The U.S. Food and Drug Administration has expanded the approved use of Imbruvica (ibrutinib) for chronic lymphocytic leukemia (CLL) patients who have received at least one previous therapy.
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 15,680 Americans were diagnosed and 4,580 died from the disease in 2013.
Imbruvica works by blocking the enzyme that allows cancer cells to grow and divide. In November 2013, the FDA granted Imbruvica accelerated approval to treat patients with mantle cell lymphoma, a rare and aggressive type of blood cancer, if those patients received at least one prior therapy.
"Today's approval provides an important new treatment option for CLL patients whose cancer has progressed despite having undergone previous therapy," said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research. "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."
Under the agency's accelerated approval process, the FDA may approve a drug based on a surrogate or intermediate endpoint that is reasonably likely to predict clinical benefit. Drugs receiving accelerated approval are usually subject to an agreement to conduct confirmatory trials verifying and describing clinical benefit. Imbruvica for CLL also received priority review and orphan-product designation because the drug demonstrated the potential to be a significant improvement in safety or effectiveness in the treatment of a serious condition and is intended to treat a rare disease, respectively.
The FDA's accelerated approval of Imbruvica for CLL is based on a clinical study of 48 previously treated participants. On average, participants were diagnosed with CLL 6.7 years prior to the study and had received four previous therapies. All study participants received a 420 milligram orally administered dose of Imbruvica until the treatment reached unacceptable toxicity or the disease progressed. Results showed nearly 58 percent of participants had their cancer shrink after treatment (overall response rate). At the time of the study, the duration of response 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 clinical study include low levels of platelets in the blood (thrombocytopenia), diarrhea, bruising, a decrease in infection-fighting white blood cells (neutropenia), low red blood cells (anemia), upper respiratory tract infection, fatigue, pain in the muscles and bones (musculoskeletal pain), rash, fever (pyrexia), constipation, swelling of tissues (peripheral edema), joint pain (arthralgia), nausea, mouth sores (stomatitis), sinus infection (sinusitis) and dizziness.
Imbruvica is manufactured by Sunnyvale, Calif.-based Pharmacyclics.