbruvica is the fourth drug approved to treat CLL that received a breakthrough therapy designation, reflecting the promise of the breakthrough therapy designation program and demonstrating the FDA's commitment to working cooperatively with companies to expedite the development, review and approval of these important new drugs."
The other three drugs approved to treat CLL that received breakthrough designations are Gazyva (obinutuzumab) in November 2013, Arzerra (ofatumumab) in April 2014 and Zydelig (idelalisib) in July 2014. Imbruvica's application for accelerated approval to treat CLL did not receive breakthrough therapy designation.
Today's approval actions for Imbruvica are based on a clinical study of 391 previously treated participants, 127 of whom had CLL with 17p deletion. Participants were randomly assigned to receive Imbruvica or Arzerra until disease progression or side effects became intolerable.
The trial was stopped early for efficacy after a pre-planned interim analysis showed Imbruvica-treated participants experienced a 78 percent reduction in risk of disease progression or death (progression-free survival). Results also showed a 57 percent reduction in risk of death (overall survival) in participants treated with Imbruvica. Of the 127 participants who had CLL with 17p deletion, those treated with Imbruvica experienced a 75 percent reduction in risk of disease progression or death.
The most common side effects associated with Imbruvica observed in the clinical study include low levels of platelets in the blood (thrombocytopenia), a decrease in infection-fighting white blood cells called neutrophils (neutropenia), diarrhea, low red blood cells (anemia), fatigue, pain in the muscles and bones (musculoskeletal pain), upper respiratory tract infection, rash, nausea and fever (pyrexia).
Imbruvica's new use is being approved more than two months ahead of the product's prescription drug user fee goal date of Oct. 7, 2014, the date the FDA was scheduled to complete review of the drug application. The FDA reviewed Imbruvica's application for this new use under the agency's priority review program, which provides for an expedited review of drugs that are intended to treat a serious disease or condition and, if approved, would offer significant improvement compared to marketed products.
Imbruvica also received accelerated approval in November 2013 for the treatment of patients with mantle cell lymphoma who have received at least one prior therapy. Clinical studies to verify and describe Imbruvica's clinical benefit in mantle cell lymphoma are ongoing.
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