Idelalisib plus rituximab improves progression-free survival in relapsed CLL

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1. Idelalisib plus rituximab improved progression-free survival in patients with relapsing CLL compared to rituximab plus placebo. This benefit was seen across all sub-groups regardless of age, gender, or specific mutations. 

2. Adverse events, including “serious” events, were noted to be similar among both groups. 

Evidence Rating Level: 1 (Excellent)     

Study Rundown: With the unique ability to recognize specific proteins and binding sites, biologic therapies have become the focus of cancer research and treatment. Idelalisib is a new potent inhibitor of a B-cell signaling molecule, phosphatidylinositol 3-kinase (PI3K), which then downregulates over-expressed B-cell genes in chronic lymphocytic leukemia (CLL). The current standard for treating relapsed CLL includes older chemotherapies, each with significant toxicity, thus limiting the treatment options for patients with various other co-morbidities or who are generally elderly and frail. Ironically, these are also the patients most likely to relapse.

This double-blinded, randomized, controlled trial assigned patients to either idelalisib and rituximab or rituximab and placebo. The results showed significantly higher rates of progression-free survival at 24 weeks in the idelalisib group compared to the placebo group (93% vs. 46%; P<0.001). The differences in median time of survival and overall survival were also statistically significant with idelalisib again showing a benefit.

While these preliminary results are promising and there was no significant difference in adverse events reported by both groups, patients in this study were only followed for up to 16 months. More follow-up is required to comment on the long-term safety of idelalisib. Nonetheless, this study shows the efficacy of a new biologic agent in treating relapsing CLL in a population typically with multiple comorbidities that may limit treatment options. Future studies should focus on comparing idelalisib and rituximab to other biologic combinations.

Click to read the study, published today in NEJM

Click to read an accompanying editorial in NEJM

In-Depth [randomized, placebo-controlled, phase 3 study]: This study involved a total of 220 patients randomized equally into two groups: idelalisib and rituximab versus placebo and rituximab. The baseline characteristics were well-matched. The primary endpoint was the rate of progression-free survival. The median progression-free survival was met at 5.5 months in the placebo group but was not reached in the idelalisib group. Progression-free survival among all subgroups showed that idelalisib was superior to placebo; this included subgroups for age, gender, and type of genetic mutation. At 12 months, the overall survival was 92% versus 80% in idelalisib versus placebo groups, respectively (hazard ratio, 0.28; 95%CI, 0.09 to 0.86; p=0.02). Serious adverse events (most frequently pneumonia, pyrexia, and febrile neutropenia) occurred in 40% and 35% of patients in the idelalisib and placebo groups, respectively.

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