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Idelalisib Significantly Improves Survival in Chronic Lymphocytic Leukemia

The novel agent, idelalisib, in combination with Rituxan (rituximab), significantly improves survival compared with Rituxan alone among patients with chronic lymphocytic leukemia who are not able to tolerate chemotherapy. These results were recently presented as a late-breaking abstract at the 2013 annual meeting of the American Society of Hematology (ASH).

Chronic lymphocytic leukemia (CLL) is a type of cancer that starts in the immune cells called B-cells. B-cells have proteins on the outside of their cells referred as CD20 antigens.

Rituxan is a commonly used treatment agent for CLL, which binds to the CD20 antigen. The binding action stimulates the immune system to attack the B-cells. In addition, researchers believe the binding of Rituxan to the B-cells may have some direct cancer killing effects.

Idelalisib is an agent that is not yet approved by the United States Food and Drug Administration (FDA). It inhibits part of a pathway of cells that is implicated in replication and growth of cancer cells, referred to as the delta isoform of phosphoinositide 3-kinase (PI3K).

Researchers from several medical institutions in the United States and Europe conducted a phase III clinical trial that compared Rituxan plus idelalisib to Rituxan plus placebo (inactive substitute) in the treatment of recurrent CLL. The trial included 220 patients with CLL whose disease progressed despite prior therapies. Approximately half of the patients received Rituxan/idelalisib while the other half received Rituxan/placebo.

At approximately 6 months, 93% of patients treated with Rituxan/idelalisib were alive with no evidence of cancer progression (progression-free survival), compared with only 46% of patients treated with Rituxan/placebo.
Patients had a 72% reduced risk of death if treated with Rituxan/idelalisib compared to those treated with Rituxan/placebo.
Treatment with idelalisib was generally well tolerated.
The researchers concluded that the addition of idelalisib to Rituxan significantly improves progression-free survival, as well as overall survival compared to Rituxan alone in the treatment of CLL that continues to progress following prior therapies.

Idelalisib is not yet approved by the United States Food and Drug Administration (FDA); however, it is in the final stages of clinical trials and evaluation of data.

Reference: Furman R, Sharman J, Coutre S, et al. A phase 3, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of idelalisib and rituximab for previously treated patients with chronic lymphocytic leukemia (CLL). Proceedings from the 2013 annual meeting of the American Society of Hematology. Late-Breaking Abstract #6. Available at: https://ash.confex.com/ash/2013/webprogram/Paper66044.html. Accessed January, 2014.