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Further Data Indicating Superiority of Idelalisib in Chronic Lymphocytic Leukemia

The addition of idelalisib to Rituxan (rituximab) significantly improved survival compared to Rituxan only in the treatment of patients with chronic lymphocytic leukemia (CLL) who had impaired kidney function. These results were recently published in the New England Journal of Medicine.

Chronic lymphocytic leukemia is a type of leukemia that tends to be diagnosed in individuals 65 years or older. Among the elderly, medical conditions other than cancer often exist, limiting effective treatment options for the disease.

Idelalisib is an agent that is not yet approved by the United States Food and Drug Administration (FDA), but is moving quickly through the clinical trials process due to its safety and effectiveness in the treatment of some types of blood cancers, such as different types of leukemia.

Idelalisib works by blocking a pathway in cancer cells that is involved in cancer spread and replication. This pathway, called the delta isoform of phosphatidylinositol 3-kinase, is mutated in some cancers, resulting in cellular replication that is out of control.

Researchers recently conducted a clinical trial to further evaluate idelalisib in the treatment of CLL. The phase III trial (the last phase of clinical trials) included 220 patients with CLL who had received prior therapy. All the patients also had compromised kidney function or other serious medical conditions besides their cancer, precluding them from being able to tolerate chemotherapy. Patients were divided into two groups: one group was treated with Rituxan (a standard biologic therapy) plus idelalisib, or Rituxan plus placebo (inactive substitute).

· Overall anti-cancer responses occurred in 81% of patients treated with idelalisib/Rituxan, compared with only 13% of patients treated with Rituxan only.

· Median progression-free survival (survival without progression of cancer) had not yet been reached at the time of data collection for those treated with idelalisb/Rituxan, compared with only 5.5 months for those treated with Rituxan only.

· At one year, overall survival was 92% for those treated with idelalisb/Rituxan, compared with only 80% for those treated with Rituxan only.

· Serious side effects occurred in 40% of patients treated with idelalisib/Rituxan and 35% of patients treated with Rituxan only.

The researchers concluded that “The combination of idelalisib and rituximab, as compared with placebo and rituximab, significantly improved progression-free survival, response rate, and overall survival among patients with relapsed CLL who were less able to undergo chemotherapy.” The trial was stopped early due to “overwhelming efficacy” of the addition of idelalisib to Rituxan in this patient population.

Reference: Coutre S, Sharman J, Furman R, et al. Idelalisib and Rituxan in relapsed chronic lymphocytic leukemia. New England Journal of Medicine. Early on-line publication January 22, 2014. DOI: 10.1056/NEJMoa1315226.